Mars’ atmosphere is currently not as friendly as Earth’s. It is extremely thin, hundreds of times less dense than Earth, and consists mostly of carbon dioxide. If a person inhales it, he soon finds that he cannot breathe.
However, on this dusty, dry alien planet, there is already a device a little bigger than a briefcase that produces oxygen suitable for breathing in the Martian atmosphere.
This is the first demonstration of in-situ production of resources for human consumption on another planet, showing a way to produce breathable air for human missions on the Red Planet.
Its name is MOXIE (Mars Oxygen In-Situ Resource Utilization (ISRU) Experiment) and it is installed in the belly of NASA’s rover Perseverance. It uses a process called electrolysis to break down Martian carbon dioxide into carbon monoxide (carbon monoxide) and oxygen.
Between February 2021 (when Perseverance landed on Mars) and the end of 2021, MOXIE has produced oxygen seven times and will continue to do so in the future.
“This is the first demonstration of using resources on the surface of another planetary body to chemically transform the resources there into something that would be useful for a human mission. It’s a historic event,” says former astronaut and MOXIE team member Geoffrey Hoffman of the Massachusetts Institute of Technology (MIT).
The production of oxygen by electrolysis is not new. For example, on the International Space Station, electrolysis is used to split water into hydrogen and oxygen, which produces the air we need to breathe.
However, water on Mars may be too precious to waste for this purpose, and another affordable method was sought.
Fortunately, oxygen is a constituent of many compounds, including carbon dioxide, which makes up about 96 percent of the Martian atmosphere. Its molecule consists of one carbon and two oxygen atoms.
Electrochemical reduction of carbon dioxide into its constituent elements is well known and studied; Here on Earth, the main challenge was to create an instrument that would do this on Mars with the available ingredients.
Oxygen production by MOXIE is a multi-step process.
First, it funnels the Martian air through a filter that cleans it. Mars then compresses, heats, and sends the instrument to the SOXE (Solid Oxide Electrolyzer). This electrolyzer breaks down carbon dioxide into oxygen ions and carbon dioxide, which is released back into the Martian atmosphere.
After that, the oxygen ions recombine into O2, or molecular oxygen, the quantity, and quality of which is then measured and released back again.
Scientists determined that this process reliably produced breathable oxygen. After several hours of heating, the instrument conducts the experiment for one hour, and then it is turned off. During one hour of operation, MOXIE can produce up to ten grams of oxygen, which should give an astronaut about 20 minutes to breathe.
Each of the seven times, MOXIE produced between 5.4 and 8.9 grams of molecular oxygen, for a total of 49.9 grams.
Because humidity and air density on Mars vary greatly, not only day-to-day but also seasonally, MOXIE is required to operate over a wide range of temperatures and air densities.
In all seven times, MOXIE was able to produce oxygen under different environmental conditions: during the day, at night, and at different times of the year.
“The only thing we haven’t tested is its operation at dawn and dusk when the temperature changes substantially. However, we will soon test this as well,” says MOXIE principal researcher Michael Hatch.
Ideally, his goal is to create a life support system that will work continuously because people need to breathe. At the same time, it needs to be much bigger than MOXIE. As Hatch pointed out last year, a small group of astronauts would need about a ton of oxygen for a year on Mars.
This does not include oxygen for the engines, which is needed to return to Earth. According to the researchers’ calculations, in total, the mission will need about 500 tons of oxygen.
What the team learned in MOXIE’s first year of operation will help them build such a large system, but there is still a long way to go.
The next experiment will be conducted at the time of year when the atmosphere is densest. According to the researchers, then they will load the instrument with full power and try to get the maximum amount of oxygen.
This shows not only MOXIE’s capabilities but also its limitations, which will also be useful for building more robust devices for future manned missions.
The study was published in Science Advances.