# Impact of Apophis

I read about the near-earth asteroid 99942 Apophis. It is in the first place of Potentially Hazardous Asteroids (visiting earth at an altitude of about 36,000km on 2028). But, scientists have calculated that the asteroid would impact earth on 2036. What is the fact behind this? I mean, Why is this difference in period of 8 years for a close-encounter and then impact? Is Apophis, a part of the asteroid belt between Mars and Jupiter or is it a part of the solar system? Would we actually get an "Armageddon"? Even if it doesn't impact, it could cause some damages either to our atmosphere or even our environment, Nah?

-

JPL has a very nice page detailing impact energies and probabilities. In the case of Apophis, the impact probability in 2036 is quite small ($4.3\cdot10^{-6}$) and the impact energy is large but not overwhelming (~500 megatons). –  mmc Aug 14 '12 at 16:55