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Martian ‘lava flow’ mystery finds muddy explanation

Image credit: lancaster uni

The mystery behind some lava-like structures seen on Mars has been solved by scientists, who found that they are caused by mud.

There are tens of thousands of these landforms on the Martian surface, often situated where there are massive channels scoured into the surface by ancient liquids flowing downstream. These channels extend hundreds of kilometres in length and usually at least tens of kilometres wide.

They are believed to have been caused by floods comparable to the largest floods ever known to have occurred on Earth; when the water seeps into the subsurface it can emerge again as mud.

A team of European researchers has simulated the movement of mud on the surface of Mars (pictured), accounting for local temperature and atmospheric pressure.

Professor Lionel Wilson, from Lancaster University, said: “We performed experiments in a vacuum chamber to simulate the release of mud on Mars. This is of interest because we see many flow-like features on Mars in spacecraft images, but they have not yet been visited by any of the roving vehicles on the surface and there is some ambiguity about whether they are flows of lava or mud.”

The scientists performed experiments at low pressure and cool temperatures (-20°C) to recreate the Martian environment. They found that free-flowing mud behaves differently under Martian conditions compared with conditions on Earth, with rapid freezing and formation of an icy crust. This is because water is not stable, and begins to boil and evaporate, removing latent heat from the mud and causing it to freeze.

Under Martian conditions, the experimental mud flows formed similar shapes to “pahoehoe” lava frequently occurring on Hawaii or Iceland on Earth, which cools down to form smooth, undulating surfaces. In this simulation, this occured when liquid mud spilled from ruptures in the frozen crust, then refroze.

Under terrestrial conditions, the experimental mud flows did not form lava shapes, did not expand, and had no icy crust, even under very cold conditions.

This “sedimentary volcanism” may also be a feature of the dwarf planet Ceres, which lies in the asteroid belt between Mars and Jupiter and may have a muddy water ocean beneath an icy crust.

Lead author Dr Petr Brož said: “We suggest that mud volcanism can explain the formation of some lava-like flow morphologies on Mars, and that similar processes may apply to eruptions of mud on icy bodies in the outer Solar System, like on Ceres.”

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