Question: The asteroid 99942 Apophis will pass within very close range of the Earth on ~April 13, 2029, which will set it on a collision course with Earth.What will be the consequences if 99942 Apophis hit Earth?

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  1. I had to look that one up! So current estimates are that it is unlikely to hit Earth before 2070. If it did hit, it would be the equivalent of 500 megatons of TNT, 10 times larger than the largest hydrogen bomb ever detonated. It would devastate an area of 1000s of square kilometres, but is unlikely to cause an extinction event like the dinosaurs.


  2. First of all, I think that the chances of Apophis hitting Earth are very, very small. The last probability of impact I saw was 1 in 250,000 and it’s becoming less likely with time.

    But, if it did hit the Earth, as Matthew said, it would be pretty devastating! The asteroid is about 270 metres in diameter and is thought to be mainly rock (rather than ice). Its impact would cause the damage that Matthew described, *plus* we’d feel an earthquake of about 7 on the Richter scale. The blastwave caused by this impact would cause most buildings and bridges to collapse in the vicinity (within 10-20km).