On the dusty red surface of Mars, nearly 100 million miles from Earth, an instrument the size of a lunchbox is proving it can reliably do the work of a small tree.
The MIT-led Mars Oxygen In Situ Resource Utilization Experiment, or MOXIE, has been successfully making oxygen from the red planet’s carbon dioxide-rich atmosphere since February 2021, when landed on the Martian surface as part of NASA’s Perseverance rover mission. .
In a study published in the journal Science Advances, the researchers report that by the end of 2021, MOXIE was able to produce oxygen in seven experimental runs, in a variety of atmospheric conditions, including during the day and night, and across different seasons Martians . On each run, the instrument achieved its goal of producing six grams of oxygen per hour, about the rate of a modest tree on Earth.
The researchers envision that an expanded version of MOXIE could be sent to Mars before a human mission, to continuously produce oxygen at the rate of several hundred trees. With this capability, the system should generate enough oxygen to sustain humans once they arrive and power a rocket to return the astronauts to Earth.
So far, MOXIE’s steady production is a promising first step toward that goal.
“We’ve learned an enormous amount that will inform future systems on a larger scale,” says Michael Hecht, principal investigator of the MOXIE mission at MIT’s Haystack Observatory.
MOXIE’s oxygen production on Mars also represents the first demonstration of “in situ resource utilization,” which is the idea of ​​collecting and using a planet’s materials (in this case, carbon dioxide on Mars) to produce resources (such as oxygen) that would otherwise have to be transported from Earth.
“This is the first demonstration of using resources on the surface of another planetary body and chemically transforming them into something that would be useful for a human mission,” says MOXIE deputy principal investigator Jeffrey Hoffman, professor of internship at the MIT Department. of Aeronautics and Astronautics. “It’s historic in that sense.”
Hoffman and Hecht’s co-authors at MIT include MOXIE team members Jason SooHoo, Andrew Liu, Eric Hinterman, Maya Nasr, Shravan Hariharan, and Kyle Horn, along with collaborators from several institutions, including the Jet Propulsion Laboratory at the NASA, which managed MOXIE’s development, flight software, packaging and pre-launch testing.
Temporary activated
The current version of MOXIE is small by design to fit aboard the Perseverance rover, and is designed to operate for short periods, starting and shutting down with each run, depending on the rover’s exploration program and the mission responsibilities. In contrast, a large-scale oxygen factory would include larger units that would ideally operate continuously.
Despite the compromises required in MOXIE’s current design, the instrument has demonstrated that it can reliably and efficiently convert the Martian atmosphere into pure oxygen. It does this by first sucking the Martian air through a filter that cleans it of pollutants. The air is then pressurized and sent through the Solid Oxide Electrolyzer (SOXE), an instrument developed and built by OxEon Energy, which electrochemically splits carbon dioxide-rich air into carbon dioxide ions oxygen and carbon monoxide.
The oxygen ions are then isolated and recombined to form breathable molecular oxygen, or O2, which MOXIE measures for quantity and purity before harmlessly releasing it 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 over the course of the Martian year, each time taking a few hours to warm up and then another hour to oxygenate before turning off again. Each run was scheduled for a different time of day or night, and in different seasons, to see if MOXIE could adapt to changes in the planet’s atmospheric conditions.
“Mars’ atmosphere is much more variable than Earth’s,” notes Hoffman. “The air density can vary by a factor of two throughout the year and the temperature can vary by 100 degrees. One goal is to show that we can run in all seasons.”
So far, MOXIE has shown that it can produce oxygen at almost any time of the Martian day and year.
“The one thing we haven’t demonstrated is running at dawn or dusk, when the temperature changes substantially,” says Hecht. “We have an ace up our sleeve that will allow us to do that, and once we test it in the lab, we can reach this final milestone to show that we really can run at any time.”
Ahead of the game
As MOXIE continues to produce oxygen on Mars, engineers plan to increase its capacity and increase its output, especially in the Martian spring, when atmospheric density and carbon dioxide levels are high.
“The next race will be during the highest density of the year, and we just want to produce as much oxygen as we can,” Hecht says. “So we’re going to put everything as high as we dare, and let it run as long as we can.”
They will also monitor the system for signs of wear and tear. Because MOXIE is only one experiment among several aboard the Perseverance rover, it cannot operate continuously as a full-scale system would. Instead, the instrument must be turned on and off with each run, a thermal stress that can degrade the system over time.
If MOXIE can operate successfully despite being turned on and off repeatedly, this would suggest that a large-scale system, designed to operate continuously, could do so for thousands of hours.
“To support a human mission to Mars, we have to bring a lot of things from Earth, such as computers, spacesuits and habitats,” says Hoffman. “But stupid old oxygen? If you can get there, do it – you’re way ahead of the game.”
This research was supported, in part, by NASA.
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