Do “icebergs” really exist on Europa?
In close-up pictures of Europa’s “chaos” region, it can be seen that there are “blocks” or “plates” which have moved about relative to one another. These have informally been referred to as “icebergs,” but this term is improperly suggestive, invoking visions of ice chunks floating in terrestrial polar seas. On Europa it would be extremely difficult, if not impossible, to melt from a subsurface ocean all the way to the surface. One reason is that a prohibitively large amount of heat energy would be needed. Another reason (demonstrated by David Stevenson) is that ice should flow faster than it can melt, meaning that even if a sufficient heat source were available, a hole in the base of Europa’s ice shell would fill in with warm, glacially flowing ice before it could melt. Instead, the chaos areas may represent areas in which Europa’s ice shell has partially melted above a large diapir or assemblage of diapirs.
