On Friday April 13th, 2029 the asteroid Apophis will make its closest approach to Earth ever!
There is no reason to be alarmed, though. NASA has ruled out the chance for an Earth impact. The biggest unknown about this asteroid passing is whether or not it will hit a gravitational keyhole and have its trajectory changed enough to causes an impact when it passes again in 2036.


To explain what could happen on April 13 2029, it would probably help if you were given an idea as to what a gravitational keyhole is. A gravitational keyhole is a region of an orbit where a small gravitational input could cause a small body to collide with the large body it is orbiting. With the asteroid Apophis the chance of a trajectory change after hitting such a keyhole would effect its passing of the Earth in 2036. The asteroids trajectory could be changed by as much as 28°. Scientists can not predict if it will be drawn towards the Earth or away. They can not tell if the change will cause it to hit Earth or another solar system body at an earlier point in its new orbital path.

The Earth is impacted by small asteroids and meteorites on a monthly basis. All of them are small enough to burn up in the atmosphere, leaving a nice light show as the only evidence of their passing. On April 13th, 2029 things could be a little different. This 2029 Apophis is 320 m wide. That is enough to destroy an area the size of the Quebec province if it hit land or to cause horrific tsunamis if it hit an ocean. A little chilling for an asteroid that was predicted to have a one in sixty chance of hitting the Earth.