NASA's 'Mechanical Tree' on Mars Will Help Perseverance Rover Create Oxygen

NASA is planning to create oxygen out of Mars' carbon dioxide-rich atmosphere using technology attached to the Perseverance rover.

The Mars Oxygen In-Situ Resource Utilization Experiment—also known as MOXIE—won't make Mars habitable, but it will aim to prove how future Mars explorers might produce oxygen for breathing.

Oxygen can also be used for rocket propellant, so making it on Mars would save astronauts the trouble of having to bring extra fuel with them for the return trip. Instead, they could just bring an empty tank and fill it up on the Red Planet.

MOXIE is a car battery-sized cube attached to the underbelly of Perseverance that scientists will use to extract oxygen out of Mars' atmosphere.

It was developed by a joint team from the Massachusetts Institute of Technology (MIT) and NASA's Jet Propulsion Laboratory (JPL). Michael Hecht, MOXIE principal investigator at MIT, said in a statement: "Not only do you need oxygen for people to breathe, but you need it for the rocket to breathe too. If you are burning fuel, you need oxygen to consume it. There is a reason why oxygen tanks are the heaviest items on a spaceflight manifest.

"Oxygen exists on Mars, just not in a form we can use it. So that is the problem we were trying to solve with MOXIE."

Oxygen is nowhere near as common in Mars' atmosphere as it is in Earth's. Oxygen makes up 21 percent of Earth's atmosphere, but on Mars it makes up just 0.13 percent. Around 96 percent of the atmosphere on Mars is carbon dioxide (CO2).

MOXIE will work by sucking in CO2 and then breaking it up into its constituents—O2 and CO. It will do this by pressurizing the CO2 to roughly the same pressure as one Earth atmosphere, and then feeding it into what is called a Solid Oxide Electrolyzer (SOXE). This essentially uses chemistry and electricity to split the gas into parts, and operates at 800 degrees Celsius.

The O2 will be analyzed for purity and then it, along with the CO, will be released back into the Martian atmosphere as exhaust.

Hecht described the cube as "a little mechanical tree," referring to the fact that plant life on Earth also converts CO2 to oxygen, albeit through photosynthesis rather than an 800-degree reaction chamber.

He said this atmospheric approach would be less complex than the alternative approach to produce oxygen on Mars, which would involve drilling down through the surface to access ice that lies underground.

This ice could possibly be processed and refined to release oxygen, but the act of using robots to dig and drill would likely lead to wear and tear on equipment and be a hassle to do remotely.

As part of its investigations, MOXIE will also examine the size of dust particles present in the Martian atmosphere to see how this might affect systems on the planet's surface.

NASA scientists working on MOXIE
In this NASA image, scientists work to lower the MOXIE experiment down into Perseverance's chassis. Taken March 20, 2019, in the Spacecraft Assembly Facility’s High Bay 1 Cleanroom at NASA’s Jet Propulsion Laboratory, in Pasadena, California. NASA/JPL-Caltech