NASA says it has found proof that water shaped the rocks on the left, in a photograph taken by the Mars rover Curiosity (left). For comparison, the agency released an image of rocks from Earth (right).
NASA's newest Mars rover, Curiosity, has snapped photos of rocky outcroppings that jut out from the alien soil, and scientists say they look like the remnants of an ancient stream bed where water once flowed on the surface of the red planet.
The exposed rocks look like broken slabs of concrete sidewalk, about four inches thick, and are made of rounded bits of gravel in a sandy matrix. The rock has eroded a little bit, and some of the smooth pebbles — about the size of M&M candies — have fallen down into a little pile.