Implications Regarding the Energetics Of the Collisional Formation of Kuiper Belt Satellites

Recently it has been discovered that more than 1% of Kuiper belt objects (KBOs) are accompanied by large satellites. Here I examine the energetics of KBO satellite formation via collisions, finding that collisions require a dynamically excited Kuiper belt. Furthermore, even under energetically optimistic formation assumptions, it is found that collisional processes cannot make a large enough number of KBOs with satellites (by a factor of order 40), unless something in the standard assumptions about the Kuiper belt and/or the KBOs themselves is seriously in error. Two possible solutions to this quandary are either that KBO projectiles large enough to generate the observed satellites were ∼40 times more numerous in the ancient past than any previous model has indicated or that the fraction of impact energy estimated to be imparted to ejecta is a factor of 5 to 10 times higher (i.e., of order unity) than experimental collision results have indicated plausible. Neither alternative is very palatable. Fortunately, an easier to accept alternative also exists: that KBO primary and/or KBO satellite surface albedos may be significantly underestimated by making the canonical assumption of 4% KBO surface albedos (an assumption for which little direct evidence exists in actual KBO observations). However, surface albedos of KBO primaries and/or their satellites of ∼15%, would reduce the required size of the impacting projectiles required to generate KBO satellites, which would in turn increase the available supply of sufficiently large KBO projectiles enough to plausibly generate the observed fraction of KBOs with large satellites. This proposition is expected to be testable by SIRTF and other means in the next 2 to 3 years.