The Martian Atmosphere
A Thin Veil of Air
Mars has an atmosphere, but it is vastly thinner than Earth’s. The surface pressure on Mars averages about 600 pascals — less than 1% of Earth’s atmospheric pressure at sea level. Standing on Mars without a spacesuit, the air would be far too thin to breathe, and the low pressure would be dangerous to the human body. Yet this thin atmosphere still drives weather, creates clouds, and generates some of the most spectacular dust storms in the solar system.
What Is the Martian Air Made Of?
The Martian atmosphere is composed primarily of carbon dioxide (CO2), which makes up about 95.3% of the air. The remaining portion includes:
- Nitrogen (N2): about 2.7%
- Argon (Ar): about 1.6%
- Oxygen (O2): about 0.13%
- Carbon monoxide (CO): about 0.07%
- Trace amounts of water vapor, methane, and other gases
By comparison, Earth’s atmosphere is about 78% nitrogen and 21% oxygen. The high concentration of CO2 on Mars is significant for future settlement plans, as CO2 can be processed into oxygen and rocket propellant using technology already being tested today.
Weather on Mars
Despite its thin atmosphere, Mars experiences real weather. The planet has seasons caused by its 25.2-degree axial tilt — very similar to Earth’s 23.5-degree tilt. These seasons bring temperature changes, shifting wind patterns, and variations in atmospheric pressure.
Temperature on Mars varies widely. Near the equator on a summer afternoon, temperatures can reach about 20 degrees Celsius (68 degrees Fahrenheit). At the poles during winter, temperatures can plunge to minus 140 degrees Celsius (minus 220 degrees Fahrenheit). The thin atmosphere cannot retain heat well, so temperatures drop rapidly after sunset.
Clouds form on Mars, though they are very different from Earth’s clouds. Martian clouds are typically thin and wispy, made of water ice crystals or frozen carbon dioxide (dry ice). They tend to form at high altitudes and near the poles. NASA’s Curiosity rover has captured stunning images of iridescent, mother-of-pearl-colored clouds drifting across the Martian sky.
Dust Storms — From Local to Global
One of the most dramatic features of the Martian atmosphere is its dust storms. Mars experiences dust storms ranging from small, localized events to massive storms that can envelop the entire planet.
Local dust storms occur frequently and can spring up within hours. They are driven by solar heating of the surface, which creates strong winds that lift fine dust particles into the air.
Regional storms can cover areas the size of a continent and last for weeks. These storms grow when multiple local storms merge and feed off each other.
Global dust storms are truly awe-inspiring events that occur roughly every few Mars years. During a global storm, dust can blanket the entire planet, blocking sunlight and raising atmospheric temperatures while cooling the surface. The 2018 global dust storm was so intense that it ended the mission of NASA’s Opportunity rover by blocking the sunlight needed to charge its solar panels.
Understanding dust storms is critical for planning human missions to Mars. Future settlers will need to design habitats, power systems, and vehicles that can withstand weeks of reduced sunlight and heavy dust accumulation.
The Mystery of Methane
In recent years, instruments on Mars orbiters and the Curiosity rover have detected small amounts of methane in the Martian atmosphere. On Earth, methane is often produced by biological processes — living organisms. However, methane can also be produced by geological processes such as the reaction of water with certain minerals.
The methane detections on Mars are puzzling because the gas appears to fluctuate seasonally and has been detected in localized plumes. Scientists are still working to determine the source. Whether biological or geological, the answer could reshape our understanding of Mars.
The Lost Atmosphere
Billions of years ago, Mars likely had a much thicker atmosphere capable of supporting liquid water on the surface. So what happened? Data from NASA’s MAVEN orbiter shows that the solar wind — a stream of charged particles from the Sun — has been steadily stripping away the Martian atmosphere over billions of years. Unlike Earth, Mars lost its global magnetic field early in its history, leaving it without a shield against the solar wind.
Understanding how Mars lost its atmosphere helps scientists study atmospheric evolution on all rocky planets and informs planning for future settlement. Restoring or supplementing the Martian atmosphere is one of the long-term challenges that scientists and engineers are already beginning to study.
Breathing on Mars
The thin CO2 atmosphere presents a challenge but also an opportunity. NASA’s Perseverance rover carries an experiment called MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment), which has successfully demonstrated the ability to extract oxygen from Martian CO2. This technology, scaled up, could one day provide breathable air and rocket propellant for human explorers — turning the Martian atmosphere from a challenge into a resource.