On Retrieving Dyson

One of the pleasures of writing and editing Centauri Dreams is connecting with people I’ve been writing about. A case in point is my recent article on Freeman Dyson’s “Gravitational Machines” paper, which has only lately again come to light thanks to the indefatigable efforts of David Derbes (University of Chicago Laboratory Schools, now retired). See Freeman Dyson’s Gravitational Machines for more, as well as the follow-up, Building the Gravitational Machine. I was delighted to begin an email exchange with Dr. Derbes following the Centauri Dreams articles, out of which emerges today’s post, which presents elements of that exchange.

I run this particularly because of my continued fascination with the work and personality of Freeman Dyson, who is one of those rare individuals who seems to grow in stature every time I read or hear about his contributions to physics. It was fascinating to receive from Dr. Derbes not only the background on how this manuscript hunter goes about his craft, thereby illuminating some of the more hidden corners of physics history, but also to learn of his recollections of the interactions between Dyson and Peter Higgs, whose ‘Higgs mechanism’ has revolutionized our understanding of mass and contributed a key factor to the Standard Model of particle physics. I’m also pleased to make the acquaintance of a kindred spirit, who shares my fascination with how today’s physics came to be, and the great figures who shaped its growth.

by David Derbes

I have a lifelong interest in the history of physics, particularly the history of physicists. Somehow I got through graduate school (in the UK; but I’m American) with only a very shaky acquaintance with Feynman diagrams and calculations in QED [quantum electrodynamics, the relativistic quantum theory of electrically charged particles, mutually interacting by exchange of photons]. This led me to a program of self-study (resulting in “Feynman’s derivation of the Schrödiinger equation”, Amer. Jour. Phys. 64 (1996) 881-884, two editions of Dyson’s AQM [Advanced Quantum Mechanics], and, with Richard Sohn, David J. Griffiths, and a cast of thousands, Sidney Coleman’s Lectures on Quantum Field Theory).

Along the way I stumbled onto David Kaiser’s Drawing Theories Apart, a sociological study of Feynman’s diagrams. Kaiser, who is now a friend, is a very remarkable fellow; he has two PhD’s, one in physics ostensibly under Coleman but actually under Alan Guth, and another in the history and philosophy of science). Kaiser mentioned the Cornell AQM notes of Dyson, never published, and I thought, hmmm… I found scans of them online at MIT, and (deleting a few side trips here) contacted Dyson about LaTeX’ing them for the arXiv (where they may be found today).

Image: Physicist, writer and teacher David Derbes, recently retired from University of Chicago Laboratory Schools. Credit: Maria Shaughnessy.

Dyson was quite enthusiastic. It probably helped that I had been a grad student of Higgs’ under Nick Kemmer at Edinburgh; Kemmer had steered Dyson towards physics and away from mathematics at Cambridge after the war. Ultimately (in my opinion) it is Dyson who was (very quietly) responsible for the recognition of Higgs’s work, and its incorporation by Weinberg into the Standard Model. Dyson had seen Higgs’s short pieces from 1964, learned (maybe from Kemmer) that he was at UNC Chapel Hill for 1965-66, wrote Higgs to give a talk at the IAS, which led to his giving a talk to Harvard (with Coleman, Glashow, and maybe Weinberg, then at MIT, in the audience).

Typing up Dyson’s Cornell lectures killed two birds: I learned more about QED, and I learned LaTeX from scratch. In retirement, “manuscript salvage” is my main hobby. (There are at least a couple of other oddballs who are doing much the same thing: David Delphenich, and there’s a guy in Australia, Ian Bruce, who has done a bunch of stuff from the 17th and 18th century, among other things a new translation of the Principia.)

Flash forward to shortly after LIGO’s results were announced. A letter in Physics Today drew attention to Dyson’s “Gravitational Machines”, so I went looking for it in the Cameron collection. I have a copy of Dyson’s Selected Works, and as you report the paper is not there. Couldn’t find it anywhere else, either. Cameron’s collection was mostly published in ephemeral paperback (I think there were a small number of hardbacks for libraries, but the U of Chicago’s copy is in paper covers).

So I wrote Dyson, with whom I had developed a very friendly relationship (there is a second edition of AQM, and it was more work than the first, due to the ~200 Feynman diagrams in the supplement), and asked if he would consent to my retyping (and redrawing the illustration for) his article for the arXiv. He was pleased by this. I very much regret that I couldn’t get it done before he died. The reason for that was copyright problems.

I’m going to give you only bullet points for that. Cameron died in 2005. His Interstellar Communication was published by W. A. Benjamin, then purchased by Cummings, Cummings was purchased by Addison-Wesley, and most of A-W’s assets purchased by Pearson; some by Taylor & Francis (UK). Took about four years to unravel. Neither Pearson (totally unhelpful) nor T&F (much better) had any record of the Cameron collection. As this may be helpful to you down the road, here was the resolution:

A work which was in copyright prior to January 1, 1964 had to have its copyright renewed in the 28th year after original copyright or lose its US copyright protection forever. Cameron’s collection was copyrighted in 1963. It took hours, but by scouring the online catalog at the US Copyright Office (you can do it in person near the Library of Congress) I was able to convince myself that the copyright had never been renewed. As far as US copyright goes, “Gravitational Engines” is in the public domain, and so I was clear of corporate entanglements (more to the point, so is the arXiv).

However, as I learned from Dyson’s Selected Papers, the article had originally been entered into an annual contest by the Gravity Research Foundation. The contributors to this contest read historically like a Who’s Who of astrophysics, general relativists and astronomers. So I got in touch with that organization’s director, George Rideout Jr. Rideout’s father had been appointed director by Roger W. Babson. who made a pile of money and set the foundation up. The story behind this is very sad: His beloved older sister drowned, and he blamed gravity. So he thought, well, if people could only invent anti-gravity, that might prevent future disasters. So he set up the foundation. (I think they also provided some funding for GR1 [Conference on the Role of Gravitation in Physics], the first international general relativity conference, Chapel Hill, 1957.)

I quickly obtained permission from George Rideout, satisfied the arXiv officials that they were free and clear to post “Gravitational Engines,” and here we are. (As I mentioned in the arXiv posting, the abstract comes from the original Gravity Research Foundation submission; it is absent in the Cameron collection.)

Incidentally, in chasing down other things, I found something I’d been seeking for a long time, the report from the Chapel Hill conference:



(So as you can see, there are several of us oddball manuscript hunters out there.)

Theoretical physics was not that large a community in 1965, and the British community even smaller. The physicists of Dyson’s generation typically went to Cambridge (which remains the main training ground for math and physics in the UK), with smaller spillover at Oxford, Imperial College London, and Edinburgh.

Kemmer hired Higgs at Edinburgh (Peter had been in the same department as Maurice Wilkins and Rosalind Franklin at King’s College, London. He was an expert at the time on crystal structure via group theory. He did not have any direct involvement with the DNA work, though subsequently he wrote an article that had a lot to do post facto with explaining the helical structure. The big boss at the lab (not Wilkins) was apparently quite annoyed with Higgs that he didn’t want to work on DNA.) Higgs wrote a Kemmer obit for the University of Edinburgh bulletin. He had been at Edinburgh for a couple of years in the 1950s in a junior position before he returned for good in 1960 (I think).

If I recall correctly, as Peter tells the story, Sheldon Glashow (who Higgs had known since a Scottish Summer School (conference) in Physics, 1960, I think) told Higgs that if he were ever planning to be in the Northeast, Glashow would arrange for Peter to give a talk at Harvard on whatever he liked. Independently of Glashow, Dyson wrote Peter to give a talk on what is now famously the Higgs mechanism at IAS, and Peter called Glashow to say something like, “Well, I’m driving from Chapel Hill to Princeton, and I see that Cambridge is only another few hours, so…” and that led to Higgs giving pretty much the same talk at Harvard, a really important event. But if Dyson hadn’t asked Peter to come to Princeton, he would not have gone to Harvard.

[Thus the contingencies of history, always telling a fascinating tale, in this case of a concept that rocked the world of physics, and wouldn’t you know Freeman Dyson would be in the middle of it.- PG]

Food production on Mars: Dirt farming as the most scalable solution for settlement

Colonies on other worlds are a staple of science fiction and an obsession for rocket-obsessed entrepreneurs, but how do humans go about the business of living long-term once they get to a place like Mars? Alex Tolley has been pondering the question as part of a project he has been engaged in with the Interstellar Research Group. Martian regolith is, shall we say, a challenge, and the issue of perchlorates is only one of the factors that will make food production a major part of the planning and operation of any colony. The essay below can be complemented by Alex’s look at experimental techniques we can use long before colonization to consider crop growth in non-terrestrial situations. It will appear shortly on the IRG website, all part of the organization’s work on what its contributors call MaRMIE, the Martian Regolith Microbiome Inoculation Experiment.

by Alex Tolley

Introduction: Food Production Beyond Hydroponics

Conventional wisdom suggests that food production in the Martian settlements will likely be hydroponic. Centauri Dreams has an excellent post by Ioannis Kokkinidis on hydroponic food production on Mars, where he explains in some detail the issues and how they are best dealt with, and the benefits of this form of food production [1]

Still from a NASA video on a Mars base showing the hydroponics section.

A recent NASA short video on a very stylish possible design for a Mars base (see still above) shows a small hydroponics zone in the base, although its small size and what looks like all lettuce production would not be sufficient to feed one person, and that is before the monotonous diet would drive the crew to wish they had at least some potatoes from Mark Watney’s stash that could be cooked in a greater variety of ways.

I would tend to agree with the hydroponic approach, as well as other high-tech methods, as these food production techniques are already being used on Earth and will continue to improve, allowing a richer food source without needing to raise animals. Kokkinidis raises the issue of animal meat production for various cuisines, but in reality, the difficulties of transporting the needed large numbers of stock for breeding, as well as the increased demand for primary food production, would seem to be a major issue. [It should be noted that US farming occupies perhaps 2% of the population, yet most commentators on Mars groups seem to think that growing food on Mars will be relatively easy, with preferred animals to provide meat. How many Mars base personnel would be comfortable killing and preparing animals for consumption, even mucking out the pens?]

Hydroponics today is used for high-value crops because of the high costs. Many crops cannot be easily grown in this way. For example, it would be very difficult to grow tree fruits and nuts hydroponically, even though tree wood would be a very useful construction material. On Earth, hydroponics gains the highly desirable much-increased production per unit area coupled with a very high energy cost. It also requires inputs from established industrial processes which would have to be set up from scratch on Mars. Should there need to be lighting as well, low-energy LEDs would be hard to manufacture on Mars and would, initially at least, be imported from Earth.

Hydroponics is attractive to those with an engineering mindset. The equipment is understood, inputs and outputs can be measured and monitored, and optimized, and it all seems of a piece with the likely complexity of the transport ships and Mars base technology. It may even seem less likely to get “dirt under the fingernails” compared to traditional farming, a feature that appeals to those who prefer cleaner technologies. Unfortunately, unlike on Earth, if a critical piece of equipment fails, it will not be easily replaceable from inventory. Some parts may be 3D printable, but not complex components, or electronics. Failure of the hydroponic system due to an irreplaceable part failure would be catastrophic and lead to starvation long before a replacement would arrive from Earth. If ever there was a need for rapid cargo transport to support a Martian base, this need for rapid supply delivery would be a prime driver [4].

Soil from Regolith

Could more traditional dirt farming work on Mars, despite the apparent difficulties and lack of fine control over plant growth? The discovery that the Martian regolith has toxic levels of perchlorates and would make a very poor soil for plants seems to rule out dirt farming. If the Gobi desert is more hospitable than Mars, then trying to farm the sands of Mars might seem foolhardy, even reckless.

However, after working on a project with the Interstellar Research Group (IRG), I have to some extent changed my mind. If the Martian regolith can be made fertile, it would open up a more scalable and flexible method to grow a greater variety of plant crops than seems possible with hydroponics. Scaling up hydroponics requires far more manufacturing infrastructure than scaling up farming with an amended regolith if regolith remediation does not require a lot of equipment.

So the key questions are how to turn the regolith into viable soil to make such a traditional farming method viable, and what does this farming buy in terms of crop production, variety, and yields?

The first problem is to remove the up to 1% of perchlorates in the regolith that are toxic to plants. While perchlorates do exist naturally in some terrestrial soils, such as the Atacama desert, they are at far lower concentrations. Perchlorates are used in some industrial processes and products (e.g. rocket propellant, fireworks), and spills and their cleanup are monitored by the Environmental Protection Agency (EPA) in the USA. Chlorates were used as weedkillers and are potent oxidizers, a feature that I used in my teenage rocket experimentation, but are now banned in the EU.

There are 2 primary ways to remove perchlorates. If there is a readily available water supply, the regolith can be washed and the water-soluble perchlorates can be flushed away. The salt can be removed from the perchlorate solution with a reverse osmosis unit, a mature technology in use for desalination and water purification today. In addition, agitation of the regolith sand and dust can be used to remove the sharp edges of unweathered grains. This would make the regolith far safer to work with, and reduce equipment failure due to the abrasive dust damaging seals and metal joints. Agitation requires the low technology of rotating drums filled with a slurry of regolith and water.

A second, and more elegant approach, is to bioremediate with bacteria that can metabolize the regolith in the presence of water [5,6,7,8]. While it would seem simple to just sprinkle the exposed Martian surface with an inoculant, this cannot work, if only because the temperature on the surface is too cold. The regolith will have to be put into more clement conditions to maintain the water temperature and at least minimal atmospheric pressure and composition. At present, it is unknown what minimal conditions would be needed for this approach to work, although we can be fairly certain that terrestrial conditions inside a pressurized facility would be fine. There are a number of bacterial species that can metabolize chlorates and perchlorates to derive energy from ionized salts. A container or lined pit of graded regolith could be inoculated with suitable bacteria and the removal of the salt monitored until the regolith was essentially free of the salt. This would be the first stage of regolith remediation and soil preparation.

There is an interesting approach that could make this a dual-use system that offers safety features. The bacteria can be grown in a bioreactor, and the enzymes needed to metabolize perchlorates extracted. It has been proposed that rather than fully metabolizing the salt to chloride, enzymes could be applied that will stop at the release of free oxygen (O2). This can be used as life support or oxidant for rocket fuel, or even combustion engines on ground vehicles. The enzymes could be manufactured by gene-engineered single-cell organisms in a bioreactor, or the organisms can be applied directly to the regolith to release the O2 [10]. The design of the Spacecoach by my colleague, Brian McConnell, and me used a similar principle. As the ship used water for propellant and hull shielding, in the case of an emergency, the water could be electrolyzed to provide life-supporting O2 for a considerable time to allow for rescue [9]. Extracting oxygen from the perchlorates with enzymes is a low-energy approach to providing life support in an emergency. A small, portable, emergency kit containing a plastic bag and vial of the enzyme, could be carried with a spacesuit, or larger kits for vehicles and habitat structures.

After the perchlorate is removed from the regolith, what is left is similar to broken and pulverized lava. It may still be abrasive, and need to be abraded by agitation as in the mechanical perchlorate flushing approach.

So far so good. It looks like the perchlorate problem is solved, we just need to know if it can be carried out under conditions closer to Martian surface conditions, or whether it is best to do the processing under terrestrial or Mars base conditions. If the bacterial/enzyme amendment can be done in nothing more than lined and covered pits, or plastic bags, with a heater to maintain water at an optimum temperature, that would be a plus for scalability. If the base is located in or near a lava tube, then the pressurized tube might well provide a lot of space to process the regolith at scale.

Like lunar regolith, it has been established that perchlorate-free regolith is a poor medium for plant growth. Experiments on Mars Regolith Simulant (MRS) under terrestrial conditions of temperature, atmospheric composition, and pressure, indicate that the MRS needs to be amended to be more like a terrestrial soil. This requires nutrients, and ideally, structural organic carbon. If just removing the perchlorates, adding nutrients, and perhaps water-retaining carbon was all that was needed, this might not be too dissimilar to a hydroponic system using the regolith as a substrate. But this is really only part of the story in making fertile soil.

Nitrogen in the form of readily soluble nitrates can be manufactured on Mars chemically, using the 1% of N2 in the atmosphere. It is also possible nitrogen rich minerals on Mars may be found too. Phosphorus is the next most important macronutrient. This requires extraction from the rocks, although it is possible that phosphorus-rich sediments also may be found on Mars.

To generate the organic carbon content in the regolith, the best approach is to grow a cover crop and then use that as the organic carbon source. Fungal and bacterial decomposition, as well as worms, decompose the plants to create humus to build soil. Vermiculture to breed worms is simple given plant waste to feed on, and worm waste makes a very good fertilizer for plants. Already we see that more organisms are going to have to be brought from Earth to ensure that decomposition processes are available. In reality, healthy terrestrial soils have many thousands of different species, ranging in size from bacteria to worms, and ideally, various terrestrial soils would be brought from Earth to determine which would make the best starting cultures to turn the remediated regolith into a soil suitable for growing crops.

Ioannis Kokkinidis indicated that Martian light levels are about the same as a cloudy European day. Optimum growth for many crops needs higher intensity light, as terrestrial experiments have shown that for most plants, increasing the light intensity to Earth levels is one of the most important variables for plant growth. This could be supplied by LED illumination or using reflective surfaces to direct more sunlight into the greenhouse or below-ground agricultural area.

One issue is surface radiation from UV and ionizing radiation. This has usually resulted in suggestions to locate crops below ground, using the surface regolith as a shield. This may not be necessary as a pressurized greenhouse with exposure to the negligible pressure of Mars’ atmosphere, could support considerable mass on its roof to act as a shield. At just 5 lbs/sq.in, a column of water or ice 10 meters thick could be supported. It would be fairly transparent and therefore allow the direct use of sunlight to promote growth, supplemented by another illumination method.

Soil is not a simple system, and terrestrial soils are rich ecosystems of organisms, from bacteria, fungi, and many phyla of small animals, as well as worms. These organisms help stabilize the ecosystem and improve plant productivity. Bacteria release antibiotics and fungi provide the communication and control system to ensure the bacterial balance is maintained and provide important growth coordination compounds to the plants through their roots. The animals feed on the detritus, and the worms also create aeration to ensure that O2 reaches the animals and aerobic fungi and bacteria.

Most high-yield, agricultural production destroys soil structure and its ecosystems. The application of artificial fertilizers, herbicides to kill weeds, and pesticides to kill insect predators, will reduce the soil to a lifeless, mineral, reverting it back to its condition before it became soil. The soil becomes a mechanical support structure, requiring added nutrients to support growth.

Some farmers are trying new ideas, some based on earlier farming methods, to restore the fertility of even poor soils. This requires careful planting schedules, maintenance of cover crops, and even no-tilling techniques that emulate natural systems. Polyculture is an important technique for reducing insect pests. Combined, these techniques can remediate poor soils, eliminate fertilizers and agricultural chemicals, improve farm profitability, and even result in higher net yields than current farm practices. [11]

Without access to industrial production of agricultural chemicals and nutrients, these experimental farming practices will need to be honed until they work on Mars.

Given we have regolith-based soil what sort of crops can be grown? Almost any terrestrial crop as long as the soil conditions, drainage, pH, and illumination can be maintained.

Unlike on Earth where crops are grown where the conditions are already best, on Mars, it might well be that the crops grown will be part of a succession of crops as the soil improves. For example, in arid regions, millet is a good crop to grow with limited water and nutrients as it grows very easily under poor conditions. Ground cover plants to provide carbon and that fix nitrogen might well be a rotation crop to start and maintain the soil amendment. As the soil improves, the grains can be increased to include wheat and maize, as well as barley. With sufficient water, rice could be grown. None of these crops require pollinators, just some air circulation to ensure pollination.

For proteins, legumes and soy can be grown. These will need pollinating, and it might well be worth maintaining a greenhouse that can include bees. Keeping this greenhouse isolated will prevent bees from escaping into the base. As most of our foods require insect pollination, root crops like potatoes, carrots, and turnips, can be grown, as well as leafy greens like lettuce, and cabbage. The pièce de résistance that dirt farming allows is tree crops. A wide variety of fruit and nuts can be grown. Pomegranates are particularly suited to arid conditions. The leaf litter from such deciduous trees will be further input to improve the soil.

So the soil derived from regolith should allow a wider variety of crops to be grown, and with this, the possible variety of cuisine dishes can be supported. Food is an important component of human enjoyment, and the variety will help to keep morale high, as well as provide an outlet for prospective cooks and foodies.

Are there other benefits? As any gardener knows, growing food in the dirt is less time-consuming than hydroponics as the system is more stable, self-correcting, and resilient. This should allow for more time to be spent on other tasks than constantly maintaining a hydroponic system, where a breakdown must be fixed quickly to prevent a loss.

Meat production is beyond the scope of this essay. I doubt it will be of much importance for two main reasons. Meat production is a very inefficient use of energy. It is far better to eat plants directly, rather than convert them to meat and lose most of the captured energy. The second is the difficulty of transporting the initial stocks of animals from Earth. The easiest is to bring the eggs of cold-blooded animals (poikilotherms) and hatch them on Mars. Invertebrates and perhaps fish will be the animals to bring for food. If you can manage to feed rodents like rabbits on the ship, then rabbits would be possible. But sheep, goats, and cows are really out of the question. A million-resident city might best create factory meat from the crops if the needed ingredients can be imported or locally manufactured. My guess is that most Mars settlers will be Vegetarian or Vegan, with the few flexitarians enjoying the occasional fish or shrimp-based meal.

If you have read this far, it should be obvious that dirt farming sustainably, is not simple, nor is it easy or quick. A transport ship carrying settlers to Mars will have to supply food to eat until the first food crops can be grown. That food will likely be some variant of the freeze-dried, packaged food eaten by astronauts. Hopefully, it will taste a lot better. The fastest way to grow food crops will be hydroponics. All the kit and equipment will have to be brought from Earth. With luck, this system will reduce the demand for packaged food and become fairly sustainable, although nutrients will have to be supplied, nitrogen in particular. I don’t see sacks of nitrogen fertilizer being brought down to the surface, but instead, there may be a chemical reactor to extract the nitrogen in the Martian air and either create ammonia or nitrates for the hydroponic system.

But if the intention, as Musk aims, is to make Mars a second home, starting with 1 million residents, the size of the population that is large enough to provide the skills for modern civilization, then food production is going to need to be far more extensive than a hydroponics system in every dome or lava tube. The best way is to grow the soil as discussed above. This will not be quick and may take years before the first amended regolith becomes rich loamy, fertile soil. The sterile conditions on Mars mean that there will be no free ecosystem services. Every life form will have to originate on Earth and be transported to Mars. But life replicates, and this replication is key to success in the long term. There will be a mixture of biodiverse allotments and tracts of large-scale arable farming. Without some new technology to deflect ionizing radiation, the Martian sunlight will probably need to be indirect and directed to the crops protected by mass shields. Every square meter of Martian sunlight will only be able to support ½ a square meter of crops, so there may need to be an industry manufacturing polished metal mirrors to collect the sunlight and redirect it.

Single-cells for artificial food

Although our sensibilities suggest that the Martian settlers will want real food grown from recognizable food crops, this may be a false assumption. In the movie 2001: A Space Odyssey, Kubrick ignored Clarke’s description in his novel of how food was provided and eaten, with the almost humorous showing of liquid foods with flavors served to Heywood Floyd on his trip to the Moon.

Still from the movie 2001: A Space Odyssey. The flight attendant (Penny Brahms) is bringing the flavored, liquid food trays to the passenger and crew.

Because the Moon does not have terrestrial day-night cycles, the food was single-celled and likely grown in vats, then processed to taste like the foods they were substituting for.

Michaels: Anybody hungry?
Floyd: What have we got?
Michaels: You name it.
Floyd: What’s that, chicken?
Michaels: Something like that.
Michaels: Tastes the same anyway.
Halvorsen: Got any ham?
Michaels: Ham, ham, ham..there, that’s it.
Floyd: Looks pretty good
Michaels: They are getting better at it all the time.

Still from the movie 2001: A Space Odyssey. Floyd and the Clavius Base personnel select sandwiches made from processed algae. Above is the conversation Floyd (William Sylvester) has with Halvorsen (Robert Beatty) and Michaels (Sean Sullivan) on the moon bus on his way to TMA1.

This is where food technology is currently taking us.

Single-cell protein has been available since at least the 18th century with edible yeast. Marmite or Vegemite is a savory, yeast-based, food spread that is an acquired taste. Today there is revived interest in various forms of SCP, some of which are commercially available for consumers, such as Quorn made from the micro-fungus, Fusarium venenatum. The advantage of single cells is that the replication rate is so high that the raw output of bacterial cells can be more than doubled daily. The technology, at least on Earth, could literally reduce huge tracts of agricultural land use, especially of meat animals. However, it does require all the inputs that hydroponic systems require, and further processing to turn the cells into palatable foods including simulated meats. Should such single-cell food production become the basic way to ensure adequate calories and food types for settlers, I suspect that real food will be as desirable as it was for Sol Roth and Detective Thorn in Soylent Green.

Still from the movie Soylent Green. Sol Roth (Edward G. Robinson) bites into an apple, stolen by Detective Thorn (Charlton Heston), that he hasn’t tasted in many years since terrestrial farming collapsed.

Physical and Mental Health with Soil

However, even if single-cell bioreactors, food manufacturing, and hydroponics do become the main methods of providing food, that does not mean that creating fertile soils from the regolith is a waste of effort. Surrounded by the ochres of the Martian landscape, the desire to see green and vegetation may be very important for mental health. Soils will be wanted to grow plants to create green spaces, perhaps as lavish as that in Singapore’s Changi Airport. Seeds brought from Earth are a low-mass cargo that can exploit local atoms to create lush landscaping for the interior of a settlement.

Changi Airport, Singapore. A luxurious and restful interior space of tropical plants and trees.

There is a tendency to see life on Mars not just as a blank canvas to start afresh, but also as a sterile world free of diseases and other biological problems associated with Earth. Asimov’s Elijah Bailey stories depicted “germ-free” Spacers as healthier and far longer-lived than Earthmen In their enclosed cities. We now know that our bodies contain more bacterial cells than our mammalian cells. We cannot live well without this microbiome that helps us withstand disease, digest our foods, and even influence our brain development. There is even a suggestion that children that have not been exposed to dirt become more prone to allergies later in life. Studies have shown that most animals have a microbiome with varying numbers of bacterial species. As Mars is sterile, at least as regards a rich terrestrial biosphere, it might well make sense to “terraform” it at least within the settlement cities. Creating soils that will become reservoirs for bacteria, fungi, and a host of other animal species will aid human survival and may become a useful source of biological material for the settlers’ biotechnology.

If Mars is to become a second home for humanity, it will need more people than the villages and small towns that the historical migrants to new lands create. The needed skills to make and repair things are vastly larger than they were less than two centuries ago. Technology is no longer limited to artisans like carpenters, wheelwrights, and blacksmiths, with more complex technology imported from the industrial nations. Now technologies depend on myriad specialty suppliers and capital-intensive factories. Mars will need to replicate much of this in time, which requires a large population with the needed skills. A million people might be a bare minimum, with orders more needed to be largely self-sufficient if the population is to be the backup for a possible future extinction event on Earth. Low-mass, high-value, and difficult-to-manufacture items will continue to be imported, but much else will best be manufactured locally, with a range of techniques that will include advanced additive printing. But some technologies may remain simple, like the age-old fermentation vats and stills. After all, how else will the settlers make beer and liquor for partying on Saturday nights?


Kokkinidis, I (2016) “Agriculture on Other Worlds” https://www.centauri-dreams.org/2016/03/11/agriculture-on-other-worlds/

Kokkinidis, I (2016) “Towards Producing Food in Space: ESA’s MELiSSA and NASA’s VEGGIE”

Kokkinidis, I (2017) “Agricultural Resources Beyond the Earth” https://www.centauri-dreams.org/2017/02/03/agricultural-resources-beyond-the-earth/

Higgins, A (2022) “Laser Thermal Propulsion for Rapid Transit to Mars: Part 1”

Balk, M. (2008) “(Per)chlorate Reduction by the Thermophilic Bacterium Moorella perchloratireducens sp. nov., Isolated from Underground Gas Storage” Applied and Environmental Microbiology, Jan. 2008, p. 403–409 Vol. 74, No. 2

Coates J.D., Achenbach, L.A. (2004) “Microbial Perchlorate Reduction: Rocket-Fueled Metabolism”, Nature Reviews | Microbiology Volume 2 | July 2004 | 569

Hatzinger P.B. &2005) , “Perchlorate Biodegradation
for Water Treatment Biological reactors”, 240A Environmental Science & Technology / June 1, 2005 American Chemical Society

Kasiviswanathan P, Swanner Ed, Halverson LJ, Vijayapalani P (2022) “Farming on Mars: Treatment of basaltic regolith soil and briny water simulants sustains plant growth.” PLoS ONE 17(8): e0272209.

Gilster, P “Spacecoach: Toward a Deep Space Infrastructure“, https://www.centauri-dreams.org/2016/06/28/spacecoach-toward-a-deep-space-infrastructure/

Davila A.F. et all (2013) “Perchlorate on Mars: a chemical hazard and a resource for humans” International Journal of Astrobiology 12 (4): 321–325 (2013)

Monbiot, G. (2022) Regenesis: Feeding the World Without Devouring the Planet Penguin ISBN: 9780143135968

The Ethics of Directed Panspermia

Interstellar flight poses no shortage of ethical questions. How to proceed if an intelligent species is discovered is a classic. If the species is primitive in terms of technology, do we announce ourselves to it, or observe from a distance, following some version of Star Trek’s Prime Directive? One way into such issues is to ask how we would like to be treated ourselves if, say, a Type II civilization – stunningly more powerful than our own – were to show up entering the Solar System.

Even more theoretical, though, is the question of panspermia, and in particular the idea of propagating life by making panspermia a matter of policy. Directed panspermia, as we saw in the last post, is the idea of using technology to spread life deliberately, something that is not currently within our power but can be reasonably extrapolated as one path humans might choose within a century or two. The key question is why we would do this, and on the broadest level, the answer takes in what seems to be an all but universal assumption, that life in itself is good.

Image: Can life be spread by comets? Comet 2I/Borisov is only the second interstellar object known to have passed through our Solar System, but presumably there are vast numbers of such objects moving between the stars. In this image taken by the NASA/ESA Hubble Space Telescope, the comet appears in front of a distant background spiral galaxy (2MASX J10500165-0152029, also known as PGC 32442). The galaxy’s bright central core is smeared in the image because Hubble was tracking the comet. Borisov was approximately 326 million kilometres from Earth in this exposure. Its tail of ejected dust streaks off to the upper right. Credit: ESA/Hubble.

How Common is Life?

Let’s explore how this assumption plays out when weighed against the problems that directed panspermia could trigger. I turn to Christopher McKay, Paul Davies and Simon Worden, whose paper in the just published collection Interstellar Objects in Our Solar System examines the use of interstellar comets to spread life in the cosmos. An entry point into the issue is the fi factor in the Drake Equation, which yields the fraction of planets on which life appears.

We need to know whether life is present in any system to which we might send a probe to seed new life forms – major problems of contamination obviously arise and must be avoided. If we assume a galaxy crowded with life, we would not send such missions. Directed panspermia becomes an issue only when we are dealing with planets devoid of life. To the objection that everything seems to favor life elsewhere because we couldn’t possibly live in the only place in the universe where life exists, the answer must be that we have no understanding of how life began. Abiogenesis remains a mystery and the cosmos may indeed be empty.

We live in the fascinating window of time in which our civilization will begin to get answers on this, particularly as we probe into biomarkers in exoplanet atmospheres and conceivably discover other forms of life in venues like the gas giant moons. But we don’t have such answers yet, and it is sensible to point out, as the authors do, that the Principle of Mediocrity, which suggests that there is nothing special about our Solar System or Earth itself, is a philosophical argument, not one that has been proven by science. We have no idea if there is life elsewhere, even if many of us hope it is there.

Protecting existing life is paramount, and the authors point to the planetary protection issues we face in terraforming Mars, the latter being a local kind of directed panspermia. They cite the basic principle: “…planetary protection would dictate that life forms should not be introduced, either in a directed mode or through random processes, to any planet which already has life.”

I like the way McKay, Davies and Worden present these issues. In particular, assuming we picked out a likely planet in the habitable zone of its star, would there ever be a way to demonstrate that life does not exist on it? The answer is thorny, it being impossible to prove a negative. This gives rise to the possibilities the authors consider when evaluating whether directed panspermia could be used. From the paper:

1. Life might exist on a target planet in low abundance and be snuffed out by seeding.

2. Alien life might be abundant on a planet but present unfamiliar biosignatures yielding a false negative.

3. A comet might successfully seed a barren target planet but go on to contaminate others that already host life, either in the same planetary system or another. The long-term trajectory of a comet is almost impossible to predict.

4. Even if terrestrial life does not directly engage with alien life, it may be more successful in appropriating resources, thus driving indigenous biota to extinction by starvation

There are ways around these issues. Snuffing out life would not be likely if we seeded a protoplanetary disk rather than a fully formed world, which would also remove objection 2, for there would be no biosignatures to be had. A planet that turns out not to be barren might be saved from our seeding efforts by using some kind of ‘kill switch’ that is available to destroy the inoculated life. But all these issues loom large, so large that directed panspermia collapses unless we establish that numerous habitable but lifeless worlds do exist. If life is vanishingly rare, then a kind of galactic altruism can be invoked, seeing our species as gifted with the chance to spread life in the galaxy.

Off on a Comet

All this is dependent on advances in exoplanet characterization and research into life’s origins on Earth, but the questions are worth asking because we may, relatively soon as civilizations go, begin to learn tentative answers. It seems natural that the authors would turn to interstellar comets as a delivery vehicle of choice. Here’s a passage from the paper, examining how spores from a directed panspermia effort could be spread through passing comets by the injection of a biological inoculum into comets whose trajectories are hyperbolic or could otherwise be modified. Such objects need not impact another planet but could be effective simply passing through their stellar system:

These small particles are subsequently shed as the comet passes through systems that have, or will form into, suitable planets, such as protostellar molecular clouds, planet-forming nebulae around stars, and recently formed planetary systems. The comets themselves are unlikely to be gravitationally captured or collide as they move through star systems… but the small dust particles released by the comet—as observed in 2I/Borisov—will be captured. Particles measuring a few 10s to 100s microns in radius are large enough to hold many microorganisms but small enough to enter a planetary atmosphere without significant heating.

Image: This artist’s impression shows the first interstellar object discovered in the Solar System, `Oumuamua. Note the outgassing the artist inserts into the image as a subtle cloud being ejected from the side of the object facing the Sun. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser.

The focus on comets is natural in the era of ‘Oumuamua and 2I/Borisov, and the expectation is widespread that we will be learning of interstellar objects in huge numbers moving through the Solar System as we expand our observing efforts. Why not hitch a ride? There is every expectation that the inoculum injected into a comet could survive the journey, to one day settle into a planetary atmosphere. Thus:

One meter of ice reduces the radiation dose by about five orders of magnitude… In a water-rich interstellar comet, internal radiation from long-lived radioactive elements (U, Th, K) would be expected to be less than crustal levels on the Earth. In such an environment, known terrestrial organisms might remain viable for tens to hundreds of millions of years. We can also take into account advances in gene editing and related technologies that might enable psychrophiles, which are able to very slowly metabolize and repair genetic damage at temperatures as low as-40°C…, to ‘‘tick over,” although slowly, at still lower temperatures. That would enable them to remain viable for even longer durations.

The time scales for delivering an inoculum to an exoplanet are mind-boggling, on the order of 105 to 106 years just to pass near another stellar system. The authors point out that given the hyperbolic velocity of 2I/Borisov, it would take the comet approximately 40,000 years to travel the distance to Alpha Centauri, and 500 million years to travel the distance of the Milky Way’s radius. Indeed, the most likely previous encounter of ‘Oumuamua with another star occurred 1 million years ago.

Perhaps orbital interventions when seeding the comet could alter its trajectory toward specific stars, to avoid the random nature of the seeding program. And I think they would be necessary: Random trajectories might well take our comet into stellar systems with living worlds that we know nothing about. Thus the authors’ point #3 above.

The Rhythms of Panspermia

Clearly, directed panspermia by interstellar comet is for the patient at heart. And as far as I can see, it’s also something a civilization would do completely out of philosophical or altruistic motives, for there is no conceivable return from mounting such an effort beyond the satisfaction of having done it. I often address questions of value that extend beyond individual lifetimes, but here we are talking about not just individual but civilizational lifetimes. Is there anything in human culture that suggests an adherence to this kind of ultra long-range altruism? It’s a question I continue to mull over on my walks. I’d also appreciate pointers to science fiction treatments of this question.

There is an interesting candidate for directed panspermia close to the Sun: Epsilon Eridani. Here we have a youthful system, thought to be less than a billion years old, with two debris belts and two planets thus far discovered, one a gas giant, the other a sub-Neptune. If there is a terrestrial-class world in the habitable zone here, it would be a potential target for a life-bearing mission. So too might a Titan-class world, which raises the interesting question of whether different types of habitability should be considered. We may well find exotic life not just on Titan but also under the ice of Europa, giving us three starkly different possibilities. Would a directed panspermia effort be restricted to terrestrial class worlds like Earth?

Whatever our ethical concerns may be, directed panspermia is technologically feasible for a civilization advanced enough to manipulate comets, and thus we come back to the possibility, discussed decades ago by Francis Crick and Leslie Orgel, that our own Solar System may have been seeded for life by another civilization. If this is true, we might find evidence of complex biological materials in comet dust. We would also, as the authors point out, expect life to be phylogenetically related throughout the Solar System, whether under Europan ice or on the surface of Mars or indeed Earth.

Always complicating such discussions is the possibility of natural panspermia establishing life widely through ejecta from early impacts, so we are in complex chains of causation here. We’re also in the dense thicket of human ethics and aspiration. Let’s assume, as the authors do, that directed panspermia is out for any world that already has life. But if life is truly rare, would humanity have the sense of obligation to embark on a program whose results would never be visible to its creators? We cherish life, but where do we find the imperative to spread it into a barren cosmos?

I’ll close with a lengthy passage from Olaf Stapledon, a frequent touchstone of mine, who discussed “the forlorn task of disseminating among the stars the seeds of a new humanity” in Last and First Men (1930):

For this purpose we shall make use of the pressure of radiation from the sun, and chiefly the extravagantly potent radiation that will later be available. We are hoping to devise extremely minute electro-magnetic “wave-systems,” akin to normal protons and electrons, which will be individually capable of sailing forward upon the hurricane of solar radiation at a speed not wholly incomparable with the speed of light itself. This is a difficult task. But, further, these units must be so cunningly inter-related that, in favourable conditions, they may tend to combine to form spores of life, and to develop, not indeed into human beings, but into lowly organisms with a definite evolutionary bias toward the essentials of human nature. These objects we shall project from beyond our atmosphere in immense quantities at certain points of our planet’s orbit, so that solar radiation may carry them toward the most promising regions of the galaxy. The chance that any of them will survive to reach their destination is small, and still smaller the chance that any of them will find a suitable environment. But if any of this human seed should fall upon good ground, it will embark, we hope, upon a somewhat rapid biological evolution, and produce in due season whatever complex organic forms are possible in its environment. It will have a very real physiological bias toward the evolution of intelligence. Indeed it will have a much greater bias in that direction than occurred on the Earth in those sub-vital atomic groupings from which terrestrial life eventually sprang.

The paper is McKay, Davies & Worden, “Directed Panspermia Using Interstellar Comets,” Astrobiology Vol. 22 No. 12 (6 December 2022), 1443-1451. Full text.


In Person or Proxy to Mars and Beyond?

Larry Klaes is well known in these parts for his extraordinary reviews of classic science fiction films. Today, however, he steps back from cinema to consider how we will expand into space. The crews on our deep space missions will doubtless be a lot different than some of those old black-and-white movies would suggest. Just how will our species adapt to the environments it will soon be exploring? There’s nothing quite so lush as our own blue and green planet, yet the imperative to move ever outward is a driver for our species. Mars is a case in point, but the long-range picture is that we’re looking off-planet and already pondering destinations beyond the Solar System. Re-shaping our expectations will be a part of what drives the scientists and engineers who equip us for the next steps. An earlier version of this essay was published by The Mars Society.

by Larry Klaes

In 1972, singer, pianist, and composer Sir Elton Hercules John (born 1947) released a song titled “Rocket Man”. This piece, which was inspired by a Ray Bradbury (1920-2012) science fiction story of the same name, has an individual who sees his job in outer space not as some grand adventure as one might expect of a typical astronaut, but rather as ordinary and isolating.

Not only does this Rocket Man miss Earth and his wife living there, declaring “it’s lonely out in space,” he also says that “Mars ain’t the kind of place to raise your kids/In fact it’s cold as hell/And there’s no one there to raise them/If you did.”

As a life-long space and astronomy enthusiast, when I first became aware of this song, I was highly disappointed with its message. “Rocket Man” was a definite reflection of the counterculture era, where many rejected what they saw as the militant flaws and antiquated traditions of society which held back all but a select privileged few.

The space program fell into that category, being seen as a vehicle of a predominantly white male military-industrial complex. That it was also so publicly prominent in the news and entertainment media only made it an even easier target for criticism, in particular the kind that asked why we were spending money on sending humans to the Moon when there were so many problems on Earth that needed fixing first.

Even as a kid I knew this was an “apples and oranges” situation. The National Aeronautics and Space Administration, or NASA, was funded far less than most other government agencies of that era, a status that remains to the present day. Diverting all its resources to social agendas would have been a temporary band aid at best, not a real solution to modern civilization’s myriad of problems.

Image: A future Mars settlement as envisioned by SpaceX. Is this how humanity will live on other worlds, or will something else be required?

Nevertheless, the general public which had supported the early bold declaration of “sending a man to the Moon and returning him safely to the Earth” within ten years had undergone a sea change by the time NASA was actually placing astronauts on our planet’s nearest celestial neighbor at the end of the 1960s and into the early 1970s.

I had grown up in that era of the early Space Age when humans were actively circling Earth in preparation for launching representatives of our species to land on the Moon while robotic probes had begun to reveal other worlds such as Venus and Mars. I bought into the future storyline of the 1968 film 2001: A Space Odyssey and all those other pro-space entertainment media so prevalent then that humanity would almost automatically spread out and colonize first the Moon and then the other places in our Sol system, before moving on into the wider Milky Way galaxy.

I did not pay much attention to the geopolitical and social forces driving and affecting the space programs then, not just because I wasn’t able to fully comprehend them as a naive kid, but also because I felt they were only temporary issues, ones humanity would conquer as easily and rightly as we were doing with our move into outer space. After all, didn’t Star Trek show a future just a few centuries from now where all of humanity was united, we were flying about the galaxy in fancy starships, and dealing with new alien neighbors as part of a collective called the United Federation of Planets (UFP)?

So, when I heard Elton John warbling a very popular tune that said the starry realm was unpleasant, lonely, and not something good for bringing up children in, I was concerned his words would only add fuel to the fire that was already setting back our “manifest destiny” in the Final Frontier in the beginning of the 1970s.

The Apollo lunar program was already being defunded after the seventeenth mission, which in turn was killing off any plans for manned lunar colonies. The logical promise of sending humans on to the planet Mars after the success of Apollo – as soon as the 1980s it was being declared in certain circles – was also placed on a shelf. No one was saying such missions were being canceled, but it was pretty obvious that no one at NASA was seriously working on such an adventure by then, nor would they be any time soon.

Many in the West thought that America’s superpower rival, the Soviet Union, would pick up the gauntlet we had dropped: Soon there would be cosmonaut bootprints on the Moon and Mars as they went on to become the dominant society throughout the Sol system and beyond.

Since then, a lot has changed. The American manned space program is not only picking up again, with real plans to settle the Moon with a new generation of astronauts in this decade as well as send these explorers on to Mars in the 2030s. There is also a new Space Race of a kind, this time mainly with China. Upon jumping into this race with their first successful satellite launch in 1970, the “People’s Republic” now has a second crewed space station circling Earth while simultaneously conducting automated rover and sample return missions to the Moon and their first wheeled explorer conducting science on the Red Planet.

My attitude and views on our ventures into the Final Frontier have also changed over the decades. I am still quite the space supporter, but I am seeing it now as happening in certain different ways, in particular how we should venture into the void directly with fellow human beings.

When I used to read and hear certain professionals, whom I automatically assumed should have been big supporters of manned space exploration and settlement, publicly state that robots were better for exploring the cosmic void than human beings, I was indignant. They were going against the virtually predestined vision for our species expansion into the Milky Way galaxy and all those other stellar islands out there. Humans had to be an integral part of this future, otherwise our species and society would end up either stagnating or outright destroying itself in the very nest of its birth. No one in their right mind would keep a child in their crib and expect them to develop properly otherwise.

What needs to be understood is that when the Space Age began in the 1950s (or the 1940s if you want to count the first rockets that breached the actual realm, if only briefly), humans were almost always the foremost choice for conducting all kinds of expeditions, be it on Earth’s surface, at sea, or in the skies. Space would have been no different.

Yes, there were many satellites that went up carrying no living organic beings at all, but their mechanisms and computer “brains” were primitive by current standards. For example, Mariner 2, the first probe to successfully explore the planet Venus in late 1962, contained a computer weighing just over eleven pounds that was capable of “a total of 11 real-time commands and a spare… along with a stored set of 3 onboard commands which could be modified,” according to Oran W. Nicks, then Director of Lunar and Planetary Programs for NASA, as he described in his wonderfully written book Far Travelers: The Exploring Machines (NASA SP-480, 1985).

Even the twin Voyager space probes, designed, built, and launched into the outer Sol system on much more complex missions over one decade after Mariner 2, had multiple computers that were still less powerful than a modern day automobile key fob. The onboard computers that helped land astronauts on the Moon with Apollo weighed over 75 pounds and had only 1,600 bits of memory in them, and they were specially designed by experts at the Massachusetts Institute of Technology (MIT).

On Earth, up until the first personal computers began showing up in large numbers in the 1970s, the majority of “thinking” machines were bulky, heavy, and most often required trained specialists to operate them. So it is easy to see why most people back then assumed the best “computer” to explore outer space was the four pounds of “gray matter” occupying the skull of a functioning and properly educated adult human.

This technology has certainly changed since the first two decades of the Space Age. The average person now routinely works and plays with lightweight computers possessing storage levels and functionalities that would have been pure science fiction to their parents and grandparents. The machines currently exploring the Moon and Mars have autonomous capabilities that allow them to independently run their own missions while also being smart enough to avoid potential hazards in these alien environments.

As one may easily imagine, computing and robotic technologies for space are only going to improve in the coming decades to the point that one may rightly question the purpose of sending humans to distant worlds when much more durable and far less expensive and resource-demanding robots equipped with sophisticated Artificial Intelligence (AI) minds could do the same tasks.

Deadly Rays and Dwellings

Fewer resources and relatively cheaper funding aren’t the only reasons for sending machines over humans to explore other worlds. The cosmic environment beyond Earth is quite hazardous indeed for a species that has spent its entire existence evolving on a planet that is a virtual paradise for our biology compared to every other place in our Sol system (and who knows how far beyond).

Mars has often been considered the world closest in comparison to Earth, yet even the least harsh places on the Red Planet make Antarctica look like a tropical island. Possessing only a very thin atmosphere composed mostly of carbon dioxide and no appreciable ozone layer or magnetic field, Mars is constantly bombarded by high levels of radiation from solar subatomic particles and cosmic rays. Solar ultraviolet rays also reach the Red Planet’s surface unabated. Meteoroids of most sizes are not deterred by the Martian air as they would be on Earth. Orbiting probes have imaged multiple results of recent impacts and the rovers have found substantiated meteorites as they roam their rather narrow swaths of the Martian landscape.

For Martian settlers to survive all these dangers, they would need to either develop structures with heavily reinforced radiation-proof roofs, cover their settlement with local regolith, or bury their dwellings deep underground. In most of these cases, unless humanity develops a type of transparent radiation shielding, the human residents will have to live without a direct view or easy access of their new homeworld.

Can humans stand being in an artificial environment underground on Mars for decades or even their entire lives? Down the road, settlements may be made large and luxurious enough to recreate the nature found on Earth, but the early pioneers will probably not be so fortunate. Will they last long enough psychologically to establish a permanent residence on Mars?

It is easy for those of us who are living now in the relative comfort and safety of Sol 3 to assume that those first settlers on our planetary neighbor can “tough it out” like the pioneers of the olden days did, but those ancestors who sought a new life did so on a world they were already adapted to physiologically. Martian settlers will require a great deal of preparation and mechanical services just to keep the climate of the Red Planet from outright killing them within minutes if they are ever exposed to the raw environment. Running back to Earth in the event of a disaster is not a quick option.

Terrestrial explorers and settlers also did not need to worry about dealing with the effects of a lesser gravity, for the pull of the mass of Mars for anyone on its surface is only 38 percent that experienced by those living on Earth. Not only will this eventually weaken those first settlers and their descendants, but it may create unexpected health issues and affect the way humans gestate in a mother’s womb and how they are born.

Our natural satellite has even less gravity and protection from the celestial threats already mentioned. There too settlers will have to live underground and deal with the same situations as their Martian brethren. The other nearby worlds with solid surfaces such as Venus, Mercury, and the Galilean satellites also have their own unique challenges in addition to all those just described.

Circling Earth in Tin Cans

Human beings have been launching representatives of their species into the Final Frontier for just over six decades now. Yet outside of those handful of brief jaunts to the Moon now fifty-plus years ago, astronauts and cosmonauts have only experienced space directly in their biggest habitat as temporary residents of various space stations in perpetual fall around Earth, where their stays currently last between six months to one year.

Unlike those space explorers going to Mars, those in Low Earth Orbit (LEO) are but a matter of hours away from rescue and safety in the event of an emergency. This also applies to the ability to resupply the residents of a space station. These facts will have a definite impact on our first venturers who will be months to years away from any kind of help from Earth.

Space is Not a Convenient Species Safety Valve

One thing we cannot count on space serving us any time soon is as a method of reducing the overpopulation of humans on Earth, which at this moment is approaching eight billion individuals. The exodus numbers required to start alleviating the environmental pressure in that direction are not going to happen in the foreseeable future, assuming reducing the human population ever even becomes a goal in the first place. Besides, we cannot just “displace” a fraction of our species without serious preparation first and this will only loop us back to the issues I have already addressed, the ones that will decide whether we can permanently settle space or not.

Of course, none of these obstacles may deter those individuals, organizations, and nations who are determined to live off Earth despite the various costs. One may easily envision the super wealthy constructing their own space habitats in what might be considered the ultimate gated community. Others may turn a hollowed out planetoid or comet into a WorldShip, or multigenerational space ark, and head off into the wider galaxy with their chosen acolytes, their fates left entirely in their hands.

Should space become profitable, corporations will most certainly start moving humans and machines out there. Will conditions for such laborers be better than on Earth, or will it be a case of the old phrase ‘the same day, just a different song?’ While more robots and other artificial devices will be required to literally mine the Final Frontier, corporations may still find humans to be overall much cheaper to utilize to collect resources and maintain the various services envisioned in space. This would also include the costs of replacing such laborers when the situation calls for it.

Adapting Ourselves to the Reality

As we are such small creatures compared to the vastness of space and its many wild and dangerous environments, would it perhaps make more sense to change ourselves rather than try to make other worlds more like Earth?

Terraforming Mars, Venus, and even the Moon have been suggested for roughly a century now as a way for humanity to expand to the stars, but would it work? At the least it may take centuries or more to convert an entire planet into one resembling what we have now. One aspect we may not be able to change that could affect such a project is that except for Venus, the other worlds will continue to have less mass than Earth.

Now imagine beings who could live and work directly in outer space, or on any number of moons and planetary bodies without the need for special suits and gear. It will very likely be easier, cheaper, and quicker to adapt humans to other places via bioengineering and cyborg technologies than try to change an entire world to suit our physiological needs. These adaptations would certainly ensure the survival of our species, even if they become quite different from their predecessors, us. This would not be all that unusual considering how different we are from our distant prehistoric ancestors, and rather few are put off by this fact.

As an additional incentive, note how humans already spend billions in unrelenting efforts to make themselves better in all sorts of ways. Such desires have only increased as our technologies for these desired changes continue to improve. Space may become the ultimate reason for human durability and advancement. Perhaps this is all part of the process of our evolution, only we are facilitating the matter faster than nature has done in the past and in the directions we want it to go.

Science fiction most often envisions interstellar vessels having human crews as the primary features and functions of such starships. Even when they include a capable AI, it is the humans running the show. However, just as autonomous machines have long been our first and continuous “ambassadors” to other worlds in our Sol system, so too will we likely see even more advanced versions plying their ways to other star systems in the galaxy.

Artilects will be the “crew” of choice not only due to their multiple levels of durability and longevity, but also because their artificial minds will be able to process and comprehend far more than any human mind could, perhaps functioning even better than a cybernetically enhanced organic human brain. This will be a vital advantage in a galaxy of unknown factors, including when they encounter other minds that may be unlike anything we have ever dealt with before. Then their roles as ambassadors from our realm will be much more than just a clever designation.

We should not be disheartened by the fact that exploring and settling space with our species as it currently is may not be the best way to go in the really long term. Instead, with our new capabilities and knowledge, humanity can supersede what we once thought was the best way to expand into the Universe and do so in a way that will ensure our survival and success.

So, Rocket Man, you may have been ultimately correct regarding the expansion of humanity into space, but for reasons rather different than you could have possibly imagined. This is with no offense intended, as we are all products of our time and place, and you did highlight some important issues regarding permanent space utilization and settlement. The good thing is that we can and will evolve our collective understanding of existence, which in turn will allow us to adapt for the future, wherever it will be.


A Nod to ‘Stapledon Thinking’

Taking a long walk in the early morning hours (and I do mean ‘early,’ as I usually walk around 4 AM – Orion is gorgeously high in the sky this time of year in the northern hemisphere), I found myself musing on terminologies. The case in point: The Fermi Paradox. Using that phrase, the issue becomes starkly framed. If there are other civilizations in the galaxy, why don’t we have evidence for them? Much ink, both physical and digital, has been spilled over the issue, but I will argue that we should soften the term ‘paradox.’ I prefer to call the ‘where are they’ formulation the Fermi Question.

I prefer ‘question’ rather than ‘paradox’ because I don’t think we have enough data to declare what we do or do not see about other civilizations a paradox. A paradox is a seemingly self-contradictory statement that demands explanation. But is anything actually demanded here? There are too many imponderables in this case to even frame the contradiction. How can we have a paradox when we are fully aware of our own limitations at data gathering, to the point that we have no consensus on what or where to target in our searches? Possibilities for technosignatures abound but which are the most likely to be productive? Should we truly be surprised that we do not see a clear signature of another civilization?

We make our best choices based on the technologies we have. On the galactic scale, that means looking for anomalies that might flag a widespread Kardashev Type III civilization. We know that such a civilization’s technologies would far surpass our own and its communications might involve methods – the use of gravitational waves, for example – that are far beyond our capabilities to detect. The Fermi Question tells us about our limitations but doesn’t point to a genuine conundrum. We should also keep in mind that although all the debates on this matter have elevated its status, the statement Fermi made could be considered relatively light lunch-time banter.

On the scale of the Solar System, it would be better to say that we do indeed lack evidence of extraterrestrial visitation, but also that we really have only begun to look for it. A lengthy book could be written on where or why another civilization might plant a ‘lurker’ probe in our Solar System, conceivably one that could have arrived millions of years ago and could even today be quietly returning data on what it sees. We have yet to examine our own Moon in the kind of detail now available to us through the Lunar Reconnaissance Orbiter, and as my friend Jim Benford never tires of pointing out, we know almost nothing about other nearby objects such as Earth’s co-orbitals. Until we sift through actual data, we’d better use caution about these matters.

So while I don’t think it rises to the level of a paradox, the Fermi Question is an incentive to continue searching for data whose anomalous nature may be useful. And while we do this, working the borders between SETI and philosophy seems inevitable. Because when we discuss extraterrestrial civilizations, we’re talking about behaviors that can be detected, without having the slightest notion of what those behaviors might be. What we call ‘human nature’ is hard enough to pin down, but how truly alien cultures would address the issues in their realm is purely imaginative conjecture.

I’m reminded of something Milan ?irkovi? said in The Great Silence: Science and Philosophy of Fermi’s Paradox (Oxford University Press, 2018):

As we learn more, the shore of the ‘ocean of unknown’ lengthens, to paraphrase Newton’s famous sentence and, while we may imagine (on some highly abstract level) that it will eventually contract, this era is not yet in sight.

Thus, we have another prediction: there will be many new explanatory hypotheses for Fermi’s paradox in the near future, as the astrobiological revolution progresses and exploratory engineering goes farther and farther.

Pondering Smaller Stars

That said, I note with interest a paper from Jacob Haqq-Misra (Blue Marble Space Institute of Science, Seattle) and Thomas Fauchez (American University) that makes the case for low-mass stars as the logical venue for expanding civilizations. If we wonder where alien civilizations are, the question might be resolved by the idea that if such cultures expanded into the cosmos, they would select K- or M-dwarf stars as their destinations. Here we’re squarely up against issues of philosophy and sociology, because we’re asking about what another species would consider its goals.

But let’s go with this, because the authors are perfectly aware of all that we don’t know, and also aware of the need for shaping our questions through broad theorizing.

Why smaller stars? Here we’re dealing with an interesting hypothesis, that G-class stars are the most likely place for life to develop in the first place. Haqq-Misra has written about this before (as have a number of other scientists referenced in the paper), and here makes the statement “We first assume that technological civilizations only arise on habitable planets orbiting G-dwarf stars (with ?10 Gyr main sequence lifetimes) because either biogenesis or complex life is more favored in such systems.” And the idea is that stars like our Sun have lifetimes far shorter than the trillions of years available to M-dwarfs or the 17 to 70 billion years for K-dwarfs.

That’s a big assumption, but it leads to a conjectured motivation: A civilization will choose to maximize its longevity, just as an individual human will try to stay alive as long as possible. A culture that manages to become long-lived will have to cope with the eventual loss of its home G-class star and will look for longer-lived destinations that can serve as more lasting home worlds. And while I’ve mentioned M-dwarfs, the K-class seems to hit the sweet spot, so that the authors title a section of their paper “The K-dwarf Galactic Club.”

K-dwarfs are plentiful compared to G-class stars like the Sun, accounting for about 13 percent of the galactic stellar inventory (G-class stars comprise about 6%). M-dwarfs are the most common star, at about 73 percent, according to the authors’ figures. We’ve already seen, though, that K-dwarfs offer significantly longer lifespans than G-class stars, and because of their size and the nature of habitable orbits, they offer possible living planets without tidal lock.

If the authors are correct that life is more likely to arise around G-dwarfs, then it could be said that a K-class star offers a living experience closer to that of the homeworld for any civilization that chooses to migrate to it. This is because the spectra of these stars are much closer to G-star spectra than to M-dwarfs. With M-dwarfs, as well, we have to contend with higher stellar activity than on the more quiescent K-dwarfs. Planetary environments are thus much closer to G-dwarf norms than around M-dwarfs.

The problem of what we might call exo-sociology looms large in this discussion, and it’s one the authors frankly acknowledge. Whether or not life exists anywhere else remains an open question, and we have no knowledge of what extraterrestrial civilizations, if out there, would consider important or desirable as guides to their activity. But if we’re asking philosophical questions, we can ponder what any living intelligence would consider its primary goal, as the authors do in this excerpt from their paper:

Newman & Sagan (1981) performed a detailed mathematical analysis of population diffusion in the galaxy and concluded that only long-lived civilizations could have established a Galactic Club; however, such a possibility was excluded because the authors “believe that their motivations for colonization may have altered utterly.” Although it remains possible that long-lived technological civilizations do not expand, it also remains possible that such civilizations pursue galactic settlement in order to ensure their longevity. The numerical simulations by Carroll-Nellenback et al. (2019) found solutions where “our current circumstances are consistent with an otherwise settled, steady-state galaxy.”

Image: M31, the Andromeda Galaxy. What might drive the expansion of a civilization outward from its native system, and how can we, with no knowledge of other civilizations, plausibly come up with motivations for such activity? Credit & Copyright: Robert Gendler.

We have a scenario, then, of long-lived civilizations preferentially expanding to particular categories of stars to ensure the survival of their species, but otherwise not expanding exponentially into the galaxy. Such a scenario would fit with what we see, being a level of activity that would not necessarily announce itself through contact with other civilizations. Cultures like these would be content to mind their own business as long as their survival could be ensured, but we might or might not expect them to actively probe stellar systems as relatively short lived as those around G-class stars. We should look in our own system, say the authors, but a failure to find evidence of extraterrestrial travelers might simply reflect a preference to visit other types of star.

This makes identifying these cultures a tricky matter indeed:

We can exclude scenarios in which all G-dwarf stars would have been settled by now, but the possibility remains open that a Galactic Club exists across all K-dwarf or M-dwarf stars. The search for technosignatures in low-mass systems provides one way to constrain the presence of such a Galactic Club (e.g., Lingam & Loeb 2021; Socas-Navarro et al. 2021; Wright et al. 2022; Haqq-Misra et al. 2022). Existing searches to-date have placed some limits on radio transmissions (e.g., Harp et al. 2016; Enriquez et al. 2017; Price et al. 2020; Zhang et al. 2020) and optical signals (e.g., Howard et al. 2007; Tellis & Marcy 2015; Schuetz et al. 2016) that might be associated with technological activity, but such limits can only weakly constrain the Galactic Club hypothesis. Further research into understanding the breadth of possibilities for detecting extraterrestrial technology will become increasingly important as observing facilities become more adept at characterizing terrestrial planets in low-mass exoplanetary systems.

Thus the value of the Fermi Question at highlighting the staggering depth of our ignorance about what is actually out there. I enjoy creative solutions to conjectural problems and am all for applying what I might call ‘Stapledon thinking’ (after the brilliant British philosopher and science fiction writer) as forays into the darkness. We can expect many more ‘solutions’ to the Fermi Question as our capabilities increase. The outcome we can hope for is that one of these days a present or pending astronomical instrument will deliver data on a phenomenon that will resolve itself into a true technosignature (or even an attempt to communicate). Until then, these stunningly interesting questions will drive thinking both philosophic and scientific.

The paper is Haqq-Misra & Fauchez, “Galactic settlement of low-mass stars as a resolution to the Fermi paradox,” accepted at the Astronomical Journal and available as a preprint. Be aware as well of Michaël Gillon, Artem Burdanov and Jason Wright’s paper “Search for an Alien Message to a Nearby Star,” Astronomical Journal Vol. 164, No. 5 (27 October 2022). Abstract. And for all things Fermi, see Milan ?irkovi?, The Great Silence: Science and Philosophy of Fermi’s Paradox (Oxford University Press, 2018).


Great Winds from the Sky

Do we need to justify pushing our limits? Doing so is at the very heart of the urge to explore, which is embedded in our species. Recently, while doing some research on Amelia Earhart, I ran across a post on Maria Popova’s extraordinary site The Marginalian, one that examines the realm of action within the context of the human spirit. Back in 2016, Popova was looking at Walter Lippmann (1889-1974), the famed journalist and commentator, who not long after Earhart’s fatal flight into the Pacific discussed the extent of her achievement and the reasons she had flown.

Here’s a passage from Lippmann’s New York Herald Tribune column, written on July 8, 1937, just six days after the aviator and her navigator, Fred Noonan, disappeared somewhere near Howland Island between Hawaii and Australia. Lippmann asks whether such ventures must be justified by a utilitarian purpose and concludes that what is at stake here transcends simple utility and speaks to the deepest motivations of our explorations. It is a belief in a goal and the willingness to risk all. Practicality carries little weight among those who actually do the deed:

“The best things of mankind are as useless as Amelia Earhart’s adventure. They are the things that are undertaken not for some definite, measurable result, but because someone, not counting the costs or calculating the consequences, is moved by curiosity, the love of excellence, a point of honor, the compulsion to invent or to make or to understand. In such persons mankind overcomes the inertia which would keep it earthbound forever in its habitual ways. They have in them the free and useless energy with which alone men surpass themselves.

Such energy cannot be planned and managed and made purposeful, or weighted by the standards of utility or judged by its social consequences. It is wild and it is free. But all the heroes, the saints, the seers, the explorers and the creators partake of it. They do not know what they discover. They do not know where their impulse is taking them. They can give no account in advance of where they are going or explain completely where they have been. They have been possessed for a time with an extraordinary passion which is unintelligible in ordinary terms.

No preconceived theory fits them. No material purpose actuates them. They do the useless, brave, noble, the divinely foolish and the very wisest things that are done by man. And what they prove to themselves and to others is that man is no mere creature of his habits, no mere automaton in his routine, no mere cog in the collective machine, but that in the dust of which he is made there is also fire, lighted now and then by great winds from the sky.”

Image: Amelia Earhart’s Lockheed Electra 10E. During its modification, the aircraft had most of the cabin windows blanked out and had specially fitted fuselage fuel tanks. The round RDF loop antenna can be seen above the cockpit. This image was taken at Luke Field in Hawaii on March 20, 1937. Earhart’s final flight in this aircraft took place on July 2, 1937, taking off from Lae, New Guinea. Credit: Wikimedia Commons. Scanned from Lockheed Aircraft since 1913, by René Francillon. Photo credit USAF.

Lippmann’s tribute is a gorgeous piece of writing, available in The Essential Lippmann (Random House, 1963). Naturally, it makes me think of other flyers who rode those same winds, people like Antoine de Saint-Exupéry and Beryl Markham, who in 1936 was the first to dare a solo non-stop flight across the Atlantic from east to west. As I’ve recently re-read Markham’s elegant West With the Night (1942), she as well as Earhart has been on my mind. What a shame that Earhart didn’t live to pen a memoir as powerful, but perhaps Lippmann in some small way did it for her.