Jupiter's new spot. Current thought is leaning towards a comet strike that's left a blast site about the size of the Earth.
We have a hard time conceiving of such sizes, but consider this: what if it had hit the Earth instead? There's plenty of documentation that we've been hit by some pretty hefty debris in the past, and the possibility of it happening in the future isn't an "if" but a "when."
Wondering why we need to go into space? Look at Jupiter. And check out the Pacific Ocean-sized scar left from the last impact in 1994.
As Robert Heinlein said, "The Earth is just too small and fragile a basket for the human race to keep all its eggs in."
And the universe just keeps chucking rocks in our direction.