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What’s making swirls on Mars?

By Fiona, 3 March 2022 News

Wispy purple marks on white pitted surface

These swirling tracks were left by Martian dust devils!
Image: ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO

By Jacinta Bowler

This image of the Argyre Planitia on Mars really is out of this world! Taken back in February 2021 by the ExoMars Trace Gas Orbiter, it shows Mars’ chaotic terrain of mounds, ripples and huge blue ‘dust devil’ tracks.

Dust devils are a type of whirlwind which can happen on both Earth and Mars. While Earth dust devils might get up to 300 metres tall, Mars dust devils can reach heights of 8 kilometres! That’s only just shorter than Mount Everest.

White wave on rough red surface

The Mars Reconnaissance Orbiter caught this dust devil in action
Image: NASA/JPL-Caltech/Univ. of Arizona

Dust devils occur when the warm ground heats the nearby air. That warm air starts to rise and sometimes, it starts to spin. As the warm air rises, it stretches, making it tall and narrow. And that makes the spinning vortex speed up, like a twirling ice skater pulling their arms in.

This windy phenomenon leaves scars that stick around a few months on the Martian surface before being slowly covered over by more dust. On Earth, the dust devils themselves last only a few minutes before disappearing, but this is likely not the case on Mars. Scientists have seen Mars dust devil tracks that go for 4 kilometres!

But why are the dust devil tracks blue? This is a false colour image, meaning that you wouldn’t see these colours if you were looking with your own eyes. Instead, 3 filters are combined to help scientists see differences in surface minerals, such as different types of iron hidden in dirt on the surface.

These kinds of images are regularly taken on Mars, as a few different imaging satellites are orbiting the planet. Keep an eye out for dust devil tracks next time you see a photo of the Red Planet.

Wispy purple marks on a white pitted surface

The full picture of the Argyre Planitia on Mars, taken by the ExoMars Trace Gas Orbiter
Image: ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO

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