Oh I agree on the politics. I just thought I'd chime in on the hypothetical humans v robots debate.

If humans aren't going anytime soon, and if robots aren't going to find bugs or fossils, then we won't be sending many robots either.

One of those essays on my "to write once I get my *real* work caught up" list was "The Coming Crisis in Mars Exploration". In the fall I was thinking about how tough it would be to sustain future missions if the exobiology goal looked unlikely. Not only because geology doesn't sells as well, but we're already done much of the easy work at Mars -- answering the fundamental geologic questions that you rightly raise will take smart rovers and sample return and all that expensive stuff.

Extending that, one point that I was going to make that I haven't seen mentioned in this vein, is that if Mars becomes "mere" geology, then it will face more competition from planetologists who study other bodies. Heck, I'm sure some "aerologists" would propos projects for other worlds themselves if they didn't think that Mars had a priviliged funding position. If life isn't there, wasn't there, or at least isn't locatable in any practical way, then why Mars vs other bodies? We actually know quite a lot about Mars relative to other bodies already; is another Mars rover really the most efficient way to add to our store of knowledge? I'm sure there are some scientists who think there's more interesting work to do on Venus, Titan, comets, whatever, and that they will press those cases more forcefully if Mars is just another lump of geology, rather than a unique case due to the possibility of life. And I don't think they'd be wrong.

Now, the prospect of human missions give us a reason to care about Mars. Except that the point of the human missions as stated so far is to look for the life that probably isn't there to find -- not by the first, furtive visit at least. So the thing still falls apart, though perhaps not as quickly.