Day and night, and across seasons, the instrument generates breathable oxygen from the Red Planet’s thin atmosphere.
By Jennifer Chu, MIT
News Office
August 31, 2022 -- In a
study published today, researchers report that, by the end of 2021, the MIT-led
MOXIE project was able to produce oxygen on seven experimental runs on the Red
Planet.
On the red and dusty
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 April 2021,
about two months after it touched down on the Martian surface as part of NASA’s
Perseverance rover and Mars 2020 mission.
In a study published today
in the journal Science Advances, researchers report that, by the end of 2021,
MOXIE was able to produce oxygen on seven experimental runs, in a variety of
atmospheric conditions, including during the day and night, and through
different Martian seasons. In each run, the instrument reached its target of
producing six grams of oxygen per hour — about the rate of a modest tree on
Earth.
Researchers envision
that a scaled-up version of MOXIE could be sent to Mars ahead of a human
mission, to continuously produce oxygen at the rate of several hundred trees.
At that capacity, the system should generate enough oxygen to both sustain
humans once they arrive, and fuel a rocket for returning astronauts back to
Earth.
So far, MOXIE’s steady
output is a promising first step toward that goal.
“We have learned a
tremendous amount that will inform future systems at 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 harvesting and using a planet’s materials
(in this case, carbon dioxide on Mars) to make resources (such as oxygen) that
would otherwise have to be transported from Earth.
“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 in MIT’s Department of Aeronautics and Astronautics.
“It’s historic in that sense.”
Hoffman and Hecht’s MIT
co-authors include MOXIE team members Jason SooHoo, Andrew Liu, Eric Hinterman,
Maya Nasr, Shravan Hariharan, Kyle Horn, and Parker Steen, along with
collaborators from multiple institutions including NASA’s Jet Propulsion
Laboratory, which managed MOXIE’s development, flight software, packaging, and
testing prior to launch.
Seasonal air
The current version of
MOXIE is small by design, in order to fit aboard the Perseverance rover, and is
built to run for short periods, starting up and shutting down with each run,
depending on the rover’s exploration schedule and mission responsibilities. In
contrast, a full-scale oxygen factory would include larger units that would
ideally run continuously.
Despite the necessary
compromises in MOXIE’s current design, the instrument has shown it can reliably
and efficiently convert Mars’ atmosphere into pure oxygen. It does so by first
drawing the Martian air in through a filter that cleans it of contaminants. The
air is then pressurized, and sent through the Solid OXide Electrolyzer (SOXE),
an instrument developed and built by OxEon Energy, that electrochemically
splits the carbon dioxide-rich air into oxygen ions and carbon monoxide.
The oxygen ions are
then isolated and recombined to form breathable, molecular oxygen, or O2, which
MOXIE then measures for quantity and purity before releasing it harmlessly back
into the air, along with carbon monoxide and other atmospheric gases.
Since the rover’s
landing in February 2021, MOXIE engineers have started up the instrument seven
times throughout the Martian year, each time taking a few hours to warm up,
then another hour to make oxygen before powering back down. Each run was
scheduled for a different time of day or night, and in different seasons, to
see whether MOXIE could accommodate shifts in the planet’s atmospheric
conditions.
“The atmosphere of Mars
is far more variable than Earth,” Hoffman notes. “The density of the air can
vary by a factor of two through the year, and the temperature can vary by 100
degrees. One objective is to show we can run in all seasons.”
So far, MOXIE has shown
that it can make oxygen at almost any time of the Martian day and year.
“The only thing we have
not demonstrated is running at dawn or dusk, when the temperature is changing
substantially,” Hecht says. “We do 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 really run any time.”
Ahead of the game
As MOXIE continues to
churn out oxygen on Mars, engineers plan to push its capacity, and increase its
production, particularly in the Martian spring, when atmospheric density and
carbon dioxide levels are high.
“The next run coming up
will be during the highest density of the year, and we just want to make as
much oxygen as we can,” Hecht says. “So we’ll set 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. As MOXIE is just one experiment among
several aboard the Perseverance rover, it cannot run continuously as a
full-scale system would. Instead, the instrument must start up and shut down
with each run — a thermal stress that can degrade the system over time.
If MOXIE can operate
successfully despite repeatedly turning on and off, this would suggest that a
full-scale system, designed to run continuously, could do so for thousands of
hours.
“To support a human
mission to Mars, we have to bring a lot of stuff from Earth, like computers,
spacesuits, and habitats,” Hoffman says. “But dumb old oxygen? If you can make
it there, go for it — you’re way ahead of the game.”
This research was
supported, in part, by NASA.
https://news.mit.edu/2022/moxie-oxygen-mars-0831
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