Although the batteries on the Pathfinder lander, which arrived on the planet on 4 July, have now run down, they managed to transmit back huge amounts of data about the atmosphere and the rocks around the landing site. There, the scattered, rounded pebbles and cobbles implied it was once a "water-rich" environment.
Writing today in the journal Science, a team led by Matthew Golombek, of Nasa's Jet Propulsion Laboratory in Pasadena, California, noted that some of these pebbles could have been liberated by larger sedimentary rocks called conglomerates. This suggested that water existed elsewhere and earlier than in the flood believed to have carved out the valley where Pathfinder landed.
The finding is helpful for Nasa scientists who have maintained that a Mars meteorite shows evidence of past microbial life - a claim that has not been backed by other independent scientists. If Mars once had plentiful water, it could have provided the basis for life.