NASA announced Thursday afternoon that Messenger has found new evidence that ice made from water "and other frozen volatile materials" exist on Mercury.
Most intriguing part about this? Water on Mercury. And water remaining on Mercury.
Meaning you've got a planet as hot as literal hell that has some areas remaining so cold as to never warm above freezing. Its the same argument as the Jupiter 'sweet spot', where pressure and temperature at one point is bearable for life. Might be hundreds of degrees on Mercury almost everywhere. But these polar craters that are -300f means, at some place, there's going to be a temperature consistently between 0-100f. Bodes well for establishing a manned presence there if radiation can be grappled, all the more that water is already there.