Dr. Mary Bourke from Trinity College Dublin and University of Oxford Professor Heather Viles have discovered a patch of land in an equatorial crater on Mars that appears to have been flooded by large volumes of water in the planet’s past.
A large pit valley in Lucaya crater, Mars: (a) exposure of putative crossbeds on windward slope of dunes, and (b) interdune strata exposed in planform showing contrasting albedo and crosscutting relationships similar to that exposed in the dune. Image credit: M.C. Bourke & H.A. Viles.
The researchers focused their study on the 6-km-long, 0.8-km-wide pit valley in Lucaya crater, a 34-km diameter crater situated on the rim of the larger Huygens basin.
“On Earth, desert dunefields are periodically flooded by water in areas of fluctuating groundwater, and where lakes, rivers and coasts are found in proximity. These periodic floods leave tell-tale patterns behind them,” Dr. Bourke said.
“You can imagine our excitement when we scanned satellite images of an area on Mars and saw this same patterned calling card, suggesting that water had been present in the relatively recent past.”
In a remote sensing study of the Namib Desert, the team had previously noted these patterns – ‘arcuate striations’ — on the surface between migrating sand dunes.
Fieldwork subsequently showed that these arcuate striations resulted from dune sediments that had been geochemically cemented by salts left behind by evaporating groundwater.
These dune sediments later become relatively immobile, which means they are left behind as the dunes continue to migrate downwind.
“Following our work in Namibia, we hypothesize that on Mars, similar arcuate striations exposed on the surface between dunes are also indications of fluctuating levels of salty groundwater, during a time when dunes were actively migrating down the valley,” Dr. Bourke explained.
“These findings are hugely significant,” she said.
“Firstly, the Martian sand dunes show evidence that water may have been active near Mars’ equator — potentially in the not-too-distant past.”
“And secondly, this location is now a potential geological target for detecting past life forms on the Red Planet, which is important to those involved in selecting sites for future missions.”
The findings were published in the December 2016 issue of the journal Geophysical Research Letters.
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M.C. Bourke & H.A. Viles. 2016. Valley floor aeolianite in an equatorial pit crater on Mars. Geophysical Research Letters 43 (24): 12,356-12,362; doi: 10.1002/2016GL071467
