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Interstellar Communication Using Microbes: Implications for SETI

Mention Robert Zubrin’s name and the planet Mars invariably comes up, given his long-time work on finding ways to establish a human presence there. Dr. Zubrin is the originator of Mars Direct, the author of The Case for Mars, and founder of the Mars Society. But his work on interstellar matters is likewise significant, including the analysis, with Dana Andrews, of the Bussard ramjet, which taught us much about magsails and drag, offering a useful way to re-think starship braking at destination. Another key Zubrin creation is the nuclear salt water rocket concept. With over 200 papers and five books to his credit, he runs Pioneer Astronautics, where he continues to focus on innovative aerospace technologies. Today’s essay goes in another direction, with a fresh look at interstellar communications using microscopic data carriers. Ponder now how information can be conveyed star to star, and how we might find it by methods far removed from conventional SETI.

by Robert Zubrin


Since the dawn of the SETI effort in 1960, it has been generally assumed that the transmission of information across interstellar distances can most practically be accomplished using electromagnetic waves, with the most popular candidate method being radio in the 21-cm wavelength (1.42 GHz) range. Accordingly, a series of searches based on this assumption have been conducted, thus far without any success. In this paper, we will advance a hypothesis that the reason for this failure is because radio is, in fact, a very inefficient means of interstellar communication between species, and that a superior alternative is available. Specifically, we will show that communication between species can be much more effectively accomplished over interstellar distances using microscopic high density data storage packages sized between 1 and 10 microns. Such packages have already been detected. They are, in fact all around us, and within us, in vast numbers and varieties. Generally known as bacteria, these spaceflight-capable data storage systems are carrying enormous amounts of information, only a small fraction of which has any identifiable purpose. Could interstellar messages be found encoded within the genomes of microbes? Could records of such past transmission be found within the genomes of multicellular organisms? In this paper we shall explore the possibilities, discuss how such transmissions could be efficiently sent, and propose methods by which such a hypothesis might be falsified or verified.


It is a general principle of science that the laws of nature should apply equally well throughout the universe. Specifically, since the dawn of modern science in the Renaissance under the philosophical banner “as above, so below” it has been taken as axiomatic that the laws of nature that prevail elsewhere in the universe should also apply on Earth, and those that apply on Earth should apply equally well elsewhere. This being the case, it necessarily follows that if life and intelligence could develop from physics and chemistry via natural processes on Earth, it should also have done so in innumerable other equally satisfactory physical and chemical environments throughout the cosmos. Indeed, the early Earth at the time of life’s first appearance immediately following the end of the heavy bombardment was in no way exceptional. Furthermore, the processes by which life can develop from simple forms to complexity and intelligence are, in broad outline, well understood. While the universe is vast in space, it also is so in time, so that a spacecraft traveling at a velocity of 0.0001 c (the speed of the Earth in its travel around the Sun) could in 4.5 million years (0.1% the age of the Earth) travel 450 light years, a radius encompassing approximately 1 million stars, with surely enough candidates for many additional origins for life and civilization. Despite these favorable odds, no such extraterrestrials have been detected, a mystery leading the physicist Enrico Fermi to ask his famous paradoxical question at a 1950 Los Alamos lunchtime meeting: “So then, where are they?”

One possible reply to the Fermi Paradox is that they are out there, but that if you want to find them you need to look for them in the right way. In 1959, Cornell physicists Phil Morrison and Giuseppe Cocconi (Cocconi and Morrison, 1959) proposed that extraterrestrials might be communicating across space using 1.42 GHz radio, as the emissions of hydrogen gas at that frequency make it the most listened-to band in radio astronomy. Moreover, it is approximately the same frequency as the L-band and S-band radio systems that were becoming state of the art for spacecraft communication at that time, a fact which added credence to the Morrison-Cocconi hypothesis, and made it readily testable as well. Accordingly, shortly thereafter astronomer Frank Drake attempted to detect such signals from Tau Ceti, without success. Undeterred, Drake, his co-workers, competitors, and successors continued with many such search searches, from that time down to the present, where the SETI Institute, among others, is continuing the effort on a greatly expanded basis with vastly improved instrumentation, but no better results.

Given this failure, it is appropriate to revisit the assumptions behind the Morrison-Cocconi hypothesis suggesting interstellar communication via S-band. Certain of its supports have already been falsified by technological progress, in that, a mere 60 years later, S-band is already obsolete. Instead our spacecraft now communicate at higher frequencies, such as X-band (10 GHz) and Ka-band (30 GHz), as these higher frequencies allow for higher bandwidths for spacecraft communication systems of a given size and power.

But while the Morrison-Cocconi hypothesis, and resulting search, can be adjusted to take into account such improvements, there are deeper problems. The first of these is that communicating effectively across interstellar distances via radio is incredibly hard and inefficient. To see this, let us consider what it would take to design such a system.

The Mars Reconnaissance Orbiter (MRO), launched in 2005, has a modern 100 W X-band communication system. Equipped with a 2-m diameter dish, it can transmit at a rate of 6 Mb/s to a 70-m receiving system on Earth at a distance of 100 million km. A modest range for effective interstellar communication would be 10 light years, or 100 trillion km. At this million-fold greater distance, the MRO communication system would have its data rate reduced by a factor of a trillion, from 6 Mb/s to 6 microbits/s, or 200 b/year. This would appear to be too slow for practical purposes, so let’s upgrade the transmitter power to 1 GW and its dish size to 70 m. Taken together these upgrades would increase the data rate by a factor of 10 billion, to 60 kb/s, which would be fine. The upgraded system would have a capability of 600 b/s at 100 ly, which is still sufficient to be useful, as those who can remember working with computer modems in the 1980s can readily attest.

Assuming that the transmitter was X-band, the diameter of the beam at 10 ly would be about 2500 AU, so it would encompass the whole solar system, and then some, but the closest neighbor solar system would be 100 times further away that the width of the beam. So ET’s 1 GW transmitter could only be used to signal one solar system at a time. How would they know who to signal?

A good place to start would be to only send signals to planets manifesting a biosphere. These could be detected using astronomical techniques by observing the spectral signal of free oxygen in the planet’s atmosphere. But Earth, for example, would have provided a positive answer to such a search criterion for the past 500 million years, but only has only possessed a species able to receive and detect such a signal for the past 50 years. Based on these odds, ET would have to set up 1 million transmitters to living planets have a 10% chance that one of its signal units would be sending at the right time. This would require a transmitter system power of 1000 TW, about two orders of magnitudes higher than the total power produced by human civilization today. If they wanted to keep their odds as good, but reduce the number of transmitters, they could do so, but only at the cost of continuing to power the transmission program for millions of years. Furthermore, to receive the signal, the inhabitants of the target planet would have to be focusing their 70-m dish at precisely the right star at the right time, be listening at the right frequency, and be technologically and intellectually prepared to recognize and decipher the signal. Using lasers instead of radio to transmit would reduce the power requirement significantly, but it would still be huge, and furthermore, it would impose a requirement that the receiving civilization have a giant telescope focused on the transmitter’s narrow beam, at the right time, with its optics limited to the transmitting frequency to avoid having the transmitter outshined by its home system’s star. This seems like a rather farfetched hope upon which to expect ET to spend such a large investment in infrastructure and energy.

Surely there must be a more efficient approach. What could it be?

Interstellar Data Transmission by Microbial Storage Drives

One problem of data transmission by radio is that it occurs in real time, leaving no record behind. Once the transmission is over, it’s gone. If the intended recipients miss it the first time, they’ve missed it for all time. As a result, the transmitting party is forced to transmit repeatedly, perhaps endlessly, in the hope that one at least one occasion, someone might be listening.

Imagine that you want to tell a story to children. So you walk onto the front porch of a house and tell the story, whether any children are there are not. In fact, they are usually out running around, so you probably have missed your audience. But the odds against you are worse, because while the house is suitable for children, they may not have been born yet, or those that are there may be too young to understand your story, or they could have grown up and moved out. Now, you could increase your odds by going from porch to porch, reading the story again and again in the hope that someone might be there to listen. But this could get exhausting. A better strategy would be to go about slipping story books into houses through their mail slots. Even if most of them ended up on the shelf or sold to used book stores, sooner or later many of them would likely get read. The only problem with this strategy is its cost; giving out a lot of storybooks could be expensive. But if you could get them for free, and have them delivered for you cheaply, it could be a very good approach, allowing you to reach many children not only today, but for decades and generations to come.

In short, I am suggesting, in agreement with Davies (Davies, 2010), that rather than transmit information across interstellar distances using radio waves, that solid objects containing records be used instead. This may seem like it would be very inefficient, but in fact every planetary civilization orbiting a star has available to it an engine that it can use to send information across space at little or no energy cost. This is the star itself.

Let us consider our own Sun as a case in point. At 1 AU, the sun attracts objects to it with a gravitational acceleration of 0.006 m/s2. It also repels objects from it via its light pressure with a force of 0.000009 N/m2. If these two forces are equal, and object will feel no attraction from the Sun, and fly out of the solar system in a straight line with the Earth’s velocity of 30 km/s. (Both of these forces change with the inverse square of their distance from the Sun, so if they are equal at 1 AU, they remain equal at any distance.) Assuming the object has a radius r and a density d, and setting these two forces as being equal we find:

If d = 1000 kg/m3 (water density), we find that r = 1 micron. This means that such an object would have a diameter of 2 microns. However, it is not necessary to cancel all the force of gravity to escape the solar system. If half of the gravitational attraction is cancelled, an object with the orbital velocity for the full gravity object will escape. In the case above, this would imply a maximum diameter of 4 microns.

If the star were brighter than the Sun compared to its gravity, which would be the case with F stars, the objects could be somewhat larger. If it were dimmer than the Sun compared to its gravity, as would be the case with K stars, the objects would be need to be smaller. If their initial orbits were elliptical, rather than circular, the objects could be bigger. So, depending on assumed conditions, the diameter of the objects could range from 1 to 10 microns, and be readily projectible across interstellar distances using no other mechanism than the pressure of the star’s light. This is precisely the size range of many typical bacteria. (Arrhenius, 1908) It is also possible that the solar wind, which moves at a velocity of about 500 km/s, could be used to propel particles out of the solar system at very high velocity. However, in order for a particle to interact effectively with the solar wind it would need be strongly magnetized, allowing it to function as a miniature magnetic sail. (Zubrin and Andrews, 1989.) Under normal circumstances even such a strongly magnetized particle would be propelled away from the Sun by the solar wind with less force than that provided by light pressure. During solar flare events, which greatly increase the force of the plasma wind emanating from the Sun, however, this could change radically.

In Table 1, we show the relationship between star type, population fraction, star mass, luminosity, orbital distance and velocity and maximum particle diameter for stellar system escape for stars of various types. In each case the launch planet is assumed to be in a circular orbit in the given star type’s habitable zone. It can be seen that for type F, G, and K stars, collectively amounting to about 22.5% of the stellar population, that starlight can readily propel bacteria sized objects to system escape velocity. At half the diameters shown the objects will be projected outward from the stellar system at the orbital velocity given, at less than half, still greater velocity. Objects larger than that shown will not escape the system by light pressure alone, but could still do so if the light pressure is enough to drive them into an elliptical orbit that intersects a large planet capable of delivering a gravity assist.

Upon reaching a destination solar system, the bacteria-sized particles could be decelerated using the same mechanism.

Table 1 Interstellar Particle Transmission Capabilities of Star Types.

In Table 1, the particles are assumed to be simple spheres. If more complex shapes are used, for example shapes with a spherical core surrounded by thinner wings, the core spheres can be thicker and still achieve the same velocities. For example, a sphere with a diameter of 4 microns surrounded by a disc with a diameter of 8 microns and a thickness of 1 micron would have the same surface/mass ratio as a simple sphere with a diameter of 1.2 microns, and would therefore be able to escape a K star. Such “microsailcraft” designs could be readily mass-produced artificially or potentially created through natural crystallization processes, as exemplified by snowflakes. They could be stabilized in a manner to effectively serve as sails either by spinning (as some snowflakes do), or by having inherently stable shapes, as exemplified by a badminton birdie.

So, bacteria can be projected across interstellar space at essentially no power cost to the transmitting party, beyond that required to launch them to planetary escape velocity. The latter could be accomplished either by artificial technological means that are well within our means today – and therefore clearly feasible for advanced extraterrestrials – or potentially through natural processes such as asteroidal impacts. They also may be cheaply mass produced. (McDowell, 2003) But can they carry useful information?

The answer is most certainly yes. The genetic material of individual common bacteria is estimated to contain between 130 kB to 14 MB of information. Current estimates that bacteria can be used to store data with a density of 900 Terabytes per gram, about 500 times the current state of the art electromagnetic hardware. This means that a bacterium 5 microns on a size could store about 120 kB of information. (Wilkins 2010, Herkewitz 2016) Taking 60 kB as typical, this means that a single bacterium can carry a record of information about equal in size to a 10,000-word (~30 page) booklet. In experiments done to date, scientists have demonstrated such capabilities by encoding entire books in DNA, and showing that bacteria can be made to replicate encoded information when they reproduce.(Ayre 2012). Most recently, researchers at Columbia University and the New York Genome project have shown that they can encode information with a density 215,000 Terabytes of information per gram in DNA, with some of the items successfully encoded including a movie, a computer operating system, and an Amazon gift card. (Service, 2017)

Traveling at a velocity of 30 km/s (0.0001 c), bacteria would take 100,000 years to fly 10 light years. This would expose them to cosmic ray doses between 1 and 10 Mrads, which is close to the limit for survivability of hardy microcrobial species such as radiodurans. This need not be a show stopper. A message sent using bacteria storage would no doubt use billions of individuals, and if even a few survived the trip the message could still get through. While ultraviolet light would kill unshielded bacteria in days, effective shielding against this hazard can be provided by a half micron of soot. (Hoyle, 1981). Such protection would be provided by design in any artificial microsailcraft, but could conceivably also occur naturally.

Such long trips might not be necessary, however. Once they reach a planet, bacteria will multiply to vast numbers. They can then be ejected again into space via cometary impact. Such impacts are most likely to occur during periods when a foreign star is passing through the Oort cloud of the bacteria’s home star, as such a passage would destabilize Oort cloud object orbits orbiting both stars, and thereby causing impacts to occur. Like frigates in the age of fighting sail, which could span the globe with their movements but only reach a few hundred yards with their guns, roving solar systems discharge their broadsides at each other only during rare close approaches. As a result, ejected bacteria might typically only need to travel distances on the order of 0.1 ly to reach a new planetary home, with radiation doses accordingly reduced by two orders of magnitude compared to those postulated above. Given the density of stars in our own region of the galaxy, and assuming a random velocity of stars relative to each other of 5 km/s, it can be shown that a star is likely to experience such a close encounter about once every 20 million years, a frequency strikingly close to the observed mean time of 26 million years between of mass extinctions on Earth. (Zubrin, 2001). It may be noted that microbes traveling embedded in impact debris would be well shielded from ultraviolet and soft x-rays, thereby increasing their survival odds. (Melosh, 1988, Hornek, Klaus, and Mancinelli, 2010)

The Milky Way galaxy is 13 billion years old. Allowing 3 billion years for several generations of early stars to seed the place with heavy elements, that leaves 10 billion years, or 500 stellar close-encounter doubling times of 20 million years each for life to spread from its first planet of origin to everywhere else. So the answer to Fermi’s paradoxical question is almost certainly this: They’re here.

The Purpose of Interstellar Communication

At this point, we need to reexamine the question of what might be the purpose of interstellar communication. Certainly, if a species were spacefaring and had sent out expeditions which established settlements in nearby solar systems, it would want to maintain communication to exchange or trade information between its various worlds. For such purposes, high-gain directed electromagnetic transmissions would be the most practical, as they are the fastest possible, the most secure, and all the required technological and linguistic conventions would be known and mutually understood between the parties involved.

But if we are talking about communication between different species originating in different and distant worlds, what is the point? In speculative SETI literature, it is frequently supposed that there are intelligent aliens out there, who for some reason want others to know that they exist, and therefore transmit signals such as the value of into the void, so that other smart folks won’t confuse them with astrophysical phenomenon. Then, assuming that someone picks up the signal, they will transmit back the value of e, or the golden mean, or some other special number, thereby completing the freemasonic handshake. This done, the two parties could then proceed to methodically expand their mutual vocabulary, eventually allowing them to exchange QST cards, recipes, celebrity gossip, novels, scientific theories, starship designs, and treaties of alliance against the barbarians from the Galactic rim.

However, as noted above, both experimental searches and theoretical considerations suggest that such a picture does not correspond to reality. Microbial data transmission is possible, but it does not lend itself to conversations of the types described above. Rather it is a superior method of interstellar broadcasting.

So the question is, what kind of information is really worth broadcasting – that is distributed as widely as possible to people who we don’t know and are not likely to hear back from? If human experience is any guide, the answer is propaganda. Think of Radio Free Europe, or its Cold War opposite number, Radio Moscow, for example, and their persistent messaging: “We are good. You should admire us. You should be like us. You should join us.” Another example would be the Gideons, placing Bibles in hotel rooms in the hope that their unknown readers would see the light and become Christians. We also try to broadcast ourselves to worlds we will never see, by using art to send our message across deep time. Thus Pericles at the Parthenon: “Future ages will wonder at us, even as the present age wonders at us now.”

The key to propaganda is in the root of the word itself: propagate. Through propaganda we seek to propagate ourselves across both space and time. This can be in spirit, as in the cases described above, or in the flesh, through physical reproduction. Indeed, while only a relative handful of people have been able to message the future through monuments, literary works, or art, the great majority of those of the past world who have sent us something of themselves have done so by propagating themselves biologically. Using this method, they have transmitted to our world not only their genotypes and phenotypes, but even their languages, beliefs, and traditions as well. Propagation is propaganda. Propaganda is propagation. It is the most desired form of communication. It is how the past has communicated with us, and how we seek to communicate with the future. This is a key point, because interstellar communication through any means must perforce be communication across time.

So, it should be clear. If we are going to transmit across the ages, we need to send instructions on how to make ourselves. Such messages are not sent via radio. They are sent using genes.

The code of life is the code of the cosmos.

Panspermia or Geospermia?

It is a striking fact that, despite several centuries of microbial research by thousands of competent investigators, no free-living organisms have been found on Earth that are simpler than bacteria. This is truly remarkable because, as simple as bacteria may be compared to more complex organisms, they are certainly not simple in any absolute sense, incorporating as they do, among other things, the entire elegant double-helix scripted language of DNA. Believing that bacteria were the first life forms to emerge from chemistry is like believing that the iPhone was the first human-invented machine. This is incredible. Just as the development of the iPhone had to be preceded by the development of computers, radio, telephones, electricity, glassware, metallurgy, and written and spoken language, to name just a few necessary technological predecessors, so the creation of the first bacterium had to be preceded by the evolution of a raft of preceding biological technologies. But we see no evidence of any such history. We still see devices all around us that use one or more of the iPhone’s ancestor technologies – telephones, light bulbs, batteries, glass windows, and steel knives, for example – but we see no pre-bacteria organisms. This observation has led many investigators, dating back to Arrhenius (Arrhenius 1908) over a century ago, to postulate that life on Earth is an immigrant phenomenon. According to this “panspermia” hypothesis, bacteria did not originate on Earth, but came here from space, after which they gave rise via generally understood evolutionary processes to all other life forms.

The panspermia hypothesis is generally disliked by origin of life researchers, because it completely ducks their central question of how life originated from chemistry in the first place. This is particularly the case for the original form of the panspermia hypothesis offered by Arrhenius, who believed that the universe and life had existed eternally, thus making the question of the origin of either meaningless. However, if the panspermia hypothesis is taken to simply open the question as to the location of life’s planet of origin, then it is by no means useless. Consider: an investigator seeking to explain the origin of Americans would be crippled in his or her research if he or she had to accept as axiomatic the conceit that humans evolved independently in North America (and even more so if Golden, CO were specified.). No, the fact is that humans originated in Africa, and only came to the Americas much later. This is why we can find evidence of humanity’s closest relatives, primate ancestors, and earliest cultures and technologies in Africa but not in North America. Knowing this, an investigator would not be bound to try to explain the independent origin of humans from native North American (or Goldenian) fauna, but instead could focus on conditions and biological foundations that were present in Africa in the relevant period. Similarly, there have been origin of life experiments, such as the famed Miller-Urey experiment, that have been discounted because they postulated conditions that did not exist on the early Earth. If the possibility of an extraterrestrial origin of life is accepted, such objections lose their force.

Indeed, insistence on geospermia by assumption puts origin of life researchers in the same absurd position as the above described unfortunate paleontologist, whose assumption of a local origin for humanity forces him or her to reject the theory that humans evolved from higher primates because there were no such species in evidence in Golden, CO at the time of humanity’s appearance. There are innumerable planets where the spontaneous formation of amino acids from chemistry, as demonstrated by the Miller-Urey experiment, could readily have occurred, as opposed to the early Earth, where it could not. Science needs to follow the data, not defy it. Therefore it is the Miller-Urey experimental results that discredit the assumption of geospermia, rather than the reverse.

Further support is offered to the panspermia hypothesis by discoveries of bacterial fossils known as stromatolites, dating back approximately 3.5 billion years, and residues of biological activities dating back 3.8 billion years, that is practically right back the end of the heavy bombardment that previously made the early Earth uninhabitable. In fact, as this is being written, a team of researchers have just reported microfossils that date back 4.28 billion years, that is to the middle of the heavy bombardment. (Drake 2017) In short, life appeared on our planet virtually as soon as it possibly could (and possibly several times, before it could last), suggesting that it was already around, waiting to land and spread as soon as conditions on the ground were acceptable.

The primary counter argument offered against the panspermia hypothesis is that there may once have been prebacteria on Earth, but that they have since been wiped out by their more developed descendants. While this may be possible, it is not consistent with the history of life on Earth, in which simpler forms generally continue to exist in abundance even after they give rise to higher or more complex varieties. In any case, this argument is only an excuse for the lack of any evidence for any prebacterial history of life on Earth. Accordingly, it has no power or potential to falsify the panspermia hypothesis.

Furthermore, it needs to be understood that the conceit that life originated on Earth is quite extraordinary. There are over 400 billion of stars in our galaxy, with multiple planets orbiting many of them. There are 51 billion hectares on Earth. The probability that life first originated on Earth, rather than another world, is thus comparable to the probability that the first human on our planet was born on any particular 0.1 hectare lot chosen at random, for example my backyard. It really requires evidence, not merely an excuse for lack of evidence, to be supported.

The panspermia hypothesis could be falsified however, if we were to send explorers to Mars and find either a) no evidence of any past or present life, b) evidence for the presence of prebacteria or c) evidence of life of sufficiently different type as to imply a second genesis. Condition (a) would falsify panspermia because Mars had liquid water on its surface during the period when life appeared on Earth, so that if Earth were seeded via panspermia, Mars should have been seeded too. Condition (b) would refute panspermia directly by revealing the prior evolutionary history of Earth life on Mars, from whence it could readily have been transmitted here via meteoric impact. Condition (c) would refute panspermia by showing two independent origins. However, if none of these conditions are met, and we find evidence of past or present bacteria on Mars similar in structure to Earth bacteria dating back to the planet’s early history, with no evidence of prebacteria, the panspermia hypothesis would be strongly supported.

In the absence of falsification, we are presented with three possibilities for interstellar microbial transmission.

1. The transmission is natural, being the result of ejection of material from microbe-inhabited planets following meteoric impacts.

2. The transmission is artificial, being the result of intentional dispersal by intelligent extraterrestrials of microbes carrying imprinted encoded information.

3. The dispersal is both artificial and natural, being the result of both processes listed above going on simultaneously.

With respect to the above listed possibilities, the one that seems most difficult to defend is (2), because if bacteria can survive interstellar trips, there will be natural transmission, regardless of whether artificial transmission is also going on. Indeed, it is hard to escape the conclusion that natural transmission has been going on for at least 3.6 billion years, if from no other original source than the Earth. If the average time between close stellar encounters is 20 million years, with number of microbe inhabited system doubling each time, we could expect 2180 solar systems in our galaxy to have been Earth-progeny-microbe-invaded by now, which is to say all of them, many times over. (This being the case, the probability that the Earth was actually the first of these billions of microbe-inhabited worlds would be vanishingly small.)

So, the question is not whether interstellar microbial transmission is going on; it almost certainly is. Further, even if is not occurring naturally, it is still clearly possible through artificial means. So indeed, far from being a necessary condition for microbial SETI, even the possibility of natural panspermia creates difficulties, as it introduces the potential for noise that could drown out the signal.

The key question for microbial SETI is whether there is artificial intelligent input being inserted into the vast flood of genetic information traveling around the Earth. Are there any real letters of importance to be found in the deluge of junk mail? If so, how could we pick them out?

Distinguishing ET’s Messages from Junk Mail

Radio SETI researchers record electromagnetic waves received from space, and examine them with algorithms to try to detect something that seems too organized to be merely the result of astrophysical phenomenon. In principle, microbial SETI researcher could take a similar approach, using gene sequencing technology to process large numbers of bacterial genomes, looking for something that just doesn’t seem natural. Perhaps buried amidst the junk DNA of some bacterial species is a sequence of amino acids that an expert cryptanalyst can decode to read; “Here is the value of π, 3.14159265…This is just our way of saying hello. You will find the primer for our language on the next gene, and starship design instructions on the gene after that.” Perhaps that is a somewhat facetious way of putting it, but certainly if we believe that extraterrestrials want to send us some such signals, a direct attempt to sort through the mail pile using gene-sequencing and cryptanalytical tools to see if anything interesting pops up might be warranted.

That said, there is, as noted above, grounds for skepticism that this is the form of communication that intelligent species would find interesting. If there is a field of life throughout the galaxy, initiated on innumerable worlds by natural panspermia, it could be expected to evolve in multitudes of new and unpredictable directions through natural processes including mutation and natural selection, driven by chance and diverse environmental conditions. It seems to me that the most portentous form of communication that intelligent extraterrestrials could undertake would be to try to propagate themselves by sending out genetic information to influence this chaotic process in their own direction. Genomes can contain dormant plans for complex traits, as evidenced by recent work in which scientists activated what had been considered junk DNA in chickens to produce long-lost dinosaur features, like teeth. (Hoggenboom 2015, Bhuler 2015) Well, chickens are descended from dinosaurs, so perhaps it’s not too astonishing to discover that they still keep some of the old body plans on file. Such plans could come in handy if new conditions require a radical evolutionary leap. But could it be possible that some such genetic plans were sent here intentionally by bacterial conveyance? Could some have been used, and others be still awaiting their chance? There are a variety of physiological features, such as the complex eye, or bird wings, whose origin is hard to explain in terms of incremental natural selection, as they appear to be completely non-functional in partially-developed form. The raising of such paradoxes has long been a stock in trade of theists arguing the case for supernatural “intelligent design.” But while there are, by definition, no supernatural phenomenon, there really are many things – including not only buildings and ships, but also domesticated animals and plants – that are the product of intelligent design. Bacteria can transfer genes among themselves, and to and from macrofauna and macroflora (Yong, 2016, Margulis and Sagan, 2008). Instead of sending us greetings and saluting us with the value of π, could extraterrestrials be sending us microbial messages for the purpose of guiding the evolution of our biosphere?

As fantastical as it sounds, I believe this is a testable hypothesis. Specifically, one could search for genetic material being carried by bacteria that can be inserted into animals or plants and result in the production of striking adaptations that have not yet manifested themselves in living species on Earth. Birds once had teeth, but they never had radar. No species is known which communicates telepathically using bioradio. There are any number of useful adaptations that are physically possible but which never have manifested themselves in terrestrial biology. Furthermore, there are traits that we do see in some species, but not in their ancestors. Mice were once fish, but fish were never mice. The fact that mice still carry fish traits has been clear since the 19th Century, when it was observed that mammal embryos exhibit fish traits such as gills. But do fish carry in their inactive DNA advance plans for mammalian traits? It is possible that such traits could be induced by the transference of bacterial genes. But from what source? If such were found, could they have been sent by extraterrestrials in the distant past, to either fish or their ancestors? Or did fish get them from mammals by natural local bacterial transference much more recently? How could these two possibilities be sorted out?

We could also consider the past. There were certain periods when a massive amount of evolutionary innovation occurred within an extremely brief period of time, with the Cambrian Explosion and the early Eocene immediately following the KT extinction immediately coming to mind. Can the sudden appearance of so many radically new traits be best explained by the prior existence of readily available genetic plans? Or perhaps could it be the result of the opening of expanded channels of communication between genetic plans? (Hoyle, 1981)

Current evolutionary neo-Darwinian “fundamental dogma” holds that all traits of a species are only passed on genetically, so that traits acquired in life are not inherited. Furthermore, new genetic traits are only created through mutation and passed down within a species own line of descent, and that only if they pass the test of natural selection within that species line. While useful in understanding biological evolution, this theory is clearly false when applied to human social evolution. This is so because in contrast to what seems to be the case with other animal species, humans can inherit acquired traits, such as technologies, and furthermore, can inherit such traits from unrelated persons or groups. As a result, such theories as national social Darwinism, (Bernhardi, 1912, Hitler, 1941) which postulate history as a battle of nations for limited resources, with advances occurring via the resulting elimination of the less militarily proficient, are not only morally reprehensible, but scientifically wrong, since inventions made in any nation can (and generally do) ultimately benefit all nations. Indeed, were it the case that technological innovations were not laterally transferable from person to person, tribe to tribe, and nation to nation, it is doubtful that humanity would ever have advanced beyond the old stone age.

Conversely, it is easy to see the quantum acceleration of human progress following the establishment of global communications through the development of the printing press and long-distance sailing ships circa 1500, and their further improvement via railroads, steamboats, telegraphs, telephones, radio, TV and the internet in the period since. Furthermore, it is unquestionable that the growth of human population has contributed to this trend, since the more people there are, the more inventors there can be, and inventions are cumulative. This is why, contrary to Malthus, as the world’s population has gone up, the standard of living has gone up, not down. For similar reasons, it is in the self-interest of intelligent species to promote the creation of and communication with as many intelligent species elsewhere as possible. The more sources of transferable invention that there are, the more inventions each will receive, and the greater will be the power of each to add further inventions in turn. Furthermore, most intelligent species must be aware that their self interest lies in increasing, rather than decreasing, the number and effectiveness of the creative agents that they draw upon, because if they were not, they could not survive for long.

This said, can it really be true that the biosphere is so defective that it is incapable of allowing analogous transfer of useful genes between species? The creation of new useful traits by random mutation is a slow process. Clearly it would benefit all species, and thus the biosphere as a whole, were each to be able to draw to some degree on the genetic innovations of the rest. A community of life that had such ability would have greatly improved odds of survival, and enjoy tremendous adaptive advantage over any that did not. In fact, contrary to the neo-Darwinian fundamental dogma, the biosphere has exactly such a capability. Such transfers from species to species are enabled by bacteria, (Hotopp 2011). Such bacterial transfers of entire genes allow the evolution of valuable new inheritable traits to appear in species not over millennia, but within the lifetime of a single individual. Yong (2016) reports many such instances, for example species of woodrats that upon acquiring certain bacteria, immediately gain the ability to digest various plants, such as creosote or cactus, that they did not have before, thereby becoming able to live and prosper in environments dominated by such species. These valuable bacterial-derived traits are then passed from mother to child during birth, along with samples of the maternal bacteria. But since the rats are constantly broadcasting their bacteria through exhalation, these traits can be transferred to other unrelated individuals and even other species. Other bacteria have been shown to provide various species with inheritable defenses against parasites such as nematodes. Margulis and Sagan (2008) report many additional examples, including cases where the acquired genes eventually move from the bacterial microbiome carried by the animal into the animal cells themselves.

To use an analogy, the genotype of an animal’s cells is its hardware, but an animal’s characteristics are also determined by its bacterial software, or microbiome, which can be rapidly changed in and out. Evolution occurs not by random changes in the hardware circuitry, but by adding or subtracting software programs, which are constantly being developed and exchanged in vast amounts by the extremely prolific bacteria. If found by natural selection to be valuable over the long haul, these programs can end up being written into the hardware.

If the software is found to be useful, the animal’s chances of survival are improved, and the trait is passed on to her descendants. But not only that, she and each of her progeny become agents for spreading the useful trait throughout the biosphere through their exhalations and excretions. As you read this article, dear reader, you are exhaling half a million of your bacteria every minute, providing every creature around you with samples of what you and your ancestors have found to be useful. Your dog or cat is broadcasting similar service. Thus the web of life on our planet shares its inventions.

Can bacteria perform the same role from world to world? If they could, they would be a tremendously positive influence on evolution throughout the galaxy, transferring entire encyclopedias of hard won biological knowledge between planetary biospheres. But while benefiting the progress of life, it is hard to see how such capabilities benefit the bacteria themselves. Could they be serving the purposes of others? Perhaps they are, particularly since it is easy to see how others could be readily sending them.

It may be objected that ET’s wishing to control evolution elsewhere in order to reproduce themselves on other planets could hardly accomplish such as objective by spreading microbes carrying their genes, as evolutionary processes occurring on destination worlds would certainly carry matters forward in unpredictable directions. This is unquestionably true. However, returning to our example of trying to talk to the children in the neighborhood by leaving books around, we can imagine a more general method of communication. Let’s say the book is Harry Potter and the Sorcerer’s Stone. There are several layers of messaging in the book. These include:

1. Being a wizard beats being a muggle. So try to get into Hogwarts, and be sure to choose a Nimbus 2000 for your broomstick.

2. Virtue will be rewarded, vice will be punished, and good will triumph over evil in the end.

3. Reading is fun!

As a (1) method for transforming children into wizards, Harry Potter fails. It can contribute to (2) moral instruction, however, and succeeds brilliantly as (3) a way to get children to become readers. After that, there is no limit to what they might learn or become.

By analogy, the purpose of microbial data transmission might not be to direct evolution in particular ways, but simply to encourage evolution to be more creative.

Finding the Most Likely Suspects

Given these observations, how can we make use of them to detect ET? A good place to start might be to focus study on those bacteria which show the strongest signs of most recent extraterrestrial origin. These would be those best adapted for spaceflight. In nature, adaptations for particular purposes always come at a cost, and therefore generally disappear over time if they become unnecessary. Some bacteria, such as radiodurans, have excellent astronautical adaptations, including extreme resistance to hard radiation and vacuum. If people exiting an airplane landing in a warm city are observed to be wearing winter coats, the chances are good that they came from someplace cold. Similarly, if certain types of bacteria are adapted to space, there is reason to suspect they came from space. Accordingly, samples containing large varieties of bacteria could be exposed to space conditions prevailing in space. Those which survive the best could then be cultured and identified for further focused study. Evolution since arrival could have erased any past encoded genetic message, but remnants might still be found. There is only one way to find out.

But bacteria can evolve quickly, thereby potentially erasing essential information about the past of those who joined Earth’s Melting Pot some time ago. Therefore the most convincing place to look for microbial astronauts would be in space itself. Spacecraft carrying aerogels or other suitable capture media could be deployed with the mission of trying to gather spacebugs in flight. In principle they could be sent anywhere, with perhaps the most promising location being the vicinity of a comet as it outgases volatiles through its trip through the inner solar system. This could be a favorable location for space microbe collecting because it is possible that Oort Cloud objects might collect such interstellar voyagers over time, and then, when heated during close solar approach, release them in large numbers along with the vapors of the frozen volatiles that preserved and held them until that time. (Hoyle 1981). However the problem with this approach is that the characteristic relative velocities of objects moving in various orbits in space exceed several kilometers per second, so that microbes on one such trajectory slamming into anything remotely as dense as an aerogel on another would almost certainly be destroyed on impact. What is needed is an extremely diffuse medium of large expanse that can be used to slow the fast-moving microbes down to a near halt to so that they can be gathered without harm on a solid collecting surface. Fortunately, there are such media available. They are called planetary atmospheres.

Atmospheric entry from space is ordinarily thought of at a very high temperature affair, and it certainly can be. But the temperature reached will be a function of the object’s mass to surface area ratio, or ballistic coefficient. Objects like the Space Shuttle or Dragon capsule typically hit the atmosphere with ballistic coefficients between 100 and 1000 kg/m3, and these glow incandescent during reentry. However, as design studies for the German Mars Society’s ARCHIMEDES mission showed in considerable detail, a balloon with a ballistic coefficient on the order of 1 kg/m2 might well survive atmospheric entry at Mars without ever exceeding the temperature limits of Mylar. A spherical bacteria with a radius of 1 micron would have a ballistic coefficient three orders of magnitude lower still, and readily be able to avoid incineration after entry at speeds on the order of the Earth’s 11 km/s escape velocity. After being slowed down in such a manner, such a microbe would continue to fall downward, with a terminal velocity of about 3 m/s at 40 km altitude, decreasing to 1.5 m/s at 30 km altitude, and still slower at yet lower altitudes. Larger bacteria would have faster terminal velocities, with falling speed increasing as the square root of the microbe radius. For similar reasons, any microsailcraft with a low enough ballistic coefficient to escape its solar system using light pressure would have no problem safely entering the atmosphere of practically any planet.

It is possible to fly balloons at 40 km altitude, and use them to try to collect microbes. In the 1960s this was actually done by (later) Viking chief scientist Jerry Soffen, who did indeed discover viable microbes at that altitude, in such numbers that the results were considered so counterintuitive that the experiments were discontinued. (Hoyle 1981). While it is clear that any microbes found in the Earth’s upper stratosphere could be the result contamination from the biosphere below, such upward delivery by upwelling is made difficult by the strong temperature inversion in the stratosphere. This inversion places very cold (-50 C at 25 km) air below warm air (30 C at 40 km), and thereby suppresses upward convection. As a result, there is reason to suspect that microbes collected at 40 km altitude might be from space.

But how could we know? One way is by looking at the nature of the organisms collected themselves. The earliest microbes of Earth were anaerobic archaea. These can no longer live on the surface of the Earth, because they cannot tolerate the presence of oxygen. However, if life on Earth were begun via panspermia, such organisms would have been right stuff to get the ball rolling, because the surface of the prebiotic Earth was a suitable habitat for them. Furthermore, if anyone – be it ET or Nature – is still trying to seed life on prebiotic worlds today, it is these organisms, rather than the Earth’s surface biosphere currently dominant types, who would be the required pioneers. So, in short, what we should look for with our balloon-borne microbe collecting systems are anaerobes, who may exist within the Earth, but not on it, and who have no business flying around the stratosphere unless they just got off the boat.

It is also possible to fly balloons in the atmospheres of Venus and Mars. Both of these planets have sterile surfaces, effectively ruling out contamination via upwelling from below. Venus is especially attractive in this regard, as its thick atmosphere readily facilitates ballooning (two Soviet Vega balloons were successfully flown in the Venusian atmosphere in 1985) and its hot surface precludes indigenous life entirely. Any microbes collected by balloon-borne platforms floating in the atmosphere of Venus – and arguably Mars – clearly would have to come there from space, although the ultimate source of many of them might still well be the Earth.

Perhaps a particularly interesting time to conduct such experiments, whether in Earth’s atmosphere or elsewhere, might be during cometary events. If collecting balloons were flown at various times, including both normal conditions and during or shortly after cometary encounters, the difference in results could be instructive.

Using such techniques, suspects for either natural panspermia or ETI influenced microbial data transmission could be identified. The genome of these top suspects should be sequenced first, identifying which genes play a role in the functioning of the microorganism itself, and which appear to be simply along for the ride. The first set pertains to the messenger, but the second could contain the message. Perhaps it can be decoded, or if not decoded, at least examined for a format suggestive of an artificial design.

Of course, if we captured not merely microbes, but actual microsailcraft, the case for ETI initiated microbial data transmission would be settled out of hand. In that case, the key question would move directly to decryption.

If the transmitter is biological in nature, it would appear to be most logical that the receiver should be as well. If messages are being sent using genes, perhaps their meaning can best be found by inserting them in samples of terrestrial life to see what comes forth. The best terrestrial organisms to use as receivers might be bacteria themselves, as of all life here, they are most adept at adopting and putting to use new genetic information. These could be used to both receive and amplify the signal and then deliver it to more complex organisms. Perhaps novel traits could be made to appear. While radar-wielding birds are not to be expected, there are large numbers of potential animal body plans that are not currently in use of Earth. Many such plans, representing whole phyla of animal life, were briefly exhibited on our planet during the period of first flourishing of multicellular life known as the Cambrian Explosion, some 550 million years ago, only to go extinct shortly thereafter. If genes carried by suspected astrobacteria were found to induce the appearance of traits representative of such extinct phyla or other unknown animal or plant types in current life, that would be very exciting.

Of course, we might not be so lucky. A mother seeking to promote the intellectual development of her child might leave works of literature for a 16 year old, chapter books for an 8 year old, picture books for a 4 year old, and letter blocks for a 2 year old about the house in places where her child might find them. By the same logic, if ET wanted to promote evolution, he might send types of microbes adapted to successive stages of biospheric evolution containing only the information needed for the next steps, rather than the whole library of potential plans right from the start. After all, it would be futile to leave a copy of War and Peace in the nursery of a 2 year old. But even letter blocks are a dead giveaway for developmental intent. So perhaps rather than finding the genes for creating fish, trilobites, edicaria, or even eukaria in anaerobes arriving from space, we might hope to find plans for just the next step, for example chlorophyll. Any microbes carrying plans for further steps might be designed to make their way after arrival in more developed (i.e. oxygenated) phases of the biosphere, and thus be harder to identify as extraterrestrial messengers.

Still, any genetic information of a forward-looking nature carried by microbes strongly suspected of recent arrival should be a Wow signal for the ETI search. If such organisms were found to induce the appearance of such traits either uniquely or with markedly greater effectiveness than more mundane microbes, the case for evolutionary influence from space would be proven.

But there might be an even simpler way to search, because the biosphere has been acting as a giant receiver and amplifier for such messages for the past 3 billion years. That is, the history of such messages may be recorded in the biosphere itself. Consider this: the mustangs of the American west are well-adapted to their current environment, and might appear to a naïve biologist to be a product of local Darwinian evolution. But, while plausible, this conclusion would not be entirely correct. In fact, mustangs are descended from horses that escaped the Spanish Conquistadors, and their ancestors were the products of selective breeding to enable them to carry medieval knights. No doubt the genes for such past incarnations as a breed of heavily-muscled carriers of armored knights are still to be found in the cells of mustangs today, and could be activated to reveal themselves as actual traits in a mustang colt by an appropriate program. This would prove that the mustangs had a previous form that was actually a product of “intelligent design.” Furthermore, it is probably the case that if someone wanted to breed mustangs back into knight-carriers, they could do it much faster than by using horses with no such genetic history in their ancestral line. In short, both their history and some potential forward-looking traits are encoded in their genome.

This brings us back to the question of the mice and the fish. We know there are fish traits encoded in mice. No surprise there; mice evolved from fish, so naturally they carry the record of their previous evolutionary career. But do fish carry in their genome plans for any of the noteworthy traits of mice? They very well might, but perhaps only because bacteria can move genetic material around from one species to another. But if this were all there were to it, they might very well carry similar amounts of genetic material transmitted to them from species, such as insects, that are not fish descendants. However, if fish were found to be carrying genes for not only mammalian traits, but the whole roadmap of amphibians, reptiles, and mammal-like reptiles leading from fish to mice, – or even just the first essential steps on that path – that would show that somebody had been doing some serious advance planning, at least taking the trouble to shout some useful advice into the arena.

Could potential draft plans for future biospheric evolution be preprogrammed into the genes of space-traveling microbial messengers? Could the history of such past messages be recorded in the genomes of species all around us? Let’s have a look and see.

Predictions and Conclusions

To be useful, any scientific theory needs to be testable and falsifiable. While the balloon borne microbe or microsailcraft collection experiments described above could potentially offer strong evidence in favor of panspermia, they cannot disprove it because a negative result could be explained away by the argument that the flux of microbes from space is simply too low to be detected by such means. Similarly, the genomic search for forward-looking traits in terrestrial organisms could reveal directed panspermia, but not disprove it. Such experiments should be done regardless because they are cheap and might produce profound results. But if they are unsuccessful in producing useful data, a more muscular approach to settling the matter will be necessary. This can be done through the exploration of Mars.

Mars was once a warm and wet planet, which could have hosted life on its surface, and there is strong evidence that there is still liquid water to be found underground on Mars, which could serve as a habitable environment for microbial life today. If there ever was life on the surface of Mars, it is reasonable to assume that it retreated into the groundwater when conditions on the surface of the planet deteriorated, much as the anaerobic archaea did on Earth after the oxygenation of the atmosphere made the surface here inhospitable for their kind. If we could go to Mars and sample the groundwater, what we find, or fail to find, therein would be very informative. There are four primary possibilities.

1. We find no life in Mars groundwater. This is a very unlikely result, because Mars almost certainly had life on its surface at one time, if from no other source than the Earth. But if that should be the finding, it would prove the case for not only geospermia, but unique geospermia, occurring on Earth but not on the similar early Mars, indicating that life is rare in the universe.

2. We find life in Mars groundwater, which uses the same biochemistry as Earth life, but including more primitive free living representatives ancestral to bacteria. This would refute panspermia as an origin of life theory, instead showing that life on Earth originated on Mars. It would also support the conjecture that life is common in the universe, as apparently it could evolve from chemistry readily on a primitive terrestrial type planet.

3. We find life in Mars groundwater which uses a different biochemistry than what we find on Earth, i.e. a second genesis. This would refute natural panspermia, but prove that life is very common and quite diverse in the universe, as it would be seen that life could originate from chemistry, de novo, two different ways, on two out of two typical primitive terrestrial planets.

4. We could find life in the groundwater of Mars that uses the same biochemistry as Earth life, manifesting similar bacteria forms, with no more primitive free-living representatives evident. This is what natural panspermia would predict. It may be argued that the same result could be achieved by the origin of life on either Earth or Mars, with subsequent transfer between them as well as extinction of the ancestral forms on both worlds. But this means that the current alibi of the geospermians – “the origin did happen here, really it did, we believe that sincerely, even though experiments show that conditions here were unfavorable, we’ve just lost all the evidence” – would need to be stretched to two worlds.

It should be noted that while operation of robotic rovers on the surface of Mars might serve to falsify alternative 1 (which is fantastical in any case as it requires accepting the conceit that not only is Earth uniquely capable of originating life, but that life from Earth cannot spread to other habitable places nearby) by discovering fossils, it cannot affirm it. More importantly, such robotic exploration techniques would be incapable of distinguishing between alternatives 2,3, or 4, which is the most critical scientific question. Resolving between these alternatives, which have profound implications for the nature of life and the universe, will require drilling to depths on the order of a kilometer to reach groundwater, bringing up samples, culturing them, and subjecting them to biological analysis. From a practical point of view, this can only be done by sending human explorers to Mars.

But which of these alternatives is most likely? I predict that number 4 is what we will find. The reason is simply this: The Milky Way galaxy predates the Earth by 8 billion years. The early Earth was not exceptional in any significant way, so that if life could evolve here, it could have evolved first on hundreds of billions of other possible locations. Furthermore, the first life that did so which developed adaptations allowing it to survive interstellar flight would necessarily spread throughout the galaxy in less than a billion years by natural collisional processes. This would result in the appearance of life on any planet as soon as conditions there were suitable, which is exactly what we observe in the fossil record on Earth.

For these reasons I believe that natural panspermia is extremely probable, and that the results of Mars exploration will prove to be consistent with it. But what about directed panspermia? While the history of life on Earth has demonstrated the ability of biospheres to evolve increasingly intelligent species (Morell, 2013), what reason is there to believe that such intelligent extraterrestrials should want to spread their kind around? None, except this: If there were any such species, it would be their kind that would get spread around. If we find any forward-looking traits encoded in the Martian biota, their handiwork would be there for all to see.

Finally, it may be observed that a program of directed panspermia using microsailcraft is well within humanity’s current technological means. If it turns out that no one else has been doing the noble work of spreading life throughout the universe, perhaps we should get the ball rolling ourselves.


I wish to thank Chris McKay of NASA Ames Research Center and Paul Davies of Arizona State University for useful comments on early drafts of this manuscript.


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Comments on this entry are closed.

  • David H December 21, 2017, 12:25

    This was a really great read. I don’t have any immediate objections to your conclusions. For now I’m just impressed at how clearly you have thought through these ideas.

  • Will December 21, 2017, 13:05

    Hi, I really enjoyed reading this.

    There’s few things that I thought were missing from the arguments about pre bacteria stuff. I didn’t see anything addressing viruses in general. Viruses are considered not a living thing but yet they carry genes or ability to modify genes. They can replicate themselves. FAR more smaller than bacteria. In my opinion, this is the pre bacteria stuff, it’s everywhere. Trillions upon trillions of harmless viruses floating in air, in water, and in everything else. There’s even an argument that said the reason how the bacteria rose from ‘slime pool’ is due to viruses transplanting various type of organelles inside cell, and over the time, it culminated into something that was able to reproduce through sexual mechanism. If you turned your pre bacteria argument into pre viruses, I believe this would paint a far more plausible picture you are trying to create. What came before viruses? Are viruses byproducts of bacteria or is it other way around?

    Fascinating stuff! I don’t think we have even scratched the surface of what’s stored in genetic information everywhere.

    • Curt Wohleber December 21, 2017, 16:48

      But don’t viruses depend on the more advanced biological machinery of cells to reproduce? Then again, maybe their ancestors adapted to exploit the fancy new organisms that started showing up and lost the ability to reproduce on their own.

      Maybe we don’t see prebacteria because they were fragile and reproduced slowly, so they did not adapt well to changing conditions, did not spread very far from their primordial birthplace, and their habitat is long gone. Perhaps there just isn’t any reproductive benefit to not being at least as advanced as bacteria. Or perhaps they’re still lurking somewhere.

      • Andrei December 22, 2017, 19:47

        Hello Curt you are correct: Viruses need more complex cells to breed. They are likely devolved life, once more complex that go trough microlife government economic cuts a few times to many! =)
        Nowadays all they can do is to breed more virus, but no ability to change their environment for their benefit, get nourishment for growth or use sunlight.

  • John G Donaldson December 21, 2017, 13:53

    I wonder if Buddhism would find the panspermia concept distasteful? The spreading of life requires the increase of suffering. If you are spreading advanced genetics, how about a trait that is capable of controlling or mitigating pain? If we have been programmed by someone, they have short-changed life as we know it.

    • J. Jason Wentworth December 26, 2017, 7:33

      You raise an interesting thought, John, that to my knowledge has seldom if ever been ruminated upon in relation to extraterrestrial beings:

      Since ending all life here, or letting it die with our Sun (not just refraining from spreading it elsewhere via panspermia) would be the only way to end suffering, *within that Buddhist philosophical mindset (spreading life increases suffering)* (since few non-Buddhists will become Buddhists and implement that faith’s [much less extreme, thankfully!] prescriptions to this perceived problem), I would hope not, and:

      Pain is, unfortunately, necessary in order to survive at all (and I speak from abundant personal experience with pain, some of which was so intense that madness or suicide–just to make the pain stop!–would have occurred had I not been quickly treated with powerful painkillers).
      I often wistfully thought about how better it would have been, if we had an ability to somehow internally “turn off” pain (or at least “turn down the volume” of pain by ourselves), but this would be a deadly “gift” to ‘program’ into living organisms, because many of us would then ignore it–like a “snooze alarm”–until it was too late.

      No…pain, as horrible as it can often be, is actually a blessing in disguise, because it grabs our attention and doesn’t relent until something is done about what is causing it (some deadly diseases sneak up on us by *not* causing pain, either at all, or not until it’s too late [although they usually have other signs that are often ignored too long]). If we were programmed, the responsible entity or entities–even if Divine (being involved in shamanic practice, I’m certainly convinced of that due to direct experience [there are realms that are beyond pain and suffering, but this one–“the astronomers’ universe”–isn’t one of those])–did us a favor by including the ability to perceive pain.

      Pain also serves a “tutelary” function (which would also serve extraterrestrials in good stead), because we avoid–or at least are much more careful about–engaging in actions that caused us physical pain (like burning a hand on a hot stove as a child; I shudder to think of how *those* incidents would turn out without pain to warn us!) or even emotional pain. Human children–and the children of other creatures, such as horses–are also taught social skills (which are, ultimately, survival skills) via the occasional (when circumstances warrant it) infliction of non-injurious pain. A mare disciplines her foal, if he or she misbehaves, through bites and kicks, because well-behaved foals live longer (I got the equivalent from my parents when necessary, and while I hated it at the time, it kept me from becoming a juvenile delinquent).

      Creatures and/or intelligent beings on other planets, who would also–whether they arose there, or were “seeded” there via panspermia–almost certainly face danger and disease as well (and would also benefit from “tutelary” pain, particularly with regard to the young coming into contact with their elders’ tools and devices if momentarily unsupervised) would also have a higher rate of survival. (Even other animals on Earth find pain “medically” useful–if no less unpleasant than human beings do–because it warns them to lie still in safe places, to eat the special healing plants that they consume at such times, etc.)

      *IF* human beings ever engage in directed (intentional) panspermia (I hope not, as it feels too close to “playing God” for my comfort; outright human settlement of promising but not-yet-life-bearing Earth-like planets seems better all around [and settling airless worlds and building O’Neill-type colonies seems better still]), I would hope that the “seeded” animal life could perceive pain, for all of the reasons given above.

    • xcalibur January 13, 2018, 8:38

      As Mr Wentworth points out, our capacity for pain evolved to help us survive in the universe, just like all our other traits.

      As for Buddhism: while perpetuating life does increase suffering and samsara, it also provides greater opportunity for sentient beings to achieve enlightenment. I’d say it balances out.

  • Antonio December 21, 2017, 14:32

    Wow! I’m really surprised (and delighted) to see Dr. Zubrin writing here. I has been following his work for a long time. Contrary to most readers here, I’m hugely in favour of human exploration, like Dr. Zubrin (most people here, at least it seems so from most comments, think that machines are much better/cheaper for the task, while I think it’s clearly the opposite, they are hugely underpowered compared to humans and not cheaper).

  • John walker December 21, 2017, 15:07

    Just one more reminder to those who missed it yesterday and might like a nice video for the whole family during the holidays! ^_^
    A Christmas gift from the American Geophysical Union:
    The AGU is in the process of releasing from the looks of it every presentation from AGU Fall Meeting 2017 onto YouTube. In full. They’ve released over 250h worth of material thus far. That’s over 1000 presentations.

    A great move on their part. Would be nice if all conferences would make this standard.
    The videos aren’t labeled well so
    go to the AGU website if you are looking for something specific. The codes for the videos you want will be listed. Search by subject or name.
    Glein for Europa and Enceladus.

  • Antonio December 21, 2017, 16:20

    It would be interesting to make a quantitative analysis of long it would take for genetic drift to erase any message enconded in primitive life.

    • Antonio December 21, 2017, 16:50

      Typo: long -> how long

      • Curt Wohleber December 21, 2017, 18:00

        Including typos was a good way to make your point about genetic drift!

        • J. Jason Wentworth December 26, 2017, 9:31

          Indeed–Antonio’s typo (which we all make at times; I’m not criticizing him at all) certainly does demonstrate, in a graphical way, genetic drift and how it could easily, over time, eventually make any encoded message unreadable (and ultimately, possibly even unrecognizable as *being*–or having been–a message at all).

          While Svante Arrhenius’ panspermia theory is quite possibly correct, as far as it goes (starlight photon pressure would propel microbes), I have doubts as to whether *viable* microbes could be transferred from star system to star system in this way, and even if they can “arrive alive,” the destination star(s)’ light pressure would push them away. But:

          If such microbes happened to land on a distantly-orbiting comet in a star’s (or stars’, in at least a fairly compact binary system, say) Oort Cloud, then maybe–if the comet’s orbit was eventually perturbed inward toward warm, favorable planets (perhaps even gas giants or ice giants, which are cozy warm at certain depths)–they would gently enter atmospheres without burning up (like micrometeorites [many of which are *not* microscopic in size, as they are sometimes found on flower petals]).

          Given all of those things sometimes “breaking right” (and if viable–if dormant–microbes *can* survive the extremely long, cold, dark, frozen-dry, and galactic cosmic rays-“riddled” journey), perhaps there are cases of (relatively) “adjacent” star systems with life, whose life has common origins. (Quite close–in interstellar distance terms–compact, or even very wide, binary stars such as Zeta 1 and 2 Reticuli [which are “just” light-weeks apart], would appear to have higher odds of undergoing successful panspermia than gravitationally unbound stars that are light-years apart.) Gravitationally speaking, globular clusters, with their very closely-packed stars near their centers, would be prime panspermia candidates, if not for the fact that such ancient stars contain little other than hydrogen and helium. However:

          Robert Zubrin’s thesis seems unlikely to me, because bacteria (and even viruses) are fragile, ephemeral, and change-prone, which would make them poor candidates for message carriers (for the same reason that a tattoo–which becomes “blurry” with age–would be a poor choice for an enduring graphical message, as compared to stone; such a “canvas” is too delicate, changeable, and short-lived). However:

          The concept of “seeding” planets (and even moons and asteroids) with huge numbers of tiny, non-biological message carriers is not at all without merit. Dr. Ronald N. Bracewell (who is perhaps best known as the originator of the interstellar messenger probe concept; such hypothetical starprobes are called Bracewell probes) also suggested another possible way that aliens might make their existence known, and it could endure in “find-able form,” even on Earth, for tens of millions of years (and for far longer on airless bodies):

          He noted that in Australia (his native country) and Texas, tektites many millions of years old have been found–in definite swaths–strewn all over the ground in those places, despite the great geological changes that have occurred there since the tektites fell in those places. He then pointed out that if an atmospheric entry capsule containing a huge number of large stainless steel ball bearings was exploded over a solid planet’s surface (after atmospheric entry), large numbers of them would also, like the tektites, remain where they fell and where they could be found by future intelligent inhabitants, millions of years later (or *billions* of years later, if they were dispersed onto an airless moon or asteroid). He then went on to suggest that rather similar small artifacts, if durably etched or otherwise encoded, could carry enduring messages that their finders could–if sufficiently intelligent and patient–decipher and read, and this suggests an “ethics-conundrum-free” alternative to sending encoded microbes to the stars (it could even use another method that has been suggested for panspermia):

          Instead of sending millions of tiny capsules (each fitted with a tiny lightsail, and containing dormant microbes, plus nutrients they would utilize first upon arrival on their “worlds of opportunity”), tiny, micro-etched hard ceramic (or refractory metal) “message chips,” capable of withstanding atmospheric entry heating, could replace the panspermia capsules. The chips might even be in the nature of non-volatile electronic memory chips (which needn’t preclude them from also bearing micro-etched messages), whose outer layers could serve as radiation shielding as well as heat shielding, and:

          Since some (rare) tektites, particularly the ones called Australites, look just like tiny planetary atmosphere entry aeroshell heat shields (see two photographs here: http://en.wikipedia.org/wiki/Tektite ), shiny “message chips” made in similar shapes would attract attention, whether they were found on inhabited planets or airless bodies in their star systems. Even if the local inhabitants thought they were natural tektites, closer examination would soon reveal their artificial nature. As a possible alternative (if desired and practical, although tiny, self-stabilizing [perhaps conical] attached lightsails should work fine), Jupiter’s magnetic field might be used to “whip” them up to well beyond solar system escape velocity via charged wires, as has been suggested for Dr. Mason Peck’s Sprite “spacecraft-on-a-chip.”

  • Bob Steinke December 21, 2017, 17:06

    Zubrin studies interstellar communication, and the result is…

    We should send humans to Mars!

    Actually, this is fascinating work, and I don’t see anything fundamentally wrong with his reasoning. It’s just humorous how any road Zubrin walks down will eventually lead to Mars.

    So an individual bacteria floating in space is effectively a microsailcraft capable of solar escape. I haven’t checked the math on that, but if it’s true, and Zubrin isn’t likely to make that kind of error, then it looks inescapable to conclude that natural panspermia is currently happening, even if from no other original source than the Earth. It’s just a question of time scale.

    I do think there needs to be an extra factor in his calculation of doubling the number of “living” solar systems every 20 million years. For each close encounter, the chance of inoculating the other system will be less than 100%. It might be that no viable bacteria happens to land on a planet or other suitable environment. Remember, the bacteria won’t be captured by the new system’s gravity. They will pass through once, and then escape that system too.

    If there’s only a 1% chance of inoculation with each close encounter then the doubling time is 2 billion years and you would expect there to be 16 solar systems with life. Of course, the chance could be close to 100%, we don’t know.

  • Geoffrey Hillend December 21, 2017, 17:26

    Sending bacteria to another star system riding on the solar wind is science fiction like the Panspermia idea, an idea that is not very carefully thought through. It’s certainly possible for to use solar wind to eject bacteria from a solar system, it will have to go against the solar wind all the way to the habitable planet to enter a new solar system so it will never reach our Earth which is a problem of such small probes.

    Also the effectiveness of radio telescopes and laser is underestimated and the power problems are exaggerated. Our power output based on technological advances will increase exponentially: one, ten and one hundred thousand years in the future; Once we have fusion reactors, sending signals to other star systems for long periods will be no problem.

    My opinion about the Fermi Paradox is the same as physicist Michio Kaku and astronomer Jeffrey Bennett: There is a galactic society which we can’t access yet because our technology is too primitive. I like the idea of a non interference prime directive with more primitive civilizations.

    • John walker December 21, 2017, 18:27

      Good point on the seeming insurmountablity of exostellar wind for isolated microbes.
      Regarding your sympathy for a nonintervention ethos of a predicated galactic community, doesn’t that lead you to regard directed panspermia as wrong?

      • Brett Bellmore December 23, 2017, 9:28

        This is a good point, which also occurred to me; Bacteria light enough to be accelerated by one star’s light, will be light enough to be repelled by another star’s light.

        A technological solution would be to engineer the bacteria so that their albedo would change over a long period of centuries in space; They start out highly reflective, and end up dark. Reflection is good for about twice the thrust absorption and thermal emission is, the darker bacteria could fall against a light level that would have originally levitated them.

        Actually, this might occur naturally, tholins tend to be quite dark.

        Another point that occurred to me though, is that we can’t really expect to find bacterial signals in undegraded form in Earthly bacteria; The mutation rate and selective pressure are too high for non-useful genes to survive long in a reproductive situation.

        Now, if I were designing a bacterial signal, what I’d do is design bacteria primarily intended to survive on an abiotic or early life planet, but each carrying a small, repeatedly encoded bit of the genome of a more complex organism. Then some mechanism so that they could assemble these bits together in one cell.

        It might look somewhat like the way bacteria today trade genes!

        In this scenario the bacteria could be designed to jump start a complex ecosystem, avoiding a new planet having to evolve its way up from bacteria to more complex organisms. You’d do this not to communicate with other intelligent races, but instead to assure that the galaxy would be full of planets with ecosystems already biologically comparable with your own species. Tera (Or whatever) forming from a great distance.

    • Yarlan Zey December 22, 2017, 19:44

      It’s certainly possible for to use solar wind to eject bacteria from a solar system, [but] it will have to go against the solar wind all the way to the habitable planet to enter a new solar system so it will never reach our Earth which is a problem of such small probes.

      Good point. So how about the following?

      Let the solar wind blow our bacteria to the Oort cloud. The bacteria land on the comets there and proliferate. A passing star grabs some of our comets. Our comets approach the new star, growing huge tails. The tiny comet particles in those tails, with bacterial hitchhickers, land gently on new planets. The bacteria love their new environment and reproduce rapidly. Thus life spreads.

      • Brett Bellmore December 24, 2017, 19:53

        How do they proliferate at cryogenic temperatures?

        • Yarlan Zey December 25, 2017, 12:41

          I’m no longer willing to rule out life in extreme environments.

          But even if bacterial reproduction isn’t possible in comets, there’s a fair chance that some species can survive indefinitely there, as tardigrades apparently can. Over billions of years, most comets in the Oort cloud should accumulate quite a collection of bacteria and tardigrades, which could spread over the galaxy in the way I outlined.

        • J. Jason Wentworth December 27, 2017, 7:10

          They would proliferate V-E-R-Y slowly… :-) But seriously, while *terrestrial* bacteria (or microbes of any kind) would be in a deep freeze at cometary temperatures out in the Oort Cloud, Yarlan Zey’s idea might be perfectly practicable for alien life–perhaps even carbon-based life–that is optimized to thrive at much lower temperatures than Earth’s. For example:

          It has long been theorized that at colder (but not cryogenic) temperatures, ammonia–rather than water–might serve as a solvent for reactions pertinent to carbon-based life.
          At still lower temperatures (down to about -300 degrees Fahrenheit), liquid methane has been suggested as a possible solvent, and even liquid hydrogen has been suggested for this role on very cold worlds. Such life forms–including intelligent ones from low-temperature biologies–are suspected to move very slowly compared to our life, but maybe not; planetary radiation and/or strong magnetic fields might make them no less lively and energetic than we are, and:

          If this is the case, micro-organisms from such a biology might find Oort Cloud cometary temperatures acceptable or even comfortable for their normal life functions. But even if they did find comets chilly (for them–Earth microbes would just freeze), they might utilize the organic “tar” (“star tar” was a term that Carl Sagan liked for it, but he went with “tholins” instead :-) ) on a comet’s surface as a habitat (and perhaps also a food source) in which to have a favorable micro-climate.

    • Project Studio December 23, 2017, 5:42

      Solar wind is not omni-directional; microbes approaching another solar system from well above or below the ecliptic would have less resistance from its solar wind.

      • Robert December 24, 2017, 11:07

        Exactly. Besides, stars vary in the strength of their solar wind, even if they didn’t, planets vary in the habitual zone distance and one would expect microbes to penetrate as far inward into a new system as they started accelerating out of another. The point being, I think there are many mechanisms suggesting it could work well enough.

      • J. Jason Wentworth December 26, 2017, 10:11

        That is true, but light pressure, which would be the dominant force acting upon objects as small as microbes, *does* “push out” away from the Sun (and all stars, of course) equally in all directions, particularly at infrared through visible light to ultraviolet wavelengths. (The solar wind’s force and velocity [especially the latter, which is far, far, slower than the speed of light] are both very low by comparison with sunlight pressure; that is why E-sails require such long, positively-charged wires and relatively high voltage.) But:

        This isn’t *necessarily* a “show-stopper” for panspermia, though, as such microbes–if they were deposited onto distantly-orbiting comets–could “ride” them in toward stars, and their warmer inner planets (or even less closely-orbiting gas giant or ice giant planets, whose atmospheres are comfortably warm at certain depths), and:

        While I personally doubt that panspermia works (because interstellar space is a huge, mostly empty place compared to the stars in it [they’re tiny targets] and because I doubt if viable microbes could survive the trip), panspermia does–potentially, at least–offer a possibility that would otherwise *not* occur:

        Hot, short-lived stars (particularly A-class ones like Sirius, Altair, etc.) probably don’t live long enough for intelligent life–or perhaps any life–to arise on any suitably-positioned planets that they might possess, but if panspermia does work (particularly with the help of comets), this process might be shortened sufficiently that such stars could host aboriginal life (and maybe even, eventually, intelligent life). But I wouldn’t envy them, because they would have to seek out new homes relatively soon (in astronomical time terms) before their home stars “went red giant and/or supernova” on them…

      • Michael December 27, 2017, 17:26

        The solar poles have much faster out going gas flows, 750 km/s versus 400 km/s.

  • Geoffrey Hillend December 21, 2017, 17:30

    Oh, and the same is true about light pressure.

    • Bob Steinke December 21, 2017, 18:43

      There is a Goldilocks size where weight exactly cancels light pressure so a microsailcraft won’t experience any repulsion at the destination system, and bacteria are around that size. Solar wind is more variable, but on average it’s weaker than light pressure so it shouldn’t change the Goldilocks size much.

      I do agree that Zubrin is optimistic in assuming a 100% inoculation rate when stars have a 0.1 lightyear close encounter, but I don’t think it’s a showstopper.

  • John walker December 21, 2017, 18:11

    “If there were any such species, it would be their kind that would get spread around”
    It’s exhausting to read stuff like this. There are so many biases, technical omissions and ethical issues, I want to throw up my hands and just walk.
    And I’ve only read about half of this appeal.
    Panspermia may be ubiquitous or not. But I suggest the author read substantially more on modern biogenetic theories and phylogenesis before summarily scoffing at the idea of a nascent origin for life on this planet. His scepticism seems based on a old view of archean biogenic variables and dynamics.

    There is referencing of horozontal gene transfer which is admittedly a significant element in microbial mutations. However, in complex eukaryotic life, while evidently present it is vastly subordinate to conventional vertical transfer processes. HGT is seen in niche areas accounting for a tiny percentage of our genome.

    The idea that eti could encode an alien genetic interloper with culturalknowledge and biogenic preferences is a triviality. The integration of such a construct into a nascent biomass on another planet however presupposes a ready made mechanism for bypassing or usurping the largely random natural mutational processes. While my imagination won’t discount such a possibility, it seems to predicate a preexisting deep knowledge of the local biology. And, preservation of that genomic code would inevitably degrade over the eons. Our genome has just 60% commonality with a fruit fly, 25% with rice and only a tiny side order of primordial bacteria.
    Secondly, I find the idea of directed anthropogenic panspermia ethically very problematic. The hubris contained therein boggles my mind. According to the author one should look for bio indicators on the target world. Really? Whether life there is a product of an earlier (random)panspermian fertilisation or nascent biogenesis, the imposition by design of our wishes on the evolutionary direction of such a world is anthropocentrism extreme even if it is clad with the descriptor “noble work”. We decide. Lex imperator.
    Unless we can magically ensure that our “message” remains inert whilst somehow “prolific”, this is unethical. Let alone attempts to overtly direct the genetic development in a manner we deem useful.
    Technical areas, particularly degradation stresses both thermal and radiological are played down. DNA is notoriously prone to bond breakage over short geological time frames. This weakness needs more analysis in the panspermia thesis when the transport of more than prebiotic organics is intended.

    There’s much more to be said against the authors assertions in my opinion. Although I find the ideas expressed interesting.

    • NS December 22, 2017, 4:28

      Whatever the situation is with natural panspermia, I am very opposed to artificially seeding other worlds with Earth life. This is both for the ethical reasons described above (the results could be very much like “The Andromeda Strain” or “Invasion of the Body Snatchers” for the unfortunate recipients) and for the scientific reason that there are many biological questions that can only be answered by studying numerous living worlds in their natural states. If panspermia does indeed occur naturally that is a very important discovery. If life arises independently on many worlds that is also a very important discovery. Neither may be possible if other worlds are deliberately seeded with Earth life before we have a chance to study them.

    • Bob Steinke December 26, 2017, 11:12

      “DNA is notoriously prone to bond breakage over short geological time frames.”

      Zubrin is talking about bacteria escaping one solar system at 0.0001 c and traveling 0.1 light year to another system when there happens to be a close approach. That’s a travel time of 1000 years, so not quite geologic time frames. We’ve gotten intact DNA from frozen woolly mammoths thousands of years old. It just takes one viable bacteria to make it out of trillions that start the trip.

  • Geoffrey Hillend December 21, 2017, 18:44

    There is a galactic society which we can’t access yet because our technology is too primitive. This idea comes from Jeffrey Bennett’s book Beyond UFO’s.

    • J. Jason Wentworth December 27, 2017, 8:32

      That is possible. We of the 21st century on Earth, knowing of no obvious alternatives to light-velocity electromagnetic radiation (modulated radio waves and laser light) for long-distance signaling and information transfer, tend to think that nothing else could come along to improve on it, but:

      Gravity wave communication–although it’s also limited to the speed of light, but should penetrate anything–is one possibility. While it isn’t feasible for us today (we’d have to vibrate very large masses very rapidly in order to produce detectable gravity waves–the recent detection successes required collisions between massive stellar objects in order for us to “hear” their gravity waves, although their distance from us was tremendous!), one day it might be practical. If we can someday manipulate mass via tinkering with Higgs bosons, or can find–or create–stable, point-size, and electrically-charged sub-stellar black holes, we might be able to communicate through the Earth itself, and anywhere else, via gravity waves. Also:

      The speed of light is a two-sided limit, and Relativity only prohibits material objects from traveling *at* c, the speed of light (where the solutions to its equations are undefined and/or unreal numbers); plugging in any velocity that is ^greater^ than c, like any number that’s less than c, yields defined and real solutions. Now:

      If a ” V > c” communications device (perhaps using–*if* they exist–faster-than-light particles [called tachyons]) could be developed, we could communicate more rapidly than c allows us with radio and lasers. (Faster-than-light *travel* is also theoretically possible, either by somehow achieving a quantum jump to above c without passing *through* c [the tunnel diode uses a similar effect; electrons “tunnel” from one side of its dielectric barrier to the other, without going through it], or by manipulating space itself as Dr. Miguel Alcubierre’s warp drive concept does, although it should be remembered that all of these concepts are far beyond current technological capabilities–but they may not always be…)

  • Alex Tolley December 21, 2017, 18:57

    This appears to be an extended, and better thought out, essay that Dr. Zubrin has published in the past.

    I will take issue with some of Dr. Zubrin’s biology.

    but we see no pre-bacteria organisms. This observation has led many investigators (…) to postulate that life on Earth is an immigrant phenomenon.

    A more accepted explanation is that more primitive life forms would have been rapidly outcompeted by more evolved ones, removing all traces of them. There is nothing hard to believe about this as we see this throughout the fossil record when populations go extinct in the face of new populations competing for the same resources.

    Unless biologists have got it completely wrong, the structure of some molecules, like ribosomes that include both proteins and RNA, hint at an earlier RNA dominant world. We also see RNA that is not translated into protein but is also functional as further evidence of a simpler biology.

    Perhaps buried amidst the junk DNA of some bacterial species is a sequence of amino acids that an expert cryptanalyst can decode to read

    I’m glad that Dr. Zubrin appears to abandon this idea later in the essay, as bacteria don’t tend to have “junk” DNA. The reason is that they reproduce and evolve so quickly, that any sequences that cost energy but don’t contribute to fitness disappear as evolved bacteria that reduce these sequences outcompete them. That doesn’t mean that bacteria don’t have such sequences, but they are not strictly junk as they have a role to play. The point, however, is that there is little point in looking for some message like pi.

    There are a variety of physiological features, such as the complex eye, or bird wings, whose origin is hard to explain in terms of incremental natural selection, as they appear to be completely non-functional in partially-developed form.

    Here we are back to arguing the creationists POV. Just because we cannot always determine the fitness value of primitive wings, it doesn’t mean they have no fitness value. For example, feathered forelimbs may have helped capture insect prey, we just don’t know.

    Dr. Zubrin’s argument that Earthlike life on Mars would support panspermia is not true. It would support local panspermia from a known living planet, Earth, or conversely from Mars, but not necessarily from galactic sources.

    The argument that it is more likely life evolved elsewhere and came to Earth is flawed logic. We have a sample of 1. However improbably that event, it is pointless to invoke a Copernican principle at this stage to argue for panspermia. Now if we detect clear biosignatures around a number of exoplanets, this hypothesis would certainly gain some a priori strength.

    Dr. Zubrin’s idea of gene transfer conferring traits, e.g. mammalian traits from a transfer into an ancestral fish is not how evolution works in most cases. Genes are not copied wholesale into an organism and at some point triggered to develop a new trait. Rather, genes tend to duplicate and one copy mutates or changes, which slowly, in combination with others, creates the new phenotype. Those genes can be homologous between different forms, albeit with somewhat different sequences, supports that hypothesis. Retroviruses do insert themselves into genomes, but usually, these cause a disease or change the expression of nearby genes, although it is conceivable they could support new traits. The advantage of bacterial microbiomes is that they are not part of our genome and therefore like culture be changed based on local environments. If they were readily able to transfer their genes, one would expect to find a lot of evidence for that. For example, bioluminescent bacteria in squid would no longer be needed as the genes might have been inserted into the squid genome directly.

    For the idea of gene transfer to work from galactic bacteria implies that they use the same DNA code that terrestrial organisms do. All the 64 3-base codons have to translate to the same amino acids, otherwise, the DNA is effectively encrypted for terrestrial organisms.

    In a previous essay, I sensed his argument was to justify a human presence on Mars. The claim that we must drill a kilometer down to reach groundwater on Mars and culture the retrieved fluid using humans seems to confirm that interpretation. We think that some of the intermittently appearing dark material on scarp faces may be aquifer leaks. Is so, we have near surface, liquid groundwater that can be sampled by near-sterile robots.

    I do like the idea of sampling Mars’ atmosphere for microbes and culturing them. This can easily be done by robots. What we do have to bear in mind is that the vast number of microbes we have on earth have not been successfully cultured in the lab. In some respects, the dredging of DNA by gross sampling and sequencing is far more useful, as shown by Venter’s experiment harvesting DNA sequences from ocean samples around the globe. With the advent of cigarette box-sized DNA sequencers, this might be a better approach if organic material that might be a microbe is retrieved. Not easy, to do in situ but maybe a sample retrieval mission might be the cheapest solution.

    I would certainly like to see sequencing or other direct life sensing experiments carried on board deep probes. Whether to sample the plumes of Enceladus, the ice on Europa, the aquifers on Mars of the gases ejected from comets. The miniaturization of the equipment could be tested on Earth using high altitude balloons which could certainly detect whether airborne bacteria are from known terrestrial species or not.

    I noted earlier that the DNA code must be the same for all organisms if panspermia is to work at all in the way for Dr. Zubrin’s hypothesis to work. Which suggests that if we found a sequence in space that had no known earth species’ homologs, and if that sequence produced viable protein when sub-sequences were transplanted to a bacterium, then this might well be a very interesting leg to support the panspermia hypothesis, only negated by the idea that such DBA codes evolve to be the same through some optimization.

    More interesting is the work biologists are doing to modify the code to use 4 base codons and also extend the range of amino acids used for proteins. Is there any possibility we might detect such novel DNA codes from space bacteria, possibly hinting at intelligent design? We need more than just DNA sequences to determine this, but how to determine such a code would be an interesting problem.

    • J. Jason Wentworth December 27, 2017, 8:49

      I agree. While we *could* be here due to panspermia, there is no compelling reason to think so, so assuming that it did happen here unnecessarily complicates everything. (That could change, of course, if some new discovery came to light.) One finding that would be consistent with panspermia–but would not require it in order to account for the finding–would be the discovery of the arsenic-based “shadow microbes” that Paul Davies speculates may exist on Earth. (So far, to my knowledge, only very “arsenic-tolerant”–but still entirely carbon-based–microbes have been found in arsenic-laden environments such as the bottom of Mono Lake in California; their cells can ^utilize^ it, up to certain concentrations [although they expel the arsenic as soon as possible], but their DNA doesn’t contain any arsenic.)

  • Brig Klyce December 22, 2017, 0:30

    Yes, bacteria can efficiently carry information, and Zubrin’s insights about the ways they can travel and survive are welcome. But the communication, would be just one-way, not dialog, right? And might the message be simply translated by ribosomes into the full variety of life here, including some beauty that seems entirely gratuitous. Also, we already see several lines of evidence for life beyond earth, including bacteria in the high atmosphere and fossilized bacteria in meteorites. “A fossil on Mars resembles one on Earth” is a web entry of mine pointing to former metazoan life there. (Dr Zubrin, have you seen it?) Also, there is mounting evidence that “de novo” genes have undeployed programs ready-to-go. I agree with Will, viruses can influence evolution more easily than bacteria. They can transform whole species in a single generation (Ohno 1970). In sum, I congratulate Zubrin for his wide-ranging, penetrating, imaginative, plausible, timely conjectures.

  • ole burde December 22, 2017, 4:47

    My own intuitive feeling is that Zubrin is fighting with ghosts …or more exactly the ghost of intelligent deign …he has need for God , but try to make ET do the job ! ….but still he manages to sniff out a lot of interesting stuff , and we might take away from all this a good reason to do a few relatively simple experiments …such as a long term sampling of genetic material in moon orbit , and IF this gives a positive result , then it would be logic to repeat the sampling more far away

  • James Stilwell December 22, 2017, 6:50

    Cosmic radiation might thwart or deform this process called panspermia, as depicted in the movie remake of Invasion of the Body Snatchers…radiation exposure might go on for thousands of years before such chemical structures encounter the ideal landfall…

  • Michael Fidler December 22, 2017, 7:54

    Could this be used to coat the microbes and also make the sail out of it?

    New Process can Change Two-Layer Graphene into Diamond-Hard Material on Impact.

    Oumuamua an alien spacecraft; instead of carbon goo, carbon Graphene?

    Carbon comets and carbon asteroids;

    The very black material on the surface is carbon-based material similar to the greasy black goo that burns onto your barbecue grill. The comet originally formed from ices (mostly water ice), silicate dust (like powdered beach sand), and this type of black space gunk.

    C-type asteroids are carbonaceous asteroids. They are the most common variety, forming around 75% of known asteroids.[1] They are distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks and minerals.

  • Harold Shaw December 22, 2017, 11:30

    The gains provided by free trade are aggregate gains and do not predict gains being made by every individual unit. Assuming that every individual effort to share knowledge will result in a gain for that individual entity is an over generalization. It is economics 101ism.

    Panspermia and abiogenesis are obviously not mutually exclusive. A people sufficiently intelligent to conduct synthetic panspermia would predict the existence of worlds that experienced or will experience abiogenesis. The ability to conduct synthetic panspermia predicts a level of mastery over genetics and a willingness and the ability to function in deep time. To achieve a gain in their level of mastery would require new information. Would seeding the galaxy increase or decrease their access to new genetic information? If abiogenesis is vanishingly rare then synthetic panspermia would be more likely to increase their access to new genetic information. However, even a minimal rate of abiogenesis combined with natural panspermia would make it more challenging for these people to gain new information through synthetic panspermia.

    Imo, what holds true for synthetic panspermia holds true for communication in general. As a people becomes more capable technologically and through maturity accrue a library of experience, they will have a harder time realizing gains using free trade with a significantly less capable and younger people. Imo, there is a finite amount we can learn about the fundamental laws governing reality and variation in value and innovation will result from the interaction of those laws with the personality of the people who discover them and/or use them. In the marketplace of deep time, the personality of a people is likely their most valuable and fragile trade good.

    Imho, I think the challenges of interstellar trade such as distance and the difficulty of electromagnetically conducting a trade in ideas and culture that protects the interests of all parties makes local agents necessary. If there is an ancient people out there, they are likely represented by a local agent that can make decisions for them.

  • Brig Klyce December 22, 2017, 12:55

    Dr. Zubrin, a team in India including Jayant Narlikar have recovered bacteria from the high atmosphere with a balloon mission. They are now seeking a NanoSIMS facility to do isotopic analysis on the bacteria. If the ratios are unearthly, it would prove that the bacteria are from elsewhere. If you are at all interested, your help would be very welcome!

  • Alex Tolley December 22, 2017, 13:24

    Unless all life in the galaxy uses the same DNA molecule, we are going to have some difficulty detecting non-terrestrial life with the tools that we have. Such “shadow life” (Davies) will need to be either cultured (which we know is difficult for most terrestrial microbes), or some other technique that is not reliant on the bases terrestrial DNA uses. Conceivably, even the sugar backbone might be different.

    Any bacteria we detect in the Earth’s atmosphere will need to be shown to be non-terrestrial to accept the panspermia thesis. Determining the origin of such bacteria is going to be difficult. If the handedness of the DNA double helix was reversed, or the same with the proteins, that would be a strong marker for non-terrestrial origin. But if that was the case, the argument that galactic bacteria are aiding terrestrial evolution would not work. Finding such life however, would be very exciting.

  • Brig Klyce December 22, 2017, 13:24

    A search for “A fossil on Mars resembles one on Earth” only finds the page. The direct link is
    Dr Zubrin, I invite your comments!

  • Alex Tolley December 22, 2017, 13:35

    Isotopic analysis that shows ratios of C12/C13 that are very different from terrestrial life might be an interesting indicator of extra-terrestrial origin. If the ratios are very similar to terrestrial ratios, that doesn’t falsify the extraterrestrial hypothesis as suggested by Dr. Zubrin.

    Even if we found life that was the same throughout the nearer stars, abiogenesis using the same molecules couldn’t be ruled out definitely, unless we were certain that DNA, the genetic code, and protein chirality and even biochemistry were sufficiently variable to make this an improbable event. If life was extremely similar on different worlds, I personally would think panspermia was the likely explanation, but I would hope our own experiments had shown that life was potentially far more variable and that therefore separate abiogenesis would result in different life processes.

    Panspermia, if true, could be the least interesting option. Life based on different molecules, or genetic codes, or biochemistry, would be far more interesting.

  • Mark December 22, 2017, 16:33

    Still reading the article but just had to say, intelligent creatures typically exchange QSL cards, not QST cards.

    • J. Jason Wentworth December 26, 2017, 11:02

      Hey Mark, 73 to you! I agree with you regarding QSL versus QST cards (QSL–“I confirm receipt of your transmission” [from a specific station] as opposed to QST–“Calling all stations” [and confirming receipt of all of their signals], to ‘translate’ the arcane, but highly useful, “shortwave & ham radio ‘shorthand'” into English :-) ), but:

      If intelligent life turns out to be very rare in the galaxy (the “Great Silence” doesn’t encourage enthusiasm for the notion of plentiful intelligent life, as Carl Sagan and Frank Drake looked forward to perhaps even “interviewing”–or at least querying–via radio telescope), the equivalent of requesting QST cards (rather than QSL cards) might, sadly, be the best option, because in that case we need not worry about being inundated with replies.

      How wonderful it would be, if we could put out the interstellar equivalent of a QST or CQ (“Who’s [out] there?”) call, only to get–at staggered intervals of several years, depending on various stars’ distances–requests to QRP (“Reduce power!” [such a thing might even actually happen if a planet–maybe even ours, one day–“RF blasted” a newly-arrived Bracewell probe, perhaps by accident with a military or planetary radar]). :-) Who knows…if some other, non-radio, non-laser method of communication (Gravity waves? Tachyons?) is the galactic standard, someday we might yet find ourselves to be the newest member on an interstellar telephone party line–while it’s not likely, we still know too little to absolutely rule out such a thing.

  • Geoffrey Hillend December 22, 2017, 17:30

    Allex Tolley’s idea that the DNA might be everywhere the same in the galaxy I think is true. I would add that it is the same everywhere in the entire universe based on the idea that scientific principles are invariant and work everywhere and the physical laws and limitations based on instinct or necessity are also the same which would make it difficult to tell the difference between ET DNA and terrestrial DNA. I don’t think the C12/C13 carbon isotope ratio would allow us to tell the difference. It would have to be the sequence in the DNA. If one found a virus in a seven billion year old rock through radiometric dating that would be a smoking gun. Good luck with that one.

    My objection to the panspermia idea is the difficulty of the trip of DNA from one solar system to another. First one would need a large impact from a huge meteor, so a chunk of rock with a virus DNA to reach escape velocity of the planet. It would also have to reach the speed of the escape velocity of it’s solar system, a difficult task. It would then have to be recaptured by a habitable planet in another solar system and survive re-entry heat. The odds are too much against this. It’s not absolutely impossible, but it is not the most probable origin of life which would have to have evolved or start on some world somewhere as life evolving by itself in outer space without a biosphere is impossible.

    Zubin’s idea of using virus spheres as a form of communication won’t work without some modifications. First, it is clear that although these spheres could leave a solar system, they can’t enter into another one without being slowed down or even ejected by the solar wind and light pressure of the destination solar system which is in the opposite direction of the sphere. The only way to make it work is to deliberately and purposefully make a spacecraft and container for the viruses and send them to another star system. The solar wind and star light could be used so slow the craft down with solar cells and iron thrusters. The container would be deployed and land safely. I don’t think is idea is a viable form of ET communication due to the ethics of contaminating another habitable world with their DNA. We wouldn’t do it so I doubt they would. It’s not a very friendly way to communicate. Also it’s too slow. Why would anyone use that when they could use radio telescopes and laser which travel at the speed of light and not take many centuries to reach a destination.

    • Alex Tolley December 23, 2017, 14:23

      I would be surprised if information storage molecules would everywhere be like terrestrial DNA (or even RNA in some viruses). But even given this, the genetic code would likely be different. The codons for each amino acid could be different, and even the amino acid composition might be different. While there might well be commonalities, exact similarity seems unlikely to me. Unless we have some proof that abiogenisis will always tend to select the same molecules and code we have, I would suspect that if life on exoplanets was found in the future to be fundamentally the same as on Earth, then I would tend to think panspermia is the cause, rather than separate geneses.

  • Brig Klyce December 22, 2017, 18:45

    If the microbes are picked up by comets, they can be safely delivered anywhere: “cometary panspermia,” pioneered by Hoyle and Wickramasinghe.

  • Geoffrey Hillend December 22, 2017, 19:33

    The deceleration of the bacteria sized particles might work, but they won’t survive the heat of re-entry into the atmosphere of a planet, but be vaporized or at least overheated. One would have to capture them in orbit with a spacecraft.

    • Robert December 24, 2017, 11:11

      As Zubrin explained, there is no heat problem for re-entry of a microbe.

  • Jesus Olmo December 23, 2017, 3:33

    Richard Powers wrote a sci-fi short story, “Genie”, that deals with the idea of alien information encoded in terrestrial microbial dna:

  • Anthony Mugan December 23, 2017, 7:32

    First of all thanks to Dr Zubrin for a very interesting and thought provoking article and also to those who have contributed to the discussion.
    In terms of the basic proposal that it would be highly desirable to make a focused effort to detect life in several environments in the solar system, including Mars, I can but agree. The evidence in favour of panspermia has been building over a number of decades and it seems very likely that it is actually occurring. It now seems clear that there was quite a complex ecosystem of micro-organisms by as early as 3.465bya which implies a period of evolution prior to that and the practicalities of the mechanisms seem to be standing up to scrutiny rather well.
    That said I wonder if I could ask a few questions around directed panspermia? When looked at from different perspectives it is hard to see why anyone would do that.
    a) From an economic or business perspective there is no payback (at least not in anything less than some tens of millions of years)
    b) From a political perspective there seems no obvious way to play this to my electoral advantage or to the detriment of my opponents.
    c) From a scientific point of view there seems to be no results to gather or papers to write (at least not for millions of years)
    d) From a practical point of view randomly seeding bacteria or viruses into habitats that would already have life (as panspermia would already have been happening for billions of years) means you have a very weak signal. For that signal to survive it would need to be competitive in whatever fitness landscape it landed in. If panspermia is operating then all life within a large volume of space is almost certainly using the same DNA based model as us (or we would have a second type here in some niche environment). It would look a lot like a species jump or HGT and hard to differentiate from normal evolution.
    e) From a cryptanalysis point of view, could there be mathematical structure within genes that could generate false positives?
    f) As noted above the ethics of this are very dubious. Anyone doing this could easily be spreading disease etc.

    In the end, if the discussions around future propulsion concepts are on the right track, it may be more focused, quicker and with more manageable results to physically go to another system and conduct whatever research, experiments, intelligence gathering etc. we may deem appropriate. I don’t discount the incommesurability problem but I just don’t see why any species would undertake directed panspermia…it is already happening naturally and there is no obvious benefit to them.

    Rather hope I’m wrong somewhere in that train of thought….

    • Alex Tolley December 23, 2017, 14:35

      Suppose directed panspermia was only to seed non-living worlds at a very early stage of formation? This would allow the homeworld’s life to be seeded on a multitude of worlds allowing them to evolve compatible lifeforms that are known to have been successful. Those worlds might be left alone permanently as a gift to posterity, or possibly colonized eventually, making modification broadly unnecessary. Unlike natural panspermia, directed panspermia could be much more efficient, using specialized vessels, populations of microbes and viruses, even metazoans. The transplantation could be less random and more like gardening to ensure successful reproduction.

      Prove directed panspermia happened on Earth, and you have a potential new religion to be founded. ;)

      • John walker December 23, 2017, 19:21

        Agree in principle. But. Proving the nonexistence of life on a planet is a pretty big order. From the evidence of very early life here like the banded iron deposits in the north, I’d be inclined to conclude that if conditions are locally conducive to life, it will emerge sooner rather than later. Where..none exist?. it’s probably due to a lack of said biofriendly environment. In that case I think your seeded microbes will also likely be overwhelmed.

        • Alex Tolley December 24, 2017, 15:10

          Where..none exist?. it’s probably due to a lack of said biofriendly environment. In that case I think your seeded microbes will also likely be overwhelmed.

          We don’t know the motives of the seeders. They may want to pre-empt abiogenesis in favor of their own life. Seeding millions or billions of potential life-bearing worlds will likely result in both successes and failures, purely by chance.

          On Earth, it took billions of years before metazoa evolved. What if metazoan life was seeded so that this evolution could be sped up drastically. On Earth, instead of the evolution of multicellular life about 1.5bya, it happened 3bya. Conceivably we might be upto 1.5by further evolved by now.

          A sustained seeding program to reform a primitive planet suitable for O2 respring life using anerobes, aerobes and photosynthesizers, followed ny multicellular life could speed up the rate of evolution. The breakout might be the equivalent of the “Cambrian Explosion” at which point further interference is stopped and the extant life is allowed to evolve on it own.

          Under certain conditions, I’m not clear that this wouldn’t be a good plan to bring life to the galaxy. If panspermia were proven to happen naturally, then I see no reason why directed panspermia shouldn’t be attempted.

          • John walker December 26, 2017, 12:06

            Why do you want to seed life?
            Really. Reflect on your motives.
            Is it your goal to delay entropic developments in the universe by maintaining the highest sustainable dynamic order? Then why prefer that? No, I am not a nihilist. I see too much emotion and too little thought being expended on the question of motive.

            I posit that the end goal for proponents of directed panspermia is a new intelligent species. More than merely a plethora of biospheres. Why should that be regarded as a desirable goal? I am not per se opposed to this. I merely think it prudent to always look deeper at ourselves in every realm of thought. And I see no philosophical nor scientific “natural imperatives” here. This undertaking will potentially lead to the undermining or subplantment of native developments on seeded worlds. What imperial right do we have to do this? Because we can? Of course not. And there is no ethical opening created should natural panspermia be demonstrated to be widespread. That does not legitimise directed panspermia. I dare say your assertion is just as imperial. I want it so. Therefore I will act.
            If we agree that the primary goal of directed panspermia is to underpin a preference for a “sentient cosmos”, then why start with bacteria? The chances of a civilisation arising from it is infinitesimal. It happened here once. And might very well have not happened at all. So seed an intelligence onto an existing biosphere. There are an infinite number of variations and preferences to be considered dependent on our goals in terms of psychology and capabilities of the new species. Why leave things to chance? This is meant as a provocation. I don’t think we posess the “wisdom” (appologies for the vague term) to justify such a move. There are chaotic elements to consider. I am loath to refer to anthropic precedents when considering fundamental judgements, but I offer one here in general form. A choice in favour of higher structure has often led to destruction simply because that structure contained an explosive element that was either unforeseen or incorrectly regarded as a negligible risk.

            But it doesn’t matter, amiright? Main thing is we do something. Better to try and fail than not to try. Etc etc. Boisterous enthusiasm is not a substitute for thorough reflection when considering the fate of lives that are not ours to control! Your arguments reflect an emotional preference. Fine. But that’s not enough.

            • Alex Tolley December 26, 2017, 20:30

              I posit that the end goal for proponents of directed panspermia is a new intelligent species. More than merely a plethora of biospheres. Why should that be regarded as a desirable goal? I am not per se opposed to this. I merely think it prudent to always look deeper at ourselves in every realm of thought. And I see no philosophical nor scientific “natural imperatives” here. This undertaking will potentially lead to the undermining or subplantment of native developments on seeded worlds.

              Humanity has been looking for others to communicate with for a long time. Whether imaginary gods in the sky, the more intelligent mammals, robots with AGI, or ETs.

              Clarke echoes this in his novel 2010: Odyssey 2:

              “And because, in all teh Galaxy, they had found nothing more precious than Mind, they encouraged its dawning everywhere. They became farmers in the fields of stars; they sowed, and sometimes they reaped.

              Regarding “natural imperatives”, life fills every niche it can evolve and adapt to, and reproduces as much as it can. If natural panspermia happens, that would be another mechanism. Technological species might just be another mechanism to spread replicators.

              If life can spread by natural panspermia, it would also supplant the potential for other biologies to evolve. What would you want, quarantines to prevent it happening? Directed panspermia can be done more intelligently and spare planets that have their own geneses.

              Life on Earth has shown remarkable adaptations as evolution has operated. Why not fill the galaxy with life where none has existed before, whether intelligent or not, just evolving to adapt to the local planetary conditions, creating new forms.

              Emotional or not, the Star Trek Vulcan dictum: “Infinite Diversity in Infinite Combinations” is a positive idea. I find that preferable to sterile worlds. Preferable to worlds populated solely by single-celled organisms. Call that terrestrial bias, but I agree with Darwin:

              There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being,…

            • Brig Klyce December 28, 2017, 12:20

              The motive for panspermia would be the propagation of life — survival.

    • Zachary December 23, 2017, 14:58

      g) Religious reasons would certainly be motivating. Suppose the aliens thought it was a divine commandment to spread life.

      h) Philosophical or spiritual reasons would also be motivating. For example I believe that life is a miracle. The further that life spreads, the further the miracle spreads. For me this is enough justification to seed Mars with life RIGHT NOW.

    • Harold Shaw December 23, 2017, 15:24

      “…it may be more focused, quicker and with more manageable results to physically go to another system and conduct whatever research, experiments, intelligence gathering etc. we may deem appropriate.”

      If the people conducting synthetic panspermia want access to the newly sown planets and their genetic data, they would need to travel to those systems. If they are able to do that, then it begs the question of why conduct synthetic panspermia instead of direct and controlled experimentation.

      That doesn’t rule out using synthetic panspermia as a propaganda tool, though I don’t like the message it could imply…”We made you and could make a claim for you.” Granted that is a pessimistic interpretation of implicit messaging, but no less plausible then the optimistic interpretation Zubrin offers.

      • John walker December 23, 2017, 19:34

        There two assumptions made amongst proponents of this seeding. Either we will do it without detailed prior knowledge of the extant local biosphere. Questionable. Or we have gained that detailed knowledge through some magical remote sensing technique. Fantastical.

  • Alex Tolley December 23, 2017, 14:13

    I’m not convinced by the arguments against bacterial dispersion. The velocities of bacetria being expelled by a star will have a wide dispersion due to size and the mechanism of propulsion. This wide velocity dispersion will allow some fraction to successfully enter the HZ of another star and rendezvous with another planet with a minimal velocity differential.

    As we do find bacteria high in our atmosphere, I suspect that panspermia as a theoretical idea is valid. Whether it actually is responsible for seeding life on other worlds is another question.

    • Harold Shaw December 24, 2017, 11:10

      I agree that panspermia is theoretically valid. If we accept the plausibility of bacteria with indefinite lifespans, what would prevent bacteria from being present in a prestellar environment? Bacteria would then be delivered to a star’s HZ via the same mechanisms that deliver anything else. Would there be biological equivalent to the snow line?

  • Alex Tolley December 23, 2017, 14:16

    As regards finding bacteria in the Martian atmosphere. If we find them, their origin could be Mars due to subsurface bacteria being carried aloft, Earth due to panspermia, or interstellar. Detection is not a slam dunk for interstellar panspernia.

  • Alex Tolley December 23, 2017, 16:07

    Codon Manipulation Experiment.

    I am not aware of this being done. The idea was stimulated by Davies “shadow biosphere” when he propounded it. My thought was “Suppose organisms” used the same DNA, but a different 3-codon code. Alternative genetic codes could be composed that would translate viral or bacterial DNA genomes. The translated proteins would then be used to create DNA sequences with terrestrial genetic codes, transplanted into bacteria and any viability or functional proteins determined.

    A viable bacteria using purely these artificial sequences would be interesting. A functional protein that has some effect might also be interesting.

    The difficulty is that the potential number of genetic codes is very large, although this could be pruned to mimic the degeneracy of terrestrial codes. A functional protein might just occur by chance and not indicative of some shadow organism’s different genetic code.

    Another possibility is to assume a simpler, 2-base codon genetic code to code for 15 amino acids and a stop codon. This reduces the possible genetic codes to a more tractable number. The same procedure could be used to test this as the 3-base genetic code.

    Biologists are experimenting with 4-base genetic codes. Suppose we were to communicate with such an organism, how would the receiver discover what the genetic code was and the needed compounds that the code would translate to? Growing an organism wouldn’t help as the needed compounds (e.g. different amino acids) would be likely be absent. Smaller genetic codes could be tested, but larger ones?

  • hiro December 23, 2017, 18:06

    Considering “zombie bacteria”: Von Neumann nano-machines “living” inside the synthetic bacteria by sucking energy from chemical reactions or other methods to power themselves. One wonders about these almost harmless tiny creatures turning out to be lethal weapons.

  • James Stilwell December 23, 2017, 18:44

    Lithopanspermia, sometimes referred to as interstellar panspermia, is a version of the panspermia hypothesis in which it is argued that impact-expelled rocks from a planet’s surface serve as transfer vehicles for spreading biological material from one solar system to another.

    Centuries of sampling will probably show the above is true. It’s too bad we could not physically investigate the cigar shaped structure recently passing through our solar system…at 200,000 miles per hour it could arrive in the Alpha Centauri system in 1,370 years, more or less, if that is where it is headed…

    • Harold Shaw December 24, 2017, 10:43

      It is unlikely Oumoumou is a one off, I have seen estimates that we will host one interstellar visitor every year. An object that behaves more similarly to a comet may be a better target for sampling. We could target the larger, lingering plume.

      • J. Jason Wentworth December 26, 2017, 11:30

        That possibility gives me mixed emotions. While the scientific possibilities (even of bringing samples of such [possibly plentiful] interstellar interlopers to Earth, or at least sending rendezvous probes to them) are very exciting, such large and massive objects, moving at solar hyperbolic velocity, would create a planetary defense nightmare if one happened to be on a collision course with the Earth, and:

        I read that estimate too, which–if it’s correct–means that each year, there is a chance (quite small, no doubt, but with huge ramifications if we’re unlucky) that a big chunk of rock, metal, or ice that we couldn’t possibly deflect *could* hit us head-on at ~200,000 mph or more. That amount of energy, even if it resulted in “just” an air-burst (particularly of a smaller interstellar object) rather than a crater-blasting impact, could easily wreck a city (if one was below it) and kill and/or maim millions of people in an instant. And if we happened to *not* see it coming (which could happen, if it came from behind the Sun), the military implications of such an “apparent nuclear attack” are terrifying to contemplate.

  • Patient Observer December 23, 2017, 23:27

    A torrent of ideas that will take a while to read and ponder. I do have one bit of confusion regarding the concept of the force exerted by sunlight balancing out the gravitational attraction of the sun. I get the idea that these two forces can cancel out. However, would that not result in the bacteria simply continuing on its own orbit about the galactic center just as the sun orbits the center. Thus the sun and bacteria would essentially maintain the relative position as both orbit the galactic center (or more properly the center of gravity of the galaxy).

    If the force of light exceeded the attraction of solar gravity then there would seem to be a diminishing acceleration from the sun:

    a =F/m

    Where F = Fl – Fg

    F would diminish per the inverse square law (assuming m remains constant). Some basic math can put meat on these equations.

    I’m probably missing something but thought it would be worth mentioning.

    • Bob Steinke December 26, 2017, 17:31

      Zubrin is hypothesizing that the bacteria are ejected from a planet. The planet, being in orbit, has some relative motion with the star, and the bacteria would start out with this velocity. Because the star’s gravity is canceled out they wouldn’t be in orbit around the star, they would escape at that velocity. Yes, you are right they would both be in orbit around the galactic center, but they would be in slightly different orbits that could lead them further apart.

      • Patient Observer December 27, 2017, 17:53

        Yes, that makes sense. I suppose the orbital velocity of the planet would provide the initial velocity relative to the star and then the balance of the star’s gravity and light pressure would add to that velocity. Thanks.

  • Curious December 24, 2017, 0:33

    While I do not have the science chops that others on this board have, I submit that the suggestion that we seed the universe with our Earth based DNA seems a bit arrogant and maybe reckless. No one here would argue that the species on this planet are perfect – certainly the human one has demonstrated irresponsibilites to our own kind, other species, and our own planet. While adaptable and having evolved to high intelligence, none of our Earth species are especialy long lived, or tolerant of really broad ranges of pressure/temperature/chemical environment, and we require certain elements for sustenance. Some of our life (e.g. pathogens) exists to kill the others. In fact I would say our life forms are in fact not at all very suitable for broad ranging space exploration. Our machines are often more capable, and in time may be capable of being filled with our intelligence/thinking while not be limited by our Earth-limited bodies, and be capable of replication using the resources they find to live off the land. What if our DNA were to fall on a planet that has already started to develop its own yet different form of life. Might our DNA outcompete it or otherwise alter it? What if that other form was going to be better in the long run had it been left alone? Is that “responsible”? Finally, doesnt seeding the universe with our DNA immediately result in polluting any possible future sample set were we to find it? Say 1000 years hence you collect DNA from a moon of Jupiter – would there not be the question of whether it was a result of what we had sent out previously, rather than being extant? This seems to contrary to the entire purpose of the sampling and comparison excercise.

  • Geoffrey Hillend December 24, 2017, 0:58

    The problem with Lithopanspermia is that solar system impact expelled rocks from giant impacts are too statistically rare; only a small amount might leave a solar system over its entire lifetime. Plus they have to have virus in them. The chances are too small for it so that life would then not be abundant in the universe and we would be a fluke. Furthermore, there is just too much scientific evidence for home planet Abiogenesis.

    All life has DNA and RNA with for base pairs. One shouldn’t assume that ET DNA must be alien or different. There is also no reason why it can’t be different. Scientific thought likes to restrict things to first principles, so if the DNA were the same everywhere in the universe, panspermia could not be considered viable but only statistically very rare or never happens which I have to assume will turn out to be true.

  • Patient Observer December 24, 2017, 12:33

    It would be easy to imagine a billionaire buying launch services and hiring a bio-tech/satellite firm to build bacterial arks to be fired off in volleys towards various stars suspected of having planets in the HZ. The arks would be designed to disgorge their contents when its sensors detect the presence of a nearby star.

    Sure, the voyages would take millenniums, the chances of the mechanisms working or even entering a star system are nil. But, if there is to be an artificial panspermia effort, it would be the scenario above or a religiously motivated effort. I don’t see a government undertaking such an endeavor.

  • Michael December 24, 2017, 13:55

    Just wondering if when the sun goes into its red giant phase could it blow microbes that have made a home on the outer ice moons as they evaporate into deep space. The stellar winds from these red giant phases is very large and would allow larger microbes to be moved through space.

  • Alex Tolley December 24, 2017, 14:52

    What if we simply seed a star-forming nebula or the planet-forming nebula around a proto-star? We can be reasonably sure that abiogenesis has not happened as the planets have not formed. A craft carrying bacteria can continue to culture and release the bacteria into the atmospheres of the planets in the HZ. At some point in time, the transplanted culture “takes”.

    IOW, I don’t think we need fantastical technology to determine that a planet is sterile before seeding it. We have that detection technology today. We probably could be seeding such environments within a millennium should we choose. Should we, is another issue.

  • ole burde December 27, 2017, 9:47

    If we find life on the best and closest exoplanets , there will be no need to seed them , and if we dont , there will be no need for Post-Colonial Guiltfeelings (exept for the obvious internal need ) ….in a short time we will probably know , and then we can concentrate on solving whatever real problems might present themselves

  • Harry R Ray December 27, 2017, 11:03

    Kind of OT, but because of POSSIBLE SETI implications, here goes. A NEW paper by Tabetha Boyajian(PRESUMABLY the LEAD author)et al on Boyajian’s Star to come out January 3(what a way to START the new year), but NOT on ArXiv, because it is currently under embargo. Remember, a few months ago, she was one of the authors of a paper claiming that the long-term fade(NOT the dips) was caused by comets, similar to her ORIGINAL interpretation. It will be very interesting to see whether she has changed her mind since then.

    • Harry R Ray January 3, 2018, 10:46

      Paul Gilster: My above comment may NOT be so OT AFTER ALL! The paper is up on the exoplanet.eu website. What fascinates me is that the obscuring objects are composed of “…optically thin dust with particle sizes on the order of 0.0015 to 0.15 microns. These particles would be smaller than is required to be resistant to blow-out radiation…”. This is a bit too small for “microscopic, high density storage packages”, BUT; would VIRUSES of the size range mentioned in the paper be able to be used for information transmission as well? RSVP.

      • Paul Gilster January 3, 2018, 11:43

        I have no idea how viruses would fare as information transmission vehicles in this situation, Harry. But given how many explanations are still in play for Boyajian’s Star, I’m not sure I’d want to add that possibility to an already crowded mix!

    • ljk January 3, 2018, 11:09

      According to this new round of research, it’s just dust:


      Over 200 people on the paper attached to the above article. I wonder how many “authors” would be on it if Tabby’s Star was found to be an alien megastructure?

      Hooray! Humans get to think they are the focal point of the Universe for another year!

      To quote:

      “If it wasn’t for people with an unbiased look on our universe, this unusual star would have been overlooked,” Boyajian said. “Again, without the public support for this dedicated observing run, we would not have this large amount of data.”

      See also:


  • ljk December 29, 2017, 12:42
  • ljk December 29, 2017, 15:22

    Stromatolites Defy Odds by A) Living B) on Land

    A life form that once ruled the planet has turned up unexpectedly in Tasmania

    By Jennifer Frazer on December 21, 2017


  • ljk January 2, 2018, 15:40

    2017 may have been a very iffy year for human intelligence, but as far as searching (and trying to contact) alien intelligences among other aspects of exobiology, it was quite a busy year – but it could always be busier and should have been decades ago.


  • David Grinspoon January 3, 2018, 9:52

    As an undergraduate I worked for Carl Sagan on a research project exploring the idea of microbial SETI in the summer of 1978. There’s a brief write-up of this in my book Lonely Planets.

  • ljk January 3, 2018, 11:16

    Please do not feed – or converse with – the humans:


  • ljk January 5, 2018, 16:15

    Upcoming Chinese Lander Will Carry Insects and Plants to the Surface of the Moon – Universe Today


    “The container will send potatoes, arabidopsis seeds and silkworm eggs to the surface of the Moon. The eggs will hatch into silkworms, which can produce carbon dioxide, while the potatoes and seeds emit oxygen through photosynthesis. Together, they can establish a simple ecosystem on the Moon.”

  • Jesus Olmo January 9, 2018, 3:17

    “We had already realized from the disaster on Mars that transplanting Earth ecology wouldn’t work. Crops would not grow without specific symbiotic fungi on their roots to extract nutrients, and the exact fungi would not grow without the proper soil composition, which did not exist without certain saprophytic bacteria that had proven resistant to transplantation, each life-form demanding its own billion-year-old niche. But Mars fossils and organic chemicals in interstellar comets showed that the building blocks of life were not unique to Earth. Proteins, amino acids, and carbohydrates existed everywhere. The theory of panspermia was true to a degree.”
    Sue Burke, “Semiosis” (a novel)

  • ljk January 11, 2018, 10:59

    Mars life clues from methane and ‘sticks’

    By Paul Scott Anderson in Space | January 10, 2018

    The Curiosity rover has made 2 new and interesting discoveries – the first about methane in Mars’ air and the other about stick-rock formations – both related the possibility of life.


    To quote:

    This coming April, the European Space Agency’s ExoMars Trace Gas Orbiter (TGO) will settle into its final orbit to begin science observations, including mapping the amount of methane in the atmosphere across the planet, with increased sensitivity. This should help to further narrow down the possible sources of the methane.

    Meanwhile, Curiosity also has discovered some interesting little stick-like or tube-like formations on some of the rocks on Vera Rubin Ridge. How they formed isn’t yet known, but they have sparked some lively discussions. They are tiny, only a few millimeters across.

    While they are probably geological, such as crystal molds or concretions, their similarity to some types of trace fossils on Earth has also been cautiously suggested by some. They were first seen initially in black-and-white images taken by the rover before it continued onward, but were considered intriguing enough for the rover team to send the rover back for a closer look.

    Could they actually be fossils? According to Ashwin Vasavada, project scientist for Curiosity:

    We don’t rule it out, but we certainly won’t jump to that as our first interpretation.

    As Pascal Lee, a planetary scientist at NASA Ames, Mars Institute and SETI Institute, told us:

    The Curiosity pic really piques our curiosity. From this picture alone, it’s hard to tell what the wiggly sticks are, and a strictly mineral origin is of course the most plausible. But as a field geologist, when I first saw the pic, the immediate thought that came to my mind is bioturbation. Bioturbation is the process through which organisms living in sediments can disturb the very structure of these sediments. A common example of bioturbation is the formation of worm burrows. The burrows, once refilled with sediments, fossilized, and then exposed by erosion, can end up looking like wiggly sticks.

    Since most scientists think that martian life, if it existed, probably didn’t evolve past simple single-celled organisms, finding evidence of bioturbation would be surprising. Lee added:

    Is any of this relevant to Mars? Well, bioturbation at the scale of the features seen in the Curiosity pic would imply macroscopic multicellular organisms at work, so something that would have evolved far beyond unicellular life.

    To claim that we’re seeing bioturbation on Mars – which I did not say – would be an extraordinary claim. I’m reminded of what Carl Sagan would say: ‘Extraordinary claims require extraordinary evidence’. We’d need a lot more evidence than this single Curiosity pic to make any such claim, including evidence that allows ruling out less extraordinary claims. But I have to say, the pic is really intriguing, and I hope Curiosity spends more time in the area to get to the bottom of this.

    This is exciting!

    Bottom line: Curiosity has made 2 new interesting discoveries – one related to atmospheric methane and the other to strange “stick” formations – that might have implications for the possibility of martian life.