re: Are the Rare Earthers Optimists?
Exactly. We must keep searching. I believe (faith, not science) that basic life is common, whether through pansphermia or whatever. If this be so, we have a chance to find confirmation much later this century underground on Mars or beneath the ice on Europa, Enceladus, et. al. Finding nothing living there alas proves nothing.
It would be ironic to have the 1st 'discovery' of ET life be around another star. Imagine a TPF style scope in the 2030s finding an extrasolar planetary atmosphere with active oxygen, something that disappears unless there's an active renewing mechanism, e.g. photosynthethis. That's MY bet on the discovery of life elswhere.