The science team behind the Mars Curiosity rover has announced that some of the images it has taken reveal signs of a significant water flow at some point in the planet's past. Although there have been numerous indications of water in Mars' past, the discovery provides a unique opportunity to understand the precise environment in which the watery deposits formed.

The deposits look strikingly similar to some found on Earth, in which rounded rocks, carried by currents, settle into a stream bed and are locked into a conglomerate. The rounded shapes show that the rocks were worn by transport over long distances, while the size of the rocks is too large for them to have been brought there by wind. The flows seem to have been sizable, too. "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 Berkeley's William Dietrich in the JPL's release.

The Gale Crater, where Curiosity landed, shows signs of extensive water flows, with a channel that leads to a break in the crater rim, and a large alluvial fan within the crater itself. The size of these features suggest that the flow was either steady, or recurred repeatedly.

Since the rocks embedded in the conglomerate were carried from above the rim, examining them with some of the rover's instruments should provide some indication of the region's geology, and the deposits in which they are embedded will tell us something about the watery conditions. But the fact that they were found in more than one location already suggests that Curiosity will come across more before too long.

JPL's statement quotes Caltech's John Grotzinger as saying the deposits are probably not a good bet for finding any organic material that might be indicative of anything living in the water. But they hope to find any organic deposits that are present preserved at Mount Sharp, the largest feature in the crater. These further indications of water, Grotzinger says, are "insurance that we have already found our first potentially habitable environment."