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The asteroid believed to be around 9.6 kilometres in diameter broke up as it entered the Earth�s atmosphere to bombard an area of more than five million square kilometres. The collision happened around 870 000 years ago, a time when Homo erectus, man�s early ancestor, was still roaming the planet. Molten asteroid slabs melted through more than 1.5 kilometres of ice and snow to reach the underlying bedrock. The new discovery was announced at the International Geographical Congress in Glasgow earlier this week.
Billions of tons of ice, snow and rock would have been vaporised and thrown into the atmosphere. Rock particles that fell to the ground have been located more that 5 000 kilometres away in Australia. The impact was so immense that it is being considered as the cause of a reversal of the Earth�s magnetic polarity around this time.
One enormous asteroid crater measuring 320 kilometres across, 100 kilometres wide and 500 metres deep has long been known to be underneath the Antarctic ice and snow, since being discovered in 1960. Using new satellite technology to help detect magnetic anomalies, scientists located up to five new impact craters. Three of them are on the continental land mass and two more are in the Weddell Sea.
The impact is likely to have caused huge tidal waves or tsunamis to sweep across the globe. However, unlike the asteroid that creating the Chicxulub crater 65 million years ago that triggered the end of the dinosaur age, the Antarctic asteroid did not cause a mass extinction. One possible explanation was that the dinosaur meteorite caused a cataclysmic cloud of dust that darkened the atmosphere for years, leading to dramatic global cooling. In contrast, much of the debris from the Antarctica impact was vaporised ice, which would have turned into water as it cooled and fallen to Earth harmlessly as rain. An estimated two per cent of the ice and snow on Antarctica would have been melted by the impact. This would have caused a general rise in the sea level of 60 centimetres.
The impact occurred during an ice age, which minimised the effects of the sea level rise. Any tidal wave devastation would have been limited due to many coastlines being protected under ice and snow.
Other planetary scientists, however, remain sceptical. Dr Phil Bland of Imperial College London, says the identification of craters cannot be achieved by gravity anomalies alone and debris from the impacts, which could be dated accurately, would be needed before the impact events could be confirmed.
More info: International Geographical Congress
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