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UK research challenges Martian ice theory

24 October 2019

New research published today from a UK-led team challenges the theory that landslides on Mars were caused by ice – despite scientists previously suggesting their presence provides unequivocal evidence of past ice on the red planet.

The UCL-led team have used detailed three-dimensional images of an extensive landslide on Mars, which spans an area more than 55 kilometres wide, to understand how the unusually large and long ridges and furrows formed about 400 million years ago.

Martian landscape annotated with London and global landmarks for scale (credit: Giulia Magnarini)

 

Until now, it has been suggested that the landslides were formed by layers of rapidly-cooled water – but the STFC-funded research published today shows for the first time that the unique structures on Martian landslides from mountains several kilometres high could have formed at high speeds of up to 360 kilometres per hour due to underlying layers of unstable, fragmented rocks.

This challenges the idea that underlying layers of slippery ice can only explain such long vast ridges, which are found on landslides throughout the Solar System.

First author, PhD student Giulia Magnarini of UCL, said: “Landslides on Earth, particularly those on top of glaciers, have been studied by scientists as a proxy for those on Mars because they show similarly shaped ridges and furrows, inferring that Martian landslides also depended on an icy substrate.

“However, we’ve shown that ice is not a prerequisite for such geological structures on Mars, which can form on rough, rocky surfaces. This helps us better understand the shaping of Martian landscapes and has implications for how landslides form on other planetary bodies including Earth and the Moon.”

The team, from UCL, the Natural History Museum in London, Ben Gurion University of Negev in Israel and the University of Wisconsin Madison in the United States, used images taken by NASA's Mars Reconnaissance Orbiter to analyse some of the best-defined landslides remotely.

Co-author, Dr Tom Mitchell, from UCL, said: “The Martian landslide we studied covers an area larger than Greater London and the structures within it are huge. Earth might harbour comparable structures but they are harder to see and our landforms erode much faster than those on Mars due to rain.

“While we aren’t ruling out the presence of ice, we know that ice wasn’t needed to form the long run-outs we analysed on Mars. The vibrations of rock particles initiate a convection process that caused upper denser and heavier layers of rock to fall and lighter rocks to rise, similar to what happens in your home where warmed less dense air rises above the radiator.  This mechanism drove the flow of deposits up to 40 km away from the mountain source and at phenomenally high speeds.”

The research team includes Apollo 17 astronaut, Professor Harrison Schmitt of the University of Wisconsin Madison, who walked on the Moon in December 1972 and completed geologic fieldwork while on the lunar surface.

More information is available on the UCL website.

Last updated: 24 October 2019

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