World 'must tackle space threat'
By Julian Siddle
Science reporter, BBC News
The international community must work together to tackle the threat of asteroids colliding with Earth, a leading UN scientist says.
Professor Richard Crowther's comments come as a group of space experts called for a co-ordinated science-led response to the asteroid threat.
The Association of Space Explorers (ASE) says missions to intercept asteroids will need global approval.
The UN will meet in February to discuss the issue.
In the ASE report, the group of scientists and former astronauts point to the historical record to highlight the dangers of asteroids; an impact 65 million years ago may have wiped out the dinosaurs, and the Tunguska impact in 1908 produced a 2,000 sq km fire in Siberia, big enough to engulf a city the size of New York.
They say the next major threatening event could occur in less than 20 years. Asteroid Apophis is due to pass close to the Earth and analyses suggest a one in 45,000 chance of a collision.
An impact by Apophis would generate the equivalent of a 500 megatonne blast, at least 100 times more powerful than the Siberian event. [The most powerful thermonuclear weapon ever tested by humans had a yield of about 50 megatons. The Hiroshima and Nagasaki bombs probably had a yield of about 15 kilotons. So an impact by Apophis would have a yield about 30,000 times greater than Hiroshima . . . 30,000 Hiroshimas. (HES)]
Tuesday, December 2, 2008
This from the BBC: