Science

‘Levitating’ sand is linked to the formation of the Martian landscape, study finds

By Buffy Beck

There are still many mysteries surrounding our neighbour, the Red Planet. Is it possible for people to live there? Is there, or has there ever been, life on Mars? (Cue David Bowie). And is there water?

Before the first successful Mars flyby in 1965 by Mariner 4, there was much speculation about the presence of liquid water on the planet’s surface due to previously observed periodic variations in light and dark patches which appeared to be seas and continents. It is now known, thanks to radar data collected in 2005, that Mars has large quantities of water ice at the poles and at mid-latitudes.

There is the suggestion that Mars once had large-scale water coverage on its surface due to the geology of the planet. Landforms such as outflow channels, alluvial fans, deltas and gullies suggest that a significant amount of liquid water has previously been present on Mars.

Leslie Tamppari, Mars Reconnaissance Orbiter (MRO) Deputy Project Scientist explains that much of this water would have left the planet from the top of the atmosphere and the remainder is present in small amounts of water vapour or as underground ice.

However, a recent study conducted by scientists at The Open University have discovered a different process that could explain how land features on Mars are formed.

Experiments carried out in the Open University Mars Simulation Chamber revel that the combination of Mars’ thin atmosphere and periods of relatively warm surface temperatures causes water flowing on the surface to violently boil. This process can then move large amounts of sand and sediment, ‘levitating’ the sediment in the boiling water.

This study could help to explain the present day movement of sediment on Mars’ surface. Dark streaks, known as recurring slope lineae (RSL), appear and grow during Mars’ warm season. In 2015, NASA provided strong evidence that these dark RSLs could be the result of hydrated salts causing a shallow subsurface flow of just enough water.

However a year later, a new analysis of the data suggest that whatever makes RSLs isn’t water. Frédéric Schmidt at the University of Paris-South and his colleagues branched out to suggest sunlight and shadow are the causes of RSL movement, though this theory too has its limitations as there are observations that do not fit.

The study by The Open University explains that their experiments could help to address the problem that RSL requires a high water budget if they propagate by infiltration alone. If boiling is causing the ‘levitating’ of sand and sediment then RSL could be achieved with ~10 times less water.

Dr Jan Raack, the lead author of the research, said that this levitation discovery is “a new geological phenomenon which doesn’t happen on Earth, and could be vital to understanding similar processes on other planetary surfaces”.

He added that “more research into how water levitates on Mars [will need to be carried out], and missions such as the ESA ExoMars 2020 Rover will provide vital insight to help us better understand our closet neighbour”.

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