Under a different sky.
A thin atmosphere connects dust, ice, weather, and a changing climate. It also helps explain why modern Mars is so different from Earth.
A thin veil of air
Near the mean surface level, atmospheric pressure is roughly 0.6% of Earth’s sea-level pressure. It varies with elevation and season. Most of the air is carbon dioxide.
| Gas | Share |
|---|---|
| Carbon dioxide | 95.1% |
| Nitrogen | 2.59% |
| Argon | 1.94% |
| Oxygen and other gases | Trace amounts |
The air is not breathable. Its low pressure and very small oxygen content mean human visitors would need pressurized life-support systems.
Seasons, cold, and moving dust
Mars has a tilted axis, so it experiences seasons. Its longer orbit means those seasons last longer than Earth’s. A thin atmosphere allows heat to escape readily.
A world of temperature swings
The global average is around −60°C, but conditions depend strongly on location, season, and time of day. Brief equatorial warmth does not make the planet broadly hospitable.
Dust on a planetary scale
Winds lift fine dust into the air. Some storms grow large enough to obscure much of the planet, reducing sunlight at the surface and affecting solar-powered spacecraft.
Where did the thicker atmosphere go?
Evidence from the surface points to a distant past with more persistent liquid water. Atmospheric escape to space is one part of the explanation for the transition to today’s cold desert.
MAVEN studied the upper atmosphere and its interaction with the Sun. Its observations remain a resource for understanding how planets lose atmospheric gases over time.
Read about MAVEN ↗Explore the evidence
Science notes are based on the sources below. Content reviewed November 3, 2026; this site does not display live mission telemetry.