A River Ran Through It -- on Mars

A team of European Space Agency (ESA) scientists have reportedly discovered an ancient riverbed on Mars, the latest evidence supporting the theory that water once flowed freely across the Martian surface. The photos, which were taken last year, were released late Thursday by the agency, according to a statement.

European Space Agency officials announced Thursday that they have discovered an ancient riverbed carved into the surface of the Red Planet. The images, snapped by the ESA’s Mars Express, have left astronomers around the world scrambling to better understand the stunning feature — quite possibly the most definitive evidence to date supporting the theory that water once flowed on Mars.

The area, dubbed Reull Vallis, contains a river-like channel likely formed billions of years ago. The 1500-km channel is lined with tributaries that seem to resemble tributaries found on Earth, according to the report, and the striking river is at some points wider than four miles. Astronomers say the ancient river is nearly 1,000 feet deep at some points, and it is likely one of the most geologically important features on the planet.