Schematic showing the location of Moxie on NASA's Mars rover. There are a total of six wheels on the rover, three on each side, with Moxie facing the rightmost wheel on the right side of the image.

‘History’ box on Mars makes oxygen at the rate of a tree

When NASA’s Perseverance rover launched to Mars last year, it brought a small golden box called MOXIE for the Martian oxygen in situ resource utilization experiment.

Since then, MOXIE has been making oxygen from thin Martian air.

In the journal Science Advances on Wednesday, the team behind the device confirmed that MOXIE has been working well, with an oxygen output comparable to that of an average Earth tree.

By the end of 2021, a wealth of data shows that MOXIE has successfully achieved its target output of 6 grams per hour of oxygen in seven separate experimental runs and under various atmospheric conditions. This includes day and night, different Martian seasons and other things like that.

“The only thing we haven’t demonstrated is operating at dawn or dusk, when temperatures are changing dramatically,” Michael Hecht, principal investigator of MIT’s Haystack Observatory’s MOXIE mission, said in a release. There’s a trump card that will allow us to do this, and once we’re testing it in the lab, we can hit that final milestone showing that we’re really ready to run.”

This is where MOXIE is on the Mars rover.


For scientists and space agencies, MOXIE’s commitment is strong, which is especially exciting given the looming timeline for an expedition to Mars full of astronauts to learn how to keep future Red Planet space explorers safe.

For example, SpaceX CEO Elon Musk’s goal of landing humans on Mars appears to be 2029, while NASA’s own The upcoming Artemis I mission to the moon Designed to pave the way for a planned trip to Mars in the 2030s or 2040s. “In order to support a human mission to Mars, we have to bring a lot of things from Earth, like computers, space suits and habitats,” MOXIE associate principal investigator Jeffrey Hoffman, an MIT professor, said in a press release. “But stupid. Old oxygen? If you can do it, go for it – you’re way ahead.”

For now, MOXIE is pretty small (basically the size of a toaster), but that’s probably a good thing. This means that if scientists can somehow scale up the size of the patterned cubes, MOXIE could produce far more than 6 grams of oxygen per hour.

“We’ve learned a lot that will inform future systems on a larger scale,” Hecht said.

Maybe one day it could finally produce oxygen at the rate of hundreds of trees to sustain astronauts once they reach Mars and fuel the rockets that need life-giving elements to bring astronauts back to Earth, researchers say.

“Astronauts who spend a year on the ground may use a metric ton between them,” Hecht said in a NASA press release last year. But getting four astronauts off the surface of Mars on a future mission will require about 15,000 pounds (7 metric tons) of rocket fuel and 55,000 pounds (25 metric tons) of oxygen, according to the space agency. Bringing all the oxygen from Earth would be super expensive and inefficient.

So, as Hoffman says, why not just make all the oxygen on a dry planet?

How does MOXIE work?

On Mars, MOXIE is actively converting carbon dioxide (96 percent of the element) in the Martian atmosphere into breathable oxygen.

A little chemistry 101 is that a carbon dioxide molecule consists of one carbon atom and two oxygen atoms. The bits are basically glued together. But an instrument in MOXIE called a solid oxide electrolyzer can, to some extent, collect the oxygen sites in those CO2 molecules of interest to scientists. Once that’s done, all the free-floating oxygen particles recombine into O2, a molecule with two oxygen atoms, the kind of oxygen we know and love.

I know it’s different, but I’ve been thinking about Pixar’s WALL-E doing this. So, as WALL-E said: Ta-da!

In what looks like a lab cleanroom, we can see the gold, patterned Moxie mechanism attached to wires and other metal devices that support it.

Technicians at NASA’s Jet Propulsion Laboratory place the Mars Oxygen In Situ Resource Utilization Experiment (MOXIE) instrument into the belly of the Perseverance rover.


“This is the first time actually using resources on the surface of another planetary body and chemically converting them into something useful for human missions,” Hoffman said. “In that sense, it’s historic.”

In the process, the process requires the use of ultra-high temperatures — reaching temperatures of about 1,470 degrees Fahrenheit (800 degrees Celsius) — which is what makes MOXIE’s unique gold coating so fascinating.

Like NASA’s groundbreaking James Webb Space Telescope, MOXIE must shield from infrared heat because it itself works on heat. Gold coating does just that, and in fact the exact reason why JWST’s mirrors are also painted gold.


One wing of the James Webb Space Telescope’s primary mirror opens into place during final testing of the mirror deployment system in May 2021. Look at that gilded beauty.


Next, the MOXIE team intends to demonstrate that MOXIE also works well under denser conditions, such that the next run will occur during “the highest density of the year,” Hecht said. “We’re going to set everything as high as possible and let it run for as long as possible.”

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