Terra Meridiani, Mars
Curiosity sends images from Mars showing pebbles that have been transported by a riverNasa/Reuters

Following on from Nasa's recent announcement that there is flowing water on Mars, the Curiosity rover has revealed that rounded pebbles on the Red Planet had been carried for tens of kilometres by a river. The Curiosity rover discovered small pebbles in formations that suggest that they had been carried downstream by a stream or river.

"We determine that the Martian basalt pebbles have been carried tens of kilometres from their source, by bed-load transport on an alluvial fan," read the report published in Nature Communications. By reconstructing a similar formation of pebbles, the researchers from the University of Pennsylvania found that pebbles became rounded as they rolled along the surface of the riverbed, as would happen on Earth.

mars pebbles
Image of Link outcrop, showing Martian soil with rounded pebbles that was analyzed in this studyNASA/JPL-Caltech/MSSS

However, they have not been able to give an exact distance for the stones' travels, but the team states in a press release: "Pebble shape can be used to infer the amount of mass lost during particle transport by water, and this mass loss equates to the amount of transport experienced by the pebble." Nonetheless, from analysing transported river pebbles in Puerto Rico and the US, they will be able to get a clearer understanding of the distance when future experiments are conducted.