MOXIE experiment succeeds in producing oxygen on Mars

Nearly 100 million miles from Earth, on the red and dusty surface of Mars, an instrument the size of a lunchbox is proving it can reliably do the work of a small tree. The Mars Oxygen In Stu Resource Utilization Experiment (MOXIE), led by the Massachusetts Institute of Technology (MIT), has been successfully producing oxygen from the Red Planet's carbon dioxide-rich atmosphere since April 2021.

That was about two months after it landed on the surface of Mars as part of NASA's Perseverance rover and Mars 2020 mission.

In a study published Aug. 31 locally in Science Advances, researchers report that by the end of 2021, MOXIE will be able to produce oxygen in seven experimental runs. These were conducted under a variety of atmospheric conditions - both during the day and at night - and during different Martian seasons. In each experimental run, the instrument reached its goal of producing 6 grams of oxygen per hour. That's about the rate of an average tree on Earth.

The scientists envision that a scaled-up version of MOXIE could be sent to Mars ahead of a human mission, where it could produce oxygen continuously at the rate of several hundred trees. At this capacity, the system should produce enough oxygen to sustain humans upon arrival and fuel the astronauts' rocket back to Earth.

So far, MOXIE's continuous production is a promising first step toward this goal.

"We've learned a tremendous amount that will inform future, larger-scale systems," said Michael Chechen, senior researcher on the MOXIE mission at MIT Haystack Observatory.

MOXIE's oxygen production on Mars also represents the first demonstration of "in sit resource utilization. This is the idea of harvesting and using a planet's raw materials to make resources such as oxygen that would otherwise have to be transported from Earth.

This is the first demonstration of actually using resources from the surface of another planetary body and chemically transforming them into something useful for human missions," said Jeffrey Hoffman, MOXIE deputy principal investigator. In that sense, it's historic."

Hoffman and Brecht's MIT co-authors include MOXIE team members Jason Boohoo, Andrew Lou, Eric Hinter man, Maya Nair, Shrank Harridan, Kyle Horn, and collaborators from multiple agencies - including NASA's Jet Propulsion Laboratory (PL) which manages MOXIE's development, flight software, packaging, and per-launch testing.

Seasonal Air

The current version of MOXIE was designed to be small enough to fit on the Trailblazer probe. It is built for short-term operations, with each operation starting and shutting down depending on the rover's exploration schedule and mission responsibilities. In contrast, a full-scale Mars oxygen plant would include larger units, preferably in continuous operation.

Despite the necessary limitations of MOXIE's current design, the instrument has demonstrated that it can efficiently and reliably convert the Martian atmosphere into pure oxygen. It does this by first pulling Martian air through a filter to remove contaminants from it. The air is then pressurized and fed into a solid oxide electrolyte (SORE). This instrument was developed and built by Ox Eon Energy and electromagnetically separates the CO-rich air into oxygen ions and carbon monoxide.

The oxygen ions are then separated and recombined, which then forms irreparable molecular oxygen (O). The amount and purity of this output are then measured by MOXIE before it is harmlessly released back into the air along with carbon monoxide and other atmospheric gases.

Since the rover landed in February 2021, MOXIE engineers have fired up the instrument seven times throughout the Martian year. Each time it takes a few hours to warm up, then another hour to make oxygen before powering down. Each run is scheduled for a different time of day or night and a different season to check if MOXIE can adapt to the planet's changing atmospheric conditions.

Mars has a much more varied atmosphere than Earth," Hoffman noted. The density of the air can vary by a factor of two over a year, and the temperature can vary by 100 degrees. One goal is to show that we can operate in all seasons."

So far, MOXIE has demonstrated that it can make oxygen at almost any time of the day and year on Mars.

The only thing we haven't proven is to operate at dawn or dusk when the temperature is changing significantly," Chechen said. We do have an ace in the hole that will allow us to do that, and once we test it in the lab we can reach the last milestone when we can run it at any time of day."

Leading the game

As MOXIE continues to produce oxygen on Mars, engineers plan to increase its capacity and increase its production, especially in the Martian spring, when atmospheric density and carbon dioxide levels are high.

"The next run will be at the highest density of the year, and we just want to make as much oxygen as we can," Chechen said, "so we'll set everything as high as we can and keep it running as long as we can."

They will also monitor the system for signs of wear and tear. Because MOXIE is only one of several experiments on board the Trailblazer, it can't run continuously like a full-scale system. Instead, the instrument must be started up and shut down during each run. This causes thermal stress and degrades the system over time.

If MOXIE can run successfully with repeated on and offs, it would indicate that a full-scale system designed for the continuous operation could run for thousands of hours.

To support a human mission to Mars, we'd have to bring a lot of things like computers, spacesuits, and habitats from Earth," Hoffman said. But stupid old oxygen? If you can do that, go for it - you're already ahead of the game."