Curiosity provides strong evidence for flowing water on Mars

Rocks analysed by NASA's Mars Curiosity rover have provided solid evidence that the red planet once had flowing rivers or streams, researchers say.
Despite satellite images that show vast networks of channels, past Mars rover missions have shown limited evidence for flowing water on Mars.
Now, rocks analysed by the rover team, including Linda Kah, associate professor of Earth and planetary sciences at The University of Tennessee, Knoxville suggest that the environment was drastically different than today's cold and dry conditions, with the potential to support life.
Since its landing in August last year, the Curiosity has been looking for clues to whether the Martian surface has ever had environments capable of sustaining, or potentially evolving, life.

Critical evidence may include hydrated minerals or water-bearing minerals, organic compounds, or other chemical ingredients related to life.
Scientists of the Mars Science Laboratory mission used images collected from the rover's MastCam, which includes two high-resolution cameras mounted onto its mast.

As the rover moved from its landing site to its current location in "Yellowknife Bay," the cameras captured images of large rock formations composed of many rounded pebbles cemented into beds several centimetres thick.
While such deposits are very common on Earth, the presence of these types of rocks on Mars has great significance for the red planet.
"These (rock formations) point to a past on Mars that was warmer, and wet enough to allow water to flow for many kilometres across the surface of Mars," said Kah, who helped work the cameras.

The clasts, or pebbles within the rock formation, appear to have been rounded by erosion while carried through water, such as in a stream or river. The size and orientation of the pebbles suggest they may have been carried by one or more shallow, fast-moving streams.
Using published abrasion rates and taking into consideration reduced gravity, the scientists estimate the pebbles were moved at least a few kilometres.
Analysing the grain size distribution and similar rock formations, the scientists believe the river was less than a meter deep and the water's average velocity was 0.2 to 0.75 meters per second.

"These rocks provide a record of past conditions at the site that contrasts with the modern Martian environment, whose atmospheric conditions make liquid water unstable," said Kah.
"Finding ancient river deposits indicates sustained liquid water flows across the landscape, and raises prospects of once habitable conditions," Kah said.
The study was published in the journal Science.