The Mars Curiosity rover has sent back photographs that show evidence of a “vigorous” streambed.
In this image, the Link, left, an outcrop of rocks on Mars, is compared with rocks on Earth. The image of the Mars rock formation was obtained by NASA's Curiosity rover. Both images show rounded gravel fragments called clasts. Erosion of the outcrop results in the gravel clasts, which fall onto the ground and create a gravel pile like the one seen. The Link image was taken by the rover’s 100-millimeter Mast Camera on Sept. 2.NASA/JPL-Caltech/MSSS and PSI