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‘Halos’ left by water on Mars discovered

SANTA FE, N.M. — Water running through the subsurface of Mars lasted longer than previous estimates, according to observations made using the Los Alamos National Laboratory’s “ChemCam” on the Red Planet.

The ChemCam – for chemistry and camera – was developed at Los Alamos in cooperation with the French space agency and is located on NASA’s Curiosity rover. Its laser shoots rocks and analyzes the vaporized materials to discover what elements lie within.

Last year, the rover’s equipment found boron within rock veins in the planet’s huge Gale Crater, evidence of a history of habitable groundwater on Mars.

Now, scientists say bedrock around the same crater displays high concentrations of silica, a chemical compound of oxygen and silicon that shows up as pale “halos” around fractures in the rock. The finding expands the window of time that liquid water was apparently present on the planet – and for when life might have existed on Mars.

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The Gale Crater is known for once being home to a lake that was around for potentially millions of years before it evaporated as Mars’ surface dried up.

Jens Frydenvang of Los Alamos National Laboratory

“This is really good evidence we had some sort of water moving through the bedrock long after the lake was there,” Jens Frydenvang told the Journal.

Frydenvang, a LANL scientist who also works for the University of Copenhagen in Denmark, is the lead author of a May 30 paper published in the American Geophysical Union’s Geophysical Research Letters.

“What we’re seeing is that silica appears to have migrated between very old sedimentary bedrock and into younger overlying rocks,” he said, over a distance of about 20 meters to 30 meters in elevation, carried by water flowing through rock fractures.

The research indicates that groundwater carried the silica until the water temperature lowered from reaching the surface. The compound latched onto the rock at that time.

The silica’s source, according to Frydenvang, is volcanic material that created a layer of silica in the Gale Crater’s former lake area.

“We have this full story of the source and then how it’s transported into these fractures,” he said. “That’s why we only see it along these 20-30 meters.”

Some of the rocks containing the halos were deposited by wind, likely as dunes, which would exist only after the lake dried up, according to the research. The presence of halos in rocks formed long after the lake was gone indicates that groundwater was still flowing within the rocks more recently than previously known.

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Answering more questions about how long the groundwater was there and if it that water alone could have supported life will take further research. Frydenvang said the picture of how long the period with water lasted and how the environment transitioned should become clearer as Curiosity continues to climb Mount Sharp, the mountain that rises more than three miles at the center of the Gale Crater.

“It’s really (now) finding out what kind of environment we had in that middle time – when we started to not have the lake anymore and it was dryer for longer periods of time,” he said.

Looking for elements and minerals, or “chemical ingredients,” that could have made the water sustain living organisms is another next step.

This can be done by looking through past data of the rock veins around the area or through additional probing, said Joel Hurowitz, assistant professor in Stony Brook University’s Department of Geosciences and another of the recent paper’s authors.

Hurowitz, who said the research adds to the “plate of evidence” that groundwater played a vital role in the planet’s environment, said the group’s first sightings of the halos were in May 2015 and subsequent research followed until the paper’s release two years later.

“(Gale Crater) really points to a really Earth-life environment,” said Hurowitz. “Its pointing out just how familiar Mars can be.” The crater is 96 miles across.

Frydenvang said it is still unknown how the boron and silica discoveries relate to each other, other than they’re both proof of the groundwaters transporting different materials. But boron is necessary for life.

Forty-two international scientists are listed authors of the new paper. Curiosity, with the ChemCam on board, landed on Mars in 2012.

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