Most people are familiar with Arthur C Clarke's 2001: A Space Odyssey. Fewer are aware there were three sequels (this is not surprising, as Clarke is honestly not that great a writer in long-form. He's a much better idea man than scene-painter, as is not uncommon with the hard scifi guys of that generation). The first, 2010, deals with the alien life developing under the frozen surface of Europa, and how the monolith aliens collapse Jupiter into a small star so those aliens can develop. The line Sheldon quotes is broadcast to all human nations in all human languages at the end of the book, and translates basically to "you can do whatever you want with everything in the solar system except this moon; you want Io, Saturn's rings, Triton, Pluto, whatever, but try to mess with Europa and we'll fuck your shit up."