Curiosity rover finds silica on Mars. A sign of ancient flowing water?

Curiosity found large amounts of silica and also the mineral tridymite, never before seen on Mars.  Both provide more clues to the Red Planet's watery past.

After more than three years of exploring Mars, NASA’s robotic detective, Curiosity, has stumbled on a couple of intriguing discoveries that could help scientists piece together the puzzle of how water formed, moved, and then either froze or disappeared from the Red Planet.

In the last several months, Curiosity has for the first time found an abundance of the rock-forming chemical silica, a mineral composed of silicon and oxygen and, on Earth, usually deposited by water.

“We don’t have a full understanding yet of what this means,” said Jens Frydenvang an astro-geologist at the Los Alamos National Laboratory in New Mexico of the discoveries in a short video.

“On earth, all the environments where we find this kind of silica require some kind of water activity,” he explained. “Often it’s also a very nice environment to find microbial life.”

And, “adding to the puzzle,” as NASA explains, some of the silica at one Martian rock Curiosity drilled, called "Buckskin," is in a mineral named tridymite, which is rare on Earth and has never been seen on Mars.

On our own planet, the mineral can be found in the silica-rich rocks spewed by volcanoes, so the discovery of tridymite at Buckskin may be evidence for the evolution of volcanoes on Mars. Or maybe tridymite is formed by a different process on the Red Planet, say scientists who are analyzing the latest findings from Curiosity.

"We could solve this by determining whether trydymite in the sediment comes from a volcanic source or has another origin," said Elizabeth Rampe, a planetary geologist at NASA's Johnson Space Center in Houston.

"A lot of us are in our labs trying to see if there's a way to make tridymite without such a high temperature," she said.

For seven months, Curiosity has been traversing an area of the Red Planet scientists call Marias Pass, near the base of a mountain called Mount Sharp. There, the rover saw a light patch of land where two geologic formations meet, an older layer of mudstone, covered by a younger layer of sandstone. The rover used a laser to identify the composition of the rocks, discovering 90 percent more silica than it had seen anywhere on or around Mount Sharp, as The New York Times reported.

"These high-silica compositions are a puzzle,” said Albert Yen, a scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., in an announcement.

“You can boost the concentration of silica either by leaching away other ingredients while leaving the silica behind, or by bringing in silica from somewhere else. Either of those processes involve water. If we can determine which happened, we'll learn more about other conditions in those ancient wet environments," he explained.

Curiosity has been studying the geological layers of Mount Sharp since 2014, after two years of exploring the plains surrounding the mountain. The rover, a self-driving cart loaded up with lasers, cameras, and detectors, has since discovered that the lakes that probably existed in the area billions of years ago could have supported life.

“What we’re seeing on Mount Sharp is dramatically different from what we saw in the first two years of the mission,” said Ashwin Vasavada, a geophysicist at JPL.

At a Thursday meeting of the American Geophysical Union in San Francisco, where researchers presented some of their latest findings on Mars, Dr. Vasavada said that scientists have observed signs of the building blocks for life on Mars, according to the Times.

“Stay tuned,” he said. “There are organics in several of these samples we’ve been seeing lately.”