>The vastly better roving capability compared to previous missions

Not only that, but better than expected for *this* mission. If Spirit had only made it as far as the mission specs said, we would have trundled up to the rim of Boneville Crater, and that would have been it. We'd have have seen just the boring plain of basalt that you feared.

The fact that the rovers are doing so well, and seem likely to stay alive a while longer, certainly makes a strong case for building more of them and getting some use out of the R&D investment. I know the chances of that are near zero, but it sure would make sense.

Hmm, I wonder if someone could propose sending an MER close as one of those missions of opportunity, like Phoenix. There should be another one for 2011. I wonder how much flight-spare hardware is sitting around.

In any case, my question for Nick or any other takers is, assuming that other MERs perform as well as Spririt and Opportunity, where would you send them? What other landing sites do you like?

Among other MER site finalists, from my non-expert perspective I liked the possibility of exploring very recent water/lava at Athabasca, though I didn't look at detaisl enough to know whether we had a good shot at examining the right terrain given actual mission plan (along those lines, if I recall NIck, you would have positive about a Gusev mission that looked at the mesas and other deposits right at the end of Ma'adim, the problem is that Spirit couldn't land anywhere near them). I would *really* love to see a mission that could date those very young flows, but doesn't sound like remote isotopic dating is something that will be coming soon.

Other finalists? Sites that never made it, but that would be within MER capabilities?