Curiosity's stream discovery raises hopes of finding life on Mars
Discovery by Curiosity rover of evidence of ancient strean bed on planet is step towards finding if micro-organisms could have survived
Nasa's Mars rover, Curiosity, has discovered gravel carried by an ancient stream that once "ran vigorously" on the red planet.
The news bodes well for the mission to investigate whether Mars could sustain life, or if life ever existed there.
Pictures beamed back by Curiosity show a "jack-hammered-up slab of city sidewalk, but it's really a tilted block of an ancient stream bed", said project scientist John Grotzinger.
Finding evidence of water is the first step towards learning whether the environment on Mars could have supported microbes. While scientists have found evidence of the former presence of water, this is the first time stream-bed gravel has been discovered.
Previous images of Mars indicate it may have been part of a broader network of streams in the area.
Professor Sun Kwok, of the International Astronomical Union's Bioastronomy Commission 51, said: "If you asked [if water or life existed on Mars' frozen surface] 20 years ago, it would have been pretty far-fetched. Now that we're closer to proving there's water, some concrete evidence may come about soon [for the existence of life]."
Kwok said that judging by the ubiquity of micro-organisms on earth, in the air, on the surface and even in the deep reaches of oceans, it was possible micro-organisms could have lived, or are living, underground in Mars in areas that are yet to be explored. "It's a big step forward. I'm excited, but we're not there yet," he said.