Huffing and Puffing on Mars: It Takes MOXIE

The Perseverance Mars rover is busy wheeling and dealing with Jezero Crater, prowling about that Red Planet scenery, stuffed with science gear. Tucked into the belly of this on-the-move Mars machinery is a novel device capable of producing oxygen from the carbon dioxide-rich Martian atmosphere.

In shorthand space lingo, it’s called MOXIE — a verbal stand-in for “Mars Oxygen In Situ Resource Utilization Experiment.” The toaster-sized device is the first experiment to harvest and process a native resource on the surface of another planet.

That technology milestone occurred on April 20, 2021, when MOXIE first converted atmospheric carbon dioxide into oxygen via its solid-oxide electrolysis assembly, two months and two days after Perseverance landed on Mars that February.

Though MOXIE cranked out a humble whiff of five grams or so of oxygen on its first run — the average person breathes a little under one kilogram per day, per a 1997 study — MOXIE in no small measure signifies something huge for the future.

Breathing room for astronauts

“We’re doing all this for the benefit of a future human mission to Mars,” Michael Hecht, the principal investigator of the MOXIE, tells SpaceRef. He is an associate director of the Massachusetts Institute of Technology’s (MIT) Haystack Observatory in Westford, Massachusetts.

MOXIE has now completed 13 oxygen-producing runs during night and day, throughout all Martian seasons, Hecht told SpaceRef. The device has even performed during cycles of dust activity. “At least half of those runs have been for the purpose of understanding how the instrument behaves, how to improve it, trying out new techniques and control methods,” he said.

On the whole, since operations began, MOXIE has shown it can make six grams of oxygen per hour. But Hecht said he expects to hit 12 grams of oxygen per hour in a run projected to take place no later than next month, toward the end of June.

MOXIE has cataloged 1,083 minutes of work time, yielding a total of 106 grams of oxygen. Hecht recounted that the test gear’s production record is about 10.5 grams of oxygen an hour.

As for on-the-job training in working MOXIE on Mars, there’s been one revelation.

“What caught us by surprise is that, so far, everything has worked as predicted,” Hecht explained. “Maybe we haven’t tried hard enough to break it.”

“Most likely, if something breaks, it’s going to be degradation, but not game over in terms of MOXIE,” he added. “But you never know.”

On the other hand, the MOXIE team has realized how critical wire resistance measurements within the assembly are, along with the impact from switching the apparatus on and off. The instrument operates at 800 degrees Celsius, so there was a limited choice of materials that can be utilized at that temperature, Hecht noted. “There’s a lot of calculation and guesswork in not knowing accurately wire resistances,” he said, which adds up to “a big impediment.”

Victory flag

If MOXIE unexpectedly conks out, Hecht said he’d still raise the victory flag. A vital technology has successfully been checkmarked.

As a technology demonstration, MOXIE’s longevity is tied to funding. NASA money for MOXIE is set to end after September, Hecht said. There’s no funded program beyond that time period.

“When humans go to Mars, a technology derived from MOXIE will be used to fill their oxygen tanks,” said Hecht. “We’ve operated successfully for a year on Mars. Everything has worked perfectly. In my mind, we have enabled a flight system that will do this job as part of a human mission. We’re ready to go. We’ve learned some simple but important changes that need to be made,” he stated.

Big MOXIE

Hecht said he would focus on building a full-scale system on Earth, dubbed by some as “big MOXIE.” That hardware would be about the size of a washing machine and a metric ton in mass. Nevertheless, making oxygen is one thing. Figuring out how to store that oxygen for two years without it boiling away is another challenge altogether, he added.

“It’s going to need to run for 10,000 hours straight, continuously operating unattended,” Hecht said of big MOXIE. “We can only run MOXIE an hour at a time on the Perseverance Mars rover. So we have no idea at this point what the limiting factors for [its] lifetime are going to be.”

“To support a human mission to Mars, we have to bring a lot of stuff from Earth, like computers, spacesuits, and habitats,” former astronaut and MOXIE deputy principal investigator at MIT Jeff Hoffman contended in a university statement. “But dumb old oxygen? If you can make it there, go for it … you’re way ahead of the game.”

Larger and more efficient oxygen generators on Mars would not only let astronauts create their own air to breathe, but also fuel a rocket, say to return humans back to the Earth. All indications are that a souped-up version of MOXIE could reliably generate oxygen in ample quantity for future Mars expeditions.

Historic milestone

Keenly watching the MOXIE results is Robert Zubrin, president of the Mars Society — an influential space advocacy group supportive of the human exploration and settlement of the distant world.

MOXIE’s feat in showcasing the prospect of churning out rocket propellant on Mars “is a historic milestone,” Zubrin told SpaceRef. Now, he added, it’s imperative to build on it by scaling up production by two orders of magnitude. “That would put it in the range necessary to support human missions to the Red Planet,” he suggested.  

“It can be done, but we need to start development now if the technology is to be ready when we will need it,” Zubrin concluded.