NASA Says Mars' Gullies Weren't Formed by Flowing Water

Monday, 01 August 2016 - 12:34PM
Space
Mars
Astrobiology
Monday, 01 August 2016 - 12:34PM
NASA Says Mars' Gullies Weren't Formed by Flowing Water
Mars' gullies have been a source of endless speculation since they were first discovered in 2000. There's no denying that they look like the remnants of ancient Martian rivers, but are they really? According to NASA, this question has been all but resolved, and unfortunately, it looks like liquid water is not responsible for the features on Mars' surface.

Mars' gullies refer to distinctive Martian topographical features that have an alcove at the top, a long channel in the surface, and then deposited material at the bottom. They excited scientists because they had similar features to Earth gullies, which are formed by liquid water, but some researchers found evidence that water might have been too rare and stable to form these ubiquitous gullies, and that freezing carbon dioxide might be a more plausible explanation. 

After years of debate, a new study compared recent Mars observational data with that of the HiRISE findings. The HiRISE images gave us a detailed look at the gullies, but since they were taken with optical cameras, researchers couldn't discern which materials were present in the gullies and their deposits. This new study used an imaging spectrometer in order to determine which materials were in the gullies, and found no sign of the clays or other hydrated materials that, when found in Earth gullies, indicates formation by liquid water.

Opening quote
"In our study, we found no evidence for clays or other hydrated minerals in most of the gullies we studied," lead author Jorge Nunez said in a NASA statement, "and when we did see them, they were erosional debris from ancient rocks, exposed and transported downslope, rather than altered in more recent flowing water. These gullies are carving into the terrain and exposing clays that likely formed billions of years ago when liquid water was more stable on the Martian surface."
Closing quote

This study provides support to the alternative explanation, which was modeled by researchers back in 2014. In that study, NASA found evidence of active gully formation in 38 sites on Mars, and discovered that the activity tended to coincide with winter, and particularly with carbon dioxide frost. As a result, they concluded that the gullies are more likely the result of cracking from seasonal freezing carbon dioxide.
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NASA
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Mars
Astrobiology