Off the top of my head, here are two other explanations: (1) Direct hit by a solar ejection (flare). (2) Direct hit by an extra-solar gamma ray burst. With the latter, a strong gamma ray burst could even boil off our atmosphere and melt the surface of the entire planet. (Odds of such happening are very very very ridiculously low.)
In short, it is a violent universe...
Or simply a meteor shower.
Or maybe a really big kiln!
(3). Wrath of God