Scientists recently found something amazing on the surface of Mars: evidence that the now-barren Red Planet may have been able to support life for much longer than had been previously thought. Evidence of streams and lakes, including one bigger than any of the Great Lakes in North America, formed between 2 and 3 billion years ago — a surprising find since scientists believed that Mars had lost most of its atmosphere by then and therefore was too cold to have liquid water.

The new paper presents evidence that water modified the surface of Mars for several hundred million years after when scientists had thought it had disappeared. And that water may have been snow rather than rain, according to a statement from NASA’s Jet Propulsion Laboratory. The research was led by the Smithsonian Institution and the University of Virginia, but it relied heavily on data from NASA’s Mars Reconnaissance Orbiter.

Sharon Wilson, the researcher who led the study, said that the team found valleys that carried water into basins where lakes once were, and that several of these basins overflowed, showing there must have been quite a bit of water. One of the lakes was about as big as Lake Tahoe.

“A key goal for Mars exploration is to understand when and where liquid water was present in sufficient volume to alter the Martian surface and perhaps provide habitable environments,” said Mars Reconnaissance Orbiter Project Scientist Rich Zurek of NASA’s Jet Propulsion Laboratory, Pasadena, California. “This paper presents evidence for episodes of water modifying the surface on early Mars for possibly several hundred million years later than previously thought, with some implication that the water was emplaced by snow, not rain.”