As if getting to Mars and establishing the first colony there wasn't dangerous enough, a new analysis of cratering rates suggests that over a three-year expedition to Mars, the planet will likely get hit by at least one asteroid large enough to cause an impact explosion in the megaton range. Good times.
Paleoselenologists are pretty sure that the Moon formed when a rogue planet about the size of Mars smacked into Earth billions of years ago. New models suggest that the rogue planet was not actually destroyed in the impact, and we don't know where it went. We also don't know where it is now. And it could strike again at any moment. RUN!