SCIENTISTS have found a pattern of impact craters in Antarctica from a huge asteroid which hit the Earth less than a million years ago and was as big as the one believed to have wiped out the dinosaurs.

The asteroid, up to six miles (9.6 km) long, broke up as it entered the Earth’s atmosphere to bombard an area of more than 3 million square miles. When it fell to Earth 870,000 years ago, man’s early ancestor, Homo erectus, was roaming the planet.

Molten asteroid slabs melted through more than a mile of ice and snow to hammer into the bedrock, the International Geographical Congress in Glasgow was told yesterday.

Billions of tons of ice, snow and rock were vaporised and thrown into the atmosphere and rock particles that fell to the ground as they cooled have been found almost 3,000 miles away in Australia.

The impact was so powerful that it is thought to have been responsible for a reversal of the Earth’s magnetic polarity. One enormous asteroid crater measuring 200 miles across, 150 miles wide and 550 yards deep has long been known to be under the Antarctic ice and snow, having been discovered inland from the Ross Sea in 1960.

Using new magnetic detection technology on satellites scientists have now located up to five more huge impact craters created by the same asteroid. Three of them are on the continental land mass and two more are in the Weddell Sea.

Frans van der Hoeven, a retired professor who discovered the original crater, said that the multiple impact field, known as a scatter eclipse, was the biggest found on Earth.

He said: “All the craters are of the same date so we are confident they were created by the same asteroid which would have broken up into several pieces in the atmosphere. Some would have burnt up but some were big enough to survive and hit the ground.

“They would have been hot so they would have melted or rather evaporated the ice and gone on until they hit the rock.”

The asteroid is believed to have struck the ice-bound continent 870,000 years ago and the shock of impact is likely to have caused huge tidal waves or tsunamis to sweep across the globe.

Unlike the asteroid that landed at Yukatan in Mexico 65 million years ago, creating the Chicxulub crater and believed by experts to have caused the end of the dinosaur age, the Antarctic asteroid did not cause mass extinctions. Dr van der Hoeven remains mystified that the impact did not have catastrophic results for life on Earth. He said that one possible explanation was that the dinosaur meteorite caused a fireball and a cataclysmic cloud of dust to darken the atmosphere for years, leading to dramatic global cooling.

By contrast, much of the debris from Antarctica was vaporised ice which would have turned into water as it cooled and fallen to Earth harmlessly as rain. An estimated 2 per cent of the ice and snow on Antactica 870,000 years ago, during an Ice Age, would have been melted by the impact.

This, said Dr Hoeven, would have caused a rise in the sea level of several feet but is unlikely to have had a significant impact on landmasses.

The effects of the sea level rise and the tidal waves caused by the asteroid would also have been limited because many coastlines would have been under ice and snow. Dr van der Hoeven told the conference at the Scottish Exhibition and Conference Centre that a more significant effect was likely to have been a reversal of the Earth’s polarity. Scientists have already established that the last time the polarity switched, a process that can take several thousand years, was at about the same time as the asteroid impact.

He said: “There are people who say that if you hit the world hard then the magnetic field will reverse. I think this asteroid did that.” The biggest section of the asteroid, presumed to come either from a dying comet or the asteroid belt, comprised about half the rock that entered the Earth’s atmosphere before breaking up and it created the crater discovered in 1960. The rest were smaller but at least one could still have been close to a mile long.

The newly discovered craters under the ice or sea were pinpointed by satelites which are able to measure the magnetic density of the ground.

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