An obsolete theory of the Earth works better than ever on Mercury, where new data reveals how much the hot little planet has shriveled since it first formed.
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.