Question: Why did shoemaker-levy 9 crash into jupiter?

Ry Cutter answered on 13 Nov 2017:

Here’s the collision (left) in infra-red (on the right is Jupiters moon Io) :

Jupiter is really heavy, this means it’s gravitational pull was great enough to deflect the orbit of this poor comet into Jupiter! Jupiter is actually very important for life on Earth for this reason. Lots of comets and asteroids that would otherwise hit us are redirected by big ‘ol Jupiter!