NASA find water on Mars . . . again

My headline sums up the rather cynical response I had from more than one space scientist last week after it was announced that the Phoenix probe had identified water vapour on Mars.

trenches dug by PhoenixThey felt that this latest “discovery” was rather hyped up to boost general interest in the US lander’s mission.

After all, it has been very clear for some time that there are vast deposits of water ice beneath the martian surface. Fresh evidence came soon after Phoenix landed.

The popular media were happy enough to follow the NASA line and treat the new find as if it were a major surprise. It would have been a bigger surprise if no water had been found.

To be fair to the Phoenix team, their instrument was the first actually to “taste” the water. A sample of sticky soil warmed in a special oven gave off the vapour that they identified.

Water is, of course, essential to life as we know it and scientists were excited to find it so close to the surface. The robotic lab will now analyse the soil further to see if chemicals containing carbon and other raw materials needed for life are also present.

This week, following stirrings in the conspiracy-theory crowd that NASA were witholding some earth-shattering discovery on life, the agency disclosed that they had detected perchlorate salts in the soil. (One of the scientists, Tom Pike, describes the problems of trying to do science under the public gaze here.)

This worried some who claimed it made less likely the possibility of life. But apart from the fact that the soil in one area of Mars need not be like that in others, others point out that organisms have been found living alongside similar salts in Chile’s Atacama desert. The soil tested by Phoenix had earlier been said to be ideal for growing certain crops, such as asparagus.

Phoenix, which landed on May 25, dug the soil from a trench about two inches deep in a region 68 degrees north called Vastitas Borealis.

The £230 million probe, which is the size of a pick-up truck, had already taken pictures suggesting there was ice in the soil. White lumps scooped from the ground in June had vanished, having evaporated on exposure to the air.

The surface of Mars is like a dry desert today. Any liquid water would evaporate straight into space. But experts believe that the planet was covered by a vast ocean 3.8 billion years ago and that much of it disappeared underground.

Two robotic rovers, Spirit and Opportunity, discovered mineral deposits that commonly form in water. And orbiting probes detected vast quantities of ice underground around the south pole.

Only yesterday, I received another press release revealing more evidence for the water – this time in layers of clay-rich rock found in Mawrth Vallis, an outflow channel in Mars’ northern highland region.

In December 2006, Nasa reported images of liquid water running down a crater slope but later found it was a landslip instead.

Nasa has extended the Phoenix mission by an extra month to the end of September. The probe is not expected to survive past November when winter sets in.

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By Paul Sutherland

Paul Sutherland has been a professional journalist for nearly 40 years. He writes regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy, plus he has authored three books on astronomy and contributed to others.

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