Hello, everyone. I told Sarah about something a few of us at the Interstellar Research Group (IRG) have been throwing around for a few weeks, and she asked me to do a guest post about it. I have to warn you all, this will have a call to action (or at least dissemination) at the end, so be ready!
Just a note on usage. I’m writing this in the first person, as if I did all this myself. Some of it I did personally, some of it was done by others or supervised by them while I did the scut-work. Just FYI.
A few weeks ago a number of us from the IRG were attending LibertyCon in Chattanooga, which was where our organization was initially started a good number of years ago. Some of us were on a panel discussing what was needed to establish an enduring human presence on Mars. During the discussion it became clear to us that pretty much all the researchers and research being done were focused on technological aspects of the question, and next to none on the biological ones. By this we meant the creation of functional “soil,” not merely regolith, which would have the biological microbial components common on Earth to allow the healthy and healthful production of vegetable crops for human consumption. It turns out that a few of us at IRG have the contacts and backgrounds necessary to conduct exactly that primary research. I decided to spend the next week or so trying to marshal commitments from the people and facilities we would need to get this research started, and then to see if we can break some new ground (yes, I realize the pun I just committed) in extraterrestrial farming!
I think the project I’m going to propose would fit very nicely into the overall Space Analog for the Moon and Mars (SAM) project (https://samb2.space/). Here in broad outline is the proposal.
We’d like to set up a “shoebox” environment, in a small sealed system, where a totally accurate Martian regolith simulant under as accurate conditions of temperature, atmospheric composition and pressure, incident radiation of all sorts and any other relevant conditions can be inoculated with various mixes of biological agents to see the possibilities of creating a microbiome of sorts within the regolith, creating an analog to terrestrial soil rather than the (presumably) sterile substrate endemic on Mars.
I did some very rough preliminary research on this idea. I thought the first thing we would need to do is a literature search to see if anyone else has indeed done some work around this idea. I hadn’t done anything yet as I wanted to gauge the possibility of getting an actual experiment started before investing the time. But my initial thinking was that if it had been done, we all probably would have heard about it, as it would have excited lots of people.
The next thing would be to assemble a competent research team of interested people. I’m thinking soil microbiologists, researchers into the composition of the Martian regolith, the Martian atmosphere and the surface radiation environment, etc. To that end I’ve come across this article:
https://www.space.com/21554-mars-toxic-perchlorate-chemicals.html from 2013, in which some of the questions we would investigate are mentioned. The questions are addressed by Peter Smith, who is a professor emeritus at the University of Arizona. I hoped we might be able to approach Professor Smith for some advice and perhaps assistance in assembling a research team.
As for materials needed, the current standard source of Martian regolith simulant is MGS-1 from Exolith Lab in Florida:
This simulant is well thought of, but doesn’t include the calcium perchlorate that would be needed to truly simulate the Martian regolith. This is because perchlorate in the needed amounts is basically poisonous. Nevertheless, to conduct the experiment properly we would need to mix the proper ratio of perchlorate into our test environments. This would likely require clean-room conditions, BIGs (biological isolation garments), and such. Ca(ClO4)2 or CaCl2O8 is available from various sources:
In my head, here is how I’m envisioning this experiment. We would need a hermetically-sealed container of moderate size to contain a depth of regolith simulant. This container would need to be capable of holding a temperature at the regolith surface of 20 C to -75 C, and a gas pressure of 6.35 mbar with a gas composition of:
gas percentage by weight
carbon dioxide (CO2) 95.32
molecular nitrogen (N2) 2.7
argon (Ar) 1.6
molecular oxygen (O2) 0.13
carbon monoxide (CO) 0.07
water vapour (H2O) 0.03
neon (Ne) 0.00025
krypton (Kr) 0.00003
xenon (Xe) 0.000008
At a guess, the noble gas components could be ignored, but I suspect the rest would need to be kept in the mix.
As for the surface radiation environment, this is the information I have:
I have no idea what would be required to duplicate this in the experiment or if it is even possible. As for visible light, the maximum solar insolation on Mars is about 590 W/m2, and would have to be variable from 0 to this maximum on the Martian solar day length of 24 hours, 39 minutes and 35 seconds.
What biological inoculants would be used for purposes of this (actually these, as I would expect different “bouquets” of inoculants would be tested) experiment is something I have absolutely no knowledge of, which is why I’m just a fan-boy rather than a principal investigator.
We knew it wouldn’t be as easy as Matt Damon made it look, just crapping on some regolith and shoving potatoes into it, but hey, we’re big-brained scientists, we ought to be able to figure it out!
I found 5 scientific papers dealing with plant propagation in Martian regolith simulant and downloaded 4 them (the 5th would cost $51 to get, which is a bit pricey for me right now) and read through them to see if there are any referenced papers in any of them that I could also get. But from a quick glance it didn’t appear to me that any of them approached the things that we were talking about.
Unfortunately, from the abstract the one paper that would cost me looked to be the one closest to what we’re proposing:
“This article aims to inform the development of biological perchlorate remediation schemes for the preparation of safer human Mars habitats and contaminant-free in situ resource utilization (ISRU) for crop production in these settings. No prior studies have attempted to remediate perchlorate from Martian regolith simulants. Thus, we draw from previous work on soil, sediment, and water biological remediation that we determined to be most relevant to Martian applications. Approaches include phytoremediation and microbial remediation. Phytoremediation utilizes terrestrial and aquatic plants for perchlorate removal, occurring by 3 different mechanisms: phytoaccumulation, phytodegradation, and rhizodegradation. We suggest potential plant candidates for phytoremediation. We discuss known microbial remediation processes utilizing both rhizosphere-derived microorganisms and extremophiles, and the most likely microorganism candidates for a successful microbial remediation of Martian regolith considering the harsh Martian environment. We also briefly discuss the economic implications of perchlorate remediation for ISRU farming
viability. We recommend this article as a reference for future attempts to successfully and cost-effectively develop biological remediation technologies to remove perchlorate from Martian regolith, improving the viability of ISRU crop production.”
Its focus was on perchlorate removal rather than microbiome construction, but it was definitely closely adjacent to what we’d been talking about. I contacted the lead author and added him to our emailing list with his consent.
It was at this point I started to get some helpful ideas and suggestions from the correspondents.
Nick Nielsen said, “Thanks for this! It is an important problem, and there are a great many directions that research could take. For example, you note that the starting point would be ‘a small sealed system, where a totally accurate Martian regolith simulant…’ If one wants to get from regolith to a functional soil, should one assume that all this is being done on a planetary surface (presumably on Mars) or is the regolith simply to be the soil ‘seed’ as it were, not necessarily tied to the planet from which it is drawn? That is to say, one could experiment with regolith on a space station apart from any planetary surface, and this raises the question where the best soil-precursor is to be found. It might be on a moon of Mars, or an asteroid, or some other place.”
Joe Meany said, “I followed up on the question of perchlorates in the martian regolith that you and I discussed after the panel. The space.com article you suggested led to a really nice review article by Chris McCay. It turns out that the perchlorate salts can be present in as much as 1%(!) with a mixture of calcium, magnesium, and ammonium cations.
“This is actually quite interesting, as those three cations are biologically important. I especially didn’t expect the ammonium perchlorate, but ammonium salts are especially valuable for habitation. There are well-identified bacterial strains capable of reducing perchlorate back to (biologically important) chloride, producing two molecules of breathable oxygen per molecule of perchlorate. Perchlorate salts are also water-soluble, so once martian regolith is introduced to a bacterial tank, it will be quickly accessible for metabolism. Importantly, the breakdown of the perchlorate salts would be exothermic, allowing some non-zero energy transfer from the exterior environment into the habitat via this metabolic process.
“Furthermore, it seems that the mechanism of perchlorate formation comes from UV exposure in the martian atmosphere, so simply disposing any unwanted regolith back outside would ‘recharge’ it for future consumption.”
The head of the SAM said, “Yes, there is a need for this, and it is a good fit for SAM (in fact, it was an original cornerstone to our science objectives). I suggest only that there is quite a bit of research into this already (mechanical, chemical, biological) so be certain that you are not duplicating research already in motion.
“From the SAM point of view, the best thing to do is to build a team that would work within SAM for a defined period of time, perhaps with Mars regolith simulant (look to https://www.offplanetresearch.com/). The team project proposal would need to take advantage of the hermetically sealed environment (meaning, what can you do in SAM that you can’t do in a normal lab). Cost is approximately $12k per week for a team of four.”
This brought up a significant cost factor, which we ignored for the moment. I then received a reply from Dr. Christopher Oze, the lead author of the one paper (above) that I hadn’t read:
“I’ve been working on Martian regolith and using it for a variety of purposes from construction to agriculture on Mars for a little over a decade now. I would probably say most of my research has been centered around dealing with the non-tech issues related to humans being able to cope/progress on Mars (www.chrisoze.com has a few examples) If you’re looking for martian regolith at bulk scales for agriculture or civil engineering purposes, we can recreate it at kilograms scale for just about any reported value (mineralogy, geochemistry, particle size, etc.) from Mars’ surface. We just spent the last year figuring out how to remove (or cope) with perchlorate in regolith. Besides that, so many other issues need to be figured out such as how to stop the naturally cementing nature of regolith related to particle sizes/texture, how seed size plays a critical role for plant success, or how perchlorate (even when removed) may have increased metal availability so much that the plants will have to deal with this as well (serpentine soils and its vegetation on Earth provide some lessons on how to get around this issue).”
I replied to him, “Thank you for your assistance in our nascent quest to find other work in this area. We haven’t gone through the literature in any detail yet, but from what I can see no one has looked at regolith inoculation in situ or attempting to create a terrestrial analog microbiome in any Martian regolith. Do you know of any work in that specific area?”
He came back with, “I’ve run a few experiments where I have added perchlorate (at martian levels) to terrestrial soils and found that it adversely affected the microorganisms as well as the plants. Part of prepping/inoculating the regolith is related to how to deal with perchlorate. There are a few microorganisms that can use perchlorate and that might be a good starting point.”
I let him know that I’d just found these papers:
I’ve found these papers during my literature search for experiments in similar areas:
Potential Biological Remediation Strategies for Removing Perchlorate from Martian Regolith
The legume-rhizobia symbiosis can be supported on Mars soil simulants
Cyanobacteria and microalgae in supporting human habitation on Mars
One of the manufacturers of Martian regolith simulants chimed in: “Mars regolith, and thus simulants for it, is a very interesting material. One of the biggest challenges- that might actually be a benefit in this area of research- is the wide range of compositions and material properties on Mars. One general Martian simulant is unlikely to be representative of much of Martian regolith. This is also an issue with lunar simulants, and the Moon has much less variability compared to Mars! Historically, the majority of our simulants are made for the lunar applications and we have four general simulants (and counting!) depending on where our clients plan to land in addition to customizing compositions for specific use cases. Looking into the specifications of a landing site would be a good first step to determining the ideal simulant properties and composition.
“The benefit to the variety of Martian regolith is that there will likely be some compositions better suited for agricultural purposes. Very recently, early studies using Apollo lunar regolith noted a difference in plant growth based on the maturity (age) of the sample. Like on Earth, targeting areas that are more ‘agreeable’ to agriculture would save a lot of effort and resources as does choosing the right crops for that region.
“Regarding perchlorates in Martian regolith, there are hazards as you noted which I assume is why UCF isn’t selling them in their Martian simulant. It is not something you want to provide to someone unused to handling them, but I also say that about regular simulants due to the dust hazards. We have been developing Martian simulants as well and are exploring the use of perchlorates for specialized use.
“One thing to keep in mind with all simulants is that understanding its use cases, strengths, and limitations is important as is accounting for these variables. This comes down knowing which properties of the simulant are vital (ie. mechanical, physical, chemical, etc.) and which ones may not be as accurately represented in the test material. Additionally, understanding how the test setup affects the test material is important. It sounds like you are looking into environmental conditions, but that will cause the simulant to act differently than it does in an ambient environment so characterizing those differences may (or may not) be important to understanding how it will affect the test results.”
It was at about this time that I wrote up a where-we-are-now summation of the initial excitement with this idea:
“I’ve spent the past few days, when I’ve had time, reading through the papers I mentioned to you all and noting papers in their references that will be interesting to read. While I haven’t finished reading all of these papers, I did notice one thing that seems to be a constant with the research being done heretofore. First though, there has been a fair amount more research into the biological and agricultural suitability of Martian regolith that I or most of my more technical-minded friends had realized. Great!
“But what I noticed is that (so far in my reading) none of this research was done in anything remotely approximating a Martian surface environment. Instead, everything seems to have been along the lines of, ‘if this Martian regolith existed on Earth, with our temperature, atmospheric composition and pressure, insolation, etc., trying to grow plants on it would give this result.’ This, while interesting, doesn’t seem particularly useful to me. It’s along the lines of the underpants gnomes from South Park, missing an important step in what is intended:
1. Regolith on the surface of Mars
“If we do move forward with the type of experiment or experiments I and others here have envisioned, I think we need to focus on that step 2, and most importantly the early part of it, what it might take to make Martian regolith under Martian surface environmental conditions more amenable (or amenable at all) to the growth of terrestrial plants. I hope these thoughts might help us define the experimental designs more rigorously.”
I followed that with: “As you can tell from my email address, I’m sending all this out through my connection with the Interstellar Research Group (IRG). That’s because when the idea came up at the recently-concluded LibertyCon science fiction convention in Chattanooga, a number of us on the panel generating the idea were in some way connected with the IRG and got support from the organization to explore the idea.
“Here is where things get a bit murky. The IRG isn’t a research institute and isn’t set up or equipped to pursue primary research such as the Mars Regolith Microbiome Inoculation Experiment (MaRMIE–I’ve just invented a shorthand acronym for this concept) experiments. Further, the remit of the IRG is interstellar topics, not intra-system ones.
“So if MaRMIE is to go further than these discussions, we will have to identify one or more institutions able and interested in such experiments and persuade one or more researchers at said institutions to propose and take charge of the experiments.”
(More on that in the final call for action below.)
A few more comments about the experiment itself, from a seasoned technologist and space entrepreneur in the group: “‘cheap’ Martian agriculture would be inflated plastic bubbles as greenhouses, pumped up with Martian atmosphere to enough pressure to let the plants grow (at least about 0.2 bar, though more may well be required), with the soil used as growth medium, irrigated with external water supply (from ice or permafrost mining most likely, though atmospheric condensation is also a possibility).
“You’d want a very low-labor way of prepping the soil; if you have to get the perchlorates out (about which I have no opinion), you’d want to do something simple — mound the soil up and let the water pull them out, or plant an initial crop of something tolerant to the perchlorates and then mulch it back in, or something.
“But yes, the combination of conditions hasn’t often been done. If you wanted to get really aggressive, you’d combine that with a clinostat to simulate the Martian gravity effects. Oh, and you hardly need an experiment to show that standard Martian surface pressure won’t work; the plants would be freeze-dried! The question is how low of a mostly CO2 atmosphere pressure will work.”
I answered, “I was thinking about the clinostat idea, but I think that would probably be a bit cost-prohibitive for the size we’d need for macro-plants in even a greenhouse environment. I’d like to start first with regolith inoculants to see if we can remediate the perchlorates biologically and retain some of the chemical components for plant use. As to increasing the pressure and probably temperature, I’m thinking of those as variables that could be part of the experiment. What I’m hoping for is an experiment that might show that the current environmental conditions aren’t at all compatible with agriculture, and might then allow the gradual modification of one condition or another till we find the minimum needed for useful agricultural production. I was thinking maybe some arctic microbes, fungi, etc., would have a shot at these temperatures and atmosphere conditions.”
It was at about this time that we started to think about who might be able to perform this experiment, or these experiments if (as it probably should) this idea expanded into multiple tests. I contacted some of the authors of papers our literature search had come across to see if they would be interested, without any success. I did have a thought that perhaps we could contact SpaceX and inquire about their assistance or even take-over in conducting such an experiment, as their stated long-term goal is colonizing Mars. This research would clearly (to my mind at least) need to be done before any such colonization could be successful.
Again, Joe Meany came up with an interesting idea: “My recommendation for strategy is to write a review article based on the currently available literature that you’ve begun to post within the earlier threads. To give ourselves a deadline, I think we would want this together for the next IRG newsletter (giving us a little over 3 months to complete). I think the coauthors on the review article need to express affirmative response by some close deadline (July 1?) so that we know exactly who is interested in this project and being actively involved. If we do this right, a summary of our findings can be published in the newsletter, but I think that a properly thorough research review article would be publishable within a journal like Acta Astronautica.
“Within the time that we are writing this article, we should have already identified how to answer the “Heilmeier Catechism” which will guide both that review research and specifically pre-answer questions as to how we’ll fund actual experiments. Narrowing down funding sources will dictate who we ultimately select as partners going forward.”
The simulant manufacturer had these thoughts: “I’m not sure I have much to contribute to the research side at this point, but I will throw in a few cents to the ‘how to start this’ discussion. It is essentially going to come down to experiment fidelity, budget, and time. I would argue that the second and third points will influence the first. If you are going for the type of fidelity I believe you are for this experiment with all the environmental parameters tightly controlled, it is going to be very costly especially given that agricultural experiments can run weeks and have multiple samples to create some level of statistical significance.
“While the organizations involved currently in the discussion may have internal funding to support the project, I would not hang my cap on that just yet. Even if they have internal funding, they may have to petition for it (while not included here, I know SwRI does this internally). If you are looking for outside funding, the project and its partners will need to be defined and a grant proposal put together. From experience, this starts to extend the timeline as there is a lot of ‘hurry up and wait.’ This is fine if there is not a rush for the information, but likewise, if there is not a defined ‘need,’ will it be funded?
“Conversely, if you pass this project on to a company, such as SpaceX, the control over the fidelity of the experiment will turn to them. In our work, we find a lot of things besides the test environment and test materials influence the budget, and thus testing is often relegated to the side until it is time to do so. By that point, budgets are mostly allocated and timing is very limited (ie. happening in the next few weeks). This greatly limits what can be done. This mentality is starting to change slowly so I am hoping more people begin testing plans sooner and with more resources, but that is not always the case.
“All that to say that if the project ends up being pursued, going in with a good, realistic game plan of what needs to be accomplished, what it will take to do that, and finding people with the same passion for good results is important!”
One more comment from an experienced space enthusiast about the experimental procedure itself: “It doesn’t seem to be a hard thing to do. I think the setup of the Martian conditions could be done quite simply with a regolith analog, placed in a low-pressure vessel with dimmable LED lights to mimic the Martian insolation (if needed).
“I would have thought this would make a good PhD program experiment. I vaguely recall having read about something like this as having been done. (It was certainly done on lunar soil and analogs in the 1970s, although the purpose was to see if crops could be grown, rather than creating terrestrial soil.) The kit seems to be fairly minimal in cost. The hard part is getting the inoculants and deciding how to measure progress – e.g. bacterial density over time, perchlorate concentration, etc.
“My question is how much does it have to mimic Mars’ external environment. Could the experiment be done with the regolith analog, but under 1 atm of air and whatever light conditions are desired because on Mars this could be inside a structure that is being prepared for agriculture?
“I would start under terrestrial conditions, and then, if successful, create a set of experiments to mimic stages towards a native Mars environment to see which, if any, conditions impact growth and perchlorate removal.”
I’ve included a list of all the papers dealing with agricultural and biological experiments in simulated Martian environments here, if you’d like to see what we found. There are many more, these are just the ones that caught our attention as particularly cogent to our idea.
So now, the call to action. We have a general description of the experiment or experiments we’d like to conduct, and are amenable to some modification of the details and procedures. What we don’t have is a research organization or researchers interested in and willing to conduct this (these) experiment(s). We are approaching various organizations as we identify them, but we’re hoping you might have some ideas of who to take this to and how to approach them. If you do, please contact me at email@example.com. And if you don’t have any ideas but have any friends in fields related to this, pass the message along to them and see if they can help!