By Leah Crane
HiRISE, MRO, LPL/University of A
Mud on Mars flows like lava does on Earth, so some features on the Red Planet that look like regular volcanoes may actually spew mud.
To examine the behaviour of mud on Mars, Petr Brož at the Czech Academy of Sciences in Prague and his colleagues looked at mud flowing down an incline at low pressures and temperatures below -8°C, similar to conditions on Mars.
They found that the surface of the mud froze quickly, but this protected the interior of the flow, which could then continue to creep forward beneath the frozen shell. This is similar to some lava flows on Earth, where the crust solidifies and the lava beneath keeps moving.
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“Before our experiments, we believed that the entire flow would freeze in seconds and it would stop moving,” says Brož. “But once you build a crust, the mud is not exposed to the atmosphere anymore and the mud can remain liquid and move under the protection of the crust.”
The experiments didn’t take into account that gravity on the surface of Mars is lower than it is on Earth, but reduced gravity would only allow the mud to flow further before slowing down and stopping, meaning the suggestion that the mud could behave like lava should be accurate.
Now that we know that mud can flow on Mars, we can’t be sure whether many of the small volcanoes dotting the surface are spewing out lava or mud. This will make it harder to figure out what is going on deep under the surface of the planet, where reservoirs of lava or muddy water are held before they erupt.
“Next time we see something that looks like a lava flow, we cannot be sure that it is lava – it could be mud,” says Brož. “You probably need ground truth, to send a rover or an astronaut with a hammer to take a sample and be sure.”
Journal reference: Nature Geoscience, DOI: 10.1038/s41561-020-0577-2
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