Brian, what you say about ice sublimating rather than melting under these conditions is true, but not at all scales.
At the surface of a forming ice crystal/layer there is a layer of water molecules one or two molecules thick, kept 'liquid' by the pressure of the van der waals forces between them (I've probably spelt that wrong).
This layer ought to be there even at much lower temperatures than occur at the phoenix site. But it's not, almost as though the water vapour in the air can't touch the soil...
It might be a bit of blow for those hoping for present day life, but we really don't know whats going on here, so at the end of the day it might not be after all.
We'll just have to hope we get enough clues from phoenix to figure it out.
