Science

Every year, this weird Martian phenomenon returns

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Even though humans have been observing Mars for centuries, it never ceases to intrigue us.

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The European Space Agency’s Mars Express Orbiter recently captured photos of a weird feature on Mars: An elongated cloud that appears every southern solstice.

ESA

The cloud always appears above a 12-mile-high volcano called Arsia Mons, but the volcano itself doesn’t produce the cloud.

ESA

At least, not directly.

ESA

The water-ice cloud forms on the leeward side of the volcano, or the side that does not face the wind.

ESA

The cloud forms over the course of a few hours and can stretch more than 1000 miles long... then fades away over the next few hours.

For about 80 days, this cycle repeats, says Jorge Hernandez-Bernal a PhD candidate at the University of the Basque Country in Space, who studies the recurring cloud.

ESA

These new photos represent the 4th viewing of the elongated cloud. We’ve also gotten to see it in 2009, 2012, 2015, and 2018.

The formation of water ice clouds in Mars’s atmosphere can tell scientists how much dust is floating around, an important measurement in understanding how the Red Planet’s atmosphere works.

NASA

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