Fossils date Dry Valleys' origin

By Jonathan Amos Science reporter, BBC News

Tiny fossils have helped refine the timing of the climate shift that gave rise to Antarctica's remarkable Dry Valleys, a landscape akin to Mars.

The famously ice-free terrain enjoyed more benign, tundra-like conditions 14 million years ago - but then flipped to the intensely cold setting seen today.

Scientists tell a Royal Society journal that ancient lake-living shrimp-like creatures can pinpoint the big switch.

The ostracods would not have coped with a harsh, dry environment, they say. Dr Adam Lewis, from North Dakota State University, US, explained: "Our dating says the lake existed 14 million years ago, and within about 250,000 years of that lake existing and holding those ostracods, all the glaciers in the surrounding area stopped melting and they become cold-based and began to evaporate.

"So after about 13.8 million years ago, there's no water - it's bone dry, dry-frozen," he told BBC News.

Antarctica's Dry Valleys, with their barren gravel-strewn floors, are said to be the closest place on Earth to Mars.

More at news.bbc.co.uk