Mars was once covered by a massive ocean, NASA scientists say

About 4.3 billion years ago, up to 20 percent of Mars was covered by an ocean that reached about a mile in depth, according to scientists from NASA's Goddard Space Flight Center. The polar ice caps today contain the 13 percent of that ocean that didn't evaporate into space when Mars' atmosphere largely disappeared.

Geronimo Villanueva and his colleagues at Goddard reached this surprising conclusion by using infrared beams to make a map of water molecules in what's left of the Martian atmosphere, they report in Thursday's issue of the journal Science. "Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space," Villanueva said in a statement.

Scientists already knew that Mars once had water, but this extends the red planet's wet period for much longer. "With Mars losing that much water, the planet was very likely wet for a longer period of time than was previously thought, suggesting it might have been habitable for longer," said Goddard's Michael Mumma, another author of the report. Mumma and Villanueva explain their research and its implications in greater detail in the NASA video below. —Peter Weber

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