Scientists Explore New Way to Generate Breathable Air on Mars

Sending robots to other planets is convenient because they don't need breathable air, and Earth is the only place we've found that. As NASA and other space agencies begin working toward crewed Mars missions, we must confront the pesky human need for oxygen. New research from the University of Warwick suggests Mars missions should ditch the traditional oxygen generator approach and instead rely on simpler photoelectrochemical devices to generate oxygen.

According to the study, which was published in Nature this week, an Oxygen Generator Assembly (OSA) like you'd find on the International Space Station is good enough at generating oxygen for the station. But these systems are notoriously clunky and prone to failure. Photoelectrochemicals could offer a more reliable option for long-term human exploration and survival on Mars.

An OGA uses water electrolysis to generate oxygen, a fairly inefficient process that consumes 1.5kW of power on the ISS all by itself. It is a significant chunk of the 4.7kW total used by the life support control system. This system relies on generated power to channel an electric current through water, but a photoelectrochemical (PEC) system doesn't need to do that.

PEC-based oxygen generation uses semiconductor materials to go right from solar energy to splitting water into hydrogen and oxygen gas without producing electricity. This has made PEC a hot topic among sustainable energy researchers for what it could do for Earth, but there's no reason similar hardware couldn't supply oxygen to astronauts. The new research explored how solar radiance on Mars and the moon would support PEC devices, concluding that it was a viable approach to human life support that would operate in microgravity and could be scaled up as needed. However, current PEC technology needs to become more efficient and compact before it can be packaged in a spacecraft. Although, we might not need to build the scaled-up life support system on Earth.

Because every ounce launched from Earth costs money, aerospace outfits are increasingly interested in in-situ resource utilization (ISRU). That means designing a mission to use materials at the destination rather than shipping everything from Earth. For example, NASA has explored using Martian soil as a building material, and numerous projects are investigating how astronauts could harvest water ice from the moon. JPL also launched an experiment with the Perseverance rover that showed it could generate as much oxygen as a single tree. Similarly, the researchers explored ways to build and maintain PEC hardware on the moon and Mars. "The device construction can draw from a variety of semiconductors and electrocatalyst materials that are available on the Moon and Mars, and the required materials can eventually be produced via ISRU," the study said.