How to spoil your breakfast...

Yesterday I had an unpleasant turn just before breakfast. I was looking at the website of the Minor Planet Centre, an American organization that registers near Earth objects, minor planets, comets and ‘close approaches’. A ‘close approach’ is an occasion when a lump of space rock, a ‘Near Earth Object’, gets too close to the Earth for comfort. The impact of a large meteorite 65 million years ago was supposed to have wiped out the dinosaurs. Just last year, a meteorite exploded over Chelyabinsk with a force 20 – 30 times that of the Hiroshima bomb. Since it exploded in the air, most of the force was dissipated in the atmosphere but 1,500 people still needed medical treatment. If it had hit the ground…

Anyway, I was looking at the September tally for minor planets when I noticed that on September 20th, three days earlier, a rock, estimated size between two and nine metres, had passed within 50,000 miles of Earth. That really is too close for comfort, and is not much further out than the communication satellites.

Its speed was around 16,000 mph. I did a quick calculation and concluded that if it had hit, the force of the detonation would have been equivalent to around three Hiroshima bombs… Just like that! I was definitely preoccupied over breakfast, but returning to check the calculation, I realized I had dropped a factor of 1,000. Actually, it would only have been equivalent to 50 tons of TNT, still enough to spoil your day...

It is a bit worrying though. Just in the period between 17th September and 7th October, 19 ‘rocks’, the largest up to 2.6 km in size, either have come or will come close to Earth; even the furthest within 50 times the distance of the Moon.