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Mars' Atmosphere: Composition, Climate & Weather

Mars has a thin atmosphere — too thin to easily support life as we know it. The extremely thin air on Mars can also become very dusty.

What is Mars' atmosphere made of?

The atmosphere of Mars is about 100 times thinner than Earth's, and it is 95 percent carbon dioxide. Here's a breakdown of its composition:

  • Carbon dioxide: 95.32 percent
  • Nitrogen: 2.7 percent
  • Argon: 1.6 percent
  • Oxygen: 0.13 percent
  • Carbon monoxide: 0.08 percent
  • Also, minor amounts of: water, nitrogen oxide, neon, hydrogen-deuterium-oxygen, krypton and xenon
The thin atmosphere of Mars today composed mainly of carbon dioxide as depicted in this artist's illustration
The thin atmosphere of Mars today composed mainly of carbon dioxide as depicted in this artist's illustration
Credit: NASA

Climate and weather

Mars is much colder than Earth, in large part due to its greater distance from the sun. The average temperature is about minus 80 degrees F (minus 60 degrees C), although it can vary from minus 195 degrees F (minus 125 degrees C) near the poles during the winter to as much as a comfortable 70 degrees F (20 degrees C) at midday near the equator.

The atmosphere of Mars is also roughly 100 times thinner than Earth's, but it is still thick enough to support weather, clouds and winds.

Giant dust devils routinely kick up the oxidized iron dust that covers Mars' surface. The dust storms of Mars are the largest in the solar system, capable of blanketing the entire planet and lasting for months. One theory as to why dust storms can grow so big on Mars starts with airborne dust particles absorbing sunlight, warming the Martian atmosphere in their vicinity. Warm pockets of air flow toward colder regions, generating winds. Strong winds lift more dust off the ground, which in turn heats the atmosphere, raising more wind and kicking up more dust.

At times, it even snows on Mars. The Martian snowflakes, made of carbon dioxide rather than water, are thought to be about the size of red blood cells. The north and south polar regions of Mars are capped by ice, much of it made from carbon dioxide, not water.

Possibility of Life

Mars could have once harbored life. Some conjecture that life might still exist there today. A number of researchers have even speculated that life on Earth might have seeded Mars, or that life on Mars seeded Earth.

Oceans may have covered the surface of Mars in the past, providing an environment for life to develop. Although the red planet is a cold desert today, researchers suggest that liquid water may be present underground, providing a potential refuge for any life that might still exist there. Several studies have shown that there is abundant water ice beneath the surface.

— Tim Sharp, Reference Editor

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Tim Sharp, Reference Editor

Tim Sharp

Tim was a Technology Editor at nytimes.com and the Online Editor at the Des Moines Register, where he helped launch that newspaper's website. He was also a copy editor at several newspapers. Before joining TechMediaNetwork as Reference Editor, Tim was the Online Content Editor at the Hazelden Foundation. He has a journalism degree from the University of Kansas. Tim is also a self-proclaimed nerd and has won several trivia contests. To find out what his latest project is, you can follow Tim on .
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