Using the MOXIE experiment on board the Perseverance rover, scientists reported producing oxygen on seven experimental runs by the end of 2021. The amount of oxygen produced in each experiment is equivalent to the production of oxygen of a small tree on Earth.
A lunchbox-sized instrument aboard Mars’ newest rover has been proving it can reliably carry out the work of a small tree on the red, arid surface of Mars.
NASA’s Perseverance rover, which touched down on Mars’ surface in February 2021, is making oxygen from the Red Planet’s carbon-dioxide-rich atmosphere using the MOXIE experiment led by MIT.
Several experiments were conducted with MOXIE during different Martian seasons and in different atmospheric conditions, including during the day and night. Research published in Science Advances reported that MOXIE could produce oxygen on seven experimental runs by the end of 2021. With each run, the instrument produced six grams of oxygen in an hour, a rate comparable to that of a modest tree on Earth.
A modified version of MOXIE will be sent to Mars in the future, which can continuously produce oxygen at a rate equivalent to several hundred trees. That capacity should be sufficient to sustain humans on the planet, and to fuel astronauts’ rockets for their return.
The steady output of MOXIE so far represents a promising first step toward achieving that goal. Michael Hecht, the principal investigator of MIT’s Haystack Observatory’s MOXIE mission, says, “We have learned a lot that will inform future systems.”
It is also the first time that a planet’s materials (in this case, carbon dioxide on Mars) can be harvested and used to produce resources (such as oxygen) otherwise required to be transported from Earth, which is called “in-situ resource utilization.” MOXIE’s oxygen production on Mars is also the first demonstration of this.
“This is the first demonstration of actually using resources on the surface of another planetary body and transforming them chemically into something that would be useful for a human mission,” says MOXIE deputy principal investigator Jeffrey Hoffman, a professor of the practice at MIT’s Department of Aeronautics and Astronautics. “It’s historical in that sense.”
MOXIE team members Jason SooHoo, Andrew Liu, Eric Hinterman, Maya Nasr, Shravan Hariharan, and Kyle Horn are among Hoffman and Hecht’s MIT co-authors. In addition, they collaborate with other institutions, including NASA’s Jet Propulsion Laboratory, which has managed the development, flight software, packaging, and testing of MOXIE.
Designed to fit onto the Perseverance rover, MOXIE runs for short periods of time before shutting down as required by the mission. An oxygen factory, however, would most likely consist of larger units that would run continuously.
Although MOXIE’s current design involves compromises, the instrument has proven reliable and efficient at converting Mars’ atmosphere into pure oxygen. To do this, it first draws the Martian air through a filter that removes contaminants. Then, by pressurizing the air and sending it through the Solid OXide Electrolyzer (SOXE), an instrument manufactured by OxEon Energy, carbon dioxide-rich air is split electrochemically into oxygen ions and carbon monoxide.
MOXIE isolates oxygen ions from the air and combines them to create breathable, molecular oxygen, or O2. O2 is then measured for purity and quantity before being harmlessly released back into the atmosphere along with carbon monoxide.
The MOXIE instrument has been started up seven times since the rover landed on Mars in February 2021, each taking a few hours to warm up and then another one to make oxygen before shutting down again. In order to test whether MOXIE could accommodate changes in the planet’s atmospheric conditions, each run was scheduled at a different time of day or night or in a different season.
According to Hoffman, the atmosphere of Mars is much more variable than Earth’s. There is a significant difference in air density and temperature throughout the year. One objective is to prove we are capable of running in all seasons. At this point, MOXIE has proven to be able to make oxygen at nearly any time of the year and day on Mars.
“The only thing we have not demonstrated is running at dawn or dusk, when the temperature is changing substantially,” Hecht says. “We have an ace up our sleeve that will let us do that, and once we test that in the lab, we can reach that last milestone to show we can run any time.”
MOXIE continues to produce oxygen on Mars, and engineers plan to increase production, especially when atmospheric density and carbon dioxide levels are high during the Martian spring. The next run will occur during the year’s highest density, so Hecht says, “we want to make as much oxygen as possible.” Hecht plans on running the machine for as long as possible during the next run.
As part of the monitoring, they will also look for signs of wear and tear on the system. Unlike a full-scale system, MOXIE cannot run continuously as a part of the Perseverance rover. Every time the instrument runs, the system must start up and shut down – a thermal stress that can wear down the system over time.
The fact that MOXIE can run continuously despite repeatedly turning on and off suggests that a full-scale system could do the same, working for thousands of hours. According to Hoffman, a human mission to Mars will require a lot of equipment from Earth, including computers, spacesuits, and habitats. “But dumb old oxygen? If you can make it there, go for it—you’re way ahead of the game.”
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