A Lake Once Existed in Gusev Crater on Mars, Researchers Say

New research shows that Gusev Crater on Mars might have held a lake in the past.

The study is based on analysis of old data by a team of researchers led by Steve Ruff, associate research professor at Arizona State University.

The enigmatic Gusev Crater                            

Spirit, the NASA rover, landed on the 100-mile-wide Gusev Crater in 2004. NASA chose to send the rover in the crater because Gusev looked like a lake. However, Spirit found no lake sediments in the crater and instead found volcanic rocks. The rover then climbed up the 300-foot-high Columbia Hills and found rocks that were altered by water. Scientists found that the region had witnessed hydrothermal activity in the past just like the hot springs found today at Yellowstone National Park.

A Columbia Hills rock outcrop called Comanche is rich in magnesium-iron carbonate minerals. An outcrop is an exposed part of bedrock and gives scientists a sneak-peak into the region's geology.

Previously the carbonates at Comanche were thought be linked with hydrothermal activity. The new study, however, suggests that the carbonates are a result of an ancient lake.

"We looked more closely at the composition and geologic setting of Comanche and nearby outcrops. There's good evidence that low temperature surface waters introduced the carbonates into Comanche rather than hot water rising from deep down," Ruff said in a news release.

According to the researchers, Comanche was a tephra or volcanic ash deposit. The ash came from volcanic eruptions within and around Gusev.

The waters entered the Gusev through the openings in the crater's southern rim. The floodwater stayed in the tephra and made a briny solution. When water evaporated, the carbonates were left behind.

"The lake didn't have to be big," Ruff explained in a news release. "The Columbia Hills stand 300 feet high, but they're in the lowest part of Gusev. So a deep, crater-spanning lake wasn't needed."

The Mars 2020 rover mission is expected to collect samples from the Red Planet.  Ruff and colleagues believe that obtaining soil samples from the Gusev crater could help scientists better understand the geology of the planet.

See images of Gusev crater, here.

The study is published in the journal Nature.