This latest research came about when Nasa's Mars Global Surveyor (MGS) spacecraft spotted gullies and trenches that scientists thought were geologically young and carved by fast-moving water flowing down cliffs and steep crater walls.
Scientists from the Malin Space Science Systems in San Diego, who have a camera aboard MGS decided to retake photos of thousands of gullies in search of evidence for recent water activity.
Two gullies that were originally photographed in 1999 and 2001, and then again in 2004 and 2005, showed changes, which could have been caused by water, the study reveals.
The scientists found bright, light-coloured deposits in the gullies that were not present in the original photos and concluded that the deposits of possible mud, salt or frost, were left there by recent water.
