An Infrared Study of Comet Mineralogy and Temporal Activity

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AST 0307466WoodwardOne of the greatest challenges in modern astrophysics is to understand the conditions in protoplanetary disks during the epoch of planetesimal formation and the aggregation of planets. Comet nuclei are the frozen reservoirs of dust and ices from the early solar nebula. During a perihelion passage, solar irradiation enhances the production rate of volatile gases and creates a coma which enshrouds the nucleus. Entrained within the coma gases are dust grains lifted from the nucleus by the escaping gas. The dust grains may be released both from the nuclear surface and from deeper layers of the nucleus via jets. Surface dust grains may posses different properties from those particles dredged up from the interior of the comet due to the long term exposure of surface material to particle bombardment, irradiation, and to collisional evolution of the parent body. The primary research objective for this project lead by Dr. Charles Woodward, University of Minnesota, is to determine the grain properties of the early solar nebula by exploring the differences in grain properties between a) long period comets formed near Jupiter (and subsequently scattered into the Oort cloud by Jupiter), and b) short period comets formed at greater heliocentric distances (in the Kuiper Belt). In this project, appropriately bright comets will be observed at multiple epochs to ascertain whether the silicate mineralogy, relative mineral abundance, and particle size distribution of the ablated dust varies as a function of heliocentric distance. Special attention will be given to comets targeted for encounter with spacecraft. Comets selected for study include 2P/Encke, 9P/Tempel 1, 81P/Wild 2, as well as newly discovered comet C/2001 Q4 NEAT. The broad scientific objective is to advance the understanding of general comet properties and the evolution of small icy bodies in our solar system. Astronomy, in part because of its stunning imagery, provides a natural gateway for engagingthe public in scientific discussions and debates. Results of this cometary research program will be disseminated to the general public through a number of education and public outreach (EPO) activities. In addition, the research program creates an environment for student mentoring activities in experimental techniques and observational astrophysics. This participation often contributes to senior theses and helps to impart to aspiring astronomers (and/or students with scientific/technicalcareer objectives) observational and technical expertise, computer programming skills, andanalysis methodology. Ph.D. dissertations should result from data analysis and modeling activities associated with this program.***