Do you want to visit Mars? Someday, you may get a chance. Several countries and companies have plans for crewed missions to Mars. Elon Musk, a famous inventor and founder of the company SpaceX, is planning one of those missions for 2026. But he has even bigger visions. In a 2021 speech, he said that he wants to “build a city on Mars to become a spacefaring civilization, a multi-planet species. ”
Living on Mars won’t be easy . The planet is as cold as Antarctica . It also has no air that people can breathe, no fresh water, no shelter or food, and no thick atmosphere to block harmful radiation from the sun. Musk and others hope to transform Mars into a more Earth-like planet, a process known as terraforming . But terraforming may be impossible, according to experts. And even if it does work, it could take hundreds of thousands of years.
In the meantime, Mars explorers and settlers will need ways to survive in the harsh environment. They can bring small amounts of equipment and materials from Earth. But they’ll have to manufacture most of the stuff they need on Mars. They’ll need to make fuel, since rockets can’t carry enough to get all the way to Mars and back again. They’ll also have to produce energy, buildings, tools, food, and so much more. How will they do it?
Sky, Brine, and Dirt
The first things Mars settlers will need are raw materials. Those will come from the sky, ground, and briny pools of water believed to be buried beneath the surface of the planet. Mars experts call this In-Situ Resource Utilization (ISRU).
The thin atmosphere of Mars is about 95 percent carbon dioxide. Each molecule of carbon dioxide contains one carbon and two oxygen atoms. A process called electrolysis, which uses electricity to split substances, can break these molecules apart. The result is pure liquid oxygen . That oxygen could be used to make breathable air. Or it could be used as fuel for rockets. (The carbon monoxide that also comes out of this splitting process could be used to make plastics.)
In 2021, the Perseverance rover demonstrated the process using a toaster-sized electrolysis instrument nicknamed MOXIE. It can make about ten grams of oxygen per hour. That’s only enough to provide twenty minutes worth of air for one astronaut, but this instrument is for experimentation only. For an actual Mars settlement, the instrument would need to be scaled up. Trudy Kortes, a NASA representative, told USA Today that MOXIE is “the first technology of its kind that will help future missions ‘live off the land,’ using elements of another world’s environment.”
Mars has other useful compounds on and under its dusty surface. While there is no fresh water on Mars, the planet does contain plenty of brine . That’s water mixed with lots of salt. At the surface, the brine is frozen, but large pools of liquid brine likely lurk below the surface. In 2020, engineers at Washington University at St. Louis in Missouri developed an electrolysis machine that works on brine. They showed that it can produce 250 grams of oxygen per hour using the same amount of power as MOXIE . Plus, their machine also makes hydrogen in the process. Hydrogen can be burned as a fuel.
Finally, the ground on Mars is made of a dusty, dirt-like material called regolith. “It’s a ready-made construction material—crushed rock— sitting on the surface of the planet,” Robert P . Mueller, an engineer at NASA’s Kennedy Space Center, told Chemical & Engineering News. No spacecraft has brought samples of regolith back to Earth. But rovers have figured out its basic composition. The dust contains mainly silicon dioxide (s and) and ferric oxide. Smaller amounts of aluminum oxide, calcium oxide, and sulfur oxide are mixed in. Regolith also contains some water ice. Heating up regolith would turn that ice into steam, so it could be collected for drinking or farming.
Bricks and Cement
Companies on Earth produce simulants, copies, of Martian regolith that researchers can use in experiments and tests. Several different teams of engineers have found ways to turn imitation regolith into bricks or a concrete-like building material. In 2017, engineers from the University of California at San Diego discovered that smashing regolith with the force of a swinging hammer forms a strong brick as long as the regolith contains enough iron oxide. The force seems to make iron oxide particles bond together. Iron oxide is the compound that gives Mars its reddish color. But it isn’t found everywhere on the planet.
Berok Khoshnevis, an engineer at the USC Viterbi School of Engineering, came up with a different way of building with regolith. “On Earth, builders mix cement or clay with water, then let it harden. But water won’t be easy to come by on Mars . “says Khoshnevis,“I started looking at other possibilities . ” He settled on sulfur . “It’s plentiful on Mars,” he says . “It’s very easy to melt, and when it cools down, it sticks to a lot of things. It sticks to ceramics, sands, rocks, and even metals. ” Melted sulfur can take the place of water to make a cement-like material out of regolith. For this approach to work, engineers have to separate the sulfur out of the regolith first, then melt it and mix it back in. Khoshnevis tested the process, which he calls Selective Separation Sintering, with imitation regolith. It worked. “We built a section of a wall. And we built interlocking tiles,” he says.
These experiments are exciting. But no one knows if real Martian regolith will behave exactly the same as the simulants. Engineers are hoping that future missions will bring back samples of actual regolith for them to test.
Fuel and Energy
Mars settlers will need to make their own fuel and energy . We already learned how they can extract basic rocket fuels, liquid oxygen or hydrogen, from the air or briny water on Mars . So far, most rockets use these fuels to lift off and fly. But NASA and SpaceX are testing rockets powered by methane fuel. Methane is easier and safer to carry than hydrogen, which explodes if it touches air. It is just suggested that methane occasionally surges into the planet’s atmosphere ., but it still lacks of the constant source, so it would have to be manufactured.
Methane (CH4 ) is a compound that contains carbon and hydrogen. To make it, settlers could first use electrolysis to get oxygen and hydrogen out of brine. Then they could react the hydrogen with carbon dioxide from the air to produce methane and water. This is called the Sabatier reaction.
That’s a two-step process, though. In 2019, researchers at the University of California, Irvine found a way to turn carbon dioxide into methane in just one step, thanks to the help of a catalyst, a substance that causes a chemical reaction. They attached individual molecules of the catalyst onto carbon nanotubes. Then they passed carbon dioxide over the nanotubes while applying an electrical current. This caused a chemical reaction in which the carbon dioxide turned into carbon monoxide and then into methane.
All of these different methods of extracting raw materials or turning one material into another require electricity. Right now, the rovers on Mars capture energy from the sun with solar panels. That provides enough electricity for their operation and experiments. The main ingredient needed to make solar panels and electronics, silicon, is easy to find on Mars. Unfortunately, solar energy likely won’t be powerful enough to keep an entire city or even a settlement on Mars running. Mars is farther from the sun than Earth, and solar energy there is only about half as strong as it is here. Plus, Mars has regular dust storms that can blot out sunlight for weeks at a time. Robots can go dormant during these periods, but humans can’t.
Nuclear power plants may be the ideal source of electricity for a Mars mission or settlement because they require very little fuel to produce electricity and heat for a very long time. However, it may not be possible to find or make new fuel for a nuclear plant on Mars. Another option is to tap into the geothermal energy of Mars. This is the heat trapped deep within the planet. On Earth, engineers drill down and pump in water . The water heats up, then travels back up to the surface, where people can use the heat directly or use it to make electricity. On Mars, a geothermal plant could pump in liquid carbon dioxide instead of water.
Buildings
Shelter will be very important on Mars. Walls will hold in air and warmth. They will also protect people from a certain degree of harmful radiation . We already learned how engineers hope to turn the regolith on Mars into bricks or cement. But how will they turn these materials into structures?
Khoshnevis’s plan is to use large robots to 3D-print entire buildings . Ideally, the robots would do their work before humans ever arrive. He calls his system Contour Crafting. On Earth, this system can build an entire house in one day. However, the robots still need human operators to oversee their work. To build on Mars, the system would have to operate autonomously, or on its own. That’s because the structures would have to be ready before people arrive.
To help encourage new creative ideas for buildings on Mars, NASA held the 3D Printed Habitat Challenge. The challenge included several different competitions. A design called the Mars Ice House won the first competition in 2015. To make the building, one robot would mine ice from under the ground. It would also melt the ice and turn it into a printable material. Another robot would spray this material, forming the walls of the building. These walls would be just five centimeters thick and translucent, allowing people inside to see the landscape all around them.
The Ice House is a design only. In 2019, NASA gathered teams together for a different sort of competition. This time, they had four days to design and 3D print a Mars habitat at one third the scale of the realthing. They had to use recyclables or materials that could be found on the moon or Mars. And they had to use robotic construction or 3D-printing techniques that require very little human oversight. This time, the winner was a tall, slim building named Marsha . The team made it from simulated regolith mixed with a polymer (a type of plastic). A giant robot arm acted like the head of a 3D printer to lay down layer upon layer of the material, forming the structure.
Growing Homes, Food and More
Another creative way to form buildings on Mars would be to grow them. The main part of a mushroom or other fungus is made of root – like threads called mycelium . These th reads g row ve ry q u ickly and when many tangle together, they are lightweight and very strong . Researchers and companies on Earth are already using mycelium to form packaging and bricks. They’re doing it because the material is much more environmentally friendly than plastic or concrete.
Lynn Rothschild, an astrobiologist at NASA Ames Research Center, saw these mycelium bricks and wondered whether the technique might work on Mars. Her idea is that engineers would prepare a very lightweight scaffold on Earth and seed it with bits of fungi and dried out food for the fungi to eat. (Fungi feed on waste). Once on Mars, the scaffold could be unfolded. Adding water would bring the fungi and its food to life. The fungi would then grow and turn the thin scaffold into a thick wall. No electricity is required. In the long term, fungi walls may even provide a source of food for Mars settlers. Her team is now in the process of building a prototype of this structure to test how the process works here on Earth.
Fungi and other microbes may also help Mars settlers to produce many of the other things they need— from fuel and air to food and medicine. Biomanufacturing means using living microbes to produce something. This is typically done with something called a bioreactor . It’s usually a metal vat that contains bacteria and something for them to eat. As the bacteria eat and grow, they give off gases or liquids that people can use. Engineers are already designing bioreactors that could work with the resources found on Mars . A team at the University of Bremen has designed and tested one that they call Atmos. They found that blue-green algae, also called cyanobacteria, can grow on gases from Mars’s air, nutrients from imitation Mars regolith, and water.
This algae, like all plants on Earth, turns carbon dioxide and sunlight into oxygen and sugars. So it could help produce breathable air. In addition, engineers could feed some of the algae to other types of bacteria, such as E. Coli. Then these bacteria could produce things like medicines or fuels.
Manufacturing on Mars would likely loo k ve ry diffe re nt fro m manufacturing on Earth . Settlers wouldn’t have much to work with. So they’d find creative and innovative ways to use all available resources . That includes things most people would consider trash or waste. Human urine can be recycled into freshwater. (The International Space Station already does this.) And if human feces gets composted for a few months, it could help feed plants. Food waste could feed fungi or bacteria in bioreactors. Any plastic waste will likely be melted down and reused in 3D printers. All of these innovations reduce trash and save energy, so they’d be very useful on Earth, too . Learning to manufacture on Mars will be good for both the Earthlings and Martians of the future!
