Mars has oxygen, but not in a form people can breathe. Its thin atmosphere is mostly carbon dioxide, and a person arriving there could not simply take a breath. In 2021, NASA’s Perseverance rover carried a small experiment designed to test a different possibility: make oxygen from the air already on Mars.
The device, called MOXIE, succeeded. Across 16 operating runs, it produced a total of 122 grams of oxygen. At its best, it made about 12 grams in an hour, with a purity of at least 98 percent, according to NASA. That is a modest amount by everyday standards. The achievement was not a supply for astronauts; it was a demonstration that a key step in making oxygen on another planet could work in the Martian environment.
Turning Martian air into oxygen
MOXIE—short for Mars Oxygen In-Situ Resource Utilization Experiment—was built to test a process called solid oxide electrolysis. It drew in Martian air, filtered and compressed it, then heated the carbon dioxide to roughly 800 degrees Celsius. An electrochemical process separated oxygen atoms from the carbon dioxide molecules.
The oxygen was collected and measured. Carbon monoxide, the other main product of the process, was released back into the atmosphere. The experiment’s job was to prove the conversion could be done reliably, not to store oxygen for later use.
That distinction matters. A future mission would need equipment able to make oxygen in far greater quantities, store it, and operate for long periods. MOXIE was a technology demonstrator about the size of a toaster, fitted inside Perseverance. It showed that the basic chemistry could function on Mars, but it was not a miniature version of a complete life-support or fuel-production plant.
A test in a real, difficult place
Laboratory equipment on Earth can be tested under controlled conditions. MOXIE had to work on a moving rover, on another planet, with a thin atmosphere and temperatures that shift over time. Its runs took place at different points in the Martian day and across changing seasons, giving engineers a chance to see how the device behaved under varied conditions.
The experiment did not run continuously. Each operating session was a test, with the rover’s power, schedule and other mission priorities part of the practical limits. NASA reported that MOXIE met its performance goals across its 16 runs. The repeated results are important: a technology intended for a crewed mission would need to work in changing conditions, not merely succeed once under ideal circumstances.
Perseverance landed in Jezero Crater in February 2021, carrying instruments intended to study the planet and support future exploration. MOXIE was not a primary rover science instrument; it was an engineering experiment riding along with the mission. Its final run took place in 2023, after which the team concluded the demonstration.
Why make oxygen there?
Oxygen has two roles in a human mission. People need it to breathe, and rockets need it as an oxidizer to burn fuel. Carrying every kilogram of oxygen from Earth would add mass and complexity to a long-distance mission. If a future expedition could produce some of what it needs using local resources, it might reduce the amount that must be launched from Earth.
MOXIE tested only one part of that larger idea: extracting oxygen from the atmosphere. It did not demonstrate a complete system for supplying a crew, producing rocket propellant at mission scale, or maintaining equipment through a full expedition. Engineers would also have to design systems for power, heat, gas handling, storage and dependable operation. The experiment’s small output makes the gap between proof of concept and practical infrastructure plain.
Still, that gap is exactly why experiments like this are useful. A mission planner can now consider evidence from hardware that actually operated on Mars, rather than relying only on calculations or Earth-based tests. The results offer a basis for designing larger systems and identifying the engineering questions that remain.
A small machine with a large assignment
MOXIE did not make Mars breathable, and it did not remove the need to bring supplies. Its achievement was narrower and more concrete: it showed that a compact instrument could take in the planet’s carbon-dioxide-rich air and produce measurable, high-purity oxygen on the surface.
That is the kind of advance that can be easy to overlook because it produces no dramatic landscape change. Yet any future effort to live and work beyond Earth will depend on practical systems that turn local conditions into useful resources. MOXIE made one of those systems real enough to test—and gave engineers results from the place where it would ultimately have to work.
