Splish, splash, Mars' water tops scientists' hit parade

Scientific proof that water once flowed on Mars has been voted the breakthrough of the year.

The journal Science said the discovery topped a list of studies that stood out from the many thousands published by scientific journals this year.

It raises the prospect that scientists will eventually find evidence of primitive life on Mars - a discovery that would dramatically increase the chances of there being intelligent beings in a distant solar system.

Two US National Aeronautics and Space Administration (Nasa) robotic rovers showed beyond doubt this year that the surface of Mars was once flooded with running water.

Science said: "The Opportunity rover found the salty, rippled sediments of a huge shallow sea; the Spirit rover discovered rock once so drenched that it had rotted.

"Their finds mark a milestone in humankind's search for life elsewhere in the universe."

Water is almost certainly essential for the evolution of extra-terrestrial life. If it can be shown that life originated and evolved independently on two planets in the same Solar System - Earth and Mars - it would suggest that life elsewhere in the universe was far more common than previously thought.

Opportunity bounced down on the vast Martian plain of Meridiani Planum on January 25, 22 days after its twin rover, Spirit, landed on the other side of the planet.

Each had cameras, a magnifying glass, a grinding wheel for exposing fresh rock, an analyser for chemical elements and other instruments for investigating minerals.

"The two rovers confirmed what many scientists have long suspected - billions of years ago, enough water pooled on the surface of Earth's neighbour long enough to allow the possibility of life," Science said.

There have been tantalising hints since the 1970s, when Nasa's Viking probes landed on Mars in the 1970s and took the first close-up images of its surface, that the planet once had rivers and seas.

But scientists could not be sure that the channels, valleys and gullies they had seen through telescopes and orbiting probes were caused by water erosion.

Data sent back by Opportunity and Spirit over the past year has now put the matter beyond dispute, Science said.

Mars was once a warm and wet planet - in marked contrast to the arid, cold and sun-bleached place it is now.

"Thanks to the hardy little robots, we know that Mars of several billion years ago was warm enough and wet enough to have a shallow, salty sea.

"This sea probably came and went, turning into wind-blown salt flats from time to time, but the puddles spanned an area the size of Oklahoma."

Steve Squyres, professor of astronomy at Cornell University and a member of the team that analysed the Opportunity data, said the findings indicate how Mars and Earth had gone their separate ways.

"We cannot determine whether life was present or even possible in the waters at Meridiani, but it is clear that by the time the sedimentary rocks in Eagle crater were deposited, Mars and Earth had gone down different environmental paths," he said.

Science judged that the runner-up to the discovery of water on Mars was the finding of a species of dwarf human who lived on the remote Indonesian island of Flores as little as 13,000 years ago.

The "startling" discovery, announced in the pages of Nature, the chief rival of Science, overturned the accepted view of human evolution which stated that modern humans co-existed only with the Neanderthals.

Homo floresiensis, as the dwarf species was named, stood barely a metre tall and appeared to have long arms relative to its size.

Its skull was big enough to house a brain the size of a small grapefruit.

Science said: "Sometimes big discoveries come in small packages."

The big two

Two big science stories captured imaginations this year.

Proof that water once flowed on Mars.

The discovery on a remote Indonesian island of a species of dwarfed humans.

- INDEPENDENT