<p>NASA's Curiosity rover, on Mars since August 6, has discovered gravel once carried by the waters of an ancient stream that "ran vigorously" through the area, the US space agency said.<br /><br /></p>.<p>Scientists had previously found other evidence of the one-time presence of water on the Red Planet, but this is the first time stream bed gravels have been discovered.<br /><br />The rocky outcrop, called "Hottah," looks "like someone jack-hammered up a slab of city sidewalk, but it's really a tilted block of an ancient stream bed," project scientist John Grotzinger said in a statement yesterday.<br /><br />Curiosity also investigated a second outcrop, called "Link."<br />The pictures transmitted by Curiosity show the pebbles have been cemented into layers of conglomerate rock at a site between the north rim of the Gale Crater and the base of Mount Sharp, where Curiosity is heading.<br /><br />The sizes and the shapes of the rocks give an idea of the speed and the depth of the stream, NASA said.<br /><br />"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.<br /><br />The scientists estimate the water was moving at a brisk three feet a second and ran somewhere between ankle and hip deep.<br /><br />Some of the rocks are rounded, indicating they traveled a long distance from above the rim, fed from a channel named "Peace Vallis," NASA said.<br /><br />And thanks to imagery previously captured from Mars orbit, the scientists said they can see an alluvial fan of material washed down from the rim -- with many apparent channels "uphill" of "Link" and "Hottah."<br /><br />The high number of channels between the rim and the newly-discovered rock bed suggests the stream wasn't a one-time occurrence, but that many streams flowed or repeated over a long time.<br /><br />Curiosity is on a two-year mission to investigate whether it is possible to live on Mars and to learn whether conditions there might have been able to support life in the past.</p>
<p>NASA's Curiosity rover, on Mars since August 6, has discovered gravel once carried by the waters of an ancient stream that "ran vigorously" through the area, the US space agency said.<br /><br /></p>.<p>Scientists had previously found other evidence of the one-time presence of water on the Red Planet, but this is the first time stream bed gravels have been discovered.<br /><br />The rocky outcrop, called "Hottah," looks "like someone jack-hammered up a slab of city sidewalk, but it's really a tilted block of an ancient stream bed," project scientist John Grotzinger said in a statement yesterday.<br /><br />Curiosity also investigated a second outcrop, called "Link."<br />The pictures transmitted by Curiosity show the pebbles have been cemented into layers of conglomerate rock at a site between the north rim of the Gale Crater and the base of Mount Sharp, where Curiosity is heading.<br /><br />The sizes and the shapes of the rocks give an idea of the speed and the depth of the stream, NASA said.<br /><br />"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.<br /><br />The scientists estimate the water was moving at a brisk three feet a second and ran somewhere between ankle and hip deep.<br /><br />Some of the rocks are rounded, indicating they traveled a long distance from above the rim, fed from a channel named "Peace Vallis," NASA said.<br /><br />And thanks to imagery previously captured from Mars orbit, the scientists said they can see an alluvial fan of material washed down from the rim -- with many apparent channels "uphill" of "Link" and "Hottah."<br /><br />The high number of channels between the rim and the newly-discovered rock bed suggests the stream wasn't a one-time occurrence, but that many streams flowed or repeated over a long time.<br /><br />Curiosity is on a two-year mission to investigate whether it is possible to live on Mars and to learn whether conditions there might have been able to support life in the past.</p>