Mars hasn’t had an atmosphere in a really long time, which has prevented it from having liquid water on its surface, but new evidence from NASA indicates that liquid water may have existed later than expected.
That evidence comes primarily from NASA’s Mars Reconnaissance Orbiter.
Large basins seem to have formed millions of years after scientists thought the atmosphere on Mars had vanished. The basins were likely formed by snowmelt working its way though valleys. That means that the water was deposited on the surface as snow, not rain.
These valleys primarily occur between about 35 and 42 degrees latitude, on both sides of the equator. They are so widespread that they indicate the snowmelt is a global rather than local or regional phenomenon.
“The rate at which water flowed through these valleys is consistent with runoff from melting snow,” says Sharon Wilson of the Smithsonian Institution and the University of Virginia, Charlottesville, one of the co-authors of a report recently published in the Journal of Geophysical Research. “These weren’t rushing rivers. They have simple drainage patterns and did not form deep or complex systems like the ancient valley networks from early Mars.”
All this water means that it is even more possible than previously suspected that Mars once supported at least microbial life. If so, that life must have been supported longer into its history than previously expected.
This wet period was likely between two and three billion years ago, which is well after Mars’ atmosphere is supposed to have vanished. To put that into perspective, here on Earth, multicellular organisms were still new, and they’d only just begun to produce oxygen.
This new information will likely spur more research into the Red Planet in the hopes of better understanding how the planet managed to warm up enough to have snowmelt when it was otherwise far too cold to allow for liquid water on the surface.