re: Unmasking Europa -- question on topography
Thanks! High features are rare, so it's hard to generalize. A good example appears in my book (Unmasking Europa) as Figure 14.3, in the chapter called (appropriately enough) Thick vs. Thin.
Your point about focusing exploration on places where there is (or has been recently) an opening to the ocean is also a big point in my book. We might be able to find life, or signs of it, without needing to drill down through kilometers of ice. We just need to land in a well-chosen place. Of course, the permeable crust also makes Europa more vulnerable to forward contamination from Earth, another point discussed at some length in the book.
Best wishes,
Richard Greenberg