PASADENA, Calif., Oct. 8 (UPI) -- Scientists running NASA's Mars rover Curiosity said Thursday new analysis of the data indicates ancient lakes once existed on the Red Planet, billions of years ago.
Mars Science Laboratory mission researchers said the data suggest water helped deposit sediment into the Gale Crater, where the rover landed three years ago. That sediment built over time to create a peak in the middle of the crater called Mount Sharp.
"A series of long-lived streams and lakes existed at some point between about 3.8 to 3.3 billion years ago, delivering sediment that slowly built up the lower layers of Mount Sharp," said Ashwin Vasavada, a project scientist at NASA's Jet Propulsion Laboratory.
"What we thought we knew about water on Mars is constantly being put to the test," Michael Meyer, lead scientist for NASA's Mars Exploration Program, said. "It's clear that the Mars of billions of years ago more closely resembled Earth than it does today."
The Curiosity rover launched in 2011 and reached Mars a year later. Before scientists had any data, some hypothesized the sediment was deposited there by Martian winds, while others hypothesized ancient lakes might have been responsible.
While NASA has a better idea of the lakes, it remains unclear where their waters came from. In order for water to have existed in the form of long-lived liquid lakes on the Martian surface, the planet must have had a thicker atmosphere and warmer climate than previously believed.
The report on the new analysis will appear in Friday's edition of Science, NASA said.
"We have tended to think of Mars as being simple," John Grotzinger, the lead author of the new report, said. "We once thought of the Earth as being simple too. But the more you look into it, questions come up because you're beginning to fathom the real complexity of what we see on Mars.
"This is a good time to go back to reevaluate all our assumptions. Something is missing somewhere."