A Streambed On Mars
Just 51 days after landing on Mars, NASA's Curiosity rover has found clear evidence of an ancient streambed. Scientists were gratified, though not surprised, to see sedimentary rocks with rounded pebbles, as in this outcrop named "Link." The size and shape of the pebbles help them estimate how fast the stream once flowed. "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," said William Dietrich of the University of California at Berkeley, one of the Curiosity science co-investigators.