A typical science course at the high school level includes some information on planets and their moons. For example, it is well-known that Jupiter has 16 moons and Saturn has 18 moons. Add to this the enthusiasm of the public in the collision of comet Shoemaker-Levy 9 with Jupiter in July 1994. This immediately raises the possibility of a collision of a comet with a moon of Jupiter. Due to this possibility a strange fact about these moons comes into the picture, that is some of them are prograde in nature and some are retrograde. Can these two types of moons pose any problems in teaching ? The present situation in education leads us to believe that they can pose some problems. It is described below, in support of this answer.