  Planetary satellites are an integral part of the heirarchy of planetary
systems. Here we make two predictions concerning their formation. First,
primordial satellites, which have an array of distinguishing characteristics,
form only around giant planets. If true, the size and duration of a planetary
system's protostellar nebula, as well as the location of its snow line, can be
constrained by knowing which of its planets possess primordial satellites and
which do not. Second, all satellites around terrestrial planets form by
impacts. If true, this greatly enhances the constraints that can be placed on
the history of terrestrial planets by their satellites' compositions, sizes,
and dynamics.
