Let’s break for a moment with interstellar issues to finish up a story I first covered at the beginning of the year. In 2022, members of the Interstellar Research Group led by Doug Loss began exploring the biological side of establishing a human presence on Mars. By ‘biological,’ what the team was looking at was how to create soil as opposed to regolith, soil with the microbial components needed to produce crops for human consumption on Mars. Alex Tolley wrote the idea up in MaRMIE: The Martian Regolith Microbiome Inoculation Experiment. Today’s post is the finalized document that has grown out of this effort, an attempt to foster further research by offering a framework for experiment. While the IRG lacks the means of executing these experiments itself, it offers this paper as a contribution to planetary studies to connect with those who can.
by Alex Tolley and Doug Loss*
* Contact: Doug Loss at douglas.loss@irg.space
Abstract
The proposed designs for the settlement of Mars include various approaches for local food production. Food will most likely be based on traditional terrestrial crops to ensure that a variety of cuisines can be cooked for the well-being of the settlers. To farm on Mars, as well as provide an environment for plants and trees, will require establishing soils using the Martian regolith. The presence of (per)chlorates at levels toxic to plants and humans requires remediation of the regolith to remove the (per)chlorates. Prior work indicates that there is a knowledge gap in how to remediate the regolith to make it ready to support various crops for Martian agriculture. We propose a framework of experiments to help bridge the gap between the state of the regolith on the surface and the initial stages of soil creation.
Introduction
With the renewed interest in settling Mars, there has been considerable attention on how to feed a base crew and its subsequent expansion into a larger settlement population. Unlike a human presence in low Earth orbit (LEO) and on the Moon where travel times are sufficiently short that food can be provided in regular shipments from Earth, the long 6 to 9-month, low-energy journeys to Mars that have 2-year gaps between flights, suggest that using local Martian resources to grow food would be a better option, both from economic and safety perspectives.
It should be noted that the flight times with current rocket transport technology are similar to that of the sailing ships traveling from England to the Botany Bay colony in Australia in the late 18th century. The resupply ship arrived 2 years later, with the colony starving from inadequate food supplies and an inability to successfully farm. Local food production on Mars would ensure that adequate, high-nutrition foods are available and avoid any supply problems from Earth.
The lower ambient light levels on Mars are sufficient for photosynthesis for a large range of plants from unicellular algae to many terrestrial crops [28]. Additional light if needed can be supplied with mirrors or artificial lighting. The question then becomes what sort of plants should be cultivated? The simplest plants, such as cyanobacteria, have been proposed as they have short lifecycles and rapid growth, requiring small production areas and a few basic nutrients. However, anecdotal evidence from supplying astronauts to the ISS indicates that food quality is a very important factor in astronaut well-being [46,47,48]. Experiments with celebrity chef-developed meals have proven the popularity of meals that are similar to those on Earth and that are tasty, not just nutritious. For crew and settlers staying for long periods on Mars with minimum 2-year rotations, foods that can be prepared with different cuisines to be cooked by a base chef or personally would seem to be preferable. Cyanobacteria and algal species may grow quickly and be technically nutritious. However, algae is not a completely nutritious diet and only Spirulina [30] has been shown to be useful as a meal supplement, used for less than 1% of the diet, and therefore should be considered as feedstuffs for animals and as soil amendments.
Growing conventional food hydroponically [28] is often mooted as the means to grow conventional crops. It has the advantage of having a pedigree of experience in terrestrial farms as well as experimental success in space. Hydroponic food production can be carefully controlled which makes it attractive to those of technical expertise. However, hydroponics requires substantial inputs of nitrogen and phosphorus which are usually applied directly from external sources, and not all plants can be successfully grown hydroponically. In addition, an expansion for a growing settlement will require either transporting equipment from Earth or finding ways to manufacture at least the simple components locally on Mars. A more attractive approach has been to try growing conventional crops in the Martian regolith. Experiments using regolith simulants [4] have shown that given added nutrients and light, a number of common terrestrial leafy crops can be grown.
The advantage of using the Martian regolith as a medium to grow conventional crops is that it provides the needed anchorage and potentially water retention medium used by terrestrial plants. Martian agriculture would work like terrestrial agriculture which is done in a greenhouse. On Mars, the atmosphere and temperature would be controlled to maximize crop growth and it is feasible that some animal species might be transported to produce the high-protein foods. For example, fish eggs could be transported and herbivorous fish species such as Tilapia could feed on the algae and convert it for human consumption. However, it should be noted that soils are not simple, but include ecosystems with a large number of species including bacteria, fungi, and animals from annelid worms to insects..
Despite the research done to date, there are considerable gaps in our knowledge concerning how Martian agriculture should proceed. The Martian environment is very cold, and dry, with a thin atmosphere around 0.1% of Earth’s, composed mainly of carbon dioxide with a little nitrogen. While aqueous algal growth experiments have been done in conditions that approximate some of the Martian conditions, it is not known which conditions must be tightly
controlled for good growth of the algae. For complex plants that are to be grown in either regolith or hydroponically, what partial pressure of CO2 in the atmosphere and at what pressure is needed to ensure healthy growth? Crops grow in different soils on Earth, from near desert sandy soils for millet to rich dark loams and different acidities for different crops. We take for granted the quality of terrestrial soils, but on Mars, the regolith is considered sterile, with no organic carbon content to retain water and provide an environment for soil organisms.
Given that these conditions can be evaluated on Earth, the big gap in our knowledge is the issue of remediation of the toxic levels of (per)chlorates in the Martian regolith. All of the various experiments on growth conditions assume that none of these toxic compounds are present. Powdered terrestrial rocks and more carefully constructed Mars Regolith Simulants are free of (per)chlorates and therefore experiments on plant growth assume the (per)chlorates are removed. With (per)chlorate levels that are far higher than any found naturally on Earth, they are at levels found around sites that manufacture munitions where the compound is used as an oxidant. The US EPA has guidelines for the remediation of soils contaminated by (per)chlorates [36].
Soils can vary, with plants varying in requirements for water, nutrients, soil carbon, soil organisms, pH, climate, and weather conditions. Nutrients and organic carbon will need to be added, as well as soil organism inoculants to improve the regolith to become a soil capable of good crop production.
To get an agricultural food system working, which factors are critical? How best to detoxify the regolith? How best to amend its properties? Which crops are best suited and at which stages?
A low-mass approach is to employ bacteria that can metabolize (per)chlorates and grow locally. (Per)chlorate metabolizing organisms are proteobacteria of which there are more than 40 species known. Dechloromonas and Azospira genera appear to be ubiquitous on Earth. They have different pH tolerances and some can function in acidic conditions as low as pH 5 [10] The Martian regolith has up to 1% of (per)chlorate [13] which is far higher than any uncontaminated place on Earth. (Per)chlorate reduction only occurs in anaerobic conditions [3]. This suggests that regolith remediation may need to be kept isolated from the crop-growing areas. Experiments with Moorella sp show that these bacteria can grow on a variety of reduced carbon sources, optimally at neutral pH and warm temperatures (40-70C) [2]. None of the experiments have tested the (per)chlorate-reducing metabolic rates and growth of the various potential bacterial inoculants under conditions between Mars and human habitation, such as lower atmospheric pressure, gas composition, and water requirements. As these bacteria need a carbon source, how would that source be provided by chemical means or by biological carbon fixation?
There is considerable interest in using cyanobacteria as carbon-fixing microorganisms. These hold promise to weather the regolith, release nitrogen and phosphorus for growth, create organic carbon to improve water retention, and allow a richer variety of solid organisms that may be needed for crop growth. These cyanobacteria have been tested in a variety of conditions to determine how they will fare under conditions closer to that on the surface of Mars. Resting states of cyanobacteria suitable for transport from Earth indicate that UV exposure is not tolerated, although survival in a vacuum is good [34]. Cyanobacteria do require a lot of water to suspend the rock dust and particles, In CO2-dominant atmospheres, full terrestrial pressure reduces growth, partly because of the lowered pH of the aqueous media, while 100 mbar appeared more favorable. Temperatures need to be maintained between 15 and 30C. Most important is the finding that cyanobacteria cannot survive in (per)chlorate-contaminated conditions, requiring its removal before growth [30]. Extensive testing of bacteria has shown that while a few can survive down to the 7 mbar of the Martian atmosphere, most require at least 25 mbar. Nitrogen-fixing bacteria can fix atmospheric nitrogen to as low as 1 mbar, but the 2.8% of nitrogen in the Martian atmosphere would require increasing the total local atmospheric pressure 50x.[40]
From this prior work, it is clear that there is a difficulty in remediating the Martian regolith from its toxic state to a soil suited for crop growth. (Per)chlorate-reducing bacteria require reduced carbon sources with nitrogen and phosphorus for growth to detoxify the regolith. Ideally, this could be supplied by cyanobacteria that fix the CO2 in the atmosphere and can release the nitrogen and phosphorus from the regolith. The cyanobacteria can also provide the organic carbon in the soil to support crop growth. However, these cyanobacteria cannot tolerate the toxic (per)chlorates. Lastly, both the (per)chlorate-reducing bacteria and the cyanobacteria need to grow in aqueous conditions with the regolith particles separated to allow rapid microorganism growth. The regolith would then need to be drained and allowed to dry out before being suited to most crop growth, although rice might be able to grow in a “paddy field” of regolith that has settled. This suggests that there may need to be separate areas for removing the (per)chlorates, supplying needed nutrients for the (per)chlorate-reducing bacteria, by cyanobacteria growing in pre-treated regolith.
The following outline experiments are suggested to fill the gaps in treating the Martian regolith to make it suited for growing crops for the Martian settlement.
Suggested experiments
The exposed Martian regolith is both too cold and dry, as well as relatively airless, for bacteria to detoxify the (per)chlorates. Ideally, the detoxification would take place in optimal growth conditions for the bacteria. Given that maintaining atmospheric composition and pressure, as well as water and humidity conditions, incurs a mass penalty, it is important to determine what are the factors that can be reduced towards Mars’ conditions to reduce this cost. This will help decide whether the detoxification process must be carried out in a greenhouse suited to growing conventional crops, or whether simpler management of the regolith is sufficient. Other questions are also evident, such as the level of detoxification necessary before crops can be successfully grown in the treated regolith.
This suggests several experiments to test for these factors:
1. Composition of Bacterial inoculant
There are many known terrestrial (per)chlorate-metabolizing bacteria, e.g. Dechloromonas that can metabolize oxygenated chlorines. All are anaerobes and therefore may function with the existing composition of the Martian atmosphere. Questions to be considered are:
a. Should the inoculant be a single species or multiple?
b. Do other species need to be included to create a viable ecosystem, or are single-species populations both sufficient and effective?
2. Atmospheric pressure
Mars’s atmosphere is about 0.7% of that of Earth. While too low to support crop plants, how much pressure is needed for bacterial growth to be maintained? Unlike plants, the bacteria are aquatic, and therefore the needed atmospheric pressure need only be sufficient to prevent water from boiling off. In a sealed reactor, water vapor will provide the needed pressure to maintain the equilibrium. As the bacteria are anaerobes, the regolith would seem likely to be processed in separate areas from the crop plants, with the detoxified regolith then added to the agricultural area in the greenhouse to increase the cultivation area.
3. Atmospheric composition
Mars’ atmosphere is primarily CO2 with a little N2. This is not suitable for crop plants, but how much of a factor is this for the bacteria? Combined with atmospheric pressure, what composition is needed for the bacteria? For example, does the nitrogen partial pressure need to be increased to supply the needed nitrogen for bacterial growth, perhaps in combination with nitrogen-fixing bacteria in the inoculant, or just added as ammonia or nitrate? [c.f. Item 1 concerning species in the inoculant.]
4. Hydration
Lastly, bacteria need wet conditions to grow and multiply. How wet does the regolith need to be for the bacteria? Do the bacteria survive and grow in an aqueous slurry, or would high humidity conditions be sufficient, saving water resources needed elsewhere?
To test these, experiments will need to be set up in conditions to test these various requirements, most probably in containers to maintain the conditions. It is assumed that surface UV and ionizing radiation do not need to be tested as simple shielding will be sufficient to mitigate these factors.
These experiments are primarily devoted to extending the existing work done on (per)chlorate removal by bacteria [2,10,13,22], extending prior work. If the regolith detoxification and preparation for traditional crops is to be the goal, the regolith will need additional preparation for crops, including nitrogen, phosphorus, and carbon supplements. Inoculants may be required to allow nitrogen-fixing bacteria to grow in association with the root nodules of crops like green beans. Prior experiments [30,34,40] with cyanobacteria have demonstrated the extraction of nitrogen from the regolith, suggesting this approach to fertilize the crop plants after the regolith has been cleared of the toxic chlorate and (per)chlorate.
A stretch goal might include gene splicing experiments to extend the capabilities of some microbial species. Can the (per)chlorate-reducing genes be added to cyanobacteria removing the need for the bacterial species? Conversely, can genes to extract the nitrogen and phosphorus from the regolith be inserted into the bacteria? Can the (per)chlorate genes be edited so that the oxygen is liberated safely in the organism, allowing the (per)chlorate to become an oxygen source for the Martian settlement? Suggestions as to possible ideas have been mooted [40, 49].
Conclusion
To start processing Martian regolith for food production on Mars, there is a substantial gap in our knowledge on getting this process underway in the volumes needed compared to the small-scale lab experiments. Firstly, the regolith must be detoxified to remove the (per)chlorates. While the lab experiments demonstrate that various species of bacteria can metabolize the (per)chlorates, there are two limitations. Firstly, the regolith needs to be in powdered form to expose the surfaces to the bacteria and be turned into an aqueous environment for the bacteria to survive. How wet the slurry needs to be is unknown and therefore the water requirements are also unknown. Secondly, the sterile regolith provides no useful food supplies for the bacteria to grow. How to supply the nutrients and from what source needs to be determined. Terrestrial starter kits may be inadequate for bulk regolith processing.
Cyanobacteria have been demonstrated in the lab to be able to fix the atmospheric CO2 and grow while extracting the needed nitrogen, phosphorus, and trace elements from the regolith, but only after the (per)chlorates have been removed.
Terrestrial crops are yet another step away as they need detoxified regolith, fertilizers, and organic carbon in the “soil” to grow successfully, suggesting that both the (per)chlorate-metabolizing bacteria and the cyanobacteria must preprocess the regolith.
While the bacterial cultures grow in aqueous conditions, terrestrial crops do not and are therefore subject to even more critical issues of the surrounding atmosphere: pressures, and composition.
Currently, it appears as if the regolith can be prepared by iteratively starting with (per)chlorate-metabolizing bacteria, followed by cyanobacteria to grow and produce the needed food for a larger amount of regolith to be detoxified so that large volumes of regolith can be prepared for conventional crops to be grown. Once the regolith has been prepared it is turned over to the agronomists to determine how best to provide the conditions and associated organisms to cultivate crops to feed the base crew or settlers. While hydroponics is favored for supplying small populations with food, more conventional agriculture using local resources including the regolith seems more likely to be the preferred approach once large settlements start to appear.
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An impressive bit of scholarship. But aren’t we a bit premature?
Perhaps we should postpone thinking about all this until we actually analyze a few liters of Martian soil. No doubt it will exhibit features and characteristics, both negative and positive, which we can’t possibly anticipate.
I have no doubt that some terrestrial organisms could be used to seed the Martian regolith and make it more hospitable for our plants. We would probably be better off genetically modifying some of our own life so it would be more effective at doing so.
And there is another consideration–wouldn’t it be prudent to first convince ourselves there was no native Martian biology present before we started introducing our own?
All good points. However, we have a very good idea of what the Martian regolith is made of and the rocks are the same as on Earth in volcanic areas, even in the Jezero region which we believe was a delta to a lake.
Genetically altering terrestrial organisms is definitely a possibility – broached in KSR’s Mars trilogy.
If there is any extant Martian biology, it will likely be subsurface. If we build a base and contaminate that area, we can still go to remote parts of Mars to collect deeper subsurface cores to look for extant life. If life is there, then its preservation will depend on international laws. I doubt that will be an issue until the 2nd half of this century at a minimum. However, our current terrestrial political, social, and economic systems do not bode well in regard to restraints.
All good points as well. But the whole idea of transplanting a technology to another planet that will allow us to start growing food sufficient to support a colony sounds impossible. No, I don’t think any natural laws need be violated, just that the colony would probably starve before all the gotchas were worked out. Look how quickly our attempts at creating self-contained closed ecosystems right here on earth collapsed. Yeah, I saw “The Martian”, too. Its a fantasy.
For example, consider the problem of growing food in Antarctica, or in a hydroponic dome on the Atlantic abyssal plain. Certainly, no natural law need be violated, but just because something is possible doesn’t mean it can be done, and certainly not the first time we try. Every single crop species is going to require an extensive research effort, and probably genetic modification as well. And recall, on both the sea floor and Antarctica, good soil, oxygen, and energy are readily available or can be imported, and decent fishing can be had nearby. If all else fails, a rescue ship can get to you in a few days.
What happens if the turnip crop fails on Syrtis Major? Earth is nine months away by Hohmann transfer orbit. On 17th century earth, North American colonists were favored with an agriculture tech which could brought over from Europe intact. They could also beg from, or trade with, the Indians. In South America, the natives had already developed their own crops and agriculture methods over centuries. I suspect it will take generations of trial and error to get self-sustaining agriculture going on another world, and it will have to be done by people living and working there year round, not a bunch of white coats in a lab back on earth.
I’m not just trying to be contrarian here. I just think we need to keep in mind these tasks are not easy, and its going to take a very long period of expensive support for the colony before it licks the local problems and can become self-sustaining. This is something we don’t seem to be teaching our futurists any more. Just because we know something is possible does not mean its going to be easy.
I would suggest we should start work today on devising compact, portable hydroponic, zero-g technologies that can feed our long-mission crews, relying on recycling human wastes and solar or nuclear power. Once that is perfected here, or in LEO, we can use this to victual our deep space missions, and provide supplies for our colonists WHILE they work out the problems of growing food on alien worlds. I think it will take years, and if our first colonists don’t have that backup, they will starve in their new home.
I don’t disagree with you about the difficulties. However, building the manufacturing infrastructure to expand the hydroponics kits for an expanding colony cannot be done either. The import costs from Earth are prohibitive.
With biology, there is at least the hope that a terrestrial type ag area can be placed “indoors” so that the variety of food crops can be grown. The colonists need to be very frugal with their imports, and the self-replicating nature of biology offers a route to allow expansion without large masses of imports.
But if you think about it, this need to develop robust life support for biologicals is circumvented if we send our intelligent robot proxies instead. As a species, we want to expand our numbers and locations, but we are unsuited to do this anywhere off our home world, and it is certainly the case that any robot will be cheaper to maintain (or be replaced) almost anywhere in space beyond cis-lunar space, and IMO, likely to be the economic drivers in space and spreading our culture as they go.
I had the opposite reaction; thinking that surely such basic questions had been previously explored.
@Michael Spencer. Because we have zero extraterrestrial colonization experience, almost everything is speculation. We don’t even know how humans adapt to low gravity conditions as we only have terrestrial 1g and microgravity experience. We have done some experiments on growing food in microgravity as well as some differential gravity effects on small organisms.
As regards Mars, the Zubrin fans take his cue and wave away any radiation issues and assume Martian gravity will be fine with no negative physiological effects. There is no end of imaginative ideas for habitats on Mars. Food production has been more seriously considered as outlined briefly in the post. [Just follow the relevant references.] But it ranges from eating cyanobacteria and green algae to terrestrial crops that can be grown in various ways. No one has seriously addressed how pollination will be done in an ag greenhouse, although I suspect it will require boring hand pollination as is done in parts of China. No one will want bees getting loose! Then there is the issue of plant diseases. These can be controlled by having everything sterile, but we know radiation can quickly mutate microbes based on experience on the space station, so who knows how this will play out? How will plants develop in low gravity – grow tall or something else? We just do not know.
We might get lucky, or Henry is right and it might take a long time to adapt terrestrial crop production on Mars. If it was me, I would ensure the crew rotations had a full food supply available with enough equipment, seeds, and root stock to experiment, so that there was no chance they would starve trying to rely on local food production. Just recall that the Australian Botany Bay colony, and the US Jamestown colony suffered from starvation until saved by resupply or help. The Roanoke colony probably was wiped out by starvation. All these colonies were closer to hone in travel time than Mars, with possible help from indigenous peoples and local foods. Mars offers no help if food runs out.
Then there is the issue of who will do the farming. It is all very well assuming everyone will muck in, but farming at scale in the West relies on migrants to harvest fields and experience shows most people in the US are unable to effectively do farm work. It is hard. Maybe robots will be needed. If animals are to be kept, who will do the butchering? I have often wondered if the people who want to live on Mars are entirely the wrong types to go. We might be better served with experienced subsistence farmers to do this work, once the basic cultivation methods have been worked out.
Agriculture in the US West depends on migrant labor mostly because here in California we grow horticultural crops that are not as mechanized as the corn/soybean system of the Midwest. It is mostly a history – culture thing of how the West was colonized: farmers did not buy out their smaller neighbors because before mechanization they were limited by labor. Ironically today this is reversed
Great to hear from you again, Ioannis!
I still want at least one Starship full of irradiated potting soil up there.
I suppose capping off a suitable lava tube with airlocks and then spraying aluminium or coating material over the roof area to seal it would allow us to create a higher pressure environment for plant and animal life. Once the lava tube is sealed we could drill some holes in the roof to allow regolith and ice and CO2 to be dumped into the tube for processing where water can be used to dissolve a lot of the toxic components out. There is plenty of uses for Perchlorate even used as fuel. We could also then cover the top of the lava tube with solar cells and drop the cables down into these predrilled holes to power LED light for plants and animals. It would give a better environment for workers to carry out their tasks of modifying regoltih into soils.
Lava tubes are good ISRU. However, they suffer from the relatively few known and their locations. However, if you also want to grow crops indoors, you need light, and photosynthesis is very inefficient. So you either need to poke lots of holes and use mirrors in the ag section, or find a way to manufacture LEDs locally if you want expanding settlements on Mars.
Solar cells on top of the lava tube allows a large area to get power to the LED’s below with no need for weakening skylights and they can be tailor made for the most productive frequencies of photosynthesis. Although lava tubes are most likely to be near volcanoes perhaps they are still giving off heat underground which would be very useful maybe even have a water table associated with them.
But how are these LEDs and solar panels going to be made locally on Mars? Eventually, they will be made locally, but an expanding colony will not be able to build the technological infrastructure to do this. This means importing everything at a huge cost from Earth.
This is the problem for colony expansion. Transport costs will not be low enough to provide manufactures to the colony. But unlike colonizing the Americas, the Martian colonists will need sophisticated technology to survive there. Earth can certainly supply a base. But not thousands and then millions of people who remain insufficient to build the needed industrial base.
The best novel depicting a Martian culture I have read is “River of Dust” by Alexander Jablokov. Humans live in underground cities that are carved out of the rock and only rarely venture out onto the surface. Almost any rocky world without a dense atmosphere will tend to have below-the-surface living space to reduce resources and avoid surface hazards such as radiation and meteoroid impacts. Lava tubes are an early possibility as they save on excavation.
LED lighting is very light weight, the weight comes from the protective coatings. So we send the LED chip waffers to be coated on mars using materials locally. We should be able to make polymers using the CO2 out of the atmosphere and hydrogen.
Yes, polymers can be made from Martian resources if you have the factory to make them. H2O, CO2, Cl04, S02, can all be used to make different monomers that can be polymerized.
The BIS’s Project Boreas – a plan for a polar base assumed manufacturing of macro components of plastic.
Project Boreas – A Station for the Martian Geographic North Pole. £5. A bit dated now, but I keep a copy in my home library.
Of course, if you can grow plants and culture animals, the range of possible polymers expands hugely, e.g. protein fibers to make threads like spider silk, cotton, linen, etc., not to mention wood. Humans have a long tradition of using live resources to create a wide range of items from clothing, to tools, and buildings. A growing civilization could make Martian
life very comfortable with this approach, limiting imports to difficult-to-make hi-tech items from microelectronics to pharmaceuticals. It takes a lot of setup as Mars would need to have these natural resources cultivated rather than exploited, but I would imagine that enterprising Martians would take this approach for economic reasons to avoid high import costs. Bags of seeds are far less costly than finished goods if they can be germinated to start local cultivation.
Interesting article for reducing perchlorates,
https://phys.org/news/2021-06-catalyst-perchlorate-martian-soil.html
It’s also worth mentioning that copies of this paper and of all the research articles listed can be found here:
https://fileshare.irg.space/index.php/s/Eg79fATeKSp2KHk
“However, hydroponics requires substantial inputs of nitrogen and phosphorus which are usually applied directly from external sources”
…
“Experiments using regolith simulants [4] have shown that given added nutrients and light, a number of common terrestrial leafy crops can be grown.”
Isn’t this a bit of a double standard? What added nutrients? Maybe… nitrogen and phosphorus?
I’m not actually arguing against growing crops in remediated Martian soil. I’m just suggesting that once you take into account the amount of effort that would have to be put into that remediation, and subsequent fertilizer production, I’m not seeing much advantage. The “soil” becomes little more than a support substrate for hydroponics!
Historically, the experiments on lunar and Martian regoliths have used simulants of the rocks and tried to grow conventional crops in that regolith under terrestrial conditions of atmosphere, temperature, light, and water. Results tend to show that plants will grow under these conditions, especially is major nutrients are added.
On Earth, large factories are where nitrogen fertilizers are created using the energy-intensive Haber-Bosch process that uses the nitrogen that dominates our atmosphere. Phosphorus is mined now that the guano deposits from seabirds is used up.
To transport low-value, bulk fertilizers to Mars does not make much sense, especially if the plan is to settle Mars. In-situ resource utilization (ISRU) pushes the need to bypass this external fertilizer production so that a population expansion can happen using local resources. On Mars, there is the problem that the atmospheric nitrogen is a small fraction of the atmosphere that is already thin to start with. This means that the terrestrial approach to nitrogen fertilizer manufacture is possible, but will require considerable mass transport to Mars to set up a factory. Rich phosphorus deposits are not yet known, and may not exist.
Even if these 2 macro-nutrients can be acquired, hydroponics (or similar) require the manufacture of parts that must be continuous to support expanding crop production for the growing population.
Therefore what is required is a way to extract the needed major and even micronutrients from the rocks directly, just as plants do on Earth utilizing the resources in the biosphere, while limiting the requirement for manufactured infrastructure.
Using the regolith is clearly the most abundant local resource. To even start using it as [base] soil, the [per]chlorates must be removed. While schemes to grow algae using the regolith as a resource for the needed nutrients (some algae can extract the nutrients from the regolith), the unpalatability of eating algae, let alone the health issues, suggests this route to food production is not going to work. People want foods they are familiar with and as the vast range of cuisines and recipes indicate, foods and meals are an important part of living well and healthily.
Therefore the need is to find effective, low-tech, ways to mitigate the toxicity of the regolith as a start, using biology that is self-replicating to do this. Then there is a need to know what conditions are needed to make this work, as it cannot be done on the exposed Martian surface. The biology should also be the method to make the regolith into a soil that supports good crop growth, just as pre-industrial intensive farming achieved.
In short, a [sterile?] Mars is unlike the Earth in that ecosystem services are absent, including earthworms to aerate the soil. [My guess is vermiculture will be important once farming using prepared regolith is the chosen method to grow conventional crops. But this is just the start because there are many species that are needed, especially pollinators for most crops unless one wants to hand pollinate crops that have flowers.]
I look forward to seeing if there is any indication of how food is provided on the growing Martian base in the new season of the alt-hist space series “For All Mankind”.
I’m just saying that, by the time you’ve remediated the perchlorates, kept the remediated soil isolated from contaminated native soil, and supplied the major nutrients, in terms of labor you’re essentially doing hydroponics anyway, using the remediated soil as support media.
The distinction between soil farming and hydroponics is pretty big on Earth, because we have an active biosphere, and plants can grow on the soil without anything added at all. Fertilizer is typically just supplied to increase yields.
On Mars, all the soil is supplying are micro-nutrients and mechanical support. And you’ll want to minimize the amount of remediated soil anyway, because remediating extra soil is unnecessary work. So a Martian ‘soil farm’ is going to end up looking a lot like an Earth ‘flood and drain’ or drip hydroponics system.
At least until you’ve been doing it long enough to create a substantial amount of more natural soil using plant wastes and sterilized animal wastes. I expect that the ratio of hydroponics to soil farming would shift over time.
In this comment you are making a statement, also made in the main article, that is not true: soil based agriculture also requires nutrients, not just hydroponics. In soil based agricultural systems we add N,P,K and any micronutrients missing and depend on the soil, and a lesser extent the atmosphere (think S from pollution) for the plant to grow. In hydroponics, because the growing medium buffer is less, we need to add more nutrients. Plant require some 20 elements as nutrients to survive, we do not know what is bio-available on Mars so let us not assume that soil based agriculture has that advantage over hydroponics. But yes, hydroponics only on Mars is going to be limited
The assumption in all this is that our terrestrial thinking assumes that we must have photosynthesis to grow our foods.
One can at least recycle waste without light using fungal saprophytes – the mushrooms we buy in the grocery store, that grow in the dark. Mushroom production can be easily carried out on a Mars base. [Edible mushrooms come in far more varieties than even high-end grocery stores offer. A recently discovered favorite is Maitake which I get from a specialist supplier.]
But let me be a bit controversial here. Carbon fixation does not require light. It occurs in the hot smoker vents in the deep ocean by bacteria. This depends on CO2 being the dominant gas with low O2 present – exactly the atmosphere on Mars. Might it be possible to use this approach to generate the organic carbon that will be needed to remediate the Martian regolith more quickly for terrestrial crop production? Even more controversially, could we engineer terrestrial crops to harness that mode of carbon fixation for food production for some crops? [O2 production might still best use chlorella vats rather than relying on farmed crops with variable photosynthesis and O2 production.]
Mars agriculture has more than one purpose, and those purposes will be in conflict. If we want to sustain astronauts cheaply and safely, we don’t want their farms to touch regolith at all. Hydroponics and vertical farming are feasible even on Earth, and on Mars there is better reason to use them. Mother Gaia doesn’t live there, and she won’t be looking out for us — to put it in a less poetic way, our cells aren’t adapted to Mars trace chemistry, nor do we have a lesser pantheon of soil bacteria working to clean up problematic compounds. It seems to be well established that the perchlorates of Mars devour organic compounds with relish ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC15945/ ), but for example dioxins can be toxic at microgram levels. I don’t know much about this, but I think the detection limit for aromatic compounds on Mars is much higher ( https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2020JE006595 ). If you make soil out of material including bits of kerogen-rich, partially oxidized meteorite rich in trace chlorinated compounds… well, let’s hope the astronauts get lucky. I would expect the role of regolith and Mars rock for any near-future colony should be as a source of defined chemicals that are highly purified before they are brought into the human biosphere.
Of course, the long-term needs of Mars farming are just the opposite: we’re talking about seeding the planet, infecting it with a Terran ecosystem that can tame and harness what resources it has to offer. Whether those resources include enough nitrogen to get very far, I’m not sure, but it does make sense that the transplanted life needs to be able to extract it effectively. The CO2 of Mars’ atmosphere is enough for plants, but clearly not sufficient to produce a breathable oxygen atmosphere for animals, so the oxygen would have to be freed by new methods, maybe even splitting sand into silicon and oxygen no matter what the energy cost, or else brought in from space for terraforming. Compromising our expectations for the ecosystem to make do without the 4/5 of the partial pressure of Earth’s atmosphere that is inert N2 seems unavoidable.
There may be a greater philosophical tension about whether the life brought to Mars should resemble Earth life closely for compatibility, or whether it should be reworked at a fundamental level (“synthetic life”, altered such as by reworking the biochemistry to need less fixed nitrogen or relying on ingestion of solid perchlorate as its main respiratory pathway under a very thin atmosphere) It seems sterile, maybe even cruel, to invest in an ecosystem meant to rely on a thick gaseous atmosphere for its survival unless Mars can be given a magnetic field stable for the next billion years or two.
There is obviously a difference between supporting a Martian base and an expanding colony.
The ISS has done hydroponics experiments (as did the Mir) and the iconic circular arrangement has been copied in several sci-fi videos. For a base, I think food supplies sent from Earth plus hydroponics for fresh veggies is the way to go for a base with rotating personnel. It is the space station model extended for long transit times. Large ships able to manage this will be needed. This was the same model used for the Australian Botany Bay penal colony.
But once the idea is to expand the base into colonization, like Bradbury’s “The Martian Chronicles” (an allegory of the western expansion in North America) then there will be a problem of technological supply. While Britain restricted American manufactures prior to Independence, the reality is that technology was far simpler during those centuries, with arms perhaps the most difficult to manufacture locally. For example, Mars would need to import microelectronic components for a very long time.
I disagree that terraforming Mars is needed during colonization, which is the implication of what you are saying. Terrestrial conditions can be maintained within enclosed structures, and the surface conditions will terminate almost all life that escapes those warm, humid conditions. ISRU is going to be important for colony expansion, and that implies more traditional food production methods, as well as the desire to have trees rooted in soils to populate the living areas. Singapore airport might be a model to aim for, with potted plants being at least a starter.
Is there really a tension between synthetic life and extant terrestrial life? Breeding programs for centuries plus current GMOs are already doing that on Earth. I suspect Mars (also the Moon, and indeed any off-Earth facilities) will be ideal places to experiment and test more radical genetic manipulation, probably aided by AI to design them. We really do not want more efficient carbon-fixing plants to escape into the wild on Earth, but clearly, they would be a boon for food production.
Personally, I have mixed feelings about the human colonization of the solar system. I do want to see humans traveling and working in our system, but I think that role will be usurped by robots for economic reasons once robots become more intelligent and able to manage themselves with minimal human oversight.
Early colonists need to utilize resources in situ, but I’m not sure they would want to bring regolith into their habitations rather than roasting it (or mined material) for specific desired compounds outside. I’d expect them to have mostly cosmetic needs for “soil” per se, and could generate it from purified slag chemicals such as silicon dioxide.
I suggested terraforming mostly because I don’t see how else dirt farming is going to catch on. But it does seem a likely direction. Colonists living in glass houses are bound to start throwing stones, or at least having them shipped without warning from detractors on Earth. Bunkers can work but then there’s a question of why to bother being on Mars.
I could be wrong (correct me!), but I think partially terraforming Mars might be surprisingly easier than we imagine: results from Mars in recent years suggest thick deposits of ice in temperate latitudes, and it has more CO2 that we know about than Earth. Its equilibrium temperature is 217 K ( https://web.njit.edu/~gary/320/Lecture16.html ) versus 255 K for Earth (that’s a 38 K gap) , but its greenhouse effect is much weaker, because water vapor is virtually absent from the atmosphere. If Mars were warm enough for liquid water to be present equatorially, then the water vapor would close the gap to reach that warmth by about half. If there are hidden reserves of CO2 to evaporate, that could do more. If humans could do 6K of damage on Earth without even really trying, what could they do with SF6 plants all over Mars? Such a heated Mars, resembling episodic wet eras of its distant history, would not have much of an atmosphere, but it might have the 20 millibars of water vapor to keep eyes and throats from boiling/drying out.
At that point, you still have the issue that you’re vacuum degassing the blood flow through such organs, and there is nothing to breathe unless you’re a plant. Mars soil is about 0.5 g per liter perchlorate. If we want oxygen like Earth’s 20 kPa from “decontaminating” that alone, we need to dig 11 km down and hope this abundance holds all the way. But nearly half the crust is oxygen and you only need 45 kg of it per square decimeter to apply this pressure – so if you can get the energy to do that, it would need just a few meters. If a “plant” is splitting silicon dioxide to make solar panels to power itself… I don’t know, but it might be a matter of time. Humans might one day live on that planet nearly unaltered.
Yet there could be other routes. You revise humans so every mitochondrion in the body is rigged with an electrical wire, either to hydrolyze water and generate O2 locally for metabolism, or to pump H+ out of the matrix without it to make ATP as if respiration were working. The humans then charge at solar stations instead of breathing. Or, there might be a fungal network that concentrates perchlorate from the soil, and people have been engineered to be able to eat that perchlorate fruit periodically without suffering toxic effects, and break the compound down at the mitochondria to generate oxygen at the respiratory complex. The synthetic route changes what it is to be human; it’s bad for tourism and orchestra conductors. But at least with the most extreme model of plug-in mitochondria, the amount of O2 released and lost into space would be much lower than otherwise, and they might roam Mars a long time as true natives.
Whether Mars can be terraformed or not, it should be inarguable that planetwide terraforming would take a very long time. Far easier to do it in small bites in enclosed habitats.
While there will no doubt be people who want to throw rocks in glasshouses, my guess is that this destructive behavior will not be tolerated. Also, if the surface structures are large, the loss of air pressure will be slow and quickly patchable, unless large-scale damage is caused.
As most of the planet’s population is now urban, and with megalopolises increasing, it seems to me that subsurface “indoor” living makes sense, even on Earth. Cixin Liu’s last novel in the Three-Body trilogy, “Death’s End” describes most of the remaining Earth population living in cities below the surface. Suitably designed to appear to be in the open, I could envisage living in such an environment. O’Neill had suggested cities being designed as arcologies to create enclosed conditions that were weather-independent. So I see little reason to tailor a planet, and our extreme biology to live on the surface of other worlds. Far easier to have machines on the surface, and use them as avatars if one wants to explore the surface. The movie “Surrogates” might be the model for that approach. Varley’s sci-fi solution was to give people an O2 source by replacing one lung, and a force field that covered the body like skin. Extreme and implausible, but less invasive than trying to drastically engineer human biology. And what if it means you are then tailored to live on Mars, but not elsewhere? Technological support should allow increased freedom, especially if we are to be a space-faring species, rather than adapting our biology to local environments. On Earth, skin pigments, nose shape, and relatively minor genetic changes were all that were needed to populate almost everywhere on Earth, as we used external artifacts to survive – clothes, fire, tools, and dwellings. IMO, this remains the better approach if we want to live off-Earth. I could be wrong.
The way I’m thinking of them, the physical adaptations would be very broadly applicable, even to life on Earth. Once electricity became available, it was inevitable that life would evolve to make use of it. A person on Earth with “wired” mitochondria might be nearly impervious to heart disease and stroke, and is preadapted to surviving in any low-atmosphere environment. Also note that “wires” can be implemented at a biochemical level — our mitochondrial electron transport chain essentially links up three types of appliance in series (the respiratory complexes I, III, and IV) simply by having different chemicals that carry electrons at different voltages and only give them up at specific biochemical sites. We ought to be able to wire a cell to a power grid with merely some membrane proteins that couple some circulating redox carrier to NAD+/NADH inside the cell. The extracellular redox carriers could be recharged near something closer to typical conductive wires, or perhaps there is some other way. Done right, the whole power backup system should be vastly less appalling than the “Neuralink” project, which I was rather horrified to see is now starting to seek out human volunteers. (Though I admit this power system is also essential scientific background for any decent zombie movie, should one eventually be made) Though a rework of several miscellaneous oxygenases would be needed, an oxygen-emancipated population also has the ultimate “antioxidant” and “caloric restriction” at the cellular level; a current school of thinking suggests this could extend their lifespans.
A heated Mars seems like it should be similar to most semi-terraformed space environments, because it is hard to avoid some biochemical dependence on a low carbon dioxide partial pressure, and any rock people want to live on (hence having ice), heated to a comfortable temperature, will have comparable water vapor partial pressure. But that’s still an atmosphere that can be domed with plastic wrap or might be brought by comet to a barren moon.
@Mike Serfas. Deep sea vent bacteria have almost infiltrated that space by using electricity.
In situ electrosynthetic bacterial growth using electricity generated by a deep-sea hydrothermal vent
There are also bacteria that do something similar in deep ocean sediment using “wires” to capture electrons and transport them below the sediment surface where they live.
In both these cases, they use the electrons for carbon fixation. [In Nick Lane’s latest book, “Transformers” he explains the Kreb’s Cycle and the reverse Kreb’s Cycle for oxygenic metabolism and carbon fixation. He makes a very credible claim for a metabolism-first abiogenesis, a claim I had read much earlier in Hazen’s “gen.e.sis”. I am becoming convinced that this is indeed a more plausible model than RNA-World.
Apart from natural vistas, I think the logic of orbital habitats is still superior to planet-bound living. All the terrestrial conditions can be met – gravity, atmospheric composition, and pressure, as well as any biome. The potential living space vastly exceeds any planetary surface anywhere in the universe.
Building arcologies on Earth to safely develop ELSS systems that become as nearly completely perfect energy harvesters and recyclers seems the most sensible way to proceed. When perfected, we can use robots to build habitats, with robots and humans working together to populate and manage their operation.
Mars and other planets can then become wilderness destinations for tourists, explorers, and scientists. Controlling where humans operate on the surface to minimize contamination, the planets can be used without totally spoiling them.
Habitats could be made to be purely nature reserves too, which will work for many ecosystems apart from those requiring migratory species that may have to remain on Earth. If we could create 1000x the area of the Earth as nature reserves, we could do more for species preservation and evolution than almost anything we can do on Earth. An alternative to the idea of making Earth the only nature preserve and space the gritty industrial center (which we will do as well as we will have so much lebensraum to play with).
To further @Henry’s comment, there does seem to be continued hubris in our expectations of control over nature. Farming is the main one on earth, and hydroponics is an even more extreme version. It never ceases to surprise me how some people seem so surprised at unexpected failures.
When Gerry O’Neill was proposing his space colonies, they were envisaged as suburban with green spaces, with farming restricted to separate structures, his argument over such failures was to expose the areas to vacuum and start again. Easy to say, but what happens if the main living space needs to be exposed to the vacuum to control a new plant disease, or organisms get out of control as the ants did in Biosphere II? Colonies around L5 in cis-lunar space are relatively reachable, but they were expected to reach 3 days out in deep space, and the idea of worldships traveling between the stars for centuries or millennia will not be able to use such methods without strict compartmentalization. Aldiss’ “Non-Stop” (AKA “Starship”) indicated that the ship’s flora got out of control and invaded the corridors.
IOW, as Henry suggests, it might be hard to establish crop farming (and animal husbandry?) on Mars. There are no local ecosystem services to support the endeavor. The engineering approach is to simplify the system, i.e. use hydroponics (much as Zubrin argued for chemistry to produce O2, not biology). My guess is that backup food supplies will need to be shipped from Earth, preferably on more efficient, larger, and faster, transport. However, this will be a limitation on colonization as the population increases. [Interestingly, in Vinge’s “Deepness in the Sky”, the issue of how the starships produce the needed food for the crews is barely indicated. This is a common missing element in most sci-fi, novels and videos.]
While I don’t think this should dissuade humans from spaceflight, the LSS issue will become ever more difficult the deeper into space we go. I don’t think we will ever have ST replicators, but just possibly recycling and food printers may become a solution. Just hope the printers don’t get software bugs!] Machines just do not have this issue to solve.
I don;t understand the need for soil. We have indoor vertical farms that use no Sun or soil and well over 90% less water (and space) than traditional farms. Why would these not work on other worlds?
Firstly, this is not about feeding a Martian base, but rather how to provide food for an expanding Martian immigrant population – like Musk’s “1 million people on Mars by mid-century.”
Secondly, Mars is months away from resupply and imports incur huge transport costs.
So for a base, a vertical farm with hi-tech spares is quite possible to add to prepackaged foods. However, it is not likely to be a solution when the farm needs to keep adding units to feed the expanding population. Even a 1 million people is insufficient to support a local industrial infrastructure to manufacture everything locally. If there is a food production failure, people cannot survive months without food until an emergency shipment arrives. We cannot even do that well on Earth when food can be supplied within hours or days to starving populations.
Martian colonists will need to be as self-sufficient as possible. That means relying on local resources and as few imports as possible. Maybe nth generation printers will solve some of the manufacturing problems, and maybe factory food production will solve the food issue. Just don’t bet on this.
Even on Earth, vertical farms are purely for supplying very fresh vegetables for local consumption with minimal transport time. Leafy vegetables are an example. But these farms are very limited in the vegetables and fruits they can grow, and you won’t see fruit trees in vertical farms, To control conditions crops requiring insect pollination are not cultivated. IDK about wind-pollinated grass crops – but these are not rapidly perishable, so why bother on Earth?
Think about scale and logistics, rather than technological capability, when thinking about space colonization.
Somewhat tangential, but a possible antidote to gung-ho ideas of Martian colonization.
Review: A City on Mars
One of the authors is a biologist (yay!). It is worth reading the sample on Amazon too. It looks like the lack of knowledge of life support systems will be addressed in the book – which should include food production.
So, if I understand correctly, the way this might work is the following:
1) The initial base brings all its food; it doesn’t depend on farming, so it can safely do all sort of experiments.
2) The base has two initial priorities (as far as farming goes):
2a) Experiment with perchlorate-removing bacteria. That means using real regolith with added “fertilizer,” (carbon, nitrogen, phosphorous, etc.) water, and some amount of pressure and radiation shielding. The goal is to find/engineer species that do the best job with the least extra help.
2b) Experiment with fertilizer-producing bacteria. The idea is that these are supposed to produce the carbon, nitrogen, phosphorus, etc. that the bacteria in 2a require. The goal here is to get species that produce the most fertilizer with the least extra help.
3) Given some positive results from 2a, set up a relatively large outdoor facility (field #1) and start cleaning regolith.
4) Once field #1 is perchlorate-free, apply the results from the experiments in 2b to make it start producing fertilizer.
5) Using the output from field #1, set up field #2 with more regolith-cleaning bacteria.
6) When field #2 is clean:
6a) Fertilize field #3 with the output from field #1 and seed it with regolith-cleaning bacteria.
6b) Start experimenting with food crops in field #2.
7) Proceed with fields #4, #5, etc. At any given time, field #1 is producing fertilizer, field #n is being cleaned, and fields 2 through n-1 are growing food. If desired, speed things up by creating additional fertilizer-producing fields from time to time.
8) When you’re confident enough of your food production, then start building your colony.
At least it would give the astronauts something to do during those long-duration missions!
Basically a logical pathway, yes.
However, most of the experimentation can be done on Earth. It should be well tested before going ahead with the actual pilot on Mars.
The regolith cleaning with bacteria will require extra nutrients at this point as the known bacteria cannot extract nutrients from the rock, and AFFAIK no cyanobacteria can extract nutrients from the rock in the presence of (per)chlorates. However, by using a graduated approach where cyanobacteria grow behind an advancing front of (per)chlorate reducing bacteria, these stages can be merged. If the (per)chlorate genes can be incorporated in cyanobacteria, then possibly only cyanobacteria can be used. That would be a more ideal end state.
To convert non-toxic regolith to soil is actually more complex. To increase the carbon content and to make the solid more water-holding, cyanobacteria and repeated additions of crop waste will be needed. Soil fungi should also be introduced. Worms to feed on the litter and aerate the solid will be needed. After that, amendments to adjust pH depending on crops. Rice could be grown in wet “paddy fields” on poor soil – mud really. Millet can be grown on quite poor, sandy, soil. As the soil improves, other crops can be grown. Nitrogen recycling will be important. This can be achieved in several ways, including nitrogen-fixing bacteria if the N2 partial pressure can be raised in the greenhouses. N,P,S and trace element recycling in the ELSS will be paramount to make this work as efficiently as possible.
Mark Watney (The Martian) might have been a botanist and “sciencing the shit” out of growing potatoes, but I think agronomists might be a better choice to help with this process. Maybe the USDA (or equivalent) could have a bureau outpost on Mars? ;-) It may be the case that “soil starter packs” can be produced to jumpstart soil production in new ag areas.
If good soils can be cultured, then the Martian habitats can be filled with ornamental trees and plants, bringing green to the planet. Unless the colonists preferred fake green landscapes of astroturf, artificial plants, paintings, or wall-screen videos of terrestrial vistas, real plants would provide a physically and mentally healthier environment for the population.
If however, technology is sufficient to manufacture, even print foods even meals from raw materials, then this may all be unnecessary except to create a natural environment in the habitats and cities. I could imagine that fast-growing algae could supply the bulk of the raw ingredients that are then modified so that foods more familiar to us in taste and form can be created, and allowing the creativity of cooks to make these foods into appetizing meals. Given the pace of technological development, I cannot guess what might be available a century from now. Will humans adapt to new ways of food production (Soylent crackers?) or will cultural resistance maintain current cuisines? [I gather whale hunting in Japan is to retain the ability to eat whale meat even though it is not necessary or even that desirable. In the US, beef production is entrenched and will remain so even if perfectly printed steaks become available. Culturally, “real men” will eat steaks from animals, not from a factory. Culture is very conservative and resistant to change in so many ways.]
Wouldn’t synthetic meat and Lipitor be easier?
Possibly.
Today, there are 2 principle routes to synthetic meat.
1. Grow plants, extract the proteins and fats, discard the cellulose, and process it with added flavors to make something that looks and tastes like ground beef. Also chicken pieces (the base for nuggets?)
2. Culture animal muscle cells and process similarly, but also print what looks like cuts of meat.
In many respects, it is far easier to just become vegetarian and bypass this desire for meat substitutes. On Mars, going vegetarian saves an awful lot of mass that is needed for building factories to culture cells and process the cells or plant material to create the “meat”, plus the myriad specialty chemicals needed to grow and process the “meat”.
OTOH, animals are very useful for processing food waste. Pigs come to mind. If algae culture is the way to go due to its fast growth, using animals is probably the best way to process it to make it palatable. Which animal species to choose is debatable. The range is very wide from vertebrates like fish, possibly mammals like rabbits, and insects (process the larvae).
There are lots of tradeoffs as you can imagine.
Whatever the means, it must be robust, so redundancy is good, as well as different approaches, to avoid single points of failure.
Statin drugs, like other pharmaceuticals, are probably best shipped to the colony.
[Emperor Musk may want his steaks and other premium delicacies shipped frozen from Earth. ;-) ]
[Emperor Musk may want his steaks and other premium delicacies shipped frozen from Earth. ;-) ]
If Musk wants to remain emperor, he would be well advised to make the arrival of freeze dried steaks a public event.
I remember an old Jerry Pournelle story where arrival frozen steaks were the excuse for celebratory communal dinners on asteroid colonies.
In ancient Greece & Rome there was a long standing tradition of public feasts. If I recall correctly, Julius Ceaser threw a public dinner in Rome as part of a political campaign & the king of the Spartans was entitled to a double share at any public feast.
@Ivan. I don’t see Musk as being politically astute. In reality, I suspect he will be too old to retire on Mars. He may be more like Heinlein’s D. D. Harriman (The Man Who Sold the Moon) who only gets to the Moon as an old man and then dies there quite quickly (in the short story, “Requiem”).
But yes, he would be advised to share his wealth with the Martian population. Whether he can warp his head around this idea is another matter.
Musk has already stated that he wants to die on Mars, just not on impact. I’d go further than that. Unless he wants to become Mars’s first murder victim, he would be well advised to do a Moses and never set foot in the promised land.
Hydroponics deliver nutrients more efficiently to plants and allow more efficient nutrient reclamation than soil farming. Imho, this alone make hydroponics a better option. Nitrogen and phosphorous are precious elements on Mars.
As well, soil farming requires just as much specialized equipment as hydroponics. To reach Earth production levels for say wheat or corn, requires even more. Are the costs of transporting or in situ manufacturing of tractors, combines, threshers, etc. being included in the analysis? The technical and manufacturing requirements for hydroponics (pipes, pumps and lights) must be met to even consider having a settlement. For a Martian colony, hydroponics is simpler.
Anything can be grown hydroponically with varying degrees of production efficiency. I still think there are uses for reclaimed soil like garden spaces, but for food production, hydroponics looks like a clear winner.
I’d like to thank the authors, Alex Tolley and Doug Loss, for this excellent article about soil on Mars, and Martian agriculture in general.
Yes there certainly are knowledge gaps, and thank you for identifying some of the challenges with growing plants on Mars. Before problems can be solved they must first be identified. You did an excellent, excellent, job of identifying problems. Although identifying problems is often met with sharp criticism, it’s an important step in solving problems.
I’m currently writing a book on how to make soil on Mars. I was doing some research and stumbled across this website. One question that often comes up is why do we need soil on Mars? Why not just use hydroponics? Wouldn’t that be simpler?
To understand the importance of soil, we need to understand a plants rhizosphere. The rhizosphere is located all along a plants root system in the soil. This is where the action is.
(Wikipedia article “Rhizosphere”).
https://en.wikipedia.org/wiki/Rhizosphere
I like to describe things in simple terms, so I refer to the rhizosphere as simply the “root zone”. Plants produce carbon compounds through the process of photosynthesis. Some of these carbon compounds, which are called “exudates” (pronounced EX-a-dates), leak out of a plants roots.
(Wikipedia article “Exudate”. See section “Plant exudates”).
https://en.wikipedia.org/wiki/Exudate
Microbes in the root zone eat the exudates and poop acids. The acids dissolve nutrients in the root zone, putting them in a form that both plants and microbes can use. Plants then suck up the nutrients through their roots.
In Dr. David R Montgomery’s book “Growing a Revolution” Dr. Montgomery writes:
“Yet roots are not simply straws. They are two-way streets through which carefully negotiated and orchestrated exchanges occur. Plants release into the soil a variety of carbon-rich molecules they make, and which can account for more than a third their photosynthetic output. For the most part, these exudates consist of proteins and carbohydrates (sugars) that provide an attractive food source for soil microbes. In this manner, plant roots feed the fungi and bacteria that pull nutrients from the soil — from the crystalline structure of rock fragments and organic matter.
When enough micro-organisms are present, the exudates don’t last long. Microbes chow down on and assimilate most within hours, modifying and re-releasing them in other forms. In addition, with the help of soil-dwelling bacteria certain mycorrhizal fungi use their thread-thin, root like hyphae to seek out and scavenge particular biological valuable elements, like phosphorus, from rocks or decaying organic matter. Then they trade the scavenged elements, now in plant-available form, for root exudates. This steps up an exchange through which both sides benefit from the commerce of the original underground economy.”
I’m a member of the Mars Society. Last spring I posted a proposal on the Mars Society’s forum. The proposal is about 95 pages long. In that proposal I describe what I call a “Cell” which is a growing area for plants. I also (briefly) talk about soil production on Mars.
(My posted proposal can be found at the following link)
http://newmars.com/forums/viewtopic.php?id=10501
The proposal contains 16 “posts”. The first post is an index to the other 15. I mentioned soil in posts #8 and post #9. Going to the link above and clicking on “Harvesting Carbon and a Martian Soil Factory” in the index will take you directly to the posts about soil.
So to answer the question “Why not use hydroponics and forget about making soil?”
I stated this in my posted proposal:
“…95% of all life that lives on land lives in the soil. If Mars is going to provide redundancy for life on Earth and we don’t have any soil on Mars, then we’d be leaving 95% of land life behind. Higher forms of life are dependent on these smaller forms of life that live in the soil.
Soil has three major systems at play. A chemical system, a biological system, and a physical system (soil structure, soil texture, etc, as was mentioned earlier). All three of these systems must be working well in order to produce healthy plants. Healthy plants are a prerequisite to producing healthy food. When all three of these systems are functioning well, soil is referred to as “functional soil”.
One of the problems with hydroponics is that it’s pretty much a chemical system only. In order to produce healthy, nutrient rich plants/food on Mars, they must be grown in functional soil.”
Here is an excerpt from Nicole Masters book “For the Love of Soil”
“As you can see, plants do not exist in isolation. Ponder this for a moment, many plant vital functions are external to their body; they outsource essential functions to microbes that are responsible for immunity, nutrient and water availability. Their gut, kidneys and thermostat are outside of their bodies. If you consider the primary goal of soil management, is to support an optimal digestive system, it is the fungi that supply powerful gut acids, vitamins, enzymes and minerals to fuel energy and health. Can you grow plants without soil and biology? Yes. Will they be healthy, have full genomic expression and be nutrient dense? No.”
Thanks again for the great article. Thought I’d stop in and let you know how much I appreciate it.
And I certainly thank you for coming by to say that, Steve. Many thanks!