The experiment, part of NASA’s Perseverance Rover mission that landed on Mars in February 2021, is the first time resources from another planet have been transformed into something useful for human missions, researchers said. The small box, made by NASA’s Jet Propulsion Laboratory and MIT, makes enough oxygen to match the output of a small tree on Earth, and can do so during the day and night during multiple Martian seasons.
“This is what explorers have been doing from time immemorial,” said Jeffrey Hoffman, a former NASA astronaut who is deputy principal investigator on the MOXIE mission and professor of aerospace engineering at MIT. “Find out what resources are available where you go and learn how to use them.”
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Space agencies, scientists and entrepreneurs are clamoring for people to explore Mars. NASA’s highly anticipated and troubled Artemis mission to the moon is considered a springboard to exploring Mars in the next decade or so. China hopes to have people on Earth by 2033. Elon Musk, the world’s richest person and CEO of SpaceX, hinted to do so by 2029.
But getting humans to Mars requires several complicated things to happen, Hoffman said. Astronauts have to endure high levels of cosmic rays during the long journey to the planet. Traveling to and from Mars can take more than 8 months, so there should be plenty of food and medicine for space travelers.
Perhaps most important is a reliable supply of oxygen, Hoffman said. Astronauts need to breathe in whatever temporary habitat they have set up on Mars, as well as in spacesuit tanks when exploring the planet. It is also a crucial propellant to fuel the rocket they need to return to Earth from Mars.
Space agencies could send enough oxygen to Mars for astronauts to breathe and make the return journey home, Hoffman said, but this would be very expensive, as it would require multiple rocket launches. Making the oxygen on Mars from the carbon dioxide in the atmosphere would be cheaper, he said. Mars’ atmosphere is made up of about 96 percent carbon dioxide.
To test their ability to convert carbon dioxide into oxygen, NASA took a small, gold box on its Perseverance Rover mission last year. Since April 2021, MOXIE has conducted several tests where it produced oxygen at different times of the Martian day and during different seasonal conditions. During each experiment, the box created about 6 grams of oxygen per hour, equivalent to the output of a modest tree on Earth. (In the most recent test, to be published in a future paper, Hoffman said the machine’s output increased to 10 grams per hour.)
Once the technology is mastered, scientists would have to scale the size of the machine significantly and allow it to run continuously. To support a human mission to Mars and get humans back, Hoffman said, at least 4.5 to 6.5 pounds of oxygen per hour would need to be created during a multi-year mission. “That would have to be scaled up several hundred times,” he said.
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The machine can run during most parts of the Martian day, except for a few specific times.
“The only thing we haven’t shown is running at dawn or dusk, when the temperature [on Mars] changes significantly,” said Michael Hecht, principal investigator of the MOXIE mission at MIT’s Haystack Observatory. “We have an asset in store that allows us to do that, and once we test that in the lab, we can hit that final milestone to show that we can really run any moment.”
Engineers plan to push the MOXIE device to its limits, increasing its oxygen production capacity and making it work during the Martian spring, when the planet’s atmosphere is dense and carbon dioxide levels are high. “We set everything as high as we dare, and let it run for as long as possible,” Hecht said.
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Engineers will check the machine for wear and tear and see if it can withstand enough stress to suggest converting it into a full system that can run for thousands of hours of continuous operation. If so, the effects could be significant.
“To support a human mission to Mars, we need to take a lot of stuff from Earth,” Hoffman said. “But stupid old oxygen? If you can make it, go for it – you’re way ahead of the game.”