Dust storms on Mars throw water from its atmosphere into space

By Leah Crane

The surface of Mars is losing water into space

NASA / Goddard

Dust storms may have played a significant role in making Mars the arid world it is today. They were caught lofting water into the planet’s upper atmosphere, where it breaks down and escapes into space.

Scientists have long known that Mars is constantly losing water, but they thought this was mainly due to a slow, steady process that breaks apart water molecules in the lower layers of the atmosphere. Data from NASA’s orbiter Mars Atmosphere and Volatile Evolution (MAVEN) has now for the first time revealed water in the upper layer of the atmosphere, indicating a more efficient process that may dump even more water from the planet.

Shane Stone of the University of Arizona and his colleagues analyzed the MAVEN data and found a seasonal pattern – the upper atmosphere contained most of the water when Mars was closest to the Sun or when there was a large dust storm. The atmospheric warming caused by these events causes water to float higher in the Martian air.

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Read more: Mars may have had hot springs millions of years ago

In the upper atmosphere, water should be broken down quickly by energetic particles. The resulting hydrogen and oxygen then float into space. This happens ten times faster than the known processes that take place in the lower atmosphere, says Stone. The researchers calculated that in the last billion years, enough water may have leaked into the upper atmosphere of Mars to cover the surface of the planet in a 61 cm deep layer of liquid.

That’s not enough to fully explain why Mars is so much drier now than it was billions of years ago, but it does bring us a step closer. “Mars must have lost the equivalent of a global ocean several tens to hundreds of meters deep in its entire history,” says Stone. “Without these flight processes we would have a warmer and wetter planet next to us.”

Journal reference: Science, DOI: 10.1126 / science.aba5229

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