Space rock? - I hope this doesn’t prove too technically worded for anyone. 
A controversial new idea suggests that a large space rock exploded over North America 13,000 years ago.
The blast may have wiped out one of America’s first Stone Age cultures as well as the continent’s big mammals such as the mammoth and the mastodon.The blast, from a comet or asteroid, caused a major bout of climatic cooling which may also have affected human cultures emerging in Europe and Asia.
Scientists will outline their evidence this week at a meeting in Mexico.
Their impact theory shouldn’t be dismissed; it deserves further investigation
Jeff Severinghaus, Scripps Institution of Oceanography
The evidence comes from layers of sediment at more than 20 sites across North America.These sediments contain exotic materials: tiny spheres of glass and carbon, ultra-small specks of diamond - called nanodiamond - and amounts of the rare element iridium that are too high to have come from Earth.
All, they argue, point to the explosion 12,900 years ago of an extraterrestrial object up to 5km across.
No crater remains, possibly because the Laurentide Ice Sheet, which blanketed thousands of sq km of North America during the last Ice Age, was thick enough to mask the impact.
Another possibility is that it exploded in the air.
Continued… http://news.bbc.co.uk/2/hi/science/nature/6676461.stm
