99942 Apophis is a near-Earth asteroid that caused a brief period of concern in December
2004 because initial observations indicated a small probability (up to 2.7%)
that it would strike the Earth in 2029. Additional observations provided
improved predictions that eliminated the possibility of an impact on Earth or
the Moon in 2029. However, a possibility remains that during the 2029 close
encounter with Earth, Apophis will pass through a gravitational keyhole, a
precise region in space no more than about 600 meters across, that would set
up a future impact on April 13, 2036. This possibility kept the asteroid at
Level 1 on the Torino impact hazard scale until August 2006. It broke the
record for the highest level on the Torino Scale, being, for only a short
time, a level 4, before it was lowered.[5]
Additional observations of the trajectory of Apophis revealed the keyhole
will likely be missed and on August 5, 2006 Apophis was lowered to a Level 0
on the Torino Scale. As of October 7, 2009, the impact probability for April
13, 2036, is calculated as 1 in 250,000.[6] An additional impact date in 2037
was also identified; the impact probability for that encounter is calculated
as 1 in 12.3 million.
結論：機會非常非常的小。