Are There Natural Resources in Near-Earth Space to Provide Life Support?
Imagine if the early settlers to the Americas had to transport all of the materials they needed across the Atlantic Ocean. Carrying all that food, water, and other materials would have been highly impractical if not outright impossible. It would also have been prohibitively expensive. That’s why settling new lands has always required making use of resources available nearby. In technical jargon, this is called “in-situ (on-site) resource utilization,” or ISRU.
Unfortunately there aren’t any easily accessible natural resources available in near-Earth space, so astronauts have to bring everything they need with them from Earth. That includes every satellite and replacement part, and all food and water. Depending on the rocket used, it costs between $2,000 and $10,000 per pound (or $4,400 to $22,000 per kilogram) for items to be shipped into low Earth orbit, where most satellites and the International Space Station (ISS) are located. Sending any payload further out costs significantly more.
The logical solution to dramatically lowering costs would be to find what we need in space, with a priority on water, food, and oxygen, all of which are necessary for life support. Are these resources available in near-Earth space (i.e. the Moon, Mars, or the asteroid belt), and if so, are they easily accessible?
Water is a valuable trading commodity that is becoming more sought after each year as global water scarcity increases. It’s called “the source of life” and is often seen as a purifying or religious symbol. Water is also the single most important natural resource in space due to its incredible versatility. We use it for drinking and growing food, hygiene, and for cleaning tools and buildings. We can also convert water into breathable oxygen as well as liquid oxygen and liquid hydrogen for rocket propellant.
Unfortunately, water is barely compressible, which makes it expensive to send to space in large amounts. Providing astronauts on the ISS with their daily recommended half gallon of water (or 1.89 liters) costs between $8,300 and $41,700. Finding an accessible source of water in space is crucial to scaling our presence outside of Earth.
Thankfully, we know that water is very common in the solar system and near-Earth space.
The first confirmed discovery on the Moon came from India’s Chandrayaan-1 mission in November 2008. Both the probe that impacted with the Moon and NASA’s instrument aboard Chandrayaan-1 detected water on the surface. One year later, NASA’s Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS) missions both confirmed those previous findings. Scientists don’t yet agree on how much water there is on the Moon, but estimates range from 440 billion to a staggering 4.4 trillion pounds of water (or 200 million to 2 billion metric tons).
We’ve suspected for hundreds of years that there was water on Mars, ever since early astronomers observed its polar ice caps. The past two decades have seen several discoveries proving the presence of water on the red planet:
- In 2002, NASA’s Odyssey spacecraft discovered enough water ice underneath the surface to fill Lake Michigan twice over;
- In 2008, NASA’s Phoenix lander discovered water ice at its landing site;
- The NASA Mars Reconnaissance Orbiter (MRO) observed in 2015 that water occasionally flowed on the surface of Mars;
- In 2016 the MRO found enough water ice to fill Lake Superior;
- The most recent discovery came in 2018 from a group of scientists using the MRO who discovered water ice around Mars’ equatorial region as shallow as 3.3 to 6.6 feet below the surface (or 1 to 2 meters) and going as far as 328 feet deep (or 100 meters).
These discoveries would make water ISRU on Mars much simpler, more feasible, and cost effective.
A dwarf planet in the asteroid belt named Ceres is also host to water ice. A 2014 study of data from the Herschel Space Observatory confirmed the presence of water vapor being ejected from Ceres into space. The Dawn spacecraft, which arrived at Ceres in 2015, made additional discoveries. It helped scientists determine that the dwarf planet’s crust was composed of 40% water ice, and that there was water ice present in polar cold traps, areas of permanent darkness where the frigid temperatures trap water ice.
Near-Earth space has plenty of accessible water, and the rest of the solar system has even more. Enceladus and Europa are two particularly exciting locations due to the abundance of water discovered there, as well as many other moons like Callisto, Dione, etc. But even if there was less water near Earth, recycling what is available is possible. In fact, the ISS already recycles roughly 93% of all liquids it receives.
Food has been equally important in the development of human civilization. The advent of farming is often identified as one of the determining moments in human history when civilization began to flourish. We no longer had to spend all our time hunting and scavenging for food, and different civilizations developed their own distinct cuisines depending on what they cultivated. Today, food plays such a defining role in our world’s cultures and heritages that to truly appreciate and experience another culture, we must immerse ourselves in their cuisine.
As the number of humans living and working in space increases, so too will the costs of feeding them. An astronaut on the ISS currently consumes between 2,000 to 3,200 calories per day, which weighs around 4 pounds in packaging and actual food (or 1.8 kilograms). That means the daily intake of food per astronaut costs between $8,000 and $40,000. Imagine spending that much money on meals in a single day!
What happens once there are 20, 100, or even 1,000 people in space at any given time? Unless we plan on fishing for seafood on Europa (an Ocean moon orbiting Jupiter, which may or may not be able to support life), we need a reliable and cost-effective way to provide sustenance to astronauts.
Government space agencies and researchers around the world have been looking into space food for decades. As such, the variety, taste, and texture of food available on the ISS has improved considerably since the early space age. Recently, a few companies have received grants or awards to look into 3D printing food, which could solve issues related to cooking in space (which is very difficult to do). Yet 3D printed food and most food consumed by astronauts today relies on ingredients being shipped from Earth, which would not be possible on long-duration missions to Mars or beyond. The only way to provide food to astronauts without having to ship ingredients from Earth is to grow it.
Plants don’t just grow anywhere, even if it may sometimes seem as if they can (especially weeds!). Like any other living organism, they have their own necessities to survive: light, air, water, and nutrients. Other factors also impact plant health and growth, such as temperature, humidity, and having enough room to grow roots and foliage. On Earth, over 99% of all plants grow in soil, so the first question is whether crops could survive and grow in the martian or lunar regolith (essentially soil).
Cultivating crops on the Moon and Mars
We know the Moon quite well. Not only is it the most visited celestial body after Earth, we have also returned surface samples from different locations. What we’ve found is that lunar regolith does not contain all the elements necessary or useful for plant growth such as nitrogen, phosphorus, or potassium. This would prove difficult for growing crops, and would at the very least require additives to make the soil more welcoming for plants (like poop).
While we haven’t returned any samples from Mars, the rovers on the surface and the probes orbiting the planet have given us a good idea of the soil’s composition. As you can imagine, martian soil is also very different from terrestrial soil. It is much finer and has none of the nutrients, bacteria, or macroorganisms (e.g. earthworms) necessary to promote plant growth. It also contains a number elements toxic to humans such as perchlorates, arsenic, and mercury. Crops grown in that soil would likely be inedible unless the toxic elements were removed first. We could theoretically purify the soil of those toxins, but that is still a big unknown and will require more peer-reviewed studies and possibly bringing samples back to Earth for testing.
Knowing the composition of the Moon and Mars has enabled NASA, universities, and private companies to develop artificial regolith called “simulants.” This has allowed researchers to experiment on growing crops in the simulated regolith. For a few years now, a team of Dutch scientists from the Wageningen University and Research Center have been conducting experiments to determine whether it is both possible and healthy to consume food grown in lunar or martian soil. Unfortunately, simulants are not perfect replicas. They are often contaminated with elements common on Earth or are missing certain key components entirely. There are also many different types of regolith on the Moon and Mars, so simulating all of them is difficult. Simulants remain an imperfect way to test how food grown on the Moon or Mars would turn out.
NASA has been testing different plant growing technologies on the ISS for a number of years. The experiment nicknamed VEGGIE grows edible food for astronauts in “plant pillows” which contain dirt, fertilizer, and nutrients. The problem is that VEGGIE is designed for microgravity, and would require either a supply of dirt shipped from Earth or using local regolith (which we don’t know enough about). CARA and APEX03–2, two other experiments conducted on the ISS and supported by NASA and CASIS, looked at the effect gravity has on plant growth, and why certain plants seem less impaired by the lack of gravity than others. The CUBES project, a Space Technology Research Institute launched and supported by NASA, is working on answering how ISRU could produce food, fuel, and medicine.
Aeroponics and hydroponics as alternative forms of space farming
We usually assume crops must be grown in soil, but alternative food growing technologies can offer significant improvements over traditional farming. This is good news, because having to use soil in microgravity could prove…dirty (picture dirt flying everywhere).
Two of these burgeoning industries are hydroponics and aeroponics. Hydroponics involves growing plants within mediums other than soil, such as water. Nutrients are then added to supply the plants with what they need to grow. Aeroponics, a variation of hydroponics, grow plants in the air, with water and nutrients supplied via mist sprayed directly onto the roots.
One of the key advantages of hydroponics is faster plant growth. Because hydroponics allow for control over every little detail about the nutrients provided to crops, the speed at which plants process those nutrients can be maximized. For instance, supplying more oxygen during the initial growth phase helps plants process more nutrients faster. What’s more, the plants no longer have to expend as much energy extending their roots to search for more sustenance. They can instead focus on sending the nutrients into their fruits or vegetables. And since this is a tightly controlled system, there are fewer chances of bugs or diseases harming the plants.
Another advantage is the incredible efficiency and returns of those systems. Aeroponics use 98% less water, 60% less fertilizer, and virtually 100% less pesticides than traditional farming. On top of that, some plants grown in microgravity have much higher yields and more crops per year, producing in one case up to 6 times more tomatoes per year compared to traditional farming.
While there is a lot we don’t know about growing crops off-Earth, it is certain that there are a lot of added benefits to doing so, regardless of the technique employed. Even if such systems often require a heavy initial investment, they would still lead to significant savings if used in space. Hydroponics or aeroponics would not only help feed astronauts and save money in shipping costs, but plants grown in space would also help conserve and recycle resources. They could turn used water into a drinkable water supply and fecal matter into fertilizer, as well as help purify the air of CO2 and convert it into breathable oxygen.
Breathable air is somewhat different to food and water because it is freely accessible on Earth. Even though we’ve historically taken it for granted, it is absolutely essential to our physical well-being.
We often think air is oxygen, but that is only partially true. In reality, oxygen accounts for less than 21% of the air we breathe. The remaining 79% is mostly nitrogen. While our bodies cannot process nitrogen and breathe it out, it is important because an oxygen-only atmosphere is very flammable, as NASA learned the hard way. Still, since nitrogen isn’t strictly necessary for survival, I’ll cover its availability in near-Earth space in a follow-up post.
Where would we find oxygen close to Earth?
Oxygen (O) is the third most common element in the universe. That, however, is not the same as the oxygen we breathe. The oxygen we breathe is called molecular oxygen (O2), and is not as prevalent as scientists initially thought. Some of our solar system’s icy moons like Dione, Europa, and Rhea have oxygen atmospheres, but they are so thin as to be nearly nonexistent and too far away to be explored by humans in the foreseeable future.
It turns out that oxygen is almost everywhere on the Moon. Based on the 842 pounds (or 382 kilograms) of lunar samples returned to Earth by the Apollo programs, roughly 43% of the Moon is made up of it. It is found in the ground as oxides, meaning it is bound to other minerals. For the most part, this oxygen is not molecular oxygen, which can only be found in small quantities in the lunar regolith. Even so, we would likely be able to separate the oxygen from the regolith by heating it up, which could then be converted into breathable air.
Mars has a much thicker atmosphere than the Moon and is largely made up of carbon dioxide. Less than 0.2% is oxygen though, so we can’t count on that to supply future astronauts. Like the moon, oxygen can be found in the ground as oxides, the abundant iron oxides giving Mars its rust red color. Both carbon dioxide and water can be converted into molecular oxygen, which means that it would possible to procure breathable air on Mars from ISRU.
As such, it is possible to either access oxygen in near-Earth objects, or convert other molecules or minerals into breathable oxygen.
The value of ISRU in making spaceflight affordable is undeniable and is looking increasingly possible, but there are a few caveats.
ISRU has never been tested in a space mission. Humans have been stuck in low Earth orbit since 1972 when we last visited the Moon. We have not returned any new samples from other celestial bodies since then, so conducting ISRU tests using space resources is limited to the asteroids we find on Earth.
Water is paramount to fueling our spacecraft, astronauts, and crops, but we don’t know for sure how much water there is in near-Earth space. We also know little about the efficiency of the robots we will use to harvest space resources because we don’t know with certainty which robots or technologies we will even use. Determining the effectiveness of those processes is crucial for us to scale human presence in the solar system.
Hopefully we won’t have to wait another forty-six years before we venture beyond low Earth orbit to establish a permanent settlement on the Moon or Mars.
Do you agree or disagree? Make sure to leave your thoughts or comments in the section below.
Originally published at www.orbitalmatters.com on June 25, 2018.