Meet NASA’s MOXIE, a box that produces oxygen on Mars


If humans want to explore Mars in the future, they need to make oxygen. Now, a small device the size of a toaster is doing it on Earth.

In a study published this week in the journal Science Advances, MIT researchers show that the Martian oxygen in situ resource utilization experiment, known as MOXIE, can create oxygen from the abundant carbon dioxide in the Martian atmosphere.

The experiment, part of NASA’s Perseverance rover mission to land on Mars in February 2021, is the first to convert resources from another planet into something useful for a human mission, the researchers said. This little box, made by NASA’s Jet Propulsion Laboratory and MIT, can create enough oxygen to match the output of a small tree on Earth, and it can be done during the day and night over multiple Martian seasons.

“This is what explorers have done since time immemorial,” said Jeffrey Hoffman, a former NASA astronaut, associate principal investigator on the MOXIE mission, and MIT professor of aerospace engineering. “Find out what resources are available where you’re going and find out how to use them.”

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Space agencies, scientists and entrepreneurs are all calling for human exploration of Mars. NASA’s much-anticipated and troubled Artemis mission to the moon is considered a stepping stone to exploring Mars in the next decade or so. China wants to send humans to Earth by 2033. Elon Musk, the world’s richest man and SpaceX CEO, hinted at doing just that: 2029.

But getting humans to Mars requires several complex things to happen, Hoffman said. Astronauts must endure high levels of cosmic radiation during the long journey to Earth. A round trip to Mars can take more than eight months, so space travelers must have plenty of food and medicine.

Perhaps most important, Hoffman says, is a reliable supply of oxygen. Astronauts need it to breathe in any temporary habitats they build on Mars, as well as in spacesuit storage tanks when exploring Earth. It is also the key propellant for the rocket fuel they need to return from Mars to Earth.

Space agencies could deliver enough oxygen to Mars for astronauts to breathe and return home, but doing so would be very expensive because it would require multiple rocket launches, Hoffman said. It would be cheaper to make oxygen on Mars from carbon dioxide in the atmosphere, he said. About 96% of Mars’ atmosphere is carbon dioxide.

To test their ability to convert carbon dioxide into oxygen, NASA brought a small golden box with it on its Perseverance rover mission last year. Since April 2021, MOXIE has conducted multiple tests to produce oxygen at different times of the Martian day and in different seasonal conditions. In each experiment, the box produced about 6 grams of oxygen per hour, the equivalent of an average tree on Earth. (In recent tests, Hoffman said the machine’s output increased to 10 grams per hour.)

If the technology is mastered, scientists will need to significantly expand the size of the machine and ensure that it can operate continuously. To sustain human missions to Mars and get people back, at least 4.5 to 6.5 pounds of oxygen would need to be produced per hour over a multi-year mission, Hoffman said. “This requires hundreds of times the scale,” he said.

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The machine can operate most of the Martian day, except for a few specific times.

“The only thing we didn’t show was running at dawn or dusk, when the temperature [on Mars] said Michael Hecht, principal investigator of the MOXIE mission at MIT’s Haystack Observatory. “We do have a trump card that will allow us to do this, and once we test it in the lab, we can hit that final milestone showing that we’re really ready to run.”

Engineers plan to push the MOXIE device to its limits, boosting its oxygen production capacity and ensuring it works during Martian spring when the atmosphere is dense and carbon dioxide high. “We’re going to set everything as high as possible and let it run for as long as possible,” Hecht said.

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Engineers will monitor the wear and tear of the machine to see if it can withstand enough stress to indicate that it can be converted into a complete system that can run continuously for thousands of hours. If so, the impact could be significant.

“To support a human mission to Mars, we have to bring a lot of things from Earth,” Hoffman said. “But stupid old oxygen? If you can do it, go for it – you’re way ahead.”

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