MOXIE experiment reliably produces oxygen on Mars

An gadget the size of a lunchbox is demonstrating its ability to consistently carry out the work of a tiny tree on the red and dusty surface of Mars, some 100 million miles from Earth.

Since it landed on Mars in February 2021 as part of NASA's Perseverance rover mission, the MIT-led Mars Oxygen In-Situ Resource Utilization Experiment, or MOXIE, has been successfully producing oxygen from the Red Planet's carbon-dioxide-rich atmosphere.

Researchers say that by the end of 2021, MOXIE was able to manufacture oxygen on seven experimental runs, in a variety of atmospheric circumstances, including day and night and throughout the Martian seasons, according to a paper published in the journal Science Advances. The instrument produced six grams of oxygen per hour on each run, or about the same amount as a small tree on Earth.

According to researchers, a scaled-up MOXIE may be transported to Mars before a human trip to create oxygen continually at the rate of several hundred trees. At that capacity, the system should be able to produce enough oxygen to support people once they arrive as well as power a rocket for astronauts returning to Earth.

As of now, MOXIE's consistent output represents a positive first step in that direction.

Michael Hecht, the MOXIE mission's chief investigator at MIT's Haystack Observatory, states that "We have learned a huge amount that will shape future systems at a bigger scale."

In addition, the oxygen produced by MOXIE on Mars is the first example of "in-situ resource utilization," which is the concept of using a planet's resources (in this case, carbon dioxide on Mars) to create resources (such as oxygen) that would otherwise need to be carried from Earth.

According to MOXIE deputy principal investigator Jeffrey Hoffman, a professor of the practice in MIT's Department of Aeronautics and Astronautics, "This is the first demonstration of actually using resources on the surface of another planetary body, and transforming them chemically into something that would be useful for a human mission." "In that regard, it is historic."

The MOXIE team members Jason SooHoo, Andrew Liu, Eric Hinterman, Maya Nasr, Shravan Hariharan, and Kyle Horn are among the co-authors from MIT alongside Hoffman and Hecht. Other contributors come from various institutions, including NASA's Jet Propulsion Laboratory, which oversaw MOXIE's development, flight software, packaging, and testing before launch.

The current MOXIE is built to run for brief times, starting up and shutting down with each run, depending on the rover's exploration schedule and mission tasks. It is compact by design to fit within the Perseverance rover. A complete oxygen factory, however, would include larger units that ideally ran continually.

MOXIE has demonstrated that, despite the inevitable trade-offs in its current architecture, it is capable of reliably and effectively converting Mars' atmosphere into pure oxygen. To do this, it draws in Martian air and passes it through a filter to remove any impurities. In the Solid OXide Electrolyzer (SOXE), a device created and manufactured by OxEon Energy, the compressed air is split into oxygen ions and carbon monoxide by electrochemical reactions.

The oxygen ions are then separated and united again to create breathable molecular oxygen, or O2, which MOXIE then analyzes for quantity and purity before harmlessly releasing it back into the atmosphere together with carbon monoxide and other atmospheric gases.

MOXIE engineers have powered on the device seven times since the rover's landing in February 2021. Each time, it took a few hours to warm up before producing oxygen for an hour before being powered down. Each run was timed to test MOXIE's ability to adapt to changes in the planet's atmospheric conditions at various times of day or night and throughout the year.

Hoffman observes that the atmosphere of Mars is far more erratic than that of Earth. "Throughout the year, the temperature can fluctuate by 100 degrees and the air density can vary by a factor of two. One goal is to demonstrate that we can run year-round."

MOXIE has so far demonstrated its ability to produce oxygen practically year-round on Mars.

Running at dawn or dusk, when the temperature is significantly changing, is the only thing Hecht says they haven't tested. We do have a trick up our sleeves that will enable us to do that, and after we test it in the lab, we can accomplish that last goal to demonstrate that we can actually run at any time.

Engineers intend to enhance MOXIE's production capacity as it continues to produce oxygen on Mars, especially in the Martian spring when atmospheric density and carbon dioxide levels are high.

The upcoming marathon will occur at the maximum density of the year, so we simply want to produce as much oxygen as we can, according to Hecht. In order to have it run as long as possible, we will set everything as high as we dare.

Additionally, they will keep an eye out for indicators of system wear and tear. As one of many experiments on the Perseverance rover, MOXIE cannot operate continually like a real system would. Instead, the instrument must start up and shut down after every run, putting heat stress on the system that over time could deteriorate it.

If MOXIE can function properly despite switching on and off frequently, a larger system that is intended to run continuously might be able to do the same for thousands of hours.

"We have to transport a lot of stuff from Earth, like computers, spacesuits, and housing, to enable a human voyage to Mars," Hoffman claims. "But dreadful old oxygen? Go for it if you can get there; you'll be much ahead of the game."

Massachusetts Institute of Technology