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MaRMIE: The Martian Regolith Microbiome Inoculation Experiment

Alex Tolley follows up his analysis of agriculture on Mars with a closer look at the Interstellar Research Group’s MaRMIE project – the Martian Regolith Microbiome Inoculation Experiment. Growing out of discussions on methods beyond hydroponics to make the Red Planet fertile, the project is developing an experimental framework, as described below, to test our assumptions about Martian regolith here on Earth. A path forward through simulation and experiment could help us narrow the options for what may be possible for future colonists. Fertile regolith, achieved through perchlorate removal, would open up possibilities far beyond what is achievable through hydroponics.

by Alex Tolley

Successful settlement of distant locations requires living off the land, which requires resourcing food. Failure can lead to disaster, as experienced by some of the early American colonies. While near Earth space settlements could be supplied with packaged food, this would be too costly for an expanding Mars base over the long term. Food and air must be supplied from local sources, a point that has been emphasized by the Mars Society’s president, Robert Zubrin (Zubrin, 2011).

In the mid-20th century, it was assumed that agriculture on Mars would be like that on Earth, with crops growing in the Martian soil, but under clear domes to maintain air pressure, and light for photosynthesis. As a result, the focus for settlement was on the shiny technologies of transport and the design of Martian bases and cities.

Image: The Martian Base: Painting for The Exploration of Space by Arthur C Clarke. Credit: Leslie Carr.

This rosy picture of farming on Mars was disturbed after the Apollo missions when it became apparent that plants did not grow well in lunar regolith samples. The Phoenix lander’s discovery of perchlorates on the surface of Mars meant that the Martian regolith would be toxic to plant growth without remediation. Perchlorates are found on Earth, for example in the Atacama desert, but in far lower concentrations than the 0.5-1.0% concentrations found on the surface of Mars. Perchlorates are used in industry, and the US EPA regulates perchlorate contamination because of its toxicity.

Because of the adverse nature of regolith on plant growth, the focus shifted to soilless agriculture using hydroponics or aquaponics, but as we saw in the previous post, there are limitations on the use of hydroponics. Plants with extensive root systems needed for support, especially trees, can’t be grown this way, eliminating the availability of tree fruits and nuts. Most of our grains cannot be grown using current hydroponic methods either. It really would be useful if the regolith could be altered to make it suitable for traditional agriculture, perhaps more like the farms in arid areas, such as the Middle East.

In 2022, after participating in a panel discussion on establishing a sustainable human presence on Mars at a science fiction convention (LibertyCon) in Tennessee, members of the Interstellar Research Group (IRG) including Doug Loss, Joe Meany, and Jeff Greason, considered how some experiments could be done to test how best the regolith might be treated to remove the perchlorates with bioremediation using bacteria, and convert the sterile regolith into soil suitable for agriculture. Some species of bacteria metabolize chlorates and perchlorates for energy, and therefore could be used to remediate the regolith. Relatively small, low mass cultures could be brought from Earth and exponentially cultured to meet the requirements for the volumes of regolith to be treated.

Bioremediation of perchlorate contaminated soils is established practice (Hatzinger 2005), suggesting that if it could be adapted to Martian conditions, this may be a viable solution to remove the perchlorates and solve the toxicity issue.

This use of bacteria, a low mass approach to remediate the regolith was the inspiration for core IRG members to propose a project, the Martian Regolith Microbiome Inoculation Experiment.(MaRMIE).

Mars is almost certainly too dry and cold to just irrigate the regolith on the exposed Martian surface with an inoculant of perchlorate metabolizing organisms. Knowledge about the required conditions for successful large scale regolith bioremediation, especially of temperature and pressure, was required, as well as the issue of UV and ionizing radiation.

Simulating the Martian Surface

The initial idea was to run experiments in a sealed chamber that mimicked the Martian surface environment to determine whether a terrestrial type soil might be created in which agriculture could be practiced. This Mars simulation chamber would contain a Martian regolith simulant (MRS) with added perchlorate, and inoculated with suitable bacteria. If the bacteria could break down the perchlorate, it would indicate that this approach could, in principle, be used to remediate the regolith from the surrounding area, which would then be used inside a greenhouse to grow the food crops. By doing so, the mass, complexity, and likely equipment failures of a hydroponic system could be avoided, and a more traditional agricultural approach could be practiced. This was a far more scalable solution than a technical one, allowing food production anywhere it would be needed, and was in much closer alignment with ISRU.

Early thinking was to design the experiment and have an outside PI with expertise and funding to refine the design and run the experiments. The IRG would publish a review article, and at some point participate in writing a paper on the results.

At this point, the initial group decided to invite others who might be interested in providing input and expertise to investigate the biological remediation of regolith. Of particular importance was the need to design experiments that could be done at suitable facilities. IRG hopes the guidelines that develop out of this work may be of use to anyone pursuing research into agriculture for future use on Mars, and offers them to any organization that chooses to draw on them.

Prior work had identified various bacteria that had the genes that encoded the enzymes to reduce the [per]chlorate and extract energy from it (Balk 2008, Bender 2005, Coates 2004). As the genes coding for the various enzymes for perchlorate metabolism were known it has been suggested that by just liberating the oxygen from the perchlorate the regolith could be a useful source of life support and rocket fuel oxidant (Davil 2013), therefore offering another avenue of ISRU using an engineered bacterium.

Will bioremediation need to be taken inside the base, and if so, can or should it be done as close to Martian conditions as possible, or should it be done as close to the living or working conditions, and plant growing conditions in the agricultural greenhouse? Would it be better to grow the bacteria in a bioreactor rather than in situ, or even extract the enzymes to treat the regolith, thus controlling the bacteria growth and both reducing the perchlorates and liberating the oxygen as a useful side product?

These questions can only be answered with experiments testing the various bacterial inoculants under varying conditions from terrestrial to Martian, as well as applying economic and other analyses to determine the more effective way to use bioremediation on the regolith as an initial step to making it a proactive soil for farming.

While bioremediation is one approach to removing perchlorates, the fact that they are readily water-soluble suggests that if free water is available, the regolith could be simply washed to flush out the perchlorates. This would require more plant to wash the regolith and then remove the salts to recycle the water. This method would work more effectively on regolith than soil and would not require the controlled conditions of bacterial growth and the time to build the culture.

The Phoenix lander detected the perchlorates as they deliquesced on exposure. Experiments have shown that the perchlorates will deliquesce under Martian conditions (Slank 2022).

Removal of the toxic perchlorates is just the start of the process to make the regolith fertile. There have been a number of experiments with regolith simulant to grow a variety of plants and crops under terrestrial conditions of temperature and pressure, the sort of conditions that might be expected in a Mars greenhouse that has humans managing the farm.

By far the best results have been achieved by increasing the illumination to terrestrial levels and adding carbon-rich soils to the regolith, which now will also include the many soil organisms that improve the soils. A partial solution that has also worked is to grow cover crops like alfalfa grass or reuse the waste from prior crops to be added into the regolith to improve its water retention and nutrient supply. (Kasiviswanathan 2022).

So far none of these crop growing experiments have been attempted at pressures and temperatures that differ from optimal terrestrial conditions. There is considerable space to repeat these experiments under different conditions, especially if it proves important to build structurally lighter greenhouses, or even use artificial illumination in below-ground farms, much like container farming today. While oxygen can be extracted from Martian air, water and rocks, nitrogen is less readily available, as is phosphorus. These macronutrients and the other micronutrients will have to be found and extracted to support plant growth whatever farming method is used.

As a result of all these questions, the MaRMIE project has expanded in scope beyond bioremediation, to include crop growth experiments under non-terrestrial conditions.

An Experimental Framework

The project has generated an outline of the experiments that might be done, starting with bioremediation, and extending out into the more general issue of agriculture under conditions that differ from terrestrial ones. Even this is the tip of the iceberg as gene engineered organisms might well be better adapted to conditions on Mars, reducing containment costs, nutrients, and allowing faster scale-up to support an expanding settlement.

The experimental framework encompassing the ideas to date has 4 phases:

1. Remediating perchlorates in the regolith, and any problematic chemicals produced as a result of the remediation. This requires acquiring Martian regolith simulants (MRS) and the addition of perchlorates, testing a number of bacterial and microfungal agents to remediate the MRS under terrestrial conditions, and then in stages of pressure and temperature modified towards Martian conditions.

2. Developing a microbiome tailored to Martian conditions with which to inoculate the regolith. The microbiome should lessen or remove tendencies toward cementation of the regolith as well as gradually convert it into actual soil, if possible. “Actual soil” implies the provision of required nutrients for plant growth. This includes testing microbiomes to add to the MRS along with testing pioneer plant species to condition the regolith to become more like soil.

3. Testing plant growth in microbiome-inoculated regolith under Martian lighting levels and atmospheric conditions, gradually increasing the atmospheric pressure until plant growth is acceptable.

4. Continuing plant growth testing per #3, but gradually lowering ambient temperatures toward Martian levels until plant growth diminishes unacceptably.

5. Developing agricultural structures to provide appropriate conditions, with inoculated regolith, lighting levels, atmospheric pressure, and temperature levels previously determined, and with shielding from ionizing radiation.

As for output, the initial idea to publish some sort of review paper on the known issues and prior work, indicating the direction of experimental work needed, is still in process.

As noted at the outset, the IRG cannot execute these experiments and offers this work as a contribution to the field of planetary studies. IRG hopes that this framework will be seen and used as a structure for designing experiments and building on the results of previous experiments, by any researchers interested in the ultimate goal of viable large-scale agriculture on Mars.


Zubrin, R. (2011). The Case for Mars: The Plan to Settle the Red Planet and Why We Must. Free Press.

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

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

Balk, M. (2008) “(Per)chlorate Reduction by the Thermophilic Bacterium Moorella perchloratireducens sp. nov., Isolated from Underground Gas Storage” Applied & Environmental Microbiology, Jan. 2008, p. 403–409 Vol. 74, No. 2. doi:10.1128/AEM.01743-07

Bender, K.S, et al, (2005) “Identification, Characterization, and Classification of Genes Encoding Perchlorate Reductase” Journal of Bacteriology, Aug. 2005, p. 5090–5096 Vol. 187, No. 15. doi:10.1128/JB.187.15.5090–5096.2005

Coates J.D., Achenbach, L.A. (2004) “Microbial Perchlorate Reduction: Rocket-Fueled Metabolism”, Nature Reviews | Microbiology Volume 2 | July 2004 | 569. doi:10.1038/nrmicro926

Davila A.F. et al (2013) “Perchlorate on Mars: a chemical hazard and a resource for humans” International Journal of Astrobiology 12 (4): 321–325 (2013). doi:10.1017/S1473550413000189

Slank, R. et al. (2022) “Experimental Constraints on Deliquescence of Calcium Perchlorate Mixed with a Mars Regolith Analog” The Planetary Science Journal, 3:154 (11pp), 2022 July

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.

{ 54 comments… add one }
  • FrankH January 31, 2023, 15:08

    Great article, especially remembering “The Martian” – however, they missed a golden (or brown…) opportunity to call it MaRMITE: The Martian Regolith Microbiome Inoculation Through Experimentation

    • Paul Gilster January 31, 2023, 16:47

      What a great name! Good point, Frank.

    • Harold Shaw January 31, 2023, 18:48

      Something was bothering me about this and the last article and I couldn’t figure out what it was. Thanks FrankH

  • charlie January 31, 2023, 19:42

    “Alex Tolley January 27, 2023, 20:38
    The samples being taken in Jezero for a later return to earth may answer that question. Data rather than speculation about the literal ground truth.”
    And if the worst is found, then what?

    • Alex Tolley January 31, 2023, 21:23

      Then the Martian regolith is as abrasive as the lunar regolith. That is where we use water and agitation to grind the regolith grains until they are smooth[er] for the soil. Nothing we can do for the equipment rolling along the surface, but the Martian rovers have shown they can manage to move slowly for years. There will need to be ways to keep the abrasive dust out of the habitat. One way is to keep the suits outside and enter and exit them from the inside, never letting the dust inside. Another is the Martian equivalent of a mud room.

      With water, simple equipment, and power, the regolith can be remediated and used for making soil as outlined.

      • Michael February 1, 2023, 8:43

        A microwave beam device should be ok to melt the dust into larger particles by sintering and round the edges of many grains near the spacecraft.

        • Alex Tolley February 1, 2023, 17:05

          Rather than using needed power for microwaves, why nor do the same with solar concentrators? On Earth they can turn sand into crude glass, so there should be enough sunshine to sinter the regolith. If the base is going to make mirrors, both flat and curved to direct sunlight into shielded greenhouses and living areas, why not create more mirrors to treat the remediated regolith around the base, making it safer to work on?

          However, it seems to me that the more useful approach is not altering the regolith except for soil production, but rather finding the best ways to protect spacesuits and equipment from abrasion. Oversuits to protect the pressure suits and similar protective methods around any moving parts that need protecting from dust. A good fabric that can shrug off dust would seem to fit the bill.

      • charlie February 1, 2023, 19:01

        “…the Martian regolith is as abrasive as the lunar regolith.”
        I mean what Martian regolith is totally devoid of plant nutrients; then what ?

      • Dale February 2, 2023, 21:27

        Great follow-up article Alex. I recall watching a Lunar/Martian buggy mockup with the spacesuits attached at the back acting as an airlock. That’s such an ingenious solution. Since 2019 Boeing have been working on a spacesuit embedded with carbon nanotubes to repel Lunar/Martian dust. I’m not sure how far they have progressed with it since then.

  • Ivan Vuletich January 31, 2023, 21:14

    How does Martian regolith compare to Lunar regolith? Seeing as Mars has some atmosphere and was likely wetter in the past, is Martian regolith as spiky and abrasive as the lunar variety?

    • Alex Tolley February 1, 2023, 11:56

      Short answer: We don’t know.

      Longer answer: The composition of the regolith is different on Mars (Mineralogy and evolution of the surface of Mars: A review) and the Moon. The Moon is dry, has no atmosphere, extreme day/night temperatures, constant meteor impacts of all sizes, and solar and cosmic ray sputtering. The surface is covered in fine dust. Samples returned to Earth have been tested for abrasiveness, e.g;
      Abresion Tester

      Mars’ surface conditions are different, there was water on the surface (c.f. “hematite blueberries”), the thin atmosphere restricts the meteor bombardment, solar and cosmic ray penetration, and wind might have some effect too. Almost certainly the state of the regolith differs from locale to locale on Mars, with old river deltas at the Jezero crater site being qualitatively different from the Martian volcanoes.

      But this is all speculation as we don’t yet have samples of Martian regolith. These samples are being collected now and await a future mission for collection and return. As we can guess at is the Martian Regolith Simulants that can be purchased are abrasive. What we don’t know is how they differ in weathering and chemical changes from actual Mars’ regolith and how this regolith differs between sites.

  • Brett February 1, 2023, 12:58

    It’s going to be water removal on the percholorates, if it works. One of the overwhelming design constraints on any Martian habitat activity is going to be keeping the amount of labor needed in any basic task to a minimum – there’s going to be a ton of work to do and probably never enough people there to do it without economizing on labor as much as possible.

    You’re already going to have the systems for extracting and using Martian ice as water, too.

    • Alex Tolley February 1, 2023, 16:56

      It’s going to be water removal on the percholorates, if it works.

      both water and biological remediation work on Earth to clean up perchlorate contamination. There is no obvious reason this shouldn’t work on Mars. It will require more equipment, and unlike on earth, this will need to be enclosed to provide some atmospheric pressure. The remediation can be tested in a Mars simulation environment on Earth, using Mars regolith simulant with added perchlorates. A very small-scale experiment has been done to show that the perchlorate leeches out of the regolith very easily, as one would expect from a soluble salt. I really like the idea of using bacteria, or better, the bacterial enzymes to break down the perchlorates in the regolith to release oxygen. Just bag up the regolith, add water and enzymes, and hey presto! free oxygen, with, I think, chloride salts remaining. Every spacesuit or vehicle on Mars should have such an emergency kit to extract O2 for emergencies.

      • Michael February 2, 2023, 8:29

        Perhaps we cap a lava tube at both ends and then drill a hole to surface to allow lots of regolith to fall in and we distributed inside to be processed.


        • Mike Serfas February 5, 2023, 16:51

          That PNAS paper talks about a shallow water table with perchlorate-containing brines. But I’ve read that perchlorate in water is only “relatively” stable, and also that ferric oxide catalyzes its decomposition. (ACS won’t even give full text from a 1923 paper, but an abstract is at https://pubs.acs.org/doi/10.1021/ja01658a006 ) The Red Planet has no lack of Fe2O3…

  • Doug Loss February 1, 2023, 13:14

    During our IRG discussion, I did try to promote a different acronym since the concept had expanded beyond just microbiome inoculation. I proposed MARLSP, which was to stand for Martian Agricultural Requirements for Large-Scale Production, but it never caught on. So just figure MaRMIE to stand for the microbiome inoculation, et. al.

  • Ioannis Kokkinidis February 1, 2023, 18:31

    I would strongly recommend partnering with a local land grant college, if you are in the United States, or your local agricultural school, if outside. There is always a professor that is specialized in mine remediation, the problem you are describing is similar. Book an appointment with him/her, explain what you want and he/she will be able to guide you. Of course you will need money for the experiment but the academic may be able to help you to give an estimate so as to know what to raise. When I was at Virginia Tech the professor that did soil remediation was Lee Daniels, but from what I see he is know retired. I wish I had more clues to give you

  • Gary Wilson February 1, 2023, 19:23

    I have been reading the recent posts with fascination. I have wondered whether there is any location on Mars with geothermal (areothermal?) heat available to provide free energy in domed crop growing areas (as well as the crew areas). What is the current state of knowledge? Thank you.

  • Jeff Wright February 2, 2023, 16:36

    Mars is the one place I want to see synthetic life set free. I seem to remember in phys.org a life form that excreted pure carbon. It may be too early for planets. I want plastic and nitrogen from Titan and iron from Mars. Our biosphere allowed life to develop industry. Mars needs the opposite.

  • H.R.C.* February 2, 2023, 17:57

    Farming on Mars? Why not ranching as well? Too bad there aren’t herds of bison running around, or Indians (excuse me, ‘Native Martians’!). We must be politically correct, shouldn’t we?


    Listen, it may very well turn out that some form of “agricultural” activity may be necessary to assist human settlement on the Red Planet. But isn’t it a bit premature to be spending such elaborate speculative resources on imagining this technology? We can’t reliably start and run a totally contained agricultural ecosystem on our home planet, there’s no chance we’ll be able to get one going on another.

    Still, this is a science chatroom, and I suppose such topics are not totally inappropriate. As my facetious link suggests, these ruminations may be more connected to some perverse nostalgia connected to some fantasy future that will never be, some deep seated cultural folk memory connected to a mythical Frontier deep in the American subconscious; a classic American daydream created mainly in Victorian penny dreadfuls and Hollywood B-pics. There’s a lot more pop cultural anthropology in these ideas than there is realistic space habitat engineering. Some folks re-create Civil War battlefields, others imagine playing Red Planet Redneck.

    We may very well be growing stuff to eat on other planets in our future, but I always visualized vats of bio-engineered algae or fungi, fertilized with human waste, mine tailings and unfortunate deceased explorers’ body parts. No doubt it will be laced with synthetic vitamins and artificial taste enhancers so it is palatable as well as nutritious..

    Mars may look a lot like West Texas, but its a whole different place. And it won’t be drawling, straight-shooting cowboys that go there, it will be the kids who took all the math their high school offered. I just hope they’re not all speaking Mandarin.

    *Henry Rodriguez Cordova

    • Alex Tolley February 2, 2023, 20:48

      (…) some deep seated cultural folk memory connected to a mythical Frontier deep in the American subconscious (…)

      There are other nations and cultures that do not share this mythos. How would the Chinese, Indians, or even Brits tackle the issue given their different histories? The dietary differences between cultures will also impact how food production is to be delivered. Cultures that eat a lot of fish might prefer fishponds rather than roaming cattle. Maybe insects/larvae might be considered more acceptable to some cultures whilst not appetizing to westerners.

      If it turns out that like the Ming dynasty’s terminating the great trading fleets and allowed the Europeans to dominate world exploration, trading, and colonization, the western nations do something similar allowing China and India to be dominant in space and on Mars, then we need to get used to the change in languages and ideas. Empires rise and fall. There is no reason to expect this will change in the future and that the Pax Americana will be replaced, as it replaced the Pax Brittanica.

      • HRC February 3, 2023, 10:41

        I remember the landing on the moon, I was dripping wet from the shower, lather on my face and a razor in my hand, weeping uncontrollable tears of joy as I watched the TV animation of the lander touching the lunar surface. I got the feeling again, that night, when the first human foot touched the surface. I can easily say it was the happiest day of my life.

        I never lost that feeling, but it didn’t take long before I realized most Americans never really grasped it, at least not in the long run. Consumerism, TV (and now, social media), and professional sports seem to be what this society is really all about. There are exceptions, of course, and we tend to collect in places like Centauri-Dreams, but not really in enough numbers to matter. We have a government that does seem to understand the necessity of space travel, but sooner or later other concerns and public preferences will drive out that spirit of exploration and wonder.

        Its appropriate you should mention the Ming Dynasty experience when faced with similar choices. But in that case, it was the authorities that put a stop to the great trading fleets, not public pressure or apathy. Perhaps the Emperor felt he had all the power and influence he needed, and felt threatened by the rising commercial enterprises that were eager to reach out beyond the Middle Kingdom.

        America will be remembered for its brave first steps into the Solar System, just as today we remember Prince Henry and the Kingdom of Portugal and its frail little caravels as they crossed the Line and first sailed into the great Southern Ocean.

        • Alex Tolley February 3, 2023, 11:36

          Purely from anecdotal personal experience, I have found that one can divide people by whether they were old enough to have watched the Moon landings, and who are too young to have done so. The almost visceral desire to see more exploration of space seems missing in the “Post Apollo” generation that I know. Maybe Artemis will rekindle the desire in the younger generations. I hope so.

          But even the older generation was limited. By Apollo 13, people were complaining about interruptions to their tv schedules. Live tv from space was already boring to many. [As bored as I am by any talk of sports. I don’t even watch any of the events of the Olympic games.] Given the spotty knowledge of even knowing the planets in the solar system, I would guess most people have little to no interest in the robotic probes, however much they are humanized using social media.

          Was this the same in Ancient Rome, where most of the year was taken up with bloody entertainment at the colosseum in the capital? That our “information” sources are stuffed with triviality while the globe cooks and we might be facing nuclear armageddon indicates that we are like the proverbial ostriches with our heads in the sand using the trivia to blot out the serious issues. Maybe it was always thus.

          I am not sure that the US public has that much influence on decisions made in Congress. Issues are fabricated but never really solved. Legislation is made for the benefit of corporations and the super-wealthy. The US legions…er, the military are bleeding the nation’s wealth and used as sledgehammers, rather than applying more appropriate tools. The lessons of the British empire are not heeded, with the US acting like Britain in the 2-3 decades after WWII, with the same results seeming probable.

          History suggests that the new frontier of space will be exploited by other, upcoming nations that are aggressively expanding their influence, not the incumbent powerful nations trying to maintain their global position.

    • Ron S. February 2, 2023, 23:18

      “We can’t reliably start and run a totally contained agricultural ecosystem on our home planet, there’s no chance we’ll be able to get one going on another.”


      • Alex Tolley February 3, 2023, 10:06

        We can’t reliably start and run a totally contained agricultural ecosystem on our home planet, there’s no chance we’ll be able to get one going on another.

        Whether we can or not, we will not do this on Earth other than as an experiment. There is no economic reason to do so.

        Extraterrestrial, enclosed food production is no longer an option, but a necessity. Whether using farming techniques or food production in factories, human survival in space will require a recycling system that is at least as good as the biosphere on Earth. If that proves impossible, one might as well give up on humans settling space. Humans in space will be just sorties, temporary base occupations, and of necessity being within the range of supply chains. Extrasolar settlement would not just be hard with propulsion as the issue, but near impossible if regular food resupplies would have to be accomplished. The only way out would be terraforming planets in advance so that terrestrial food production techniques would work within the terraformed biosphere. That will be a very long-term project, certainly not the apparently short-term economic “shake and bake” technology of the Weyland-Yutani Corp.

        Let’s suppose a year is the maximum time for a resupply ship to deliver food from Earth to a settlement. Economics and logistics of no issue. What does that imply for the farthest range of human reach with a permanent settlement in the solar system? Mars, certainly. Perhaps Jupiter, maybe even Saturn if advanced, high-velocity cargo ships can be built. At light speed, that extends to 1 light year, although time dilation might allow a more distant settlement to be possible. But clearly, if this is the scenario, then galactic expansion would not be possible. Logistically, food depots would have to be set up at the maximum range of delivery, all supported by food production on Earth. But Earth’s capability of food production is finite, which means that no possible expansion of populations can happen once that limit is reached. Suppose that is a ten-fold increase from today, able to support 100 billion people. How far would that allow populations of 10s of millions per planet to extend into the galaxy assuming the food delivery and storage logistics can be solved?

        • Ron S. February 3, 2023, 11:09

          That’s an unnecessarily long response to a simple and straight forward point.

          “Whether we can or not, we will not do this on Earth other than as an experiment.”

          Are you suggesting we should proceed to constructing human habitats in space or on Mars without first having successfully done the experiment on Earth?

          • Alex Tolley February 3, 2023, 15:42

            Not at all. It should be taken as self-evident that we should design and test on Earth (or LEO) first. What I was saying was that the incentive to test such a system will not come from commercial interests. Ideally we would have lots of setups and experience would allow the evolution of best designs and practices. Normally commercial competition would give us this option. However, in this case, that driver will be absent as it would be more expensive to produce food for consumption by the inhabitants. We are left with science experiments and wealthy individuals “vanity projects”, like Biosphere II.

        • HRC February 3, 2023, 12:00

          Hi, Alex

          I hope I didn’t give the impression I was hostile to the whole idea of extraplanetary agriculture. I do agree it will eventually become necessary–in some form. I just believe emphasis on it now is way premature. And the forms it will take will probably be totally different from the way we grow our own food here, or how we anticipate we’ll grow our food there.

          The development of closed and mobile biosystems will have to be done here on earth, whether it is financially profitable or not, so they will be fully proven, tested and operational whenever we transition from an exploratory to a colonial mode. Who would want an entire mission and all its personnel to rely on a food production system that was not bulletproof? It would be suicidal, not to mention bad for business, if we had to watch our remote colony gradually starve because some totally unanticipated chemical reaction or accidentally imported pest had interfered with our agricultural establishment.

          By the time we are ready to send out interstellar missions, or even plant permanent colonies in the solar system, we will be able to grow food in robust, self-contained and portable vats just as we now brew beer, or manufacture vaccines. And we will have learned all the skills necessary to maintain these chemical reactors. We have realized only recently that biochemistry and chemical engineering are a lot easier than understanding the infinite subtleties of ecological systems that have evolved over geologic time.

          The hardy and noble Martian farmer is a Heinleinian fantasy, just like his benign libertarian entrepreneurial regimes. Space colonization is going to be a hierarchical social enterprise, like a military unit or a ship’s crew, and probably a socially repressive one at that. Bravely challenging the unknown as free men is all well and good, but someone’s going to have make sure the utility bills are paid because in space, there is no free lunch,…or air, or water, or soil, or spare parts, or electricity, or sewage treatment. In fact, if we decide to stay, we will have to bring everything we need with us and someone’s going to be in charge of passing it out. If we need a tube of vacuum adhesive to repair a space suit tear, we better have one in stores because it may take months for a new one to be delivered. And heaven help you if you lose the one you were issued.

          Let us pick a prosaic example to guide us here. “Primitive tribes” have shown themselves to be very good at adapting to harsh terrestrial environments. We know that Neolithic tribesmen have been able to survive and flourish in the Arctic regions by exploiting local resources with great human ingenuity. But if modern, technological man moves into the Arctic, to drill for oil, hunt whales, or build a military base, he has to bring everything he needs with him. In addition, he needs to build and maintain all the infrastructure required to manage all that material: airports, harbors, warehouses, supply clerks, the lot.

          We don’t even know which local wildlife provides the right kind of fur to provide insulation for our clothing. We have to chemically synthesize it from oil in factories thousands of miles away.

          In short, its not just growing food that will be a problem, it will be everything.

          • Alex Tolley February 3, 2023, 16:06

            Your argument is why I have said before that perhaps the best colonists will not be the rich-world’s population, but rather the subsistence farmer who has little need of comforts, gadgets, and technological support. However, maintaining a base on a world like Mars will require technical expertise and all the things a technologically sophisticated base will require. And therein lies a paradox.

            If you ever played the game Sim-City, the growing city infrastructure required an ever larger maintenance budget that becomes overwhelming with the right balance of income. This is pretty much what we see in the USA today, where towns and cities cannot maintain the infrastructure they have. In our settlement case, we have a similar problem except that the more technology one needs, the greater the supply requirements needed to maintain the base. Failure to do so could prove fatal.

            Unlike self-contained farming, there is an incentive to create viable factory food production, especially using cell culture. We really need this on Earth to support the population with a higher standard of nutrition. The rich nations are leading the way and I expect eventually such methods will prove economic. Add in a moral element concerning animal husbandry (Douglas Hofstadter is vegetarian because he will not entertain the idea of killing conscious animals for food, and he sees consciousness as a continuum) and populations will abandon animal meat in favor of alternatives. If edible plant crops can be similarly synthesized more efficiently than farming, then these may become synthetic too. From a biodiversity POV, reducing farmed land area is a positive for Earth’s flora and fauna, and possibly for our mental health as well.

            If it proves viable, and the supply chains manageable, then this might be the way for humanity to settle space. If critical supplies are needed, these may be small packages of crucial biologicals to maintain the factory output. Supply ships will therefore mainly be these biologicals as well as microelectronics that today need large, expensive fabs to make, but are small in size and mass and therefore readily transportable. Add in advanced 3-D printers that can make a wide variety of items and parts from local materials and therefore reduce the spare parts stockroom issue, and settlement might be viable with just a small supply of critical, hard to manufacture items from Earth.

          • Harold Shaw February 3, 2023, 16:12

            How, by all that is reasonable, can it be premature to study food production if food production is essential for self-sustaining habitats? Same goes for any of the necessary infrastructure. Counter to what you claim, our ability to get people to Mars is outpacing our ability to keep them alive on Mars.

            I think our view on Heinlein-type libertarianism is similar. I would describe “Time Enough for Love”, with the near constant apologism for slavery, incest and pedophilia as a better example than “The Moon is a Harsh Mistress.” The desire to grow wheat on Mars, however impractical, does not make one a Heinlein-type libertarian.

      • Mike Serfas February 4, 2023, 16:39

        Mars doesn’t really need a “totally contained” ecosystem. A colony would inevitably receive shipments of personnel, the latest scientific instruments, nutritional supplements and rare elements from Earth. The goal of the Mars farming would only be to avoid the huge cost of sending broccoli and hamburger across the Solar system, when they consist mostly of water that can be found under the colonists’ feet.

        Of course, studying contained ecosystems can still pay off: for building nuke-proof refuges under cities, for moving agriculture beneath the suburbs as they turn surface farmland into backyards, for colonizing Antarctica, for creating invasive-free homes for endangered organisms. Mars and Earth should work together to keep such useful research moving forward.

        • Alex Tolley February 4, 2023, 18:16

          The spinoff of contained ecosystems was made by O’Neill. His book, “2081: A Hopeful View of the Human Future” was about using those ideas to build arcologies in inhospitable areas, like Northern Canada. I would hope we build underground farms to allow a rewilding of nature on the surface, rather than the expansion of suburbia, but that is not the capitalist way, at least in the US.
          If you have read Cixin Liu’s “Three Body” trilogy, humans do live in huge underground cities while trying to deal with the alien Trisolarian invastion. This segues to the excellent Chinese tv series “Three-Body” which is a faithful adaptation of the first book in the trilogy. I hope there are following seasons to cover the next 2 books.

    • Harold Shaw February 3, 2023, 13:39

      I understand the relatively minor pragmatic difference but conceptually, what exactly is the difference between growing traditional crops in living soil or hydroponically and growing algae in tanks? Both qualify as farms. I fail to see the fertile ground to sow your judgement.

      • Alex Tolley February 3, 2023, 16:17

        I disagree, The pharmaceutical industry growing bugs to produce insulin does not consider itself a farming industry. Fermentation production companies making beer, wine, and soy sauce do not consider themselves as farmers. Do bioethanol producers consider themselves as farmers or as part of the fuel industry? When I cultured cells on a tiny scale I was doing biology, not farming.

        Farming, even vertical farming, is based on methods of cultivation of multicellular organisms. Once that becomes more like brewing, the connotation changes, IMO. People involved in cell culture to produce cultured meat will ally themselves with the food processing industry, not the farmers. This may be little different in principle for framing in the wider sense, but it will be different from a perception POV. In California, I have never met a winemaker who considered him/herself as a farmer, despite the grape wines in the fields outside the building with the fermentation tanks, where the “real magic” happens.

        • Harold Shaw February 3, 2023, 23:44

          Farmers produce calories for their community. Vitners and brewers are a just sub-species of farmer making cold barley and fancy grape soup! The pharmaceutical and bioethanol industry don’t produce consumable calories, of course they don’t consider themselves farmers. I think you are making this more complicated than it need be. Food production is food production.

  • Harold Shaw February 3, 2023, 13:31

    The demand that habitats be ‘totally self-contained’ is a straw man. Self-sufficiency is enough. A self-sufficient habitat will be just like a living organism eating and pooping its way through its environment.

    • Alex Tolley February 3, 2023, 15:36

      How would that work with an O’Neill space colony unless there was ready access to the needed material to replace any recycling losses? A worldship traveling between the stars would have very thin gruel to feed upon, and its low velocity would mean that for a long time, it would have to be self-contained. As recycling at 100% is not possible (even terrestrial organisms need fresh micronutrients from volcanic emissions) eventually a space habitat will wind down even with lots of external energy to maintain the system.

      • Harold Shaw February 3, 2023, 23:30

        A Martian habitat doesn’t have to meet the same standards of closed system, self-sufficiency as a world ship. As you say, no system will run forever without external inputs. The claim that a habitat meet this impossible standard is a straw man.

    • HRC February 3, 2023, 17:05

      A farm is intimately connected to its environment, and the farmer has learned to modify that environment, or learned to adjust his own practices in order to accommodate it. Even if the environment or local ecosystem has been highly modified from its “natural ” state, it still incorporates many elements of the natural environment: sunlight, soils, climate, pests, terrain, and the agricultural practices of the farmer himself. This simply cannot be transplanted to a totally alien, perhaps even toxic, environment, overnight.

      By industrializing and modularizing food production, that is, synthesizing our food using chemical means, we can feed our settlers with a contained, portable system that we understand and have extensive experience with. Hopefully, these reactors will only require raw materials we have already found to be plentiful in our new home, or which we can bring with us and recycle. After some time in the new world (or some other space habitat if you prefer) we can slowly develop and perfect the methods that will allow us us to grow crops in the new environment in a more “traditional” way. Hopefully, we are already much closer to manufacturing protein and carbohydrates using microbes and chemistry than we are to growing earth plants and animals (even genetically modified ones) in the Martian wasteland.

      That will not happen overnight, as the last few threads have suggested. On earth, it took generations for farmers to learn to switch from say, slash-and-burn to plow agriculture, to hydraulic grain farming using irrigation, and even the latter evolved slowly in different climates, regions, soils and using different food species. In many cases, we had to modify the species genetically to make them truly effective food sources. The maize we eat and feed our livestock barely resembles what the Maya and Olmec grew in the jungles of Yucatan.

      We have technology now that will make that process faster, but it will still take a long time before we can establish it. In the meantime, we will still have to eat, and our vats, or yeast reactors, or our microbial fermentation solutions, whatever, will keep us alive. We have already recognized that on Mars the sunlight will be weak, water scarce, atmosphere thin, nutrients nonexistent and the soil toxic. We need to live there a long time to learn to farm there, talking about it on a chat room isn’t going to cut it.

      • Harold Shaw February 4, 2023, 0:18

        I am not sure how this relates to my comment that the demand for closed system habitats is a straw man.

        Unlike synthetic food production, hydroponics and aquaponics can be mastered by any Martian. A reliance on synthetic food will trap the average Martian.

  • charlie February 3, 2023, 15:43


    would u or would u not agree that the best course of action for colonists is to make sure that NO INSECTS (exception honeybees) are imported into the system ? Once present they’d be impossible to control; ques. is how could u do that ?

    • Michael February 4, 2023, 7:48

      I am not sure the honey bee with its sting is a welcome thing, it could potentially piece a suit as I know it goes through my leather gloves. However you do get stingless honey bees but I don’t think they are as productive though.

      • HRC February 4, 2023, 10:39

        No matter how carefully we design and test an agricultural system here on earth, we have no guarantee it will work when we deploy it in space. There are too many variables, too many unforeseen circumstances. A motivated and skilled team of colonists on an alien habitat will eventually be able to develop a viable scheme for agriculture, but it will take a lot of time, and a lot of trial-and-error experimentation. What will they eat in the meantime?

        What I have objected to in these threads is the pollyanna attitude of “Oh, we can’t carry enough food, fine we’ll grow our own when we get there. Just like the pioneers did in the American West.” This adolescent cowboy enthusiasm could get a lot of space colonists killed–needlessly. It certainly got a lot of settlers in the New World killed. THAT’s what I mean about Heinleinian exceptionalism.

        “Can a chicken fly on Mars?’ Just listen to us!

        • Alex Tolley February 4, 2023, 18:05

          I agree it is likely to take time to work out local food production methods. Eventually, to feed a planetary population food production will have to be local. A small base can be supplied with freeze-dried food, but as we see on the various space stations this is not satisfactory for permanent occupation.

          Tech people will prefer technical solutions – cell culture, aquaponics. But these can fail catastrophically. Dirt farming is more reliable, although not perfect, and terrestrial crops may need to be adapted to Mars and other locations.

          But the spinoff of creating soil is that it can be used for other purposes to make the indoor Mars environment more Earthlike. Potted plants and trees will provide the needed green, living areas for our Earth-adapted psyches. [One reason why those old illustrations of the inside of O’Neills looked like Hawaii, not W. Texas and states to the west before reaching California and Oregon.]

          City folk from Europe and the settled cities of the eastern US were clearly going to have problems as dirt farmers out west. There was a PBS series about people trying to live in Montana as settlers. Almost all had insufficient wood cut to survive a winter and would have died in reality. The droughts we are having today in the US would kill families without a social safety net, and suicides are a problem.

          Having said that, a settlement with experienced agronomists and controlled watering and fertilizer application is going to be more stable than farming on Earth with unpredictable climate and weather.

      • Alex Tolley February 4, 2023, 18:26

        Any bee is likely to be more productive than robotic bees, and less tedious than hand pollination. While honey bees have long been domesticated, there are many other pollinators, but then you run into insect control problems which is what you want to avoid.

        Honey bees rarely sting, and the stings are not life-threatening unless you are allergic to the sting. A shot of epinephrine is the treatment. It is the beekeepers that can get stung while managing the hives to collect the honey and check on the health of the hive. Also, there has to be some way to control the annual swarming. You surely want to make sure bees do not get out of the ag greenhouses into the main base.

        • Michael February 5, 2023, 17:05

          I am a bee keeper with 5 hives, swarming is a royal pain !
          Once you see the signs of the Queen cups been closed a split is generally needed but not always successful. We do what we think they need and they do what they want ! And getting stung is part of the hobby I guess.

  • Alex Tolley February 3, 2023, 18:53

    It might be problematic restricting insects to only honeybees. While they solve the pollination issue, I am not sure removing all other insects is the right course.

    For example, suppose you want to introduce birds. Many are insectivores. Without insects, will they healthily switch to other foods, even synthetic cultured cell types?

    Also, if we go with creating soil, I am not sure that we can eliminate all insects. We do require arthropods and annelid worms, and I gather ants can be very important insects. [But note the ants took over Biosphere II.]

    As you know humans shed considerable quantities of dead skin. These are consumed by mites. If they are eliminated, how do we dispose of the dead skin flakes – robots?

    So to answer your question it may depend on the ecosystem being built. Dirt farming may require insects. Cell culture may avoid them, but I am dubious. We certainly would want to keep cockroaches, houseflies, and mosquitoes out of the base. But if we do get houseflies, then spiders maybe your friends to keep them under control.

    I’m sure experts could give you a better answer, but these were my first thoughts in trying to answer your question. IOW, there is no definitive Yes or No answer.

  • charlie February 5, 2023, 20:50

    “It might be problematic restricting insects to only honeybees. While they solve the pollination issue, I am not sure removing all other insects is the right course.

    For example, suppose you want to introduce birds. Many are insectivores. Without insects, will they healthily switch to other foods, even synthetic cultured cell types?

    Also, if we go with creating soil, I am not sure that we can eliminate all insects. We do require arthropods and annelid worms, and I gather ants can be very important insects. [But note the ants took over Biosphere II.]

    As you know humans shed considerable quantities of dead skin. These are consumed by mites. If they are eliminated, how do we dispose of the dead skin flakes – robots?”

    I’ve thought about it, and the ans. (except Honey bees) is probably, : No to bugs, but Yes to bacteria

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