Writing in the journal Science, the team -- including Linda Kah, a professor of earth and planetary sciences at the University of Tennessee, Knoxville -- suggests the environment of the Red Planet was once drastically different from today's cold and dry conditions, with the potential to support life.
As the Curiosity rover moved over the martian surface, its cameras captured images of large rock formations composed of many rounded pebbles cemented into beds several inches thick.
While such deposits are found all over Earth, finding these types of rocks on Mars has great significance for the Red Planet, the researchers said.
"These (rock formations) point to a past on Mars that was warmer, and wet enough to allow water to flow for many kilometers across the surface of Mars," Kah said.
Pebbles within the rock formation appear to have been rounded by erosion while carried through water, such as in a stream or river, Kay said in a university release Thursday, and the size and orientation of the pebbles suggest they may have been carried by one or more shallow, fast-moving streams.
"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," she said. "Finding ancient river deposits indicates sustained liquid water flows across the landscape, and raises prospects of once habitable conditions."