Data acquired from NASA's MESSENGER probe suggest that Mercury used to have an ocean of molten rock. ->
Mercury is the closest planet to the sun; it is therefore the least likely place to find a reservoir of water ice. It seems surprising, then, that water ice may be present inside its shady craters.
As if the debate over what is and what is not a planet hasn't gotten confusing enough, we are beginning to see a class of object that could be called "Comet-Planets."
A surprising discovery has been made during a successful search for ice inside the small planet's shadowed craters.