Astronomy Colloquium

Comet nuclei coalesced from the refractories and ices present in the outer-planets region of the proto-solar system. The interiors of comets have remained at low temperatures in the Kuiper Belt or Oort Cloud that over the past 4.5 Gyr of solar system history. Thus, comets are time capsules -- records of the thermal, chemical, and dynamical environment of the protoplanetary disk. However, comets are not wholly pristine and before we can definitively link their dust and ice properties to the conditions of the early solar system, we must understand their ensemble histories. To that end, we compare the physical properties of comet nuclei to related planetesimals to probe the evolution of small bodies in the solar system. Jupiter-family comets are well-suited to the study of comet surfaces because their nuclei are more accessible than those of the long-period comets. We have an optical/mid-infrared survey of 100 Jupiter-family comets (nearly one-third of all known JFCs) designed to measure their sizes and albedos. We use our completed mid-infrared survey to derive a new and independent estimate of the current Jupiter-family comet size distribution. The optical component of the survey is in progress. The albedo and size distributions are important characteristics in comparisons of comets to their dynamically related bodies: Trojans, Centaurs, and transneptunian objects.