To me there are 2 major missions we now need to work on as a human species - all the rest is just less important.
We need to save our biosphere & create new biospheres that can serve as human habitat. The first is a process that seems to be generally accepted & we have started remedying some of the environmental bummers, but we are moving very, very slowly. Check out what Saul Griffith has to say on this topic here: http://blip.tv/file/1018152
The second is something that is much less accepted. However, seemingly a lot less urgent, I think this is not less important. We know for at fact that life on earth will go extinct, just not exactly when. So far serial terra-forming of other planets is the only known way to save the human species after earth collapses. I have read somewhere that an estimate of the time it would take to terra-form Mars (it being the most likely candidate) is roughly 5 centuries. Momentarily we are lucky that the world’s most powerful empire, the US, does prioritize space travel. If this empire abides the same historic rules as the Roman empire did - it also has roughly 5 centuries of rule from its hegemony was challenged. If that challenge was 9/11 the clock is counting. Now, this is extremely unscientific, borderline bogus, but we just don’t know if the next great empire will fund space travel as the US has & we don’t know what catastrophic exterior element could short cut events the next 500 years. I think we need to get terra-forming Mars on the political agenda - even during recession. Specifically what I think we need to do first is to contaminate Mars with terrestrial life, a kind of dirty bomb, which will prevent preservationist to keep us from spreading life. We need to rethink space exploration in general: Elon Musk is contributing: http://ecorner.stanford.edu/authorMaterialInfo.html?mid=382