UCLA

In this thesis, I investigate the nature of two small body populations; the irregular satellite populations of the giant planets and the properties of fragmented nuclei of comets. In both cases the objective is to understand evolutionary processes acting on primitive solar system objects. An optical color survey of 43 irregular satellites enabled color comparisons with other small body populations that may reflect upon the origin of the irregular satellites. Ultrared matter (color index B-R ≥ 1.6), while abundant in the excited Kuiper belt and Centaur populations, is depleted from the irregular satellites. Also, the color distributions of the irregular satellites at each giant planet are statistically similar to each other, consistent with a common source region and/or evolutionary mechanism. Separately, the current observed supply of comets allows for estimates on the masses of their outer solar system source regions, however, comet fragmentation may occur more often than previously thought, which will lead to shorter estimates of comet lifetimes than predicted. As a case study, I analyzed archival Hubble Space telescope images of comet 73P/Schwassmann-Wachmann 3 (73P). The measured rotation period of the nucleus is much longer than the critical period for rotational instability for any reasonable nucleus density and shape, even in the absence of tensile strength. The data also show hundreds of fragments within 73P-B and 73P-G on which photometry was used to measure the brightness distribution of the fragments. I also measure the motion of these fragments and find the relative speeds of the fragments within 73P-B are a few m/s, implying an impulsive breakup about 7 days prior to the observations. Both the irregular satellites and comets are small bodies comprised of primitive material. The origin and evolution of the small bodies describe the early formation and evolution of the solar system itself.