On the red and dusty surface of Mars, nearly 100 million miles from Earth, a lunchbox-sized device proves it can reliably handle the work of a small tree. The MIT-led Mars Oxygen Resource Exploitation Experiment, or MOXIE, has been successfully producing oxygen from the red planet’s carbon dioxide-rich atmosphere since landing on the surface of Mars in February 2021 as part of NASA’s Perseverance rover mission. MOXIE was able to produce oxygen in seven experimental cycles, in different atmospheric conditions, including during day and night, and during different Martian seasons. . In each run, the device achieved its goal of producing six grams of oxygen per hour about the rate of a humble tree on Earth. A scaled-up version of MOXIE could be sent to Mars to continuously produce oxygen at the rate of several hundred trees, the researchers predict, before a human mission. At this capacity, the system should generate enough oxygen to sustain humans once they arrive, as well as power the rocket to return the astronauts back to Earth.
MOXIE’s consistent performance so far is a promising first step toward that goal. “We learned a tremendous amount of information that will inform future larger-scale systems,” says Michael Hecht, principal investigator of the MOXIE mission at MIT’s Haystack Observatory. MOXIE’s oxygen production on Mars also represents the first demonstration of “in-situ resource utilization,” the idea of harvesting and using the planet’s materials (in this case, carbon dioxide on Mars) to produce resources (such as oxygen) that would otherwise have to be transported from Earth.
“This is the first demonstration of actually taking resources on the surface of another planetary body and chemically converting them into something that would be useful for a human mission,” said MOXIE Deputy Principal Investigator Jeffrey Hoffman, a professor of practice at MIT. aviation and cosmonautics. “In that sense, it’s historic.” Hoffman and Hecht’s co-authors at MIT include MOXIE team members Jason SooHoo, Andrew Liu, Eric Hinterman, Maya Nasr, Shravan Hariharan, and Kyle Horn, along with collaborators from various institutions including NASA’s Jet Propulsion Laboratory, which managed MOXIE’s flight software development, packaging, and testing before being put on the market.
The current version of MOXIE is small in design to fit aboard the Perseverance rover and is designed to operate for short periods of time, powering up and shutting down with each run, depending on the rover’s exploration plan and mission responsibilities. In contrast, a full-scale oxygen plant would involve larger units that would ideally run continuously.
ment has shown that it can reliably and efficiently convert the Martian atmosphere into pure oxygen. It does this by first sucking Martian air through a filter that cleans it of impurities. The air is then pressurized and sent through the Solid OXide Electrolyzer (SOXE), a tool developed and manufactured by OxEon Energy that electrochemically splits carbon dioxide-rich air into oxygen ions and carbon monoxide. The oxygen ions are then isolated and recombined to form breathable molecular oxygen, or O2, which MOXIE then measures for quantity and purity before releasing it harmlessly back into the air along with carbon monoxide and other atmospheric gases.
Since the rover’s landing in February 2021, MOXIE engineers have fired up the instrument seven times during the Martian year, each time taking several hours to warm up and then another hour to produce oxygen before shutting down again. Each run was scheduled for a different time of day or night and in different seasons to see if MOXIE could adapt to shifts in the planet’s atmospheric conditions.
“Mars’ atmosphere is much more variable than Earth’s,” notes Hoffman. “The air density can change twice a year and the temperature can vary by 100 degrees. One of the goals is to show that we can run in all seasons.” So far, MOXIE has demonstrated that it can produce oxygen at almost any time of day and year on Mars. “The only thing we haven’t demonstrated is running at dawn or dusk, when the temperature changes substantially,” Hecht says. “We have an ace up our sleeve that will enable us to do that, and once we test it in the lab, we can reach that final milestone to show that we can really run at any time.”
Before the match
As MOXIE continues to churn out oxygen on Mars, engineers plan to increase its capacity and increase its output, especially in the Martian springtime, when atmospheric density and carbon dioxide levels are high.”The next run will be during the highest density of the year, and we just want to produce as much oxygen as possible,” Hecht says. “So we set everything as high as we dare and let it run as long as it can.
They will also monitor the system for signs of wear and tear. Because MOXIE is only one of several experiments aboard the Perseverance rover, it cannot run continuously as a full-fledged system. Instead, the device must start up and shut down every time it runs—a thermal stress that can degrade the system over time. If MOXIE can successfully operate despite being turned on and off repeatedly, it suggests that a full-fledged system designed to run continuously could do so for thousands of hours. “To support a human mission to Mars, we need to bring a lot of things from Earth, such as computers, spacesuits and habitats,” says Hoffman. “But stupid old oxygen? If you can get there, go for it – you’re way ahead.” This research was supported by NASA.