NASA has figured out how Mars was stripped clean of water

An artist’s depiction of a solar storm hitting Mars.
An artist’s depiction of a solar storm hitting Mars.
Image: NASA
We may earn a commission from links on this page.

What happened to Mars’ atmosphere? NASA thinks it knows.

Around 3.7 to 4.2 billion years ago, the red planet’s atmosphere was the same size or bigger than the Earth’s, but today it’s about 100 times thinner than on our planet. The answer, it turns out, is blowing in the wind.

Solar winds, to be precise. NASA’s Mars Atmosphere and Volatile Evolution Mission (MAVEN) has spent a year orbiting the planet, and has found that when Mars is hit by a solar storm, its atmospheric particles are quickly stripped away.

Currently, around 100g of air on Mars is escaping the atmosphere every second. But during solar storms, air leaks out around 10 to 20 times faster.

Winds from the sun blast a stream of charged particles speeding at one million miles an hour, which then knock particles off of Mars’ atmosphere. And so, over millions of years, Mars’ atmosphere has been blown away to almost nothing. NASA recreated what they think Mars could have once looked like in the Vine below.

Earth hasn’t lost atmosphere in the same way as Mars, because our planet has a strong magnetic field, which protects us from the strong winds of solar storms.

NASA reported these findings, based on the first six months of MAVEN’s data, at a press briefing on Thursday (5th November). Bruce Jakosky, principal investigator at MAVERN and his team have reported their findings in four scientific papers published in the journal Science.

Understanding Mars’ atmosphere helps to build a picture of what the planet was once like. When Mars lost its atmosphere, bodies of water also disappeared and the planet became less habitable. Today there are just tiny amounts of liquid water on Mars. But at one stage, before the atmosphere began to be blown away, Mars could well have been a suitable place for live.

“So it begs the question of whether there ever was any life there,” said Jakosky at the briefing. “As we go into the future, these question about life and climate and the history of the planet as a whole really are at the centre of exploration.”