A team from Brown University studied data returned by the Compact Reconnaissance Imaging Spectrometer for Mars, which is designed to find traces of minerals that interact with water, Wired reports.
In a paper published this week in the journal Nature, the researchers suggest that Mars may have been mostly covered in water during the planet’s first 600 million–700 million years.
Most importantly, the water may have been temperate enough to support life. The Phoenix Mars Lander recently collected ice from the Red Planet and, on the opposite end of the thermometer, scientists have hypothesized in the past that if water existed on Mars, it would have been far too hot for living creatures.
But the new images show deposits of claylike minerals that form at relatively low temperatures, meaning “benign seas” that could have hosted these minerals—and, possibly, life—may have once existed on the planet’s surface, according to Wired.
“I think the prospects for present life were dim, but for past life, during this habitable era, they were really quite good,” said geologist John Mustard, who co-authored the paper.