Why does Mars have such a thin atmosphere compared with Earth?
Quick Answer
Mars is smaller and lost much of its early atmosphere because weaker gravity and solar wind made it harder to retain gases.
The Full Story
Mars has only a tiny fraction of Earth’s atmospheric pressure, less than 1 percent at the surface. Because Mars is smaller, its gravity is weaker and it could not hold onto gases as effectively over billions of years. It also lacks a strong global magnetic field today, so the solar wind can strip atmospheric particles away more easily. NASA’s MAVEN mission, launched in 2013, has been studying this process. The result is a cold, dry planet with a very thin air layer that cannot support liquid water on the surface for long.
Key Facts
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Suggested video title for this topic:
"Mars once had more air—so where did it all go?"
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