NASA Mars Curiosity rover finds an 'ancient oasis'

James Marshall
October 8, 2019

NASA's Curiosity rover, a space exploration vehicle created to move across the surface of Mars, has detected sulfate salt sediments in Gale Crater, a dry lake bed on the planet, suggesting that the crater once contained salty lakes which could have supported life. But the planet's climate changed drastically in the past few billion years.

One of the rover's missions is to determine exactly how liquid water disappeared from the Red Planet's surface. That leads scientists to believe this is evidence that a lake at Gale Crater was particularly salty around this time. This is evidence that a salty lake was evaporating from the surface around that time, scientists reported Monday in a new paper in Nature Geoscience.

LOS ALAMOS, N.M., October 7, 2019-The surface of Mars was once home to shallow, salty ponds that went through episodes of overflow and drying, according to a paper published today in Nature Geoscience.

He and his co-scientists describe salts found across a 150-metre-tall section of sedimentary rocks called "Sutton Island", which Curiosity visited in 2017.

"Streams might have laced the crater's walls", NASA said Monday, adding "climate fluctuations" changed the environment from wet to desert.

Salts had not been found in this form - or to such an abundance - in the older Martian rocks previously analysed by the Curiosity rover. These salts, however, are a mineral salt, and are mixed with other sediments, "suggesting they crystallized in a wet environment - possibly just beneath evaporating shallow ponds filled with briny water", according to the statement. Now exposed on the mountain's slopes, each layer reveals a different era of Martian history and holds clues about the prevailing environment at the time.

"We went to Gale Crater because it preserves this unique record of a changing Mars", said William Rapin of Caltech. "Understanding when and how the planet's climate started evolving is a piece of another puzzle: When and how long was Mars capable of supporting microbial life at the surface?" But the Sutton Island salts suggest the water also concentrated into brine. This is significant because normally dried-up lakes leave behind pure salt crystals.

In June 2013, Curiosity found powerful evidence that water good enough to drink once flowed on Mars.

It found concentrations of calcium and magnesium sulfates indicating conditions that were likely more arid that those of the older rocks already analysed by Curiosity.

One comparison on Earth is the Altiplano, a high plateau in South America where saline lakes are fed by mountain streams and rivers and influenced by climate shifts. This tells researchers that the lake-bed rocks must have dried out nearly completely at times, pointing to fluctuations in the Martian climate. "The fact that they're vegetation-free even makes them look a little like Mars". "There were very wet periods and very dry periods-as these sulfate-rich rocks show us".

Mars is now in the middle of an ice age, and before this study, scientists believed liquid water could not exist on its surface.

Other reports by Click Lancashire

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