The Mars Curiosity rover has been making its way around the Red Planet for almost two months, and it has now discovered evidence that a stream once ran vigorously in her path, PC Magazine reports.
Though data gathered from NASA's Mars Reconnaissance Orbiter already uncovered the possibility of flowing water on Mars, NASA said the images of rocks containing ancient streambed gravels uncovered by Curiosity are "the first of its kind."
The images were captured by Curiosity's mast camera, which examined two outcrops dubbed Hottah and Link, as well as another outcrop that was exposed by thruster exhaust as Curiosity touched down.
"Hottah looks like someone jack-hammered up a slab of city sidewalk, but it's really a tilted block of an ancient streambed," said Mars Science Laboratory Project Scientist John Grotzinger.
Scientists are now studying pictures of stones that are embedded in a layer of conglomerate rock, the size and shape of which offer clues to the speed and distance of streams that once flowed there.
"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," Curiosity science co-investigator William Dietrich said in a statement. "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."
The stream was found between the north rim of Gale Crater and the base of Mount Sharp, which lies inside the crater. Combining these new images with existing photos captured by the orbiter "shows an alluvial fan of material washed down from the rim, streaked by many apparent channels, sitting uphill of the new finds."
The large number of channels "suggests flows continued or repeated over a long time, not just once or for a few years."
The substances at the Hottah and Link outcrops are as small as a grain of sand or as big as a golf ball, and most 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.
