A demonstration like a small tree: the MOXIE instrument on board the Perseverance rover can reliably extract oxygen from carbon dioxide in the Martian air under different atmospheric conditions, results from 2021 show. In seven test runs, the device achieved a rate of six grams of oxygen per hour. So far, the concept has proven successful. Large plants, as planned, could produce the air that Martians breathe, as well as gas for rocket propulsion on the Red Planet.
Mars is the target of manned space travel after the Moon: one day the first humans will set foot on the Red Planet. Many of the challenges include supplying oxygen for the breathing air and rocket propulsion on the return flight. Carrying the required quantity would be a huge burden. So scientists are working on concepts to produce gas on site from the resources provided by the planet. The “Mars Oxygen In-Situ Resource Utilization Experiment” (MOXIE) is dedicated to this goal: as part of the Mars rover mission Perseverance, it is investigating the extent to which oxygen can bind to carbon dioxide in the thin Martian atmosphere. can be obtained. Instruments of electrolysis.
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The Mars rover, which has been on the planet’s surface since February 2021, was equipped with a device the size of a lunch box. It first sucks up the Martian air, which consists of 96 percent carbon dioxide, to remove the dust. It is then compressed and then passed through a device that electrically splits the carbon dioxide-containing air into oxygen ions and carbon monoxide. Then the oxygen ions combine to form O₂. The MOXIE instrument records the amount and purity of the gas. It is then released back into the Martian atmosphere along with carbon monoxide.
As the developers report, the MOXIE instrument had to be designed as small as possible so that it could be accommodated in the Persistence rover. For this reason, the concept has so far been a trial version that doesn’t work consistently: the device is switched on and off for temporary experiments. This is done in a targeted manner in as many different atmospheric conditions as possible, the team explains. “The atmosphere of Mars is much more variable than that of Earth,” says lead author Jeffrey Hoffman from the Massachusetts Institute of Technology (MIT) in Cambridge. “The density of the air can vary by a factor of two during the year, and the temperature can fluctuate by as much as 100 degrees. So our goal is to show that the system works all the time,” Hoffman says.
Reliable even in unstable conditions
Since the rover’s landing, the MOXIE instrument has been operated seven times a year to Mars, each time taking a few hours to warm up and another hour to produce oxygen before shutting down again. Each run was scheduled for a different time of day or night and a different time of year. As the team now reports, the system has shown so far that it can withstand changing conditions with ease. With each run, the device met its goal of producing six grams of oxygen per hour—the equivalent of a small tree on Earth. “We are using resources on the surface of another planet by chemically converting them into something that would be useful for a human mission,” Hoffman says. “In this sense, the success is historic,” says the scientist.
In concrete terms, reliable oxygen production now shows the potential of the concept of manned space missions to Mars: “We’ve learned a lot that will help us in large-scale systems of the future,” says co-author Michael Hecht of MIT. The researchers estimate that an expanded version of MOXIE could be sent to Mars before a manned mission to continuously produce oxygen on the order of several hundred trees. At this capacity, the system must produce enough oxygen to both feed people after their arrival and to power a rocket for the astronauts’ return to Earth.
Testing of the MOXI instrument aboard the Perseverance rover will now continue, scientists say: They plan to increase capacity and increase production, especially in the Martian spring when atmospheric densities and carbon dioxide levels are particularly high. “So we’re going to set everything as high as we dare and let it go for as long as we can,” Hecht says.
Source: Massachusetts Institute of Technology, NASA, Article: Science Advances, DOI: 10.1126/sciadv.abp8636
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