Mars rover Curiosity sees key water indicator

The US space agency (Nasa) has reported that its Curiosity rover has made another significant discovery on Mars.

The robot has drilled into a rock that contains clay minerals - an indication of formation in, or substantial alteration by, neutral water, The BBC reports.

Scientists say the find is one more step towards showing conditions on the Red Planet in the distant past could have supported life.

Many rocks studied previously were probably deposited in acidic water.
While this would not have precluded the possibility of micro-organisms taking hold on Mars, it would have been more challenging, scientists believe.

Identifying clays shows there were at least some locations on the planet billions of years ago where environments would have been much more favourable.

"We have found a habitable environment that is so benign and supportive of life that probably if this water was around and you had been there, you would have been able to drink it," said John Grotzinger, Curiosity's project scientist.
The rover drilled a powdered sample from a mudstone at its exploration site in Gale Crater, a deep impact bowl on Mars' equator.

This was delivered to the two big onboard laboratories, Sam and Chemin, for analysis.
The rock sample was found to contain 20-30% smectite - a particular group of clay minerals.
Their high abundance and the relative lack of salt are strongly suggestive of a fresh-water environment for the mudstone's formation.

The presence of calcium sulphates, rather than the magnesium or iron sulphates seen in previous rock analyses at other locations on the planet, adds to the evidence that the sampled rock in Gale was deposited in a neutral to mildly alkaline pH environment.

Scientists think Curiosity probably drilled into an ancient lakebed.