LOS ANGELES-NASA’s Curiosity rover has discovered rocks on Mars enriched in mineral salts, which was believed to be evidence of shallow briny Martian ponds that went through episodes of overflow and drying, according to a Nature Geoscience paper published on Monday.

The salts were found across a 150-meter-tall section of sedimentary rocks called “Sutton Island,” which Curiosity visited in 2017.

Based on a series of mud cracks at a location named “Old Soaker,” the team already knew the area had intermittent drier periods, but the Sutton Island salts suggest the water also concentrated into brine.

“We went to Gale Crater because it preserves this unique record of a changing Mars,” said lead author William Rapin of Caltech.

“Understanding when and how the planet’s climate started evolving is a piece of another puzzle: When and how long was Mars capable of supporting microbial life at the surface?”