Curiosity finds streambed, proves water flowed on Mars

Though earlier evidence provided clues that water once existed on Mars, NASA's Curiosity rover has found evidence of a stream that once ran across the surface.

The site, lying between the north rim of the Gale Crater and the base of Mount Sharp, contains streambed gravel and conglomerate rock. Images taken by Curiosity have provided detailed images of various sizes and shapes of the gravel that are helping scientists piece together how the stream once flowed.

"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 Curiosity science co-investigator William Dietrich of the University of California, Berkeley in a NASA press release.

By examining the size of the gravel and stone, NASA scientists can even extrapolate the water was moving at three feet per second, and the streambed was somewhere between ankle and hip deep. The rounded shapes of the stones indicate they likely traveled long distances.

Earlier photos of the region taken in orbit around Mars also helped piece the evidence together. Imagery of the region around Gale shows an alluvial fan, streaked by many channels sitting just uphill of the gravel finds. Scientists believe the amount of channels in the fan between the rim and the gravel-filled conglomerate suggest flows of water that continued or repeated over a long period of time.

The evidence comes after examining two specific outcrops named "Hottah" and "Link," captured in telephoto images taken by Curiosity's Mastcam. Hottah is a jagged piece of rock that appears to be a mass of conglomerate from the streambed that titled upwards over time, perhaps due to tectonic activity. Rocks found there are as small as sand and as large as golf balls, and many of them are rounded.

"The shapes tell you they were transported and the sizes tell you they couldn't be transported by wind. They were transported by water flow," said Curiosity science co-investigator Rebecca Williams of the Planetary Science Institute in Tucson, Ariz.
So now with the evidence of an ancient streambed, what does the NASA team plan next? While they may try to examine the gravel to determine its make up, the main mission of Curiosity remains reaching the slope of Mount Sharp in the Gale crater.

Mount Sharp is of particular interest as the clay and sulfate detected there from orbit can be preservers of carbon-based organic chemicals that are potential ingredients for life. Curiosity will look for evidence of whether the crater could have supported microbial life.

NASA, via Space.com

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