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Curiosity drills into the watery origins of Mars

Minerals found in Mars rocks strengthen case for past life-friendly conditions

The Martian rock samples dug up by NASA's Curiosity robotic rover show that there is a wide diversity of minerals, allowing scientists to piece together the planet's past.

The results have been published in the journal Earth and Planetary Science Letters. Elizabeth Rampe, first author of the study and NASA researcher at the Johnson Space Center in Houston, Texas, said the rocks might reveal how Mars became a dusty, barren wasteland.

"We have all this evidence that Mars was once really wet but now is dry and cold. Today, much of the water is locked up in the poles and in the ground at high latitudes as ice. We think that the rocks Curiosity has studied reveal ancient environmental changes that occurred as Mars started to lose its atmosphere and water was lost to space."

Four samples were taken after Curiosity drilled into different sites at the lower layers of Mount Sharp in Gale crater, an area thought to have once harbored an ancient lake.

Curiosity's Chemistry and Mineralogy Instrument, which uses X-ray diffraction to identify compounds, found minerals like Hematite which are rich in iron and magnesium at the base of Mount Sharp. The mixture is similar to basalts in Hawaii and suggests it could have come from a primitive magma source.

At higher elevations, the rocks contained more silica and were more similar to quartz. Tridymite, a polymorph of silica, had been found in a previous study. It's normally found on Earth from rocks that have been partially melted in our planet's continental crust, and is a surprising find because Mars has never had plate tectonics. So explaining its presence on the Red Planet is tricky.

Everything points to water in the past

Clay minerals hint at the presence of liquid water. Scientists say it would have had a neutral pH, increasing the chances for the emergence of life. Jarosite, a salt that favors acidic solutions, and magnetite, an oxidized and reduced form of iron, were also detected.

"These layers were deposited about 3.5 billion years ago, coinciding with a time on Earth when life was beginning to take hold. We think early Mars may have been similar to early Earth, and so these environments might have been habitable," said Rampe.

The researchers believe a potential explanation behind the different minerals found was that after the rock sediments settled, acidic, oxidizing groundwater trickled in to fill the area. As the water dried, minerals like jarosite and hematite formed from the solution.

It requires that the environmental conditions in the lake and the groundwater have different acidity levels – a scenario suited for microbial life. The NASA scientists may be onto something, as their hypothesis supports a different study recently published in Science, which found that the lake in Gale crater was stratified.

Various layers of the water contained different oxidation levels, creating an environment where microbes could have potentially thrived. ®

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