For the first time ever, scientists have discovered the mineral tridymite on Mars — as well as huge amounts of silica, a sign of ancient flowing water on the Red Planet.

NASA’s Curiosity rover has just uncovered some important evidence that could explain away some big mysteries surrounding the existence of water on Mars, and where it went, according to a Christian Science Monitor report.

Curiosity found a large amount of rock-forming silica, which is a mineral that is composed of silicon and oxygen and on Earth typically indicates the past presence of water. It’s usually a good spot to find microbial life on Earth — perhaps it’s a sign that such life could have existed on Mars. At the very least, it adds to scientists understand of the Red Planet.

But the discovery of tridymite is perhaps more intriguing. This mineral is rare on Earth and it’s the first time scientists have found it on Mars. When it’s found on Earth, it’s typically found in rocks thrown out by volcanoes, indicating that such volcanoes may have once existed on Mars.

Curiosity has been hard at work as it climbs Mount Sharp, and it was while it was near an area called teh Marias Pass that it came across a patch of land that were covered by a younger layer of sandstone. The rover examined the composition of the rocks and found 90 percent more silica than found anywhere else in the area.

Scientists have a lot of work to do to unravel the mystery surrounding the silica discovery, said Jens Frydenvang of the Los Alamos National Laboratory and the University of Copenhagen in a statement.

“The high silica was a surprise,” Frydenvang said. “While we’re still working with multiple hypotheses on how the silica got so enriched, these hypotheses all require considerable water activity, and on Earth high silica deposits are often associated with environments that provide excellent support for microbial life. Because of this, the science team agreed to make a rare backtrack to investigate it more.”