QUESTION FROM ROBIN KNOWLES
An impact from Apophis has been effectively ruled out in 2029, but what about 2036 or later, is there still a threat, I’m worried?
ANSWER BY RUSTY SCHWEICKART (ADXP)
Immediately after Apophis was discovered in Dec 2004 and with minimal tracking on it there was a potential 2029 Earth impact. However by the 28th of Dec, 2004 with additional tracking it was clear that the asteroid would make a close pass, but definitely miss the Earth. There remained however a potential 2036 impact due to gravitational effects during the 2029 close pass. With additional tracking that 2036 potential impact dropped to below 1 in 250,000 and then finally to zero. Today Apophis has several very low probability potential impacts, the highest being 1 in 149,000 on April 12, 2068. It is highly likely that with additional tracking between now and then that this impact probability will also drop to zero.
If you want to see what’s going on go to the JPL website where all this is publicly listed… http://neo.jpl.nasa.gov/risks/. Scan down to the lower table and you will find Apophis. You should also look at our Asteroid Day Expert Panel page where we have answered this and other questions re Apophis (http://www.asteroidday.org/adxp-qa/)
There are always asteroids with low probabilities of impact headed our way. However as we get more and more tracking on them the accuracy of the predictions increases and the potential impacts disappear. We keep tracking them because one day one may not drop to zero… and that’s when we will have to deflect it. So worrying doesn’t help… keeping an eye on them is what will enable us to prevent future impacts.
Rusty Schweickert, Asteroid Day Expert