Strange Streaks on Mars Are Sand, Not Water

Rodiano Bonacci
Novembre 22, 2017

While the surface of Mars immediately boils water due to its low pressure, we thought water stored underground might be seeping to the surface.

Scientists from the USGS, the University of Arizona, Durham University (England) and the Planetary Science Institute analyzed narrow, down-slope trending surface features on Mars that are darker than their surroundings, called Recurring Slope Lineae, or RSL.

These findings indicate that it is hard for Earth-like life to exist near the surface of Mars owing to the water-restricted conditions that exist on the planet.

These RSL features grow incrementally, fade when inactive and recur annually during the warmest time of the year on Mars.

While water on Mars was one of the most biggest discoveries in the field of space, a study has revealed that the dark features earlier proposed as evidence of liquid water flowing on the Red Planet may actually be granular flows, where sand and dust move rather than liquid water.

"We've thought of RSL as possible liquid water flows, but the slopes are more like what we expect for dry sand", said Colin Dundas, a scientist at US Geological Survey.

"What we found in this paper is that they end on slopes that match the "angle of repose" for dry sand, which is the slope that you get if you heap up dry sand and it slides under its own weight", he explains.

Water nearly certainly is not responsible for this behaviour, which would require the volume of liquid to correspond to the length of slope available, producing more liquid on longer slopes, the study said.

However, all of the 151 RSLs examined in the study were found to all end on similar slopes despite very different lengths.

But according to a new study published by the journal "Nature Geoscience", those streaks may actually be the result of granular flows like sand and dust. The authors conclude that liquid on present-day Mars may be limited to traces of dissolved moisture from the atmosphere and thin films of water. Small amounts of water could still be involved in their initiation in some fashion, as hydrated minerals have been detected at some RSL locations.

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