The case for flowing water on Mars is drying up


In 2015, NASA introduced that it had “the best evidence yet” for water flowing on the floor of Mars: Dark, apparently damp streaks noticed on the Red Planet contained salts related to liquid water.

The information had NASA’s head of planetary science, Jim Green, imagining future astronauts slurping up the salty sludge as they explored the Red Planet. “Mark Watney could have taken advantage of this discovery,” he informed The Post on the time, referring to the central character of the film “The Martian.” Others urged that the streaks may harbor microbial life.

But then U.S. Geological Survey scientists — these infamous crushers of goals — determined to have a look. In a research revealed Monday within the journal Nature Geoscience, USGS says that these promising streaks are merely marks made by flowing sand or mud.

“This new understanding . . . supports other evidence that shows that Mars today is very dry,” lead writer Colin Dundas mentioned in a information launch.

The discovering is the newest disappointment for scientists who hoped that the streaks, technically referred to as “recurring slope lineae,” may point out that Mars is not fairly the desolate desert wasteland it is generally made out to be.

While the RSL weren’t ever direct proof of water, they appeared like a powerful indicator. Scientists had seen that the streaks grew and shrank in response to the seasons — nearly as if salty water was being heated by the solar after which flowing down ridges and hills. Not solely that, however the streaks contained perchlorates — molecules that badist water keep liquid over a broader vary of temperatures.

But when Dundas and his colleagues examined photographs of dozens of RSL at a number of websites, they discovered the “streaks” did not behave like flowing water. For one factor, they solely existed on the tops of very steep slopes. For one other, the streaks all appeared to finish when their slopes matched the dynamic  “angle of repose” — the steepest angle at which a given materials might be piled with out slumping.

If you’ve got ever tried to construct a sand citadel, you are aware of this idea. It’s why dry sand — which has a really shallow angle of repose — tends to slip out of practice, however moist sand — with a steeper angle of repose — might be piled into towers and turrets.

“The RSL don’t flow onto shallower slopes, and the lengths of these are so closely correlated with the dynamic angle of repose, it can’t be a coincidence,” co-author Alfred McEwen of the University of Arizona in Tucson informed McEwen is the precept investigator for HiRISE, a digital camera on the Mars Reconnaissance Orbiter that was used to picture the RSLs.

The RSL aren’t created by water, Dundas and McEwen concluded. Instead, they resemble the markings left by dry grains that slide down the perimeters of a tragic, slumping sand citadel.

This doesn’t suggest there is not any water by any means within the RSL, they write. The tendency for these streaks to look in heat seasons, together with the presence of perchlorates, counsel that water may badist the streaks type. “However, liquid water volumes may be small or zero,” the authors say.

That matches with a research revealed final 12 months within the journal Geophysical Research Letters that discovered the streaks may include not more than three p.c liquid water — making them little greater than mildly damp, barely salty dust.

Mars’ bizarre streaks most likely could not preserve an astronaut alive, they usually most likely aren’t residence to tiny alien organisms. But they’re nonetheless price learning, McEwen mentioned.

“RSL probably form by some mechanism that is unique to the environment of Mars,” he informed, “so they represent an opportunity to learn about how Mars behaves, which is important for future surface exploration.”

Read extra:

The harsh fact about Mars water and NASA’s ‘Journey to Mars’

New badysis says Mars as soon as had a big ocean

Why NASA nonetheless believes we would discover life on Mars

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