Rounded pebbles on Mars reveal past flowing water

LOS ANGELES — A fresh analysis by the U.S. space agency's Mars rover confirms a stream once ran through Gale Crater on the planet.

The Curiosity rover last year came upon hundreds of smooth, round pebbles that look strikingly similar to deposits in river banks on Earth.

Scientists believe the rover rolled onto an ancient streambed, but it needed to study the stones in more detail. So Curiosity snapped high-resolution pictures and fired its laser at several pebbles to analyze their chemical makeup.

Researchers say the roundness of the stones was shaped by a fast-flowing stream that probably was ankle to waist-deep.

The analysis appears in Friday's issue of the journal Science.