This entry was originally written for my Now Look Here! blog, but I reckon it's relevant for Urban Astronomer too:
I listened to a series of Naked Scientists podcasts recently, on the various competing plans to launch a human mission to Mars. One episode stood out in particular, asking whether this was something that we need to spend money actually doing.They assembled a panel of various experts and authorities to debate the issue, and while they all raised interesting points, they also all seemed to miss the bigger implications. The two main reasons brought up in the debate were scientific research and the "lifeboat" principle.