Planetary Astronomy Late-morning Seminar for 2018-05-07

Series: Planetary Astronomy Late-morning Seminar
Date: Monday 07-May-2018
Time: 11:15-12:15
Location: ATL 1250
Speaker: Adam McKay (GSFC)
Title: The Peculiar Volatile Composition of CO-Dominated Comet C/2016 R2 (PanSTARRS)

Comets contain primitive volatile material that is reflective of the physics and chemistry operating in the protosolar disk during planet formation. The volatile content of comets is typically dominated by H2O, followed by CO2 and CO, and then trace amounts of species such as CH4, NH3, CH3OH, C2H6, H2CO, and HCN. However, this is not always applicable, especially for CO, for which abundances compared to H2O vary by several orders of magnitude. N2, while difficult to detect remotely, has been found to be heavily depleted in comets, with NH3 being the dominant volatile reservoir for nitrogen. In December 2017 we obtained optical spectra of comet C/2016 R2 (PanSTARRS) that were extremely atypical for comets observed at optical wavelengths. Usually dominated by neutral species such as CN and C2, the optical spectrum of C/2016 R2 was devoid of these features and was instead dominated by ionic emissions from CO+ and N2+, with the N2+ detection being the most secure detection of N2+ in a comet obtained in the age of digital detectors (Cochran and McKay 2018). Additional sub-mm observations showed strong CO emission (Wierzchos and Womack 2017, 2018, de Val Borro et al. 2018, N. Biver in prep.), confirming the hypervolatile-rich nature of this comet suggested by the optical spectra. We present additional observations of C/2016 R2 obtained with the IRAC instrument on the Spitzer Space Telescope, iSHELL on the NASA IRTF, ARCES at Apache Point Observatory, the Tull Coude Spectrograph at McDonald Observatory, and Arizona Radio Observatory 10-m Submillimeter Telescope during January-February 2018 aimed at characterizing the volatile composition of this unusual comet. We will discuss our measured abundances of key species and discuss implications for the chemistry in the early Solar System.

For further information contact PALS coordinator Dr. Matthew Knight at or (301)-405-2629.


Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.


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