Collaborative Research: Pushing the Boundaries of Post-Rosetta Cometary Science with the New Generation of Near-Infrared Spectrographs

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Comets are thought to be primordial building blocks of the solar system. However, most comets have undergone some alteration since the solar system was formed. This team will study volatile molecules trapped in the cometary ice since their formation. By observing comets with varying degrees of exposure to the Sun, they can determine how much alteration each comet has undergone. They will compare new observations from ground-based telescopes with results from two recent space missions. They will mentor graduate students through every phase of the work. They will conduct not only teacher training in cometary science, but also leverage an adult education program through American University to provide life-long learning on comets and Solar System formation. The results of this work should give a fuller picture for the original composition of comets in our Solar System, and therefore of our origins.The team will collect high resolution infrared spectroscopic observations of Jupiter-family comets as well as Oort Cloud comets to determine the relative abundances of a series of volatile compounds that should exist in comets only as parent species, or species that accreted as ices during the comet’s original formation. Instruments to be used will include the NIRSPEC-2 spectrometer on the Keck Observatory and the iSHELL instrument on the IRTF, and the team will examine archived data as well. ‘Ground truth’ for the observations will be provided by making observations of comets 67P/ Churyumov–Gerasimenko, visited by the Rosetta mission, and 103P/Hartley 2, visited by the EPOXI mission. The overall objective of the work is to examine compositional differences in primordial ices between Jupiter-family comets, which have seen extensive alteration due to their repeated exposure to intense sunlight in the Inner Solar System, and Oort Cloud comets, which have never been exposed to intense sunlight, and therefore should be more indicative of the solar system’s original composition. The team will collect multiple observations of each target to minimize the effects of ‘snapshot bias,’ which can lead to inaccurate composition determinations because of a limited number of solar phase angles in the ensemble of observations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.