Curiosity snaps signs of vigorous stream on Mars

Lisa Grossman, physical sciences reporter

(Image: NASA/JPL-Caltech/MSSS)

Dreams of swiftly flowing water on Mars have coursed through human heads since astronomer Percival Lowell mapped what he thought were the Red Planet's canals in the 1870s. So Lowell would surely be smiling at the latest pictures from NASA's Curiosity rover.

Shots of rocky outcrops in Gale Crater, including the one above, show rounded gravel that mission scientists say provides concrete evidence of an ancient stream bed. The sizes of the stones suggest the water was moving at about a metre per second, and was somewhere between ankle and hip deep.

The discovery adds to data from previous rovers, landers and orbiters showing features on Mars, such as gullies and hydrated minerals, that most often form in the presence of liquid water.

"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," said science co-investigator William Dietrich in a statement.

Curiosity's new images, taken with its telephoto mast camera, show two outcrops called "Hottah" and "Link".

Cemented in the outcrops are round pebbles that can be as big as golf balls, so rover geologists concluded that the rocks had been transported quickly from a long way away. Larger stones require more energy to move, which means wind wouldn't have done the job, and the water must have been flowing vigorously.

(Image: NASA/JPL-Caltech/MSSS and PSI)

Earlier images snapped from orbit suggested that the rover landed on an alluvial fan, a bed of rocks that had been washed down from the rim of Gale Crater. The new finds support that idea. The large number of channels between the crater rim and the newfound outcrops also hint that water flowed continuously or repeatedly over many years.

It's difficult to say when the water flowed. "We have no real way of estimating ages on Mars quantitatively," said Michael Malin, who is in charge of the cameras on Curiosity, at a press briefing at NASA's Jet Propulsion Laboratory in Pasadena, California. "Probably several billion years would be the canonical estimate by most scientists about how old things are in this region of Mars."

But the rover still has its wheels pointed towards Aeolis Mons, also called Mount Sharp, the 5-kilometre-high mountain in the middle of Gale Crater. The team hopes the clay and sulfate minerals there may have preserved evidence of organic carbon, a potential ingredient for life.

"A long-flowing stream can be a habitable environment," said project scientist John 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."

Source: http://feeds.newscientist.com/c/749/f/10897/s/23e4c374/l/0L0Snewscientist0N0Cblogs0Cshortsharpscience0C20A120C0A90Ccuriosity0Esnaps0Efirst0Eproof0Eof0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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