Among Europa scientists there are two warring factions: the thick-icers and the thin-icers. The question is how thick is the ice shell that overlies Europa's subsurface ocean (the existence of which pretty much everyone agrees on).
Time to open the third door in the advent calendar. Until the New Year, I'll be opening a door onto a different landscape from somewhere in the solar system. Where in the solar system is this wispy terrain?
Galileo, the scientist, discovered the Galilean satellites of Jupiter four hundred years ago next month, while Galileo, the mission, arrived at Jupiter to study those moons in situ fourteen years ago Sunday.