Now, yes, obviously, throw in a grizzled marine and you've got the making of an awesome movie about discovering aliens. But that's not (the only reason) why Kottke thinks the announcement will be about life on another world. Here's what he says:
So, if I had to guess at what NASA is going to reveal on Thursday, I'd say that they've discovered arsenic on Titan and maybe even detected chemical evidence of bacteria utilizing it for photosynthesis (by following the elements). Or something like that. (thx, sippey)