We are doomed.

Unless we get off this planet.

I hate to borrow from a pop culture blip like Armageddon, but as Charlton Heston said "It has happened before, and it will happen again." Other than the Pioneer and Voyager spacecrafts, we have done nothing to assure that we will be remembered if an asteroid, a plague, or some other calamity befalls us. So long as we remain bound to one planet, we are doomed.

We are in a unique position. Technology is rapidly accelerating, no terrible plague is currently on the horizon, we seem (for the moment at least) to not be on the verge of a nuclear holocaust; if we are going to make a big push for space this is it. The moon, for many reasons, is a waste of time. We haven't found liquid water, the gravity causes problems with bone density loss, and it is generally mineral poor. Mars is a much better choice. Recently, deep caves have been found. It would be far easier to seal, pressurize, and adapt these cave systems then to transport gigantic living containers. Is this a pipe dream? Maybe at the moment, but over the next few hundred years, if we make it a priority, it could happen. With the develop of carbon nanotubes, a space elevator might be on the horizon. Inhabiting other planets might be just around the corner. Of course, Mars is a stopgap; a testing ground for the real journey.

Getting out of the galaxy is a lot harder. But, maybe closer than we would think. Back in the 60's, a workable plan for an interstellar ark was in fact created.

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

Sounds plausible. It would be a pretty friggin' long journey to the nearest star system. I don't think a spacecraft would work, but a hollowed out, pressurized asteroid just might. Interesting thought.

In any event, we stay on this planet, we're doomed. At least with an asteroid we'd have years to prepare. A comet would give us days, maybe weeks.

Let's see what happens with this one: http://en.wikipedia.org/wiki/99942_Apophis