Asteroid Collision Alert!

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The Times has a report of a potentially devastating asteroid collision next month. However, it’s not the Earth in danger, it’s Mars and the probability of collision is less than 1.5%.

The newly discovered space rock known as 2007 WD5 has a one in 75 chance of colliding with Mars on January 30. While the probability of an impact is slim, the odds have been cut from one in 350 when the object was first identified, and they are much shorter than is usual for new asteroids. If 2007 WD5, which is about 100 metres in diameter, does strike Mars on January 30, it would cause an explosion equivalent to several megatonnes of TNT.

“These odds are extremely unusual,” said Steve Chesley, an astronomer with the Near Earth Object Program at NASA's Jet Propulsion Laboratory in Pasadena, California. We frequently work with really long odds when we track threatening asteroids. We know that it's going to fly by Mars and most likely going to miss, but there's a possibility of an impact.”

If the asteroid does hit, it would give astronomers a rare opportunity to study the effects of such a strike. The object is broadly similar in size to the one that hit Tunguska in Siberia in 1908, which felled an estimated 80 million trees over 810 square miles. Had the Tunguska rock hit a city, it would have wiped it out.

The likely impact would be on the threshold of visibility from the largest of Earth's observatories, but its effects would readily be seen by probes orbiting the Red Planet such as the European Space Agency's Mars Express. The asteroid would probably hit a spot near the Martian equator, close to the point where Nasa's Opportunity rover has been exploring since 2004.

Not much of a story, perhaps, but it would be very useful to see the effects of a large strike without running the risk of major destruction on Earth...