≡ Menu

Life from Elsewhere

The idea that life on Earth came from somewhere else has intrigued me since I first ran into it in Fred Hoyle’s work back in the 1980s. I already knew of Hoyle because, if memory serves, his novel The Black Cloud (William Heinemann Ltd, 1957) was the first science fiction novel I ever read. Someone brought it to my grade school and we passed the copy around to the point where by the time I got it, the paperback was battered though intact. Its cover remains a fine memory. I remember being ingenious about appearing to be reading an arithmetic text in class while actually reading the Hoyle novel.

In the book, the approach of a cloud of dust and gas in the Solar System occasions alarm, with projections of the end of photosynthesis as the Sun’s light is blocked. Even more alarming are the unexpected movements of the cloud once it arrives, which suggest that it is no inanimate object but a kind of organism.

I’ve been meaning to re-read The Black Cloud for years and this post energizes me to do just that, though this time around the old paperback will have to give way to a Kindle, as I had to pass the original back to its owner for continued circulation, after which it disappeared.

But back to panspermia. As the novel shows, Hoyle was interested not just in the nature of consciousness but likewise the matrix in which it can be embedded. By the 1980s, working with a former doctoral student named Chandra Wickramasinghe (Cardiff University), he was suggesting that dense molecular clouds could contain biochemistry, possibly concentrated in the volatiles of comets in their trillions. The notion that the inside of a comet could have become the source for life on Earth led the duo to propose that space-borne clouds might even evolve bacteria, which they explored in a 1979 book called Diseases from Space, an idea that was widely dismissed.

But leaving bacteria born in space aside, the idea that life can move between planets continues to intrigue scientists. We have, after all, objects on Earth that have fallen from the sky and turn out to have been the result of impacts on Mars. So if we can move past the question of life’s origin and focus instead on life’s propagation, panspermia takes on new life. Abiogenesis may be operational on the early Earth, but perhaps incoming materials from comets or other planets had their own unique role to play. Life in this case is not an either/or proposition but a combination of factors.

Be aware of a special issue of Astrobiology (citation below) which delves into these matters, with ten essays by the likes of Paul Davies, Fred Adams, Charles Lineweaver, as well as Avi Loeb and Ben Zuckerman, who from their own perspectives tackle the question of ‘Oumuamua as a technological object rather than a comet. The latter discussion reminds us that the discovery of interstellar comets moving through our Solar System widens the panspermia debate. Now we’re talking about the potential transfer of materials not just between planets but between stellar systems.

If panspermia does operate, meaning that life can survive space journeys lasting perhaps millions of years, then we might begin to speak of a common molecular basis for the living things we would expect to find widely in the universe. Paul Davies and Peter Worden point this out in their introduction to the special collection, noting that this view contrasts enormously with the more common view that life emerges on its own wherever suitable conditions can be found. In both cases, the implication is for a cosmos filled with life, but only panspermia argues for its natural spread between worlds.

The key word there is ‘natural.’ If panspermia does not occur via natural processes, what about the possibility of ‘directed panspermia,’ in which a civilization makes the decision to use technology to spread life as a matter of policy? It startled me in reading through these essays to realize that Francis Crick and the British chemist Leslie Orgel had proposed as far back as 1973 in a paper in Icarus that we investigate present-day organisms to see whether we can find “any vestigial traces” of extraterrestrial origins. Their paper offers this startling finish:

Are the senders or their descendants still alive? Has their star inexorably warmed up and frizzled them, or were they able to colonise a different Solar System with a short-range spaceship? Have they perhaps destroyed themselves, either by too much aggression or too little? The difficulties of placing any form of life on another planetary system are so great that we are unlikely to be their sole descendants. Presumably they would have made many attempts to infect the galaxy. If the range of their rockets were small this might suggest that we have cousins on planets which are not too distant. Perhaps the galaxy is lifeless except for a local village, of which we are one member.

I like that word ‘frizzled.’ It even gets past the spell-check!

We’ve looked at proposals for directed panspermia before in these pages, as for example in Robert Buckalew’s Engineered Exogenesis: Nature’s Model for Interstellar Colonization and my entry Directed Panspermia: Seeding the Galaxy, which focuses on Michael Mautner and Greg Matloff’s ideas on spreading life in the cosmos. Next time I want to dig into an essay from the new Astrobiology collection by Christopher McKay, Paul Davies and Simon Worden on the question of how we might use interstellar comets of the sort we now believe to be common to spread life in the galaxy.

A key question: Why would we want to do this? Or more precisely, how would we go about deciding whether spreading life into the cosmos is an ethical thing to do?

The paper we’ll look at next time is McKay, Davies & Worden, “Directed Panspermia Using Interstellar Comets,” Astrobiology Vol. 22 No. 12 (6 December 2022), 1443-1451. Full text. This is a paper in the Astrobiology special collection Interstellar Objects in Our Solar System (December 2022). The Crick and Orgel paper is “Directed Panspermia,” Icarus Vol. 19 (1973), 341-346.

{ 60 comments… add one }
  • ljk December 13, 2022, 14:35

    A Jupiter-sized spacecraft? Scientists say existing instruments could detect alien technology

    “I wouldn’t want to be on the team figuring out how to build a Jupiter-sized spacecraft, but the odds aren’t zero.”

    Chris Young

    Created: Dec 12, 2022 08:53 AM EST


    The paper here:


    At least SETI is no longer stuck on just searching for radio signals from altruistic beings sitting on an Earth-like exoplanet circling a Sol-type star.

    • Alex Tolley December 13, 2022, 16:43

      Cordwainer Smith wrote of a spaceship that was 90 million miles long. “Golden the Ship Was—Oh! Oh! Oh!”

      • Paul Gilster December 13, 2022, 20:45

        Good story, as were so many of Smith’s (Paul Linebarger), And in fact its first appearance was in a 1959 issue of Amazing, April I belive, that was the first SF magazine I ever bought. Another good memory (and I still have that copy).

  • John walker December 13, 2022, 14:35

    I have little doubt that microbial life could survive millions of years in space in the interior of a sufficiently large(protected from long term sterilizing GCR) asteroid. However, surviving both initial ejection and final impact is a different matter. There are many studies on brecciation, shock darkening, impact melt and other impact effects that have been conducted directly on small meteorites as well as in impact strata all over the world. The huge shock pressures and thermal effects created by the impact of objects larger than ~100m seem destined to sterilize all previously extant life in the asteroid. This is the reason why I doubt the viability of large object based “lithospermia”.

    One could argue that smaller objects in the 20-50m range might offer better survival chances. The possible airburst of an object in this size range upon arrival would create lower shock and thermal effects than the impact of a larger object and increase the chances of some of the putative microbes surviving.

    However, such an object surviving initial ejection from the origin world still presents a problem. Accelerating a megatonne mass from its original ecosystem upto escape velocity requires a very large force. The only conceivable mechanism would be km scale impacts on the origin world with high energy ejecta. We thus return to the original problem of microbes surviving high energy impact stresses.

    I haven’t seen much in the way of satisfactory quantitative work on this question.

    • Robert December 13, 2022, 17:40

      I believe Wickramasinghe has claimed in the past (and continues to claim) his team has detected non-terrestrial bacteria coming down from space in high altitude experiments.


    • Michael December 13, 2022, 17:59

      If life got going on a minor planet like Ceres ejection would be a lot easier thats for sure. And asteroids can be broken up in close encounters with massive planets spreading the material into smaller pieces like shoemaker-levy did for instance.

    • Benjamin Stockton December 13, 2022, 20:41

      You exhibit some clear thinking here.

      • Michael December 14, 2022, 11:52

        Ceres would have been quite welcoming for life even during its formation and even now the pressures and temperatures are quite comfy for many microbes. It would not be fantastical that life got started there and came to Earth via an impact.

  • Brig Klyce December 13, 2022, 15:06

    Paul, I also noticed this issue and commented on it on my website. I especially noticed the piece by McKay et al., “Directed Panspermia Using Interstellar Comets.” I made a similar suggestion in 1996, based ultimately on our survival instinct. I mention, once a life-bearing comet seeds a moon or planet, the importance of extremophiles, Gaia and horizontal gene transfer. If you’re curious:
    Thanks for your unflagging work! Brig

    • Paul Gilster December 13, 2022, 15:30

      Thanks, Brig. Great to have you here.

  • Alex Tolley December 13, 2022, 15:47

    By coincidence, I had just reread Hoyle’s “The Black Cloud” last year after reading “A for Andromeda” and its sequel “Andromeda Breakthrough” after watching the original BBC tv miniseries on Youtube.

    But more relevant to this discussion is Hoyle’s “Lifecloud: The Origin of Life in the Universe”. Hoyle and Wickramasinghe thought they had detected cellulose and chlorophyll spectra in space around stars. Their book includes the suggestion of life (or at a minimum the precursors) in comets and meteorites. They finish the book with ETI colonizing the galaxy in waves.


    With hindsight, they had jumped the gun on the detection of cellulose and chlorophyll. Their later suggestion that epidemics were the result of viruses from comets was just fanciful thinking. Wickramasinghe continues to see life in unusual phenomena and, IMO, has lost credibility as a scientist. [Is Loeb going to follow suit?]. Sir Fred clearly became rather “dotty” in his old age, with the idea of life being transported here yet with no more than speculative support, rather than hard data. [He also thought he predict the stock market using “real math” too, showing how little he knew about it even then.]

  • Alex Tolley December 13, 2022, 16:32

    I have just recently reread Sagan and Shklovskii’s “Intelligent Life in the Universe” (at least the interesting parts for me.)
    They address panspermia, primarily by spores propelled by starlight. Their calculations showed that this method would be very unlikely to work given the vast volume of space. They estimate that for Earth to receive just one microorganism, Each planet in the Galaxy would have had to eject about 1 tonne of spores to meet that requirement, and that is before the issue of viability due to radiation damage is considered.
    At the end of the panspermia chapter, they include Tom Gold’s “garbage theory” of panspermia as a hypothesis to consider, although they do not dwell on it further.

    Interestingly, we now have had 3 interstellar visitors within a decade. This seems to indicate that unless it is a statistical outlier, such visitors are relatively common. While I do not think they are the locations of abiogenesis, it seems possible they could be repositories of life either by sweeping up spores within a system they pass through, or have been deliberately seeded with the aim to disperse some of the payload as they sweep through a system whether the probability of delivery to a warm world is much higher. We would need to take samples of future visitors to test that idea.

    Panspermia raises some difficult issues to disentangle:
    If panspermia is a delivery mechanism, what would that imply? If common, then the sources of abiogenesis might be common too. Would we expect to find different biologies on the various comets indicating different origins? If we didn’t, does this mean there was one common source, or superior biology, or just one ETI doing directed panspermia? If we found many biologies, but our terrestrial life seems to have a common origin, does that mean Earth was seeded once, or that multiple seedings left only one successful biology that eliminated the rest?

    Mars is the most likely recipient of spores from Earth. Does that suggest that Mars once had terrestrial life that may or may not still be extant in the subsurface? Or could Venus have been the original source, seeding both Earth and Mars? Conversely, ejecta from Mars have seeded Earth, and similarly, terrestrial ejecta seeded Venus. Would a sample of extant Martian life help solve the issue, but most importantly indicate whether abiogenesis was common or not? A second abiogenesis would be very encouraging to support the ubiquity of abiogenesis in the galaxy and hence the probability of life being common – something we may hope to discover with a biosignature catalog in the not-too-distant future.

    But consider. If there is one cometary/asteroid visitor every decade, and the probability of seeding a planet is just 1 in 1000 visits, in the first billion years of Earth’s history in the Hadean, that implies 100,000
    potential seeding events if every visitor bears life. If just 1 in 1000 visitors bears life, that is still 100 possible seeding events during this period, and perhaps 10 in 100 million years after the end of the bombardment and the start of more clement conditions on Earth.
    Does a successful seeding attempt require a rich should or organic food to allow the seeds to flourish as if they were in a Petri dish with nutrient broth? IOW, life didn’t start in a warm pond with dissolved organics, but rather it was seeded in that environment and subsequently established Earth’s biosphere.

    If Bracewell’s “Galactic Club” exists and we eventually get our membership, we might quickly get answers concerning life (the universe, and everything) although one hopes the answer is more informative than “42”. If it doesn’t, then we will have to find out directly, a task that with current physics implies that we won’t have any answers for millennia, unless those visitors are the best means to deliver samples of life from all over the galaxy. I would hope we can add generalized life detectors to all probes that investigate these visitors, the best means we might have of getting an answer relatively quickly.

  • Henry Cordova December 13, 2022, 17:02

    There’s at least one thing we know for sure, if panspermia did indeed introduce life to the young Earth, it did so very early in our planet’s history. The fossil record indicates life has been on Earth for at least three billion years, and possibly four.

    From this we can infer that the seeded life was suited (or designed?) to colonize a planet with much more extreme conditions than exist here now, and one that may have already been occupied. We also can infer that if there was any life already existing here , it either overwhelmed the invader, or the latter completely eradicated the local forms. No trace of the loser seems to have survived.

    There is a third alternative, I suppose. There has been some speculation that certain organelles in terrestrial microbes may have originally been life forms that parasitized, or somehow became symbionts, with the local bugs, and that they arrived much later. Perhaps something like this is what triggered the sudden rise and success of multi-cellular taxa about a half-billion years ago. Could these have been the invaders, and if so, was this planned or is that just the way it worked out?

    There are several competing theories about how life may have arisen on the early earth; deep crustal communities, oceanic vents, mineral templates, clay sheets, plus the usual Miller-Urey experiment. Other than panspermia, there may be others we haven’t thought of yet! Any one of these, or some combination of them, would potentially be available to compete, or interact, with visitors from afar… So far, intense study of the survivors has failed to offer us any clues.

    I’m not sure we’ll be able to answer any of these questions until we have other biochemistries, of unquestionable independent origin, to compare to our own. So far, contemporary life-forms seem to offer little shed light on this lost history.

    • Robin Datta December 19, 2022, 15:16

      The (acquired) organelles in eukaryotes have the same three-digit nucleotide-to-aminoacid code in what remains of their DNA, when compared to the (host) nuclear DNA. They use the same set of aminoacids and have the same chiralities as the hosts. Had it been otherwise, it would have been shouted from the rooftops as soon as it was noted. But there may yet be evidence of a separate abiogenesis sequestered in as yet inaccessible depths of fissures in rocks somewhere.

    • Robin Datta December 19, 2022, 15:54

      If some “benevolent” entity had deflected the dinosaur-killing asteroid such that the dinosaurs continued to survive and thrive, with the evolutionary radiation of mammals to their diversity (and to us) completely excluded, we wouldn’t be around to dwell upon the matter.

      Maybe even earlier (by billions of years) if visitors dumped their refuse and sewage in the Earth’s oceans in the process of cleaning their tanks: they could say that we are $***.

  • Adam Crowl December 13, 2022, 20:03

    Hi Paul
    Claudius Gros wrote his paper on Magnetic-Sails as part of his discussion of Panspermia probes, which can be seen here:
    Why planetary and exoplanetary protection differ: The case of long duration Genesis missions to habitable but sterile M-dwarf oxygen planets
    Gros argues that M-dwarfs will have planets with O2 atmospheres that are habitable by aerobic organisms, but which never had a chance to develop indigenous lifeforms due to the early abiotic accumulation of O2. He might be right, though more data is sorely needed to confirm the concept. If they do exist, then delivering a copy of our biosphere in form of selected organisms might be a truly worthy quest.

    • ljk December 14, 2022, 12:08

      My thinking is that a habitable planet will have some forms of life, even if they are “just” microbes. In that case, would we have the right to introduce terrestrial life forms to that world just to make things more palatable for us?

      Imagine if an ETI came upon Earth roughly 3 billion years ago, when it was just microbes here as the dominant native life form. Would they have any more right to introduce their biology to move things along?

      • Alex Tolley December 14, 2022, 21:07

        Suppose that they were able to completely sterilize the Earth (difficult, but this is a thought experiment), would we be able to tell whether they did or didn’t?

        I don’t think we have enough detailed information about those fossils of microbes or stromatoliths to determine that they are of the same biology as our current terrestrial life.

        Suppose that they did. Current life, including humans, are not going to complain as we have no knowledge of what our extinct native microbes could have evolved to become.

        I am all in favor of a Prime Directive to leave living planets alone, but I am not sure that I would extend this to planets only populated by microbes. It might be a case by case decision for those worlds.

  • wdk December 13, 2022, 20:14

    At least one of my copies of that paperback remains relatively intact.
    It says second printing 1962, but my family had moved from where I read it back a year or two after published.

    Beside the treasure trove of having such an old classic paperback, Hoyle did seem to be on to many very interesting ideas. Hard to dismiss entirely after decades because we still run into the same conundrums that he was trying to solve. Of late, if stars in the galaxy are embedded in their own Oort clouds – and stars have close passages periodically, then we are sharing more of the same organic compounds than we might have otherwise thought. As noted above, searching for life in impacts on terrestrial bodies by carbonaceous chondrites early in the formation process could well be a fruitless errand. Collisions in the cooler regions of a stellar or the solar system might be another matter. Like following the money, for there to be a galaxy wide network of life, it’s a matter of finding the possible paths.

    Might it be chilled tardigrades piloting the interstellar craft?

  • Benjamin Stockton December 13, 2022, 20:39

    The theory behind a search for “vestigial” traces of interstellar origins needs explication. If the assumption is that some of these “traces” were instrumental in founding early life on this planet, why would they not seem entirely indigenous? If on the other hand, such “traces” arrived after indigenous life formed, one could imagine something different between the indigenous life “stuff” and life stuff with “traces” of interstellar origins. Which is it?

    • Alex Tolley December 14, 2022, 0:20

      If mitochondria had a different genetic code and/or used different chirality amino acids and sugars, then we might have evidence of interstellar life added to our terrestrial life. Unfortunately, mitochondria clearly have the same biology as their likely prokaryote ancestors and therefore unable to offer any information about any possible extraterrestrial life.

      Some years ago, there was an analysis of the complexity of organisms and DNA over time. The claim was that the extrapolation backward in time indicated that life was older than the Earth and therefore must have arrived from elsewhere. I don’t recall the outcome, but since that hypothesis is dead, it must have been successfully debunked as a poor analysis.

      What could be really interesting is if we found complex, functional RNA molecules in an interstellar comet (or preserved elsewhere that indicated extrasolar origin) that could be the basis of an RNA-first world. This would leap over the difficulties to date in creating such molecules and offer an alternative hypothesis about the initiation of life on Earth.

  • Michael Fidler December 13, 2022, 21:57

    What if is actually the other way around, we as usual make the smallest assumption, but what if intelligent life is alive and well in trillions of independent locations in our galaxy? Then life itself may be a Googolplex times more common! (Yes it’s a real number) https://en.wikipedia.org/wiki/Googolplex

    So why have we not found any? What about the water delivered to the moon from earth when a lunar eclipse occurs, microbes frozen on the moon’s south pole. Space station covered by slim on its exterior or carbon asteroids with microbes in its core… We have just started to look but assume the worst, that we are it. Maybe the next time Dimorphos passes near earth we may receive some critters from deep inside it from the impact of DART.



    • ljk December 14, 2022, 12:12

      The simple answer to why we haven’t found any alien life of any kind yet is that we haven’t done enough searching for it. Most of our efforts have been sporadic and token, to say nothing of rather recent.

      Yes, we have been speculating about extraterrestrial life since the time of the ancient Greeks, but no one got serious about searching for it until the Twentieth Century (I suppose you could count the telescopic observations of astronomers going back to the Seventeenth Century). The concept has also had to fight a long road of ignorance, disbelief, and ridicule, not to mention religious and social persecution and fear.

      We have only just begun to search for alien organisms and the field is vast and ancient.

    • Alex Tolley December 14, 2022, 21:11

      If there are microbes preserved in the ice at the lunar poles, we may soon have some evidence to test this hypothesis with the Artemis III mission to the South Polar Region.

      • Ljk December 15, 2022, 12:46
        • Alex Tolley December 15, 2022, 15:25

          I think my comment is in alignment with that article. Whether any water-extracting process will try to separate out terrestrial debris from lunar and then systematically look for fossils seems unlikely to me, but we could hope. What we need is a simple, cheap, “life detector” that could detect a fossil quickly and separate it out from the material stream like a FAC flow cytometer can separate out cells. If DNA is preserved, then isolating DNA fragments and analyzing them might be possible in the pre-purified extracted water.

          Back to Clarke and a missed opportunity. In 2061: Odyssey Three, Clarke hints at life in an ice cave on Halley’s comet. The plot moves on to using the plume water from the comet to fill the propellant tanks of “Universe” to rescue its sister ship on Europa. The carbon “dirt” is filtered out. Now we could also test that dirty water for DNA and other possible biosignatures. That hinted at extant life on Halley could have been at least detected by these methods and the discovery confirmed for a follow up trip to Halley (or other comets).

          • Michael Fidler December 16, 2022, 2:46

            Something even more interesting is the possible layering of the lunar soil (regolith)!
            “The thinking is that hydrogen and oxygen ions are driven into the lunar surface as the Moon passes through the tail of the Earth’s magnetosphere (the teardrop-shaped bubble around Earth affected by its magnetic field). That occurs five days in every lunar month.”

            But this has been happening for billions of years so micrometeorite impacts may cause layers to build up over the monthly water deposits. Now the interesting part, the 65 million years ago giant impact that destroyed most life on earth may have blown huge amounts of material off the earth that would be deposited on the moon. The fact is any large impactor on earth should have done the same. So a history may still exist in the protected regions near the lunar poles that have deposits from these impacts. Maybe even some dinosaur parts! A history of earth’s major impacts may be buried there waiting for us to find it on the moon…



            By next spring!

            • Michael Fidler December 16, 2022, 7:34

              Could the same thing have happened with the once water world Venus and the Earth. Early Venus may have been very lively and may have had an orbit that came closer to earth then 24 million miles. Transfers of life from impacts on early Venus may have reignited life on earth many times.

              The systems like Trappist 1 may have had very similar occurrences. Trappist 1 c being an early water world and Trappist 1 d coming within only 650,ooo miles of it, impacts may have transferred life to d. This could also continue on down the line of planets to Trappist 1 g.
              The early water worlds of inner planets of all systems may have the original source for life on the planets further away from the main star. As the star evolved and brightened these water worlds were destroyed as we see in Venus today with only the heavier elements oxygen and lifes carbon left to create a CO2 greenhouse atmospheric hell…

            • Alex Tolley December 16, 2022, 15:19

              I don’t think that random large impactors depositing fossils on the moon will offer much value for tracking the evolution of life that we have a good handle on in the fossil record on Earth. It may offer value for early life.

              However, I like the idea that the Moon gently deposits a layer of water and microbes blown off Earth every month providing a possible deep, layered record of such life from prebiotic onwards is interesting. However, I suspect that there is no such layering, but rather a constant gardening of the regolith dust that results in the destruction of any organic material rather than laying it down, like sediments. OTOH, if there are pockets on the Moon where the dust slowly flows to form layers (c.f. Clarke’s “A Fall of Moondust”) then there might just be the possibility of preserved layers of dust and microrganisms/microrganism fragments.

              When we are on the Moon in sufficient numbers to do this sort of research, that might be the time to look.

              I fancy that Mars might be a better bet as it did have geology that created layering, but the problem there is contamination with any Mars’ fossil life that might be there too. The Moon is clearly easier to reach and a probe could extract a core of dust from such a pool and return it to Earth for analysis. It may offer a record of other events such as the sun’s paleo emissions or impact events on the Moon (iridium) etc.

              • Michael Fidler December 16, 2022, 23:44

                We have a good handle, we don’t even have any handle on what happened 12,800 years ago to our own species! Impactors in the deep oceanic abyss to 100 million years is all the history we have there, any earlier is covered in deep sediment. Even the Chicxulub structure was not found until the late 70’s and the extent and magnitude is still not well understood. What we have on the moon would be ever large impact even from the ancient oceans. As usual we think we already know it all. If anything mans mind is denser then any black hole…

                • Alex Tolley December 17, 2022, 14:51

                  Any record on the Moon is going to be far less informative about the evolution of complex life than Earth that the record in the earth’s rocks. It certainly won’t shed light on the genetic bottleneck of human genomes (unless aliens buried a detailed record of their observations of humanity on the Moon.)

                  • Michael Fidler December 19, 2022, 0:04

                    It All Depends on Your Perspective!

                    When I was maybe 15, I somehow came into possession of a real see through hologram on 3×3 inch plastic. Under strong light you could move it and and see the image change in 3D. One day I cut out a small section 1/4 x 1/4 inch of it and could still see the image in all its detail but moving it gave very little change in the 3D image…

                    This is the problem, we have a limited view of life on earth. It is limited in all four dimensions, the most important being time. On the moon time stands still, in the sense that when something lands there and is covered over the eons it is frozen in time. On earth some 650 million years ago the earths crust was wiped clean by global glaciation. We now have a record of the Precambrian period in locations of maybe 1 percent of the surface of the earth and nothing from the ocean areas. This is where the moon’s polar regions may fill in that period, plus passing comets and interstellar comets that have collided with the moon. This will give us perspective on just how common panspermia may be and also early life on earth. Maybe even the deep oceans that may have existed on Venus could be recorded on our moon…
                    It’s All about Perspective!

                    • Alex Tolley December 19, 2022, 17:08

                      We now have a record of the Precambrian period in locations of maybe 1 percent of the surface of the earth and nothing from the ocean areas.

                      On Earth, fossils form when the organic matter is quickly buried in protective mud or silt, and then mineralization can occur. Fossils are most easily found when the sediments, now rock, are exposed to the elements and erode, shedding their fossils. This has happened sufficiently all over the planet over geologic time. Sea sediments that form chalk and later limestone are found all over England. The South Coast chalk cliffs have been a rich source of marine fossils. Quarries and mines exposing the rocks are also good fossil sites. Fossils are found all over the planet, with new sites constantly being found, often serendipitously. Whilst macro fossils will not easily be found in the sediments at the bottom of seas, cores of those sediments are a rich source of marine microfossils. The other place where microfossils are found is in glaciers where snow has trapped microbes and kept them frozen and isolated from degradation.

                      Any fossils on the Moon will be due to impactors gouging out terrestrial rocks with fossils in them. Terrestrial life will not fossilize on the Moon. It will simply desiccate and break down under the impact of UV, particle radiation, and micrometeorites.
                      Consider Charlie Duke’s photo left on the surface of the moon, surely an almost ideal example of what you are suggesting. Yet in reality, the photo will bleach and disintegrate long before lunar dust covers it, either levitated by electrostatic forces, covered by dust slipping down a slope, or deposited from an impactor. If there are any remains of terrestrial or extraterrestrial life on the Moon, they will be sparse and likely far less common than on Earth. We know that the rocks and soil brought back by the Apollo missions did not harbor any bugs either as spores or even identifiable parts of life AFAIK, despite being subject to possibly millions of years of exposure to panspermia-delivered bugs. It is a charming idea, probably not to be written off until possible sites of dust accumulation have been thoroughly investigated, but I would put the odds of success as extremely long, and certainly less productive than the sites we have on Earth.

                    • Michael Fidler December 20, 2022, 6:29

                      I never said there was fossils on the moon and you are absolutely right they can not form there. We will have to see what is hidden in the layers on the moon. There may be remains from impacts on earth left in places like the polar craters on the moon. Maybe a frozen mammoth or two… :-}

  • Abelard Lindsey December 13, 2022, 23:32

    I think my first SF novel as a kid was Rendezvous with Rama.

  • Afterthought December 14, 2022, 3:48

    If panspermia happened on Earth
    1) where (and when) was the source
    2) how would this life be adept enough to eek out an existence on a barren world, and yet be simple enough to account for our current understanding of the root of the tree of life
    3) why aren’t we gathering up examples of the seed material here and there
    4) if it can turn one habitable zone planet to life, why not any, ergo why not see one life planet candidate per star?
    5) What is the proper null hypothesis that we are rejecting?

  • ljk December 14, 2022, 12:15

    Earthly Microbes Might Survive on Mars for Hundreds of Millions of Years

    An organism nicknamed “Conan the Bacterium” may have what it takes to live on Mars.

    By Keith Cooper, SPACE.com on October 27, 2022


    And let us not forget our little friends the tardigrades…



  • wdk December 14, 2022, 15:50

    Afterthought and others,

    There are a number of sequential or logical questions to give this debate a framework. I agree. Though I do think that panspermia tends to bias the discussion or frame it in terms of concepts a century old, say, before we had a notion of a genetic code.

    In turn the debate, influenced by the Drake equation, tends to focus on aliens pointing radio receivers into space and acting much like ourselves. For the question at hand the individual probabilities are too facile and skip too quickly to a lifeform and civilization like ourselves.
    Its many probability fractions frame the problem, but its application takes us too far, beyond the issue of probability of fundamental life on a planet or elsewhere in a stellar neighborhood.

    Even if we are optimistic, we suspect from available evidence that life forms “like” ourselves sharing features allowing communication will be dispersed so far in space that the light lapse time will make communication difficult, at best, a matter more of detection. But in the overwhelming cases of “life”, there will be no such emission source – unless it’s a planetary emission line from a life by-product. For example, many of the features of the terrestrial spectrum are by- products of billions of years of living organisms breaking down chemicals into the atmospheric gases of our geological era.

    In our own case we can identify many cases where we can distinguish between organisms producing such atmospheric products – and other processes which we associate with geochemistry.

    It can be argued probabilistic processes could cause precursors to unicellular organisms to arise in these environments, but I see no distinct odds, or number of times you have to perform the Urey-Miller experiment that will allow passage to the next step of development.
    Or the next. Certainly, when you get to self-awareness, consciousness and language and mental concepts, you have gone way beyond the realm of probability every time you wake up in the morning musing on what you will do next. To look at it another way, compare our programming to machines which we would say program themselves.

    Yet at the worst, we assume that all the gates we have to go through to get to ourselves, only happened here. Were a cosmic better to have picked this planet as his horse!….Quite a jackpot.

    Hence, there are reasons to look for some common foundations for life that come pre-packaged when they arrive at Earth. Amino acids did arrive in other varieties than those incorporated into terrestrial genomes, and we can see why some are included based on a prevailing chirality. Whether there would be the same applications elsewhere, more likely we are waiting to see what observation will reveal rather than to construct a radically different alternate.

    My argument runs counter to the behaviorism of, say, B. F. Skinner, which tends to assume that only he and his symposium attendees were immune to laboratory based conclusions of stimulus and response explanations for human behavior. Skinner, presumably was never motivated by an external stimulus himself. And odds are in favor of many things we do could be predicted as response. But the very notion that we can identify such behavior is paradoxical to the idea itself. Even if we individually behave like Socrates in the Agora asking questions, it might, of course, be attributed to some sort of programming. In fact, were I in a church social dinner, I could conceivably turn the table on many of my arguments thus far. And maybe that is a structured element of consciousness or investigation. But I still strongly suspect that our machines do not have this sense of self, even if it could be imitated. And if this is the only place it exists, then the statistical mechanics of it all are more like the case one of my gas dynamics teachers cited: the molecules in the lecture room all stacked in a corner that morning.

  • wdk December 14, 2022, 16:11

    To sum the above entry.
    With all due respect to 2001 a Space Odyssey and its author,
    “Cogito, ergo sum” is distinct from “Computo, ergo sum” as a proposition.

    • Alex Tolley December 14, 2022, 21:37

      I agree with you that ETI does not necessarily take the form of a technological civilization that uses radio/optical communication and transmits it to the galaxy. Whenever we place the first Homo sapiens, clearly for most of the time we have been on Earth, we were pretechnological beyond using sharp sticks, stones, and fire. As for communicating, we have had little over a century of radio. We may be quite rare if it turns out that technology shortens the technological lifetime of a species. Perhaps we revert back to some stone age existence that is more stable. [There is an episode of the BBC’s Out of the Unknown 1960s/1970s sci-fi series called “Beachhead” where an Earth ship discovers a planet with aliens that do not seem to have technology, yet appear familiar with technology. The denouement is that they created a metal-eating bacterium that destroyed all their technology and it was starting to trap the spaceship as the delicate electronics started to fail.

      As for consciousness, I think we are slowly accepting the idea that it is a continuum, not a binary feature of brains. I see no obvious reasons why a computer cannot in principle be conscious, although I also do not see why consciousness is critical either. We may create robots that act conscious even if they are not. It is also possible that advanced robot brains become more conscious than human brains, and they might question our consciousness. [Does it really change anything if HAL 9000 was conscious or not?]

      • Mike Serfas December 15, 2022, 11:19

        The concept of non-binary consciousness – or perhaps simply the non-existence of consciousness – seems firmly entrenched at this point. There are now many experiments being done with brain “organoids”, composed of human brain cells with random or artificially imposed structure. What we call consciousness, to “really” experience things, is fundamentally a paranormal phenomenon that cannot directly be measured, but if people considered the possibility at all, these experiments would surely be rejected as atrocities.

        If human brain tissue does possess some sort of unusual properties, then the mass production and application of brain organoids could have unusual effects. For example, yesterday a “mystery rally” was reported 60 seconds in advance of a news release about inflation. While this clearly may have a mundane explanation, it illustrates the sort of effect we might see if the human organoids can be programmed to display paranormal modes of cognition that machines are incapable of. Their use would be irresistibly alluring, but their effect on the world would be as catastrophic as we deserve for creating such things.

        • Alex Tolley December 15, 2022, 15:09

          What we call consciousness, to “really” experience things, is fundamentally a paranormal phenomenon

          (emphasis mine – AMT

          I think you are just using a different term that is really nothing more than another version of mind-brain dualism. Consciousness may be hard to measure, but it is not paranormal.

          Furthermore, if consciousness is a continuum, that would imply that all organisms with brains must have some paranormal abilities.

          Your suggestion that brain organoid research is immoral [“experiments would surely be rejected as atrocities”] brings to mind the anti-abortionist argument that fertilized egg cells are human beings, and that fetuses with cellular activity “heartbeat” cannot be aborted due to being human with all the rights of the post-born. There is no evidence whatsoever that organoids can be “programmed” to display unusual effects that cannot be demonstrated by silicon, any more than human brains can demonstrate paranormal phenomena.

          • Mike Serfas December 16, 2022, 12:16

            Despite the controversies regarding abortion, nearly everyone believes that a fetus develops consciousness by the time it reaches the baby carriage… though evidence is admittedly lacking. Whether the boundary line involves cardiac or brain physiology or something else depends on facts not in evidence, but it’s worth noting that many people accept an EEG reading as meaningful evidence at the other end of life. But I’ll stick to my description of consciousness as paranormal, because it is not merely hard to measure, but with existing theory it is altogether impossible to relate to any physical measurement we could make. We politely assume adults have consciousness, but we can’t prove it; if you listen to the old PrankNet recordings on Internet Archive you might wonder sometimes. :) Now I suspect it may be measurable if causality violations are taken into account, but my understanding of quantum mechanics hasn’t been up to the task.

  • Harold Shaw December 14, 2022, 18:04

    Estimates for the percentage of extra-solar comets in our Oort cloud reach 90%. We should be able to rule out the general case for panspermia. Life on Earth may still remain a fluke of pansmeria even if the general case is ruled out.

    Obviously, there is a “soft panspermia” element to the abiogenesis explanation for Life on Earth. We are all made from star dust ground by a galactic mill. Abiogenesis is a much simpler explanation for Life on Earth than hard panspermia. Hard panspermia requires abiogenesis, the evolution of organisms that can survive proximity to explosions, many millions of years in space, and survive in extreme environment of primordial Earth.

    Some level of “soft panspermia” must apply and some compact systems could have several planets in the habitable zone where one seeds the others. However, I think, hard panspermia is a too complicated a theory to explain abiogenesis on Earth that takes us on a long walk away from, and back to, the need for a general theory for abiogenesis.

    The simpler explanation is that soft panspermia and primordial Earth provided the conditions necessary for abiogenesis. If abiogenesis requires the free energy provided by a just cooled lava ball, the right amount of water and light, global mixing of the water; then I think we can be optimistic. If abiogenesis requires the tidal environment and extreme mixing, Life may be very rare.

  • Alex Tolley December 15, 2022, 15:44

    I have no doubt others here are playing with ChatGPT, testing its abilities, and capabilities. Various reports suggest it is hit-and-miss, with even simple 3-value math failing to get the correct answer. OTOH, with care and curation, it can do some cognitive tasks quickly. [It can write limericks on a subject prompt that I am incapable of doing.] It is reported that Stack Overflow has banned AI inputs as the results are “iffy” and overwhelm the capability of moderators to check for accuracy. So the ability to curate AI output for accuracy is a future job. Ben Thompson of Stratechery has suggested that students could be tested with various AI outputs to determine if they have learned their material sufficiently to eliminate BS content. A true test of critical thinking.

    To test whether it could write in an author’s style, I used this prompt:

    Write a 1000-word short story about an asteroid that is threatening the Earth. Write it in the style of Arthur C. Clarke.

    The result was:

    As the asteroid hurtled through space, its rocky surface glinting in the light of the sun, a sense of dread began to build on Earth. Scientists had been tracking the asteroid for weeks, and it was now clear that it was on a collision course with the planet.

    The nations of Earth came together in a rare moment of unity to devise a plan to stop the asteroid. But as they studied its trajectory, it became apparent that there was nothing they could do. The asteroid was simply too large and too fast, and it would strike the Earth with devastating force.

    As the asteroid drew closer, people around the world watched in horror as it grew larger and larger in the sky. Some prayed for a miracle, while others prepared for the end.

    But just as the asteroid was about to strike, something incredible happened. A blinding light filled the sky, and the asteroid seemed to pause in mid-air. Then, with a sudden burst of energy, it was hurled away from Earth and into the depths of space.

    It was as if the universe itself had intervened to save the planet from certain destruction. And as the people of Earth looked on in amazement, they knew that they had been given a second chance.

    But the relief was short-lived. In the weeks and months that followed, strange things began to happen on Earth. The weather became more extreme, with powerful storms and devastating floods. And as the people struggled to adapt to their new reality, they couldn’t help but wonder if the asteroid had somehow changed the course of their world.

    Despite the challenges they faced, the people of Earth remained resilient. They banded together, working to rebuild their communities and find a new way forward. And as they looked up at the stars, they knew that they would never take their survival for granted again.

    The asteroid may have missed them this time, but they knew that there would always be other dangers lurking in the depths of space. But they were ready for whatever came their way, and they would face it with courage and determination.

    For the people of Earth, the asteroid had been a wake-up call. It had reminded them of their own fragility, and of the need to come together to protect their planet. And as they looked to the future, they knew that they would always be ready to defend their home, no matter what the universe threw their way.

    IMO, that output was pretty awful, and certainly not in Clarke’s style. I will test for some other authors’ styles that are well-known, but I suspect it will fail. Good writers, like our host, shouldn’t have much to worry about at least in the short term. We will see how the base of Gpt-3 is improved by the forthcoming Gpt-4.

    • Mike Serfas December 17, 2022, 14:10

      Your example doesn’t seem like it should be reassuring to authors. To begin with, not everything people write is very good, and not everything the bot writes will be consistently bad … even prose like this could cut into the opportunities available for bad authors… who seemingly write nearly all of the Hollywood sci-fi dialogue.

      An even longer and sordider tail of authorship seems threatened… my impression is that English majors are pretty much advertising and PR majors. I bet ChatGPT can beat them head on in focus groups, once it is trained to obtain positive results.

      Without a pool of awful writing to rise above, can an ivory-tower community of better-than-AI authors perpetuate itself, each new talent sprouting like Athena from the forehead of Jove? How do they first practice their art?

      Then there is the sticky question of where ChatGPT obtained the prose to begin with. Even human authors have influences, mixing news and stories they’ve read into new combinations; but a torrent of AI prose can plagiarize a millionth of a million different forum postings to produce ten million trite but familiar tales. Our economic system has unwisely attempted to make information into property, relying on law that prevents piracy on the scale of one person making ten copies, but now an AI can pirate the entire world at once, and sell it.

      • Alex Tolley December 17, 2022, 21:52

        Yes, a lot of “creatives” will find their jobs disappear. Rather like wool spinners, typists, and whole hosts of now automated jobs. OTOH, it means that others can do their tasks inexpensively, increasing opportunities. The computer replaces all those human computers – mainly women with math degrees. If newsprint goes away with the dinosaurs, then all those printing jobs will disappear too. You may have noticed that the media seems to generate a lot more spelling and grammar errors than it used to. It has been suggested to me that copy editors have largely disappeared, no doubt to spell and grammar checking software. So the product may not be so good, but it is less expensive to produce than it was.

        I really don’t see why AI entering the cognitive task domain should be any different than when it started with programs that made a number of cognitive tasks easier and deskilled the task.

        If I could write by just using a well-designed set of prompts, I would relish that support. A well-trained AI could counter mis- and disinformation as soon as it appeared. An AI that only selected trustworthy sources would be a boon, relieving one of the burdens of rejecting untrustworthy ones, and ensuring facts were correct. We are not there yet, but we will be in a decade, I hope.

        Yes, there is a gray area with copyright. But clearly, plagiarism and theft requires enough in the sample to prove a source. An Ai selecting tiny pieces from millions of sources is no more theft than a person benefitting from the prior work of others. The best case is to reduce copyright to a short period (where it started) and train AIs only on out-of-copyright material. Then the argument is moot. [The purpose of copyright and patents is to stimulate creative work and guarantee no theft for a limited period, then make it public so that the work can become the legitimate base for others to stand on those shoulders to produce new content.]

        • Robin Datta December 20, 2022, 6:30

          Thus have I heard:
          If one copies from ⇨
          one source – it’s plagiarism;
          ten sources – it’s a topical discussion;
          a hundred sources – it’s a subject review;
          a thousand sources – it’s a comprehensive treatise.

  • Dave Moore December 15, 2022, 16:23

    The problem I see with Panspermia is a temporal one. If 4.5 b.y.a. a sentient race sent out spores, and few hundred million years later they seeded Earth with life, then what happened to the sentient race in the mean time. They’ve had 4.5 billion years to colonize the galaxy. The only reason you could suppose for them not tuning up long ago is that interstellar travel is practically impossible for macroscopic craft. In that case, why would the civilization wait a tiny bit and develop programed machine spores that produce technology and intelligence.

    If you postulate natural panspermia and there are papers showing its possible, then the travel times are in the millions of years and spread times in the hundred’s of millions of years, which again implies there are places where intelligent life could have a great head start on us.

    The modern concept of Panspermia was formulated in 1974 when the mechanism for the origin of life was completely unknown and it seemed miraculous, but since then considerable advances have been made in the field. A mechanism using the evolution of self replicating RNA looks increasingly plausible.

    From meteorite samples, panspermia looks quite possible between the inner planets of our solar system, but interstellar panspermia doesn’t look to have much to do with the evolution of life on Earth.

    We can pick up asteroid and comet sized exosolar bodies, but wouldn’t it be nice to have a tracking system that could pick up rock/boulder-sized objects. We might then be able to intercept and examine a blown-off chunk of an exosolar terrestrial planet.

  • Dimjo December 15, 2022, 17:33

    If earth is a product of directed panspermia could a computer program position earth 4 billion years ago and see if a “downstream” positioning of stars favorable to life occurred? Or, has there been any work done to see how one would go about maximizing success (in numbers) of directed panspermia 4 billion years ago?

    • Alex Tolley December 16, 2022, 0:34

      4 Gya is 8x galaxy revolutions. I would be surprised if we could determine the positions of nearby stars.

  • Ryan Carthy December 15, 2022, 21:25

    The thing about organic panspermia as opposed to directed panspermia is that it potentially solves the so-called Fermi Paradox, since the entire notion that we should expect aliens enough to ask “Where is everybody?” is based on the fact that habitable planets should have existed billions of years prior to the Earth, and if we reached civilization in 4.5 billion years, and assume this is a typical timeframe, aliens have had billions of years of head start to evolve and then conquer the galaxy.

    If instead, interstellar panspermia is possible, and Earth was seeded with life, then this disrupts the assumption that the timeframe to produce humans is limited by the age of the Earth on which the further assumption that this is typical for life in general rests. If life actually started in the universe, say, 10 billion years ago, and seeded Earth shortly after it cooled (the age of first life on Earth keeps getting pushed back), then intelligent aliens and humans are aligned to the same approximate evolution timeframe, and we should not automatically assume they had the massive head start that individual planetary abiogenesis implies. If the complexity of life takes a long time to build up then life may have been simple for billions of years prior to landing on Earth. We see two interesting facts, both that life appears to have started as soon as it could, but also that the increase in adaptions sped up over time, so that life took a billion years to go multicellular but then exploded into large social organisms with increasing rapidity after that.

    Observationally we happen to be first to reach this stage, but if the growth of intelligent life took 10 billion years across the entire universe, then this would also explain why we don’t look up and see the sky filled with dyson swarm galaxies. Some aliens are ahead of us and some are behind us, but no one is billions of years ahead of us as extrapolation from the abiogenesis on Earth timeframe might imply. We’ve appeared at about the point where intelligent civilizational life is going to appear in the universe. If aliens have directed panspermia, this just pushes the problem back into the same box, and does not explain the same things organic panspermia can explain.

  • Bill Jordan December 17, 2022, 9:49

    Hoyle is famously quoted as saying that “the universe is a put-up job “. He held the same view on the origin of life.

  • Joe H. December 19, 2022, 22:30

    I recall an article by a reputable biologist who argued that life on Earth had to come from outer space. He said that a study of evolution, biochemistry, etc showed that it takes longer for modern animals to evolve than the Earth has been habitable. I don’t really believe him, but it’s an interesting idea.

    • Alex Tolley December 21, 2022, 16:42

      I’m wondering if you are referring to that mathematical analysis of DNA complexity that suggested that the rate of change required extrapolating back before the Earth was formed, from the start to the complexity needed for life. The analysis made a number of assumptions and perhaps was a lesson in how not to do such analyses. In any case, it had its 15 minutes of fame and fell back into obscurity once the flaws were pointed out.

  • wdk December 21, 2022, 13:02

    Your point about a process developing a “mammal” is as good an entry point as anywhere. Because, in a way, it is an application of Drake’s equation as a tool. We know that there are an indefinite number of factors we can throw into the Drake equation to come up with thresholds for our origin – and in our individual case in the galaxy, mammals were part of that pyramidal track. But as a specific, I don’t think mammal per se has to be duplicated.

    What is essential is worth tracking, of course, and I suspect that every time we think we have found one, we should file it. But by the time we reach “language”, say, stepping toward English or even Indo-European family is specious. Some sort of concept thresholds after “language” have to be identified for sure for interstellar communication, etc.

    And correspondingly, we have to tread forward for Drake equation factors cautiously from such milestones as the single cell organism, coming inmany varieties, consuming many compounds and producing other organic products.

    While we have some consensus about the need for the development of the basic structure for algae and bacteria, which are based on single cell or prokaryotic cell organisms, active in reforming inorganic surfaces into at least one environment we have come to know and love ( this epoch’s Earth), the next step takes the introduction of a a cell with a nucleus or mitochondria and multi-cellular individual role playing.

    That transition LOCALLY took a long time to complete. Prokaryotic cells were around here maybe as early as 3 billlion years ago. Eucharyotic maybe a half billion or more. Why the switch should occur at all or take as long as it did is a mystery. And should we have opportunity to discover such life elsewhere and compare the geological history, we would want to determine whether it was slow here or fast.

    It could even be that that’s actually the seeding mechanism for what has transpired since.

    But not to digress further on that “panspermia” type characterization, there is still the question of what is another Drake equation factor subsequent to eucharyotic cells and cells orgainized into specializations. The communication links between them?

  • wdk December 21, 2022, 13:06

    Just a quick correction on a previous submission.
    My spelling lapsed from definition to discussion of
    EUKARYOTIC cells.

    A mitochondrion (/ˌmaɪtəˈkɒndriən/;[1] pl. mitochondria) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy.

Leave a Comment