How to make sense of Enceladus? The moon's famous jets of water vapor, mixing with organic compounds, salts and silica, first revealed the possibility of an ocean beneath the icy surface, and the Cassini orbiter has treated Enceladus as a high priority target ever since. But why the asymmetry here? After all, while the south polar region includes the active 'tiger stripe' fractures associated with the plumes in a geologically young area, the northern pole shows much more cratering, evidence for a considerably older surface and, obviously, no plumes at all. Perhaps, say astronomers from NASA, the University of Texas and Cornell, we're dealing with an ancient impact, one that completely re-oriented Enceladus by tipping it about 55 degrees away from its original axis. Thus we get fractures well over 100 kilometers long in the south, evidence for an asteroid strike in what would have once been an area close to the moon's equator. Radwan Tajeddine (Cornell University) is a Cassini imaging...