NASA’s Curiosity rover is currently cruising around an area of Mars known as the Gale Crater. It’s a massive impact site that has existed for billions of years, and the version of it we see today hints at a much wetter time on Mars, when water flowed freely into the crater to form rivers and lakes.

Researchers are using observations from Curiosity to paint a picture of Mars as a watery world, and there’s no shortage of evidence to support it. As NASA’s Jet Propulsion Laboratory highlights, a new paper published in Nature Geoscience uses the layers of sediment that make up the towering structure within the crater, known as Mount Sharp, to estimate when the climate of the Red Planet changed.

The Gale Crater is a perfect place for scientists to try to look back in time. On a much wetter Mars, researchers believe water flowed into the crater, building up and then drying up over and over again. Each time it happened, the sediment carried into the crater by flowing water formed a new layer. Winds that carved the peak of Mount Sharp have exposed these layers and now those layers offer clues about the history of the planet’s climate.

Figuring out when Mars was wet, and for how long, can give scientists an idea of when life may have existed on the planet. If surface conditions were warm enough for liquid water for an extended period of time means that life would have had a chance to take root.

“We went to Gale Crater because it preserves this unique record of a changing Mars,” Caltech’s William Rapin, lead author of the research, said in a statement. “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?”

We’re certainly not to a point where we can say that life definitely existed on Mars, but we’re getting closer. When that day comes, studies like this one could tell us what the planet was like for those organisms.