Dust Mineralogy, Volatiles, and Taxonomy of Comets

AST 0706980

Woodward

Determination of organic and inorganic materials in cometary dust provides insight into the protosolar system environment and reveals clues to the process of planetary systems origins. Dust grains are reservoirs for condensable elements during their transport from the circumstellar winds of evolved stars, novae, and supernovae into ISM clouds that give rise to new stellar and planetary systems. Of all solar nebula bodies, comets contain the least processed materials, both ices and dust. The chemical composition and evolution of comet material can be studied during perihelion passage when solar irradiation enhances the production rate of volatile gases leading to the release of dust from the nucleus and the exposure of refractory material to ultraviolet (UV) flux. This research program is a comprehensive, systematic investigation of two distinct dynamical populations, Jupiter-family (JF) and Oort Cloud (OC) comets. This study of comet dust properties and physical characteristics will: (1) facilitate assessment of the importance of crystalline silicates as a diagnostic of solar nebula evolution and turbulent mixing models; and (2) explore whether comet dust mineralogy is correlated with observed organic volatile production rates.

Understanding how planetary formation occurs in protoplanetary disks is a scientific challenge for the astrophysical community. This initiative contributes to broad cross-disciplinary areas of inquiry. First, the determination and inter-comparison of grain properties in OC and JF comets enable study of the processes that determine the characteristics of bodies in the Solar System and the operation and interaction of these processes. Secondly, comets provide insight into the initial processes of planetesimal aggregation and planet building in the early solar nebula. Specifically, the thermal history of dust grains extant in the early solar nebula can be probed by constraining the properties of dust from comets. Lastly, this program will test the new hypothesis, arising out of comparison of the investigators' observations of the Deep Impact target 9P and the split comet 73P with recent studies of comet gas-phase organics, that comet taxonomy based on current orbital (dynamical) classification should be supplanted by a taxonomy based on physical characteristics of dust mineralogy and grain properties and organic composition and super-volatile production rates.

This program creates an environment for educational mentoring activities in experimental techniques and observational astrophysics at large public institutions with diverse student populations and talent bases. Research opportunities provide an infrastructure to promote student development as scientists and critical thinkers while exposing individuals to how scientific discourse, intellectual exchange, and public outreach are conducted in a dynamic environment of contemporary astrophysics. The investigators' students will utilize a variety of facilities to collect observational data, and participate directly with scientific analyses and dissemination. These activities contribute to workforce development and imparts to aspiring astronomers (and/or students with scientific/technical career objectives) observational and technical expertise, computer programming skills, and analysis methodology. Astronomy, in part because of its stunning imagery, provides a natural gateway for engaging the public in scientific discussions, and helps to foster a broad appreciation for the impact of science and technology. The researchers will disseminate research highlights to the public through a number of education and public outreach activities and venues.

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