On February 15, 2013 a small asteroid exploded over the Russian city of Chelyabinsk. There were a large number of injuries, which is unusual - very few people have ever been injured in the past from meteors. And these injuries weren't to people being hit by fragments, most of them were due to flying glass as the shock wave hit. However there were some who suffered from eye problems due to the brightness of the explosion, which was much brighter than the Sun. Some people were even treated for burns.

Chelyabinsk fireball February 15, 2013

I was expecting to see pictures of gold medallists receiving their meteorite medals in the Sochi games yesterday, which was the anniversary of the Chelyabinsk fireball. But the Olympic Powers-That-Be have forbidden this. The organizers can give the medals to the athletes when the games are finished, but they want to keep the games "free of any outside influences". I guess you can't get much farther outside than something that's come from a hundred million miles away!

Chelyabinsk may be remote for most people reading this, but the anniversary is an important reminder for all of us of the potential hazards of Earth meeting an asteroid or comet.

Astronomers estimate that they have found over ninety percent of near earth objects over 1 km in size. Comforting, I suppose, but that still leaves a number of ones we don't know about. Not to mention ones smaller than 1 km that could cause substantial local damage.

The Planetary Society website says "Over the next three centuries, there is a 1 in 30 chance that a Tunguska-like impact will result in some human casualties." This was written before Chelyabinsk whose asteroid was smaller than the Tunguska object. No one was killed, but around 1500 people had injuries that made them get medical attention.

Alan Fitzsimmons, who spoke at European Astrofest recently, says that we need to revise upwards our estimates for the likelihood of an impact.

An ESA (European Space Agency) video deals with Accidents and Asteroids as well as a brief look at some other recent news. A 100-meter asteroid is small enough to fit in a football field, but could completely destroy an urban area on impact. The one that exploded over Chelyabinsk was only about 20 meters across. An international group has been formed, with the support of the United Nations, to work out how to deal with such a threat.