PARIS, Sept 8: Mars may be cold, dry and dusty today but it once had a watery climate that lasted for much of its history, according to a study published in the British science journal Nature on Thursday.

The research compared images sent back by the US rover Opportunity from the plain of Terra Meridiani with thermal spectrometer scans made by a NASA orbiter, Mars Odyssey.

Both missions found visual evidence of grey haematite, a mineral containing iron ore which, on Earth, is only formed by prolonged contact with liquid water. "For this to occur, the ancient global climate of Mars must have been very different from its present climate and have lasted for an extended period," suggests Mr Hynek. -AFP