Cover Image: Pat Rawlings/NASA
Farming on Mars
Another chapter in our Living on Mars series -- a collection of articles on what technology and systems will be needed to survive - and thrive - on Mars.
Other articles in the series include:
What will be the first thing you do when you get to Mars?
Will you hop around taking rock samples? Check the hab? Jump in a rover for a quick drive?
Maybe you'll just pause for a while -- and take it all in.
That might work for the first explorers, but if you want to live on Mars -- if you want to survive, and thrive, on Mars -- you'll need to get to work on your farm.
To establish a sustainable settlement on Mars, the first settlers will have to learn how to grow things where nothing grows. It's a job that could turn out to be one of the most vital, challenging and labor-intensive tasks the first settlers face.
In fact, at the 2013 Humans 2 Mars Summit at George Washington University, Penelope Boston, director of the Cave and Karst Studies program at New Mexico Institute of Mining and Technology, put it this way:
One of the things that every gardener on the planet will know is producing food is hard — it is a non-trivial thing. Up until several hundred years ago it occupied most of us for most of the time.
As she suggested, the first Mars colonists may have to revert to this mode of life to ensure their own survival.
But what will they need? And how will they grow it?
And what exactly would a farm on Mars look like? How big will it have to be?
These are the questions we will need to answer before the first settlers arrive. Let's take a look at them ...
What Will We Need?
As on Earth, farming on Mars will involve much more than just growing food to eat. Food may be the most immediate need, but in the long term, we will need more. Things like:
- clothes (cotton, flax or hemp)
- paper (wood, rice or grasses)
- synthetics (oils and rubber)
All of which will need to be grown in a controlled -- and preferably -- automated way.
Let's break it down ...
We all know that when we eat, we need take in as much as we burn. Any more - we get fat. Any less - we lose weight -- and will eventually starve.
For most humans, that amount can vary from about 1,500 to 2,000 calories per day, depending on a variety of things -- metabolism, activity, temperature, and more. On Mars, though, we might need more. At least initially.
Some experts estimate 3,000 calories or more. The level of activity, they argue, warrants the increase in calories
On average, that comes out to about 3 kg per day -- per person.
For small missions that last only a few months or even years, the amount of equipment -- and effort -- to produce that much food for a mission to Mars would be prohibitive. For longer missions, though, and for and larger, self-sustaining settlements, it won't be possible to take all the food we need - even with the occasional resupply.
For example, a large settlement of 1,000 people, like what we envision at Mars for the Many, would require 3000 kg of food each and every day.
That's about 6,600 pounds.
And it can't be just any food. It can't be just, say, potatoes. That would get pretty boring -- fast!
No. We need a little more variety in our diet than just potatoes.
It's a problem astronauts, and other military personnel, have experienced for a long time. It's even got a name -- "menu fatigue".
Angelo Vermeulen, a Belgian artist/scientist who was the crew commander of the HI-SEAS research team in 2013 (HI-SEAS is the Hawaii Space Exploration Analog and Simulation site -- a six-person, NASA-funded team that spent time in a simulated Mars habitat on the hills of the Mauna Loa volcano in Hawaii to study and experiment with ways to prepare foods on Mars), explained it like this:
It's a psychological phenomenon also found in the military that you develop when you eat the same foods over and over again. After a while you start eating less and your physical condition goes down. The last thing you want is a skinny, underfed astronaut.
The trick then, for farming on Mars, is to produce enough food for a thriving settlement, with enough variety to keep us from going crazy -- all while maintaining a healthy dietary balance.
To put it another way, we need a mix of vegetables, starches, proteins, fats and fiber to maintain our health -- and our sanity.
Here's a list of what that might look like:
The key, of course, is maintaining this balance in an environment where nothing grows.
Previous studies have discounted the use of animal products for a Martian diet (I won't go into the pros and cons here, but basically it's too inefficient a way to produce food). This undoubtedly pleases the vegans among us, but what it really means is that proteins, dairy and fats will have to come from other sources
Here is a possible -- but by no means exclusive -- list of what we might grow:
- leafy greens -- lettuces, kale, chard, spinach, cabbage, etc.
- legumes -- peas, beans, soybeans, lentils, etc.
- roots -- radishes, onions, shallots, carrots, beets, turnips, garlic, ginger etc.
- tubers -- potatoes (yes!), yams, etc.
- other vegetables -- cucumbers, squashes, tomatoes, asparagus, broccoli, etc (I know -- some are technically fruits.)
- fruits -- strawberries, raspberries, grapes, melons, etc.
- nuts & seeds -- peanuts, sunflowers, etc.
- grains -- wheat, rice, quinoa, etc.
There are undoubtedly many more things we might want to grow for food. This is just a quick sampling of what might be possible.
The important thing is that it demonstrates why many of the first settlers will need to be farmers and botanists.
And remember, it's not just food we will need to grow. Medicinal plants. Textile crops. Wood. These are all things any long term settlement will need.
But growing non-foodstuff plants is a pretty complex and extensive topic. It's important enough to warrant its own discussion -- so we'll skip over it for now and address it in a future article.
There is one material that we should touch on briefly, however, and that's wood.
Wood can be used to make all sorts of things and for all sorts of purposes: general construction, furniture, medical supplies (think splints and crutches) -- even paper.
It might be really good to grow some wood.
The problem, though, is that wood comes from trees.
Which makes growing them a problem for the small spaces that might be initially available on Mars.
And -- even worse - trees don't grow very fast. They can take years to grow to a size that is usable here on Earth.
Except for bamboo.
Depending on the species, bamboo can grow up to 5 feet per year, meaning it can quickly supply a lot of wood to a burgeoning colony.
If you've ever read Red Mars by Kim Stanley Robinson, you might remember this is exactly why the first settlers in that series grew bamboo. It gave them a fairly quick supply of wood for scaffolding and the construction of forms and braces they needed to build their first habitat.
It was a great idea. One that we might want to borrow.
But how, exactly, will we grow it? And how will we grow all the other plants as well -- the fruits and vegetables? The medicinals? The textiles?
Let's explore some possible methods ...
How Will We Grow It?
Traditional Dirt Farming
We all know what this is. Put some seeds in the soil, give them some water and sun -- and watch them grow.
On Mars, though, there's a couple of problems with this. Namely, there is:
- no soil, and
- no water.
Alright --- there's dirt on Mars, but not any with the nutrients that are needed to grow plants, So technically, it's not soil.
And yes, there's water too. But it's extremely high in salt and will kill anything that uses it -- including humans.
In order to grow plants the way we do traditionally here on Earth, we will need to provide both soil and water.
How do we do that?
Soil can be made by introducing nutrients and microbes that plants need. This can come from artificial fertilizers, human or animal waste, and the decomposition of food or other organic elements.
In fact, many of the nutrients and fertilizers can come as a recycling byproduct of the colony's life support system, as explained in our previous article about making clean water on Mars.
It might take some time, but we can definitely make nutrient-rich soil on Mars.
That's good. But do we even need to bother? Most plants don't really need soil.
Some might -- like bushes and trees. But these really only need the soil for stability -- a stable base to support their root systems -- not for nutrients.
In fact, most plants don't need soil at all -- and will actually grow better without it. All they need is a way to get the food and light they need, which can be done very well in controlled and automated environment.
You might know it better as ...
Hydroponics is the art and science of growing plants without soil. It basically involves mixing the right blend of minerals and nutrients in water and delivering that solution directly to the roots of your plants. There's no need for nutrient-rich soil, although sometimes hydroponic systems grow plants in some type of inert medium like gravel or perlite.
The gravel doesn't provide nutrition. It simply provides stability -- something a plant's root system can grab to keep itself from falling over.
And Mars has a lot of gravel.
There are 6 basic type of hydroponic systems:
- Water Culture
- Ebb & Flow (also known as Flood & Drain)
- Drip (recovery or non-recovery))
- NFT (Nutrient Film Technique), and
Drip systems are probably the most common type of hydroponic system in the world, but water culture is the simplest.
In a Drip System, a timer controls a pump submerged in the nutrient-rich water. The timer turns the pump on and the nutrient solution is dripped onto the base of each plant by a small drip line.
In a Recovery Drip System the excess nutrient solution that runs off is collected back in a reservoir for re-use.
The Non-Recovery System does not collect the run off.
That means that a Drip-Recovery system is more efficient since the excess solution is reused. But it also means the solution has to be periodically adjusted to get the right pH and nutrient levels.
A non-recovery Drip system, on the other hand, requires much less maintenance. Just set it and forget it.
A Water Culture system is even simpler. In this type of hydroponic system, the plants are put in a floating tray, typically Styrofoam, that sits directly on top of a bath of nutrient-rich solution. An air pump keeps the solution aerated and provides oxygen to the plant roots.
Ebb and Flow systems are also very popular. Like Drip systems, Ebb and Flow systems use inert, non-reactive material likes pebbles to support the plants. The planting bed is flooded periodically, then slowly drained before repeating itself over and over.
The draining allows air to get to the roots and keeps the plant roots from getting water-logged.
Whatever the method, hydroponics will most likely be the growing method of choice for farming on Mars. At least for most plants. Testing (like they are doing in the HI-SEAS experiments) will determine what works best for all the plants we might want to grow.
There's one other type of farming system we might want to experiment with, though, that is not often talked about for a farm on Mars. And that's ...
If hydroponics would work so well for a farm on Mars, what about aquaponics?
Aquaponics is basically a combination of aquaculture (the raising of aquatic animals like fish) with hydroponics.
Wait. What? Fish? I thought bringing animals to Mars would be too inefficient for food production.
Bear with me for a moment...
In normal aquaculture, the waste from the fish accumulates in the water, which increases algae growth and toxicity. Unrestrained, that will eventually kill the fish.
So the water needs to be treated. Or you need a large enough environment where the waste can be recycled naturally.
It's why so many aquaculture operations are simply floating cages in inlets and ocean shallows.
Aquaponics, on the other hand, collects the waste -- and uses it.
After collection, the waste is diverted and fed to a hydroponic system where it is used as fertilizer for the plants.
The plants break down the waste and absorb the nutrients, while at the same time cleaning the water.
Pump that water through filtration systems like activated charcoal and it is then available for pumping back to the fish tanks to starting the cycle all over.
It's an elegant solution - and it may allow for the introduction of fish into the martian diet (there go the vegans!).
It does require a lot of water, much more than a typical hydroponic garden, so it might not be something the first settlers would start with when farming on Mars.
For example, it shouldn't add too much weight or take much time to set up fish tanks. And the fish could be brought in as eggs and hatched once in place.
But until a method is developed to produce large quantities of water on Mars, the whole concept might have to wait.
Now that we have an idea of what we might want to grow and how we could grow it, let's take a look at the physical side of our farm on Mars.
Growing food on Mars presents several significant challenges. While research on the International Space Station suggests plants can grow in microgravity, we don't really know how the reduced gravity on Mars might affect Earth crops. Several issues need to be studied and explored, most of which can be done, and in some cases has already been done, here on Earth, including:
- atmospheric pressure
- CO2 content,
- oxygen levels, and
- radiation protection
Mars surface only receives about half the sunlight Earth does, and any pressurized greenhouse enclosure will block the sunlight even more. That means the natural light source will have to be supplemented by artificial sources.
And that means that farming on Mars will take a lot of power.
D. Marshall Porterfield, Life and Physical Sciences division director at NASA's Human Exploration and Operations Mission Directorate. NASA has been studying how to use lower energy LED lighting to give plants the wavelengths of light they need to boost efficiency - and only those wavelengths.
It's not trivial.
As Porterfield said:
In terms of the systems engineering required, it's not an insignificant challenge.
The good news is that LED lighting is becoming a common practice in self-enclosed growing containers like Freight Farm's LGM 2105 hydroponic growing system.
And that means the energy requirements can be easily calculated and planned for in any settlement design.
Since the greenhouse will be a self-contained enclosure, do we really need to keep it at the same atmospheric pressure we have here on Earth?
Researchers have been studying whether plants can survive under different pressures than normally found at sea level here on Earth. We don't want higher pressure, though -- the more pressure inside a greenhouse, the more massive that greenhouse must be to contain it.
But what about lower pressures?
As Robert Ferl, director of the Interdisciplinary Center for Biotechnology Research at the University of Florida said:
You don't have to inflate that greenhouse to Earth-normal pressure in order for plants to grow. Maintaining a full atmosphere of pressure is difficult on a planetary surface. You can take plants down to a tenth of an atmosphere and they'll still function.
But what happens to the gardeners at pressures that low?
With one-tenth normal atmospheric pressure , humans may need to wear some sort of environmental suit to protect themselves. A lower pressure also means the greenhouse will need to be sealed off from the crew's living quarters, meaning airlocks and all the complexities that implies.
As Taber MacCallum, chief executive officer of Paragon Space Development Corp., said
Gardening in a pressure suit is going to be a real trick.
But would a pressure suit really be necessary? Perhaps a biosuit would be enough.
The Armstrong Limit, named after the founder of the US Air Force's Department of Space Medicine Harry George Armstrong, is the lowest pressure a human body can withstand before the water in our blood starts to boil -- about 6.6% normal atmospheric pressure.
That means we could survive in the low pressure environment Ferl discribes -- one-tenth normal atmosphere -- At least for short periods of time. We would need some sort of breathing apparatus, though, since the oxygen level would be so low, but it could be done.
We might also be in danger of hypoxia -- at least if no pre-breathing is done before entering the farm.
NOTE: Hypoxia can occur when the human body undergoes rapid changes in environmental pressure, like when astronauts get into a space suit. Or when divers surface too quickly. The change in pressure causes the nitrogen to boil, creating 'bubbles' in the blood and bursting blood vessels -- the 'bends'. It's why astronauts 'pre-breathe' before space walks or divers pause and acclimate before surfacing. Pressures need to equalize slowly enough for the body to adapt.
A better choice, therefore, may be to raise the pressure in our farm high enough that gardeners could comfortably operate without an environmental suit, or even a biosuit.
Perhaps an atmosphere of about 50% Earth normal - about the same as the top of Mount Everest.
That would still offer benefits to the plants, while minimizing issues for the farmers.
Studies on this issue still need to be done to find the best option for a farm on Mars.
We all know that carbon dioxide is critical to plant growth and development. Photosynthesis, the process through which plants use light to create food, requires it.
On earth, normal CO2 levels range from 300-500 parts per million (ppm). If you are growing in a greenhouse, though, those levels will be decrease as the plants use it up during photosynthesis.
In a closed environment, therefore, CO2 needs to be constantly reintroduced in order to maintain optimal levels. Luckily, there is plenty of CO2 on Mars. If we don't get enough from simply breathing, we can always tap into air outside (Mars' atmosphere is 95% CO2)
But, for growing plants, we need to ask ourselves if maintaining this level of CO2 is the best we can do. What if we increased it?
Experiments have been done that show increasing the CO2 to three to four times the 'normal' level is actually quite beneficial for growing plants -- up to 1500 ppm,
With CO2 maintained at this level, yields can be increased by as much as 30%!
Commercial greenhouses know this, which is why they use CO2 generators to increase their production.
But what does that do to the gardeners?
1,500 ppm is not a problem for people. Humans can tolerate CO2 levels up to about 10,000 ppm -- the equivalent of 1% concentration, as explained in this report from Inspectapedia, before they start to feel a little drowsy or light-headed.
NOTE: 1,000,000 ppm of a gas = 100% concentration, so 10,000 ppm = 1%
Most people won't even be aware of the increased levels until the concentration hits 20,000 ppm, or 2%. At these levels, you might experience a heaviness in the chest and find it hard to breathe.
After a few hours, you could start to develop "acidosis" -- an acid condition in the blood, which, if not treated, could cause death.
But it isn't until a 5% concentration is reached that CO2 becomes directly toxic.
Luckily, our greenhouse will never need to reach concentration levels that high, but even at 1,500 ppm -- about 0.15% -- it would be prudent for workers who tend the farm over long periods to have breathing gear.
One thing most people don't think about in greenhouse operation is the concentration level of oxygen in the air.
Although we die of anoxia when oxygen levels drop below 11 percent, too little oxygen is not really the problem for a farm on Mars.
It's having too much oxygen.
Like carbon dioxide, too much oxygen will kill you. It's a gradual effect -- in a high oxygen environment you will, over the course of a few days, develop an inflammation of the lungs and eventually die.
But it's not just the effect a oxygen-rich environment has on your body. The more immediate impact is the increased likelihood of fire.
It's one of the things MIT studies pointed to as a reason Mars One plans are technically flawed.
In their argument, oxygen levels rose quickly above safe levels and would require the introduction of nitrogen to sustain normal levels. This would quickly deplete the nitrogen that was brought with the colonists.
You can't just simply vent the oxygen. That would also vent the nitrogen.
And you need the nitrogen to maintain a 'safe' oxygen level that doesn't make fire such a risk.
So what's a high level? How much oxygen is 'unsafe'?
While normal atmosphere contains between 20.8 and 21 percent oxygen, OSHA, the US government's Occupational and Safety Health Agency, defines as oxygen deficient any atmosphere that contains less than 19.5 percent oxygen, and as oxygen enriched, any atmosphere that contains more than 22 percent.
As stated on their web site:
may be created when oxygen is displaced by inerting gases, such as carbon dioxide, nitrogen, argon, or the ship's inert gas system or firefighting system. Oxygen can also be consumed by rusting metal, ripening fruits, drying paint, or coatings, combustion, or bacterial activities.
may be produced by certain chemical reactions. Oxygen enriched atmospheres present a significant fire and explosion risk.
The plants don't really care, and humans can survive in an oxygen-enriched environment. Again, the problem is the fire risk.
We will need to find a local source of nitrogen on Mars (or possibly some other inert gas - deep sea divers use helium) or develop a way to separate the nitrogen from the air and reuse it.
As in all aspect of Martian life, farmers and plants must also contend with the issue of radiation. Mars lacks Earth's thick protective atmosphere, so particles from space reach its surface that would be damaging to both people and plants.
Some kind of shielding or mitigation will be necessary.
As Taber MacCallum from Paragon Space Development Corp. commented:
To maintain the infrastructure is the expensive part to grow plants, coupled with the need for redundancy if something fails.
The winner of NASA's recent 3D Printed Hab Design Contest had a novel approach. They proposed building a habitat out of martian ice. Not only would that provide light during the day, it would also provide a thick layer of radiation protection.
That's one way to do it. But are there others? Could you bury the hab -- and the greenhouse?
It starts to make you think ...
What Will Farms on Mars Look Like?
What pops into your mind when you think of a farm on Mars?
My guess is that you imagine a typical greenhouse -- a long semi-cylindrical structure or half dome.
That's the picture artists typically present.
But is that the best structure for a greenhouse on Mars?
The sunlight on Mars is only about half that we receive on Earth. That means artificial lighting will be needed.
And if we need artificial lights, why do we need a transparent dome or cylinder?
Well, for one, it might be good for the settlers psychologically -- to feel like they have that wide open space available to them.
But it might not be the most efficient.
In cold weather areas in the US, companies have been experimenting with growing fresh vegetables year-round in enclosed spaces. Many of them are using refurbished cargo containers -- those long steel rectangles that are used to transport cargo on ships and trains -- to grow lettuce and tomatoes year round.
They are completely enclosed and use low-power LED lighting and hydroponic systems to produce their yield.
They are often cited as an ideal way to reintroduce farming into urban environments.
In fact, one of these companies, Freight Farms, claims their systems can produce the equivalent of an entire acre of high-yield crops -- in only 320 square feet! (An acre is 43,560 square feet).
On Earth, that might be enough to feed a couple of people for an entire year. This fun infographic claims an entire family of four can feed themselves from only two acres of land, or about half an acre per person. But that assumes normal growing conditions, outdoors, for only six months out of the year and includes growing food for animals.
With hydroponics, we can do much better.
Even if we conservatively estimate double the production, that still means one of these Freight Farm containers could conceivably feed four people year-round.
It's not much, but it might be exactly what the first settlers need.
Send a self contained cargo module, with a fully equipped farm with the first crews, or even before them, and have fresh vegetables available in just a matter of a few weeks.
Add on an inflatable for those crops that might need more traditional dirt farming, and we have the beginnings of a real farm on Mars!
Eventually, as the needs increase, larger, inflatable domes might make more sense -- especially for medicinal plants and trees. But initially we will need to satisfy the most pressing need -- food.
The first settlers will undoubtedly bring enough food and supplies with them to last a long time. Even so, one of their first, and most important activities will be to begin farming on Mars.
Perhaps that farm will come with them, as a separate, self contained unit.
Or perhaps it will need to be assembled from scratch.
Either way, farming on Mars will be achieved. It will be challenging, but it will get done.
As Robert Ferl said:
Every great migration in history happened because we took our agriculture with us. When you learn to take your plants with you, you can not only go to visit, you can go there to stay and live.
What do you think? How will we be farming on Mars? Share your thoughts in the comments below.