Holiday Thoughts on Deep Time

An old pal from high school mentioned in an email the other day that he had an interest in Adam Frank’s work, which we’ve looked at in these pages a number of times. Although my most recent post on Frank involves a 2022 paper on technosignatures written with Penn State’s Jason Wright, my friend was most intrigued by a fascinating 2018 paper Frank wrote for the International Journal of Astrobiology (citation below). The correspondence triggered thoughts of other, much earlier scientists, particularly of Charles Lyell’s Principles of Geology (1830-1833), which did so much to introduce the concept of ‘deep time’ to Europe and played a role in Darwin’s work. Let’s look at both authors, with a nod as well to James Hutton, who largely originated the concept of deep time in the 18th Century.

Adam Frank is an astrophysicist at the University of Rochester, and one of those indispensable figures who meshes his scientific specialization (stellar evolution) with a broader view that encompasses physics, cultural change and their interplay in scientific discourse. He fits into a niche of what I think of as ‘big picture’ thinkers,’ scientists who draw out speculation to the largest scales and ponder the implications of what we do and do not know about astrophysics for a species that may spread into the cosmos.

Now in the case of my friend’s interest, the picture is indeed big. Frank’s 2018 paper asked whether our civilization is the first to emerge on Earth. Thus the ‘Silurian’ hypothesis, explored on TV’s Doctor Who in reference to a race of intelligent reptiles by that name who are accidentally awakened. The theme pops up occasionally in science fiction, though perhaps less often that one might expect. James Hogan’s 1977 novel Inherit the Stars, for example, posits evidence for unknown technologies discovered on the Moon that apparently have their origin in an earlier geological era.

Image: Astrophysicist Adam Frank. Credit: University of Rochester.

I won’t go through this paper closely because I’ve written it up before (see Civilization before Homo Sapiens?), but this morning I want to reflect on the implications of the question. For it turns out that if, say, a species of dinosaur had evolved to the point of creating technologies and an industrial civilization, finding evidence of it would be an extremely difficult thing. So much so that I find myself reflecting on deep time in much the same way that I reflect on the physical cosmos and its seemingly endless reach.

Consider that we can trace our species back in the Quaternary (covering the last 2.6 million years or so) and find evidence of non-Homo Sapiens cultures, among which the Neanderthals are the most famous, along with the Denisovians. Bipedal hominids show up at least as far back as the Laetoli footprints in Tanzania, which date to 3.7 million years ago and were apparently produced by Australopithecus afarensis. Frank and co-author Gavin Schmidt also note that the largest ancient surface still available for study on our planet is in the Negev Desert, dating back about 1.8 million years.

These are impressive numbers until we put them into context. The Earth is some 4.5 billion years old, and complex life on land has existed for about 400 million of those years. Let’s also keep in mind that agriculture emerged perhaps 12,000 years ago in the Fertile Crescent, and in terms of industrial technologies, we’ve only been active for about 300 years (the authors date this from the beginning of mass production methods). Tiny slivers of time, in other words, amidst immense timeframes.

So as Frank and Schmidt point out, we’re talking about fractions of fractions here. There is a fraction of life that gets fossilized, which in all cases is tiny and also varies according to tissue, bone structure, shells and so forth, and also varies from an extremely low rate in tropical environments to a higher rate in dry conditions or river systems. The dinosaurs were active on Earth for an enormous period of time, from the Triassic to the end-Cretaceous extinction event, something in the range of 165 million years. Yet only a few thousand near-complete dinosaur specimens exist for this entire time period. Would homo sapiens even show up in the future fossil record?

From the paper:

The likelihood of objects surviving and being discovered is similarly unlikely. Zalasiewicz (2009) speculates about preservation of objects or their forms, but the current area of urbanization is <1% of the Earth’s surface (Schneider et al., 2009), and exposed sections and drilling sites for pre-Quaternary surfaces are orders of magnitude less as fractions of the original surface. Note that even for early human technology, complex objects are very rarely found. For instance, the Antikythera Mechanism (ca. 205 BCE) is a unique object until the Renaissance. Despite impressive recent gains in the ability to detect the wider impacts of civilization on landscapes and ecosystems (Kidwell, 2015), we conclude that for potential civilizations older than about 4 Ma, the chances of finding direct evidence of their existence via objects or fossilized examples of their population is small.

Image: The Cretaceous-aged rocks of the continental interior of the United States–from Texas to Montana–record a long geological history of this region being covered by a relatively shallow body of marine water called the Western Interior Seaway (WIS). The WIS divided North America in two during the end of the age of dinosaurs and connected the ancient Gulf of Mexico with the Arctic Ocean. Geologists have assigned the names “Laramidia” to western North America and “Appalachia” to eastern North America during this period of Earth’s history. If a species produced a civilization in this era, would we be able to find evidence of it? Credit; National Science Foundation (DBI 1645520). The Cretaceous Atlas of Ancient Life is one component of the overarching Digital Atlas of Ancient Life project. CC BY-NC-SA 4.0 DEED.

Intriguing stuff. The authors advocate exploring the persistence of industrial byproducts in ocean sediment environments, asking whether byproducts of common plastics or organic long-chain synthetics will be detectable on million-year timescales. They also propose a deeper dive into anomalies in current studies of sediments, the same sort of analysis that has been done, for example, in exploring the K-T boundary event but broadened to include the possibility of an earlier civilization. I send you to the paper, available in full text, for discussion of such testable hypotheses.

Back to deep time, though, and the analogy of looking ever deeper into the night sky. In asking how long a civilization can survive (Drake’s L term in the famous equation), we ask whether we are likely to find other civilizations given that over billion year periods, they may last only as a brief flicker in the night. We have no good idea of what the term L should be because we are the only civilization we know about. But if civilizations can emerge more than once on the same world, the numbers get a little more favorable, though still daunting. A given star may be circled by a planet which has seen several manifestations of technology, a greater chance for our detection.

A cycle of civilization growth and collapse might be mediated by fossil fuel availability and resulting climate change, which in turn could feed changes in ocean oxygen levels. Frank has speculated that such changes could trigger the conditions for creating more fossil fuels, so that the demise of one culture actually feeds the energy possibilities of the next after many a geological era. How biospheres evolve – how indeed they have evolved on our own world – is a question that exoplanet research may help to answer, for we have no shortage of available worlds to examine as our biosignature technologies develop.

Culturally, we must come to grips with these things. In an essay for The Geological Society, British paleontologist Richard Fortey discusses the seminal work of James Hutton and Charles Lyell in the 18th and 19th Centuries in developing the concept of geological time, which John McPhee would present wonderfully in his 1981 book Basin and Range (I remember reading excerpts in The New Yorker). The Scot James Hutton had literary ambitions, publishing his Theory of the Earth in 1795 and changing our conception of time forever. Hutton knew Adam Smith and spent time with David Hume; he would also have been aware of French antecedents to his ideas. But despite its importance, even Lyell would admit that he found Hutton’s book all but unreadable.

It took a friend named John Playfair to turn Hutton’s somnolent prose into the simplified but clear Illustrations of the Huttonian Theory of the Earth in 1802, making the idea of deep time available to a large audience and leading to Lyell. Which goes to show that sometimes it takes a careful popularizer to gain for a scientist the traction his or her work deserves. The emphasis there is on ‘careful.’

Lyell’s Principles of Geology, published in three volumes between 1830 and 1833, famously traveled with Darwin on the Beagle and, as Fortey says, “donated the time frame in which evolution could operate.” He goes on:

“…once the time barrier had been breached, it was only a question of how much time. The stratigraphical divisions of the geological column, the periods such as Devonian or Cambrian, with which we are now so familiar, were themselves being refined and put into the right sequence through the same historical period. Just to have a sequence of labels helped geologists grapple with time, and, in a strange way, labels domesticate time.

But domestication co-exists with wonder. I imagine the most hardened geologist of our day occasionally quakes at the realization of what all those sedimentary layers point to, a chronological architecture — time’s edifice — in which our entire history as a species is but a glinting mote on a rockface of the future. Our brief window today is reminiscent of Hutton and Lyell’s. Like them, we are compelled to adjust to a cosmos that seems to somehow enlarge every time we probe it, inspired by new technologies that give birth to entire schools of philosophy.

John Playfair would write upon visiting Siccar Point, the promontory in Berwickshire that inspired Hutton’s ideas, that “The mind seemed to grow giddy looking so far into the abyss of time.” We are similarly dwarfed by the vistas of the Hubble Ultra Deep Field and the exquisite imagery from JWST. Who knows what we have yet to discover in Earth’s deep past?

The paper is Schmidt and Frank, “The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record?” published online by the International Journal of Astrobiology 16 April 2018 (full text). Gregory Benford’s Deep Time: How Humanity Communicates Across Millennia (Bard, 2001) is a valuable addition to this discourse. For a deeper dive, Fortey mentions Martin Rudwick’s Bursting the Limits of Time: The Reconstruction of Geohistory in the Age of Revolution ( University of Chicago Press, 2007). Fortey’s own Life: A Natural History of the First Four Billion Years of Life on Earth (Knopf, Doubleday 1999) is brilliant and seductively readable.

SETI: Musings on the Barrow Scale

John Barrow has been on my mind these past few days, for reasons that will become apparent in a moment. In my eulogy for Barrow (1952-2020), I quoted from his book The Left Hand of Creation (Oxford, 1983). I want to revisit that passage for its clarity, something that always inspired me about this brilliant physicist. For it seemed he could render the complex not only accessible but encouragingly pliable, as if scientific exploration always unlocked doors of possibility we could use to our advantage. His was a bright vision. The notion that animated him was that there was something in the sheer process of research that held its own value. Thus:

Could there be any shortcuts to the answers to the cosmological questions? There are some who foolishly desire contact with advanced extraterrestrials in order that we might painlessly discover the secrets of the universe secondhand and prematurely extend our understanding. Such a civilization would surely resemble a child who receives as a gift a collection of completed crossword puzzles. The human search for the structure of the universe is more important than finding it because it motivates the creative power of the human imagination.

You can see that for Barrow, the question of values was not separated from scientific results, and in a sense transcended the data we actually gathered. He goes on:

About 50 years ago a group of eminent cosmologists were asked what single question they would ask of an infallible oracle who could answer them with only yes or no. When his opportunity came, Georges Lemaître made the wisest choice. He said, “I would ask the Oracle not to answer in order that a subsequent generation would not be deprived of the pleasure of searching for and finding the solution.”

Image: Cosmologist, mathematician and physicist John D. Barrow, whose books have been a personal inspiration for many years. Credit: Tom Powell.

Leave it to Lemaître (and Barrow to quote him) as we reach beyond the immediately practical to unlock what it is about human experience that compels us to push into new terrain, whether it be physical exploration or flights of the imagination as we pursue a new hypothesis about nature. Barrow comes to mind because we’ve just been talking about the scales by which a civilization can be measured. Some of these are well established, as for example the Kardashev scale, with its familiar Types I, II and III keyed to the scale of a civilization’s energy use. In Clarke’s The Fountains of Paradise we find an alien scale based on the use of tools. It’s possible to imagine other scales, and Barrow’s own contribution takes us into the nano-realm.

As best I can determine, Barrow first floated the scale in his 1998 book Impossibility: The limits of science and the science of limits (Oxford University Press). Inverting Kardashev, Barrow was interested in a civilization’s ability to control smaller and smaller things, relying on the observed fact that as we have explored such micro-realms, our technologies have proliferated. Nanotechnology and biotechnology are drawn out of our ability to manipulate matter at small scales, and in fact the development of nanotech is one marker for a Barrow scale IV culture.

Barrow I: The ability to manipulate objects at the same scale as the person or being involved. In other words, simple activities involving basic tools.

Barrow II: The control of genetic information.

Barrow III: The ability to control molecules.

Barrow IV: The ability to control individual atoms.

Barrow V: The manipulation of atomic nuclei..

Barrow VI: Control of elementary particles.

Barrow Omega (Ω): The ability to control fundamental elements of spacetime.

Table: Energetic and inward civilization development. Kardashev’s (1964) types refer to energy consumption; Barrow’s (1998, 133) types refer to a civilization’s ability to manipulate smaller and smaller entities. Credit: Clément Vidal.

I’ve drawn the above table from a paper by French philosopher and SETI scientist Clément Vidal, who is one of the few who have explored this realm (citation below). Here we get both Kardashev and Barrow at once, a convenience, and central to Vidal’s argument that black holes are going to draw advanced civilizations to extract their energies and explore what he calls “the computational density of matter.” On this score, it’s interesting to note that Freeman Dyson proposed in 1979 that a civilization exploiting time dilation effects near black holes could survive effectively forever (a later revision had to take into account the accelerating expansion of the universe).

What all this means for SETI is intriguing – almost punchy – and I’ll send you to Vidal’s superb The Beginning and the End: The Meaning of Life in a Cosmological Perspective (Springer, 2014) for a deep dive into the concepts involved. But consider this for a starter: Dysonian SETI assumes civilizations far more advanced than our own, the reasoning being that their works should be apparent even at astronomical scales. Thus searching our astronomical data as far back as we can could conceivably flag an anomaly that merits investigation as a possible civilizational marker.

What Clément Vidal has been investigating is where such markers would turn up, and for this he deploys the scales of both Kardashev and Barrow. I think the easiest assumption is that we would find an alien civilization at its home world, but of course this needn’t be the case. Vidal speaks of ‘attractors’ as those sources of energy that an advanced civilization would increasingly exploit. Take a culture a billion years older than our own and ponder energy needs that might require it to exploit things like the energies of close binary neutron stars or black holes themselves. Such a civilization would be far flung, with operations well beyond its local group of stars.

Now ponder Barrow Type Ω. This ‘omega’ culture is free of the constraints of spacetime, having achieved the ability to manipulate both. It’s anyone’s guess whether such a civilization would be noted by achievements on a truly celestial scale, or whether its works would actually be embedded in the nature of space and time themselves, so that to us they appear the simple functioning of nature. In this mode of thinking, the more advanced a civilization becomes as it moves up the Barrow scale, the more it begins to effectively disappear. Barrow thus channels Richard Feynman and anticipates Lee Smolin’s notions about cosmological evolution, a kind of self-selection for universes.

I’m going to swipe the chart below from Vidal’s 2010 paper on black hole attractors, showing the entertaining fact that as he puts it, “from the relative human point of view, there is more to explore in small scales than in large scales.”

Table: That humans are not in the center of the universe is also true in terms of scales. This implies that there is more to explore in small scales than in large scales. Richard Feynman (1960) popularized this insight when he said “there is plenty of room at the bottom”. Figure adapted from (Auffray and Nottale 2008, 86). Credit: Clément Vidal.

Futurist John Smart has dug into what he calls STEM Compression, with STEM in this case meaning Space/Time/Energy/Matter, and the compression being the idea that in terms of density and efficiency, we can as Vidal puts it “do more with less.” For going deeper into the Barrow scale, we see that as things get smaller, we are not hampered by the speed of light problem. In fact, our endgame barrier is at the Planck scale. A Kardashev II civilization extracting energy from a rotating black hole using technologies far up the Barrow scale may well be indistinguishable from an X-ray binary of the sort that has been cataloged in the astronomical literature.

Such speculations are on the far edge of SETI (and again, I refer you to Vidal’s book), but it’s also true that whether or not extraterrestrial civilizations exist, our own ability to chart futures for an expanding civilization may well come in handy if we can somehow punch through whatever ‘great filter’ may be out there and become a species that survives on the scale of deep time. There is no knowing whether this is even possible, and it may be that the galaxy is filled with the ruins of those who have gone before us.

It is also true, of course, that no one may have gone before us. Maybe N really does equal 1. But I return to Barrow: “The human search for the structure of the universe is more important than finding it because it motivates the creative power of the human imagination.” And the human imagination is currency of the realm in matters like these.

The Vidal paper is “Black Holes: Attractors for Intelligence?” presented at the Kavli Royal Society International Centre, “Towards a scientific and societal agenda on extra-terrestrial life”, 4-5 Oct 2010 (abstract). The Dyson paper is “Time Without End: Physics and Biology in an Open Universe,” Review of Modern Physics 51: 447-460 (abstract). My eulogy for Barrow is On John Barrow. John Smart contributed a fascinating essay on cosmic evolution in these pages in The Goodness of the Universe.

Is Interstellar Flight Inevitable?

The wish that humans will one day walk on exoplanets is a natural one. After all, the history of exploration is our model. We look at the gradual spread of humanity, its treks and voyages of discovery, and seamlessly apply the model to a future spacefaring civilization. Science fiction has historically made the assumption through countless tales of exploration. This is the Captain Cook model, in which a crew embarks on a journey into unknown regions, finds new lands and cultures, and returns with samples to stock museums and tales of valor and curiosity.

Captain Cook didn’t have a generation ship, but HMS Endeavour was capable of voyages lasting years, stocking itself along the way and often within reach of useful ports of call. A scant 250 years later, however, we need to consider evolutionary trends and ask ourselves whether our ‘anthropocene’ era will itself be short-lived. Even as we ask whether human biology is up for voyages of interstellar magnitude, we should also question what happens when evolution is applied to the artificial intelligence growing in our labs. This is Martin Rees territory, the UK’s Astronomer Royal having discussed machine intelligence in books like his recent The End of Astronauts (Belknap Press, 2022) and in a continuing campaign of articles and talks.

I won’t comment further on The End of Astronauts because I haven’t read it yet, but its subtitle – Why Robots Are the Future of Exploration – makes clear where Rees and co-author Donald Goldsmith are heading. The title is a haunting one, reminding me of J.G. Ballard’s story “The Dead Astronaut,” a tale in which the Florida launch facilities that propelled the astronaut skyward are now overgrown and abandoned, and the astronaut’s widow awaits the automated return of her long-dead husband. It was an almost surreal experience to read this in the Apollo-infused world of 1971, when it first ran:

Cape Kennedy has gone now, its gantries rising from the deserted dunes. Sand has come in across the Banana River, filling the creeks and turning the old space complex into a wilderness of swamps and broken concrete. In the summer, hunters build their blinds in the wrecked staff cars; but by early November, when Judith and I arrived, the entire area was abandoned. Beyond Cocoa Beach, where I stopped the car, the ruined motels were half hidden in the sawgrass. The launching towers rose into the evening air like the rusting ciphers of some forgotten algebra of the sky.

“[T]he rusting ciphers of some forgotten algebra of the sky.” Can this guy write or what?

You’ll find no spoilers here (Ballard’s The Complete Short Stories is the easiest place to find it these days) but suffice it to say that not everything is as it seems and the scenario plays out in ways that explore human psychology coming to grips with a frontier of deeply uncertain implications. As uncertain, perhaps, as the implications Ballard did not explore here, the growth of artificial intelligence with its own evolutionary path. For that, we can investigate the work of Stanislaw Lem, in particular The Invincible (1964). N. Katherine Hayles wrote a fine foreword to the novel in 2020. Non-human, indeed non-biological evolutionary paths are at the heart of the work.

The scenario should intrigue anyone interested in interstellar exploration. Assume for a moment that a starship carrying both biological beings and what we can call artilects – AI enabled beings, or automata – once landed on a distant planet, where the biological crew died. The surviving artilects cope with the local life forms and evolve gradually toward smaller and smaller beings that operate through swarm intelligence. The driver is the need to function with ever smaller sources of power (the artilects operate via solar power and hence need less as their size decreases), creating an evolutionary pressure that results in intelligent ‘mites.’

A long time later, another crew, the humans of the starship Invincible, has arrived and must cope with the result. As long ago as 1964, before the first Gemini mission had flown, the prescient Lem was saying that swarm intelligence was a viable path, something that later research continues to confirm. As Hayles points out in her foreword, it takes only a few rules to produce complex behaviors in swarming creatures like fish, birds and bees, with each creature essentially in synch with only the few creatures immediately around it. Simple behaviors (in computer terms, only a few lines of code) lead to complex results. Let me quote Hayles on this:

Decades before these ideas became disseminated within the scientific community, Lem intuited that different environmental constraints might lead to radically different evolutionary results in automata compared to biological life forms. Although on Earth the most intelligent species (i.e., humans) has tended to fare the best, their superior intelligence comes with considerable costs: a long period of maturation; a lot of resources invested in each individual; socialization patterns that emphasize pair bonding and community support; and a premium on individual achievement. But these are not cosmic universals, and different planetary histories might result in the triumph of very different kinds of qualities.

In this environment, a visiting starship crew must confront an essential difference in values between the two types of being. Humans bring assumptions drawn out of our experience as a species, including the value of the individual life as opposed to the collective. Remember, we are some years off from Star Trek’s Borg, so once again Lem is pushing the envelope of more conventional science fiction. Hayles will point out that shorn of our anthropocentrism, we may find ourselves encountering forms of artificial life whose behavior can only be traduced by profoundly unsettling experience. A world of collective ‘mites’ may overwhelm all our values.

Given all this, we have to ask whether several more centuries of AI will produce artilects we are comfortable with. The question of control seems almost moot, as what Martin Rees refers to as ‘inorganic intelligence’ quickly moves past our own mental functioning if left to its own devices. We are in the realm of what today’s technologists call ‘strong AI,’ where the artificial intelligence is genuinely alive in its own right, as opposed to being a kind of simulacrum emulating programmed life. A strong AI outcome places us in a unique relationship with our own creations.

The result is a richer and stranger evolutionary path than even Darwin could have dreamed up. We don’t have to limit ourselves to swarms, of course, but I think we can join Rees in saying that creatures evolving out of current AI will probably be well beyond our ability to understand. In a recent essay for BBC Future, Rees quoted Darwin on the entire question of intentionality: “A dog might as well speculate on the mind of [Isaac] Newton.” Not even my smartest and most beloved Border Collie could have done that. At least I don’t think she could, although she frequently surprised me.

A side-note: I would be interested in suggestions for science fiction stories dealing with swarm concepts — as opposed to basic robotics — in the early years of science fiction. Were authors exploring this before Lem?

Rees is always entertaining as well as provocative. He takes an all but Olympian view of the cosmos that draws on his lifetime of scientific speculation, and writes a supple, direct prose that is without self-regard. I’ve only met him once and at that only briefly, but it’s clear that this is just who he is. In a way, what I might consider his detachment from the nonsensical frenzy of too much tenured academic science mirrors deeper changes that could occur as intelligence moves into inanimate matter. Why, for example, keep things like egotism or pomposity (and we all know examples in our various disciplines)? Why keep aggression if your goal is contemplation? For that matter, why live on planets and not between stars?

But for that matter, can we ever know the goal of such beings? As Rees writes:

Pessimistically, they could be what philosophers call “zombies”. It’s unknown whether consciousness is special to the wet, organic brains of humans, apes and dogs. Might it be that electronic intelligences, even if their intellects seem superhuman, lack self-awareness or inner life? If so, they would be alive, but unable to contemplate themselves, or the beauty, wonder and mystery of the Universe. A rather bleak prospect.

For all these what-ifs, I strongly second another Rees statement about first contact: “We will not be able to fathom their motives or intentions.”

As you might guess, Rees is all for pursuing what I always call ‘Dysonian SETI,’ meaning looking for evidence of non-natural phenomena (he includes the study of ‘Oumuamua as possibly technological in the realm of valid investigation). From the standpoint of our interests on Centauri Dreams, we should also consider whether fast-moving AI will not be our best path, at least in the early going, for interstellar exploration of our own. Our biological nature is a tremendous problem for the mechanics of starflight as presently conceived, given travel times of centuries. Until we surmount such issues, I find the prospect of exploration by artilect a rational alternative. What’s intriguing, of course, is whether we can even prevent it.

Dreaming to the Stars

Suspended animation shows up early in science fiction after a long history in prior literature. In Shakespeare, it’s the result of taking a “distilling liquor” (thus Juliet’s ‘sleep,’ which drives Romeo to suicide). In the SF realm, an early classic is John Campbell’s 1938 story “Who Goes There?”, which became the basis for the wonderful “The Thing from Another World” (1951). Here an alien whose spacecraft has crashed remains in frozen suspension for millennia, only to re-emerge as the barely recognizable James Arness. In the essay below, Don Wilkins points us toward a new study that could have implications for achieving the kind of suspended animation that one day might get a crew through a voyage lasting centuries. A frequent contributor to Centauri Dreams, Don is an adjunct instructor of electronics at Washington University, where the work took place. Echoes of van Vogt’s “Far Centaurus”? Read on. I’ll have another take on this topic in the next post.

by Don Wilkins

Humans have often observed with envy the ability of certain animals to extend sleeping periods from mere hours to months. If bears can do it, why cannot a suitably prepared person do it? Artificial hibernation is often used in science fiction to transport an individual into a distant future without the bother of aging or achieving relativistic speeds or conserving scarce resources. A practical hibernation system, in a more terrestrial function, provides medical support, improving survival by decreasing metabolic activity of a critically ill patient. Some writers hypothesize that a certain number of sleepers, particularly hibernations of decades or more, will suffer disabilities or death.

Research has focused on inducing torpor, a condition of significantly decreased metabolic rates and body activity, producing hibernation without adverse side-effects or horrifying experiments with cryogenics. A practical system remains within the realm of science fiction.

Torpor, like hibernation, is a physiological state in which various animals, including certain fish, reptiles, insects and mammals, actively suppress metabolism, lower body temperature and slow other life processes to conserve energy and survive fatal conditions and cold environmental temperatures.

A research team led by Yaoheng Yang (Washington University, St. Louis) has demonstrated a novel method for inducing torpor in rodents: Deep ultrasonic stimulation of a mammal’s brain [1]. Animals in torpor states experience reduced metabolism and body temperatures. Ultrasound was selected as the stimuli as it noninvasively and safely penetrates bone, and can be tightly focused with millimeter precision. The team hypothesizes that the central nervous system organizes the multitude of reactions needed to induce torpor.

In the experiments, as shown in Figure 1, a mouse wore a tiny “hat”, a lead zirconate titanate ceramic piezoelectric ultrasonic device with a center frequency of 3.2 MHz. The output was focused on the animal’s brain in the hypothalamus preoptic area (POA). Activating the POA neurons induced a torpor state for periods greater than 24 hours.

Fig. 1: Ultrasound device for inducing a torpor-like hypothermic and hypometabolic state. a, Illustration of ultrasound (US)-induced torpor-like state. b, Illustration of the wearable US probe (top). The probe was plugged into a baseplate that was glued on the mouse’s head. MRI of the mouse head with the wearable US probe shows that ultrasound was noninvasively targeted at the POA (insert). Photograph of a freely moving mouse with the wearable US probe attached is shown at the bottom. c, Illustration of the US stimulation waveform used in this study. ISI, inter-stimulus interval; PD, pulse duration; PRF, pulse repetition frequency. d, Calibration of the temperature (T) rise on the surface (top) and inside (bottom) the US probe. The temperature inside the probe was measured between the piezoelectric material and the mouse head when US probes were targeted at the POA or the cortex.

When the POA was stimulated, the body temperatures of the test animals dropped approximately three degrees C, although the environment was held to room temperature. Metabolism switched from carbohydrates and fat to solely fat. Heart rates declined about 47%.

The system used an automatic closed-loop feedback controller with the animal’s body temperature as the feedback variable. Tests which kept the subject’s body 32.95 ℃ for 24 hours were successfully concluded when the ultrasonic influence was removed and the animal returned to normal body temperature. According to previous studies, the body temperature must be below 34 ℃ to induce torpor.

Increasing the acoustic pressure and duration of the ultrasound stimulus further lowered body temperature and slowed metabolism. Each ultrasonic pulse produced consistent neuronal activity increases together with body temperature reductions in the test subjects.

The team, through genetic sequencing, discovered ultrasound could restrain the TRPM2 ultrasound-sensitive ion channel in the POA neurons. The precise mechanism providing the torpid state is unknown.

In a rat, which does not naturally enter torpor or hibernation, ultrasound simulation of POA neurons reduced skin temperature and core body temperature.

Ultrasonics can, with great spatial accuracy, reach deeply within the brain to stimulate the POA neurons. This approach could serve as the foundation of a system providing long term, noninvasive, and safe induction of torpor.


1. Yang, Y., Yuan, J., Field, R.L. et al., “Induction of a torpor-like hypothermic and hypometabolic state in rodents by ultrasound,” Nature Metabolism 5, 789–803 (2023). Full text.

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/, 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?


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