Mars holds immense scientific interest for humanity. The prospect of human exploration and habitation highlights oxygen’s fundamental role. Producing this life-sustaining resource locally is a significant step for future space endeavors.
Oxygen’s Natural Presence on Mars
The Martian atmosphere is much thinner and colder than Earth’s. It is predominantly composed of carbon dioxide (CO2), accounting for approximately 95% of its volume. Other gases include about 2.8% molecular nitrogen and 2% argon.
Molecular oxygen (O2) exists in trace amounts, making up roughly 0.174% of the Martian atmosphere. This concentration is far too low to support human respiration or combustion processes. For comparison, Earth’s atmosphere contains about 21% oxygen. The atmospheric pressure on Mars is also very low, averaging about 6 to 7 millibars, which is less than one percent of Earth’s sea-level pressure.
Why Oxygen is Essential for Martian Missions
Oxygen serves two primary functions for human missions to Mars: sustaining life and powering spacecraft. Astronauts require oxygen for breathing during extended stays. An average person needs about 0.67 kilograms of oxygen per day.
Beyond life support, oxygen is a powerful oxidizer for rocket fuel. This is important for both landing on Mars and for the return journey to Earth. Transporting vast quantities of oxygen propellant from Earth is impractical due to immense weight and costs. For instance, launching a rocket with four astronauts from Mars would require approximately 25 metric tons of oxygen as an oxidizer.
MOXIE’s Role in Producing Oxygen
The Mars Oxygen In-Situ Resource Utilization Experiment, or MOXIE, is a technology demonstration aboard NASA’s Perseverance rover. Its purpose is to prove the feasibility of producing oxygen directly from the Martian atmosphere. MOXIE is about the size of a car battery and operates by drawing in the CO2-rich Martian air.
The instrument heats the atmospheric gas to approximately 800 degrees Celsius. This heated CO2 is passed through a solid oxide electrolysis (SOXE) assembly, where it is electrochemically split into oxygen ions and carbon monoxide. The oxygen ions are then isolated and recombined to form molecular oxygen (O2), which MOXIE measures for quantity and purity before releasing it back into the Martian atmosphere.
Since its landing in February 2021, MOXIE has successfully produced oxygen multiple times, demonstrating the viability of in-situ resource utilization (ISRU) technology. It has generated a total of 122 grams of oxygen, with a peak production rate of 12 grams per hour at 98% purity or better. This marks the first time a natural resource has been experimentally extracted from another planet for human use, proving “living off the land” is possible for future space exploration.
The Future of Oxygen for Human Exploration
The success of MOXIE paves the way for larger-scale oxygen production systems on Mars. Establishing a sustainable supply of oxygen on the planet would significantly reduce reliance on Earth-supplied resources. Producing oxygen locally would enable longer human stays, facilitate Martian bases, and provide necessary propellant for return journeys.
A full-scale oxygen factory on Mars would need to be approximately 100 times larger than MOXIE to produce sufficient oxygen for human missions and rocket fuel. This capability would allow future explorers to “live off the land,” making deep-space exploration more affordable and sustainable. The ability to generate oxygen on Mars is a significant step toward a long-term human presence beyond Earth.