Signs of water currents and sediments are seen in the latest
photos NASA's Curiosity rover sent home from Mars, the space agency said
Monday. The images suggest "ancient Mars maintained a climate that could
have produced long-lasting lakes," NASA says.
In the huge Gale Crater where Curiosity has been exploring,
the water and sediment flow might have been massive enough to build a mountain
— the 3-mile-high Mount Sharp — NASA researchers say. But they acknowledge that
they're still working to solve the mystery of how the mountain formed in a
crater.
"If our hypothesis for Mount Sharp holds up, it
challenges the notion that warm and wet conditions were transient, local or
only underground on Mars," said Curiosity deputy project scientist Ashwin
Vasavada of NASA's Jet Propulsion Laboratory in Pasadena. "A more radical
explanation is that Mars' ancient, thicker atmosphere raised temperatures above
freezing globally, but so far we don't know how the atmosphere did that."
This isn't the first time NASA has announced signs of water
at Gale Crater.
One year ago, NASA analysts saw sedimentary rocks that led
them to believe the Martian lake had held freshwater.
And back in 2012, the space agency said images taken by
Curiosity showed gravel-like rocks that were smoothed by water and pushed into
the shape of an alluvial fan.
"A River Ran Through It," the rover's operators
tweeted back then. "I found evidence of an ancient streambed on Mars,
similar to some on Earth."
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