Our polymath, Teignmouth Probus Club member Peter Lewis, stepped in at short notice as our regular speaker was unwell.

As asteroid no. 99942 ‘Apophis’ was in the news that it was on course for planet earth in 2029 with a 2.7% probability of an earth strike, Peter presented an illustrated exposé of Earth’s worst nightmare - a meteor impact.  Work of the much-respected Stephen Hawkins was cited predicting that a high magnitude asteroid strike was guaranteed by the law of physics and probability, similar to the event 66 million years ago seeing the extinction or 67% of all life forms including the dinosaurs’ – The Yucatan Gulf of Mexico Chicxulub crater. Most of the evidence is no longer visible due to erosion, sea inundation and sediment of more than a kilometre deep. Modern technology has confirmed its location with known magnetic anomalies of such events and layers of Iridium formed with such huge impacts. This lump of space rock was estimated to be 10 kilometres wide with an impact force of 100 teratons of TNT.  

Apophis is merely 375 metres wide about the size of a cruise liner. This asteroid elliptically circles earth moving ever close on each cycle. Its impact force would be equivalent to 1200 megatons of TNT.

The best preserved visible crater – the Barringer cater in Arizona landed about 50,000 years ago at 29,000 mph, was a 50 meters diameter rock with a force of 10 megatons producing a crater 1500 metre wide and 200 metre deep having vaporised on impact. (the size is less today by natural erosion). Google images for the Barringer Crater.

Apophis would cause serious damage with a 5 kilometre wide crater. (Picture this against the Hiroshima atomic bomb with impact force of mere 15 kiloton TNT)

There were pictures of other earth strikes and shooting stars bringing more than 15 tons of space rock to earth every day mostly burning up on contact with our atmosphere.

The members will be reassured with the thought that the best world cosmic scientists cannot foresee such a meteor strike in the next 100 years – but in reality who knows?

The vote of thanks for a most informative and interesting talk was proposed by member Keith Underhill with thanks for stepping in at the last minute.

Posted by Press Officer Rick Purnell