The White Sky, however, was going to put many more rocks into their path. Big ones could be detected from a distance and avoided, but little ones could do a lot of damage, and so the most important parts of Izzy needed to take shelter in the lee of Amalthea, crowding up against her aft surface. Some rocks might still come in from unexpected directions, but in general there would be a "prevailing wind" in the drift of lunar debris. Amalthea was aimed into it.