Gullies observed on the surface of Mars might have been created by carbon dioxide gas causing sand to flow downhill, not liquid water eroding into soil, a pair of French researchers reported in the latest edition of the journal Nature Communications.
In their new study, authors Cedric Pilorget from Université Paris-Sud and Francois Forget from Sorbonne Universités believe that a layer of dry ice (CO2 frost) forms on many parts of the Red Planet’s surface, and traps gaseous carbon dioxide as it begins to defrost.
This, in turn, causes pressure to build up, and could well be responsible for carving out the deep, mid-latitude gullies on Mars surface, especially since the frost is most abundant in places where the small valleys are most prominent, according to BBC News and the Los Angeles Times.
In addition, as Colin Dundas from the US Geological Survey explained in a commentary on the research (which he was not involved in), gully activity “appears to be seasonal,” usual occurring during spring and winter, “when CO2 frost is observed on mid-latitude slopes.”
‘Gas-lubricated debris flow’ explains (most) of the features
Scientists had been somewhat puzzled by these gullies, with some arguing that they were proof of a wet period that took place sometime in the planet’s past. However, many of the features are relatively young, geologically speaking, and others are still forming, BBC News noted.
For that reason, something other than water must have been the cause, as the surface of modern-day Mars is simply too cold to support liquid H2O. The new method developed by Pilorget and Forget does not require liquid water. Instead, as CO2 frost begins to sublime into gas at the end of the Martian winter, a portion of it becomes trapped beneath a layer of dry ice.
The French scientists developed a model that shows how the process could occur on a dune in Russell Crater, where NASA satellites have spotted newly formed gullies, the BBC said. As the pressure builds up, it produces what the authors call a “gas-lubricated debris flow” which carves out a small valley as it travels down the slope.
While their model does appear to be a better fit over the behavior of the Red Planet over the past one million years or so, Dundas noted that there are a few gullies located near the equator which cannot be explained by dry ice frost alone. This does not mean that the CO2 explanation was not responsible for the mid-latitude valleys, only that there may be multiple processes responsible for the planet’s surface features, he explained.
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Feature Image: NASA/JPL/University of Arizona
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