On the red, dusty surface of Mars, nearly 100 million miles from Earth, a box-shaped instrument developed by engineers at the Massachusetts Institute of Technology (MIT) has shown it can reliably do the job of a small tree The Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) has been successfully producing oxygen from the Red Planet’s carbon dioxide-rich atmosphere since February 2021, when it touched down on the Martian surface as part of the Perseverance mission. from NASA. In a study published in the journal Science Advances, the authors indicate that by the end of 2021 MOXIE was able to produce oxygen in seven tests, under different atmospheric conditions, during the day and night, and through different Martian seasons. In each of the experiments, the instrument met its goal of producing six grams of oxygen per hour, about the rate of a small tree on Earth. Increasing oxygen production capacity The researchers believe that an enlarged version of MOXIE could be sent to Mars before a human mission, to continuously produce oxygen at the rate of several hundred trees. With that capacity, the system would generate enough oxygen to support humans once they arrive and to fuel a rocket that returns astronauts to Earth. “We’ve learned a lot from this instrument that will form the basis for future larger-scale systems,” says Michael Hecht, principal investigator for the MOXIE mission at MIT’s Haystack Observatory. The authors note that the production of oxygen by this Mars experiment 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). carbon on Mars) to make resources (such as oxygen) that would otherwise have to be transported from Earth. MOXIE, currently on the surface of Mars, is part of NASA’s Perseverance rover, seen here in a selfie with the Ingenuity helicopter. / NASA / JPL-Caltech / MSSS “This is the first demonstration of actually using resources on the surface of another planet to chemically transform them into something useful on a human mission,” says MOXIE Deputy Principal Investigator Jeffrey Hoffman. “It’s something historic,” he stresses. The current version of MOXIE is small to fit aboard the Perseverance rover, and is built to work for short periods; it starts and shuts down with each drive, depending on the exploration schedule and mission responsibilities. Instead, a large-scale oxygen factory would include larger units that would ideally run continuously, the engineers explain. Despite limitations in the design of the instrument, it has proven effective in producing oxygen. To do this, it first sucks in the Martian air 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 the company OxEon Energy, which electrochemically splits carbon dioxide-rich air into oxygen and carbon monoxide ions. . The oxygen ions are then isolated and recombined to form breathable molecular oxygen, or O2, the quantity and purity of which is measured in the MOXIE before it is safely returned to the air, along with carbon monoxide and other atmospheric gases. Since the rover’s landing in February 2021, MOXIE engineers have powered up the instrument seven times throughout the Martian year. It takes a few hours to heat up and then another hour to make oxygen before shutting down again. Each time it was timed for a different time of day or night, and in different seasons, to see if it could adapt to changes in the planet’s atmospheric conditions. “The atmosphere of Mars is much more variable than that of Earth,” notes Hoffman. “Air density can vary by a factor of two throughout the year, and temperature can vary by 100 degrees. One of the goals is to show that we can work in all seasons.” So far, MOXIE has determined that it can make oxygen at almost any time of the Martian day and year. “The only thing we haven’t shown is that it works 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’ll be able to hit that last milestone to show that we really can run anytime.” Taking the lead As the experiment continues to produce oxygen on Mars, engineers plan to expand its capacity and increase its production, especially in the Martian spring, when atmospheric density and carbon dioxide levels are high. “Next time it will be during the highest density of the year, and we want to produce as much oxygen as we can,” says Hecht. “So we’ll put it as high as we dare and let it run as long as we can.” They will also monitor the system for signs of wear. As MOXIE is just one experiment among several aboard the rover, it cannot function 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 function successfully despite being repeatedly turned on and off, this would suggest that a full-scale system, designed to run continuously, could do so for thousands of hours. “To make a human mission to Mars possible, we have to bring back a lot of things from Earth, like computers, spacesuits and habitats,” says Hoffman. “But something like oxygen? If it can be produced there, it will. That would give us a big advantage.” This research has been funded, in part, by NASA. Reference: Michael Hecht, Jeffrey Hoffman et al. ‘Mars Oxygen ISRU Experiment (MOXIE)—Preparing for human Mars exploration’. ‘Science Advances’ (August, 2022).