NASA Rover finds old streambed on Martian surface
NASA's Curiosity Rover mission has found evidence showing that a stream once ran across the area of Mars where the rover is driving.
There is earlier evidence for the presence of water on Mars, but this evidence - images of rocks containing ancient streambed gravels -- is the first of its kind.
"From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep," said Curiosity science co-investigator William Dietrich of the University of California, Berkeley.
"Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we're actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it."
Satellites at Mars have long captured images of channels on the planet's surface that were cut by some kind of flow, assumed to be liquid water. Curiosity's discovery at its landing site in the equatorial Gale Crater provides the first real ground truth for those observations.
By luck, the rover just happened to roll past a spectacular example of the conglomerate. A large slab, 10-15cm thick, was lifted out of the ground at an angle.
"We've named it Hottah," said rover project scientist John Grotzinger. The name refers to a lake in Canada's Northwest Territories. The team is using names from this region to catalogue objects at Gale.
He joked, "To us it just looked like somebody came along the surface of Mars with a jackhammer and lifted up the sidewalk that you might see in downtown LA at a construction site."
"A long-flowing stream can be a habitable environment," said Grotzinger. "It is not our top choice as an environment for preservation of organics, though. We're still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment."
The science team may use Curiosity to learn the elemental composition of the material, which holds the conglomerate together, revealing more characteristics of the wet environment that formed these deposits. The stones in the conglomerate provide a sampling from above the crater rim, so the team may also examine several of them to learn about broader regional geology.
During the two-year prime mission of the Mars Science Laboratory, researchers will use Curiosity's 10 instruments to investigate whether areas in Gale Crater have ever offered environmental conditions favourable for microbial life.
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