[stevenwoo]

The two largest impact craters we know of are on the Moon and Mars, and those happened about four billion years ago. Of course we'll never know for the gas giants. Not doing the math, but this makes the odds seem pretty low after the initial "flurry" of our solar system's birth, barring Jupiter perturbing an existing asteroid into a collision into earth. https://en.wikipedia.org/wiki/List_of_largest_craters_in_the...