NASA’s Curiosity rover has captured images of bedrock that suggest a fast-moving stream once flowed on the Martian surface.
“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,” explained Curiosity science co-investigator Dr William Dietrich of the University of California in 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,” he said.
The site lies between the north rim of Gale Crater and the base of Mount Sharp, a mountain inside the crater. Earlier imaging of the region from Mars orbit allows for additional interpretation of the gravel-bearing conglomerate. The imagery shows an alluvial fan of material washed down from the rim, streaked by many apparent channels, sitting uphill of the new finds.
The rounded shape of some stones in the conglomerate indicates long-distance transport from above the rim, where a channel named Peace Vallis feeds into the alluvial fan. The abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time, not just once or for a few years.
The discovery comes from examining two outcrops, called ‘Hottah’ and ‘Link,’ with the telephoto capability of Curiosity’s mast camera. Those observations followed up on earlier hints from another outcrop, which was exposed by thruster exhaust as Curiosity, the Mars Science Laboratory Project’s rover, touched down.