Systematic Characterization and Monitoring of Potentially Active Asteroids: The Case of Don Quixote

Over the previous decades, activity has been observed in about 20 Solar System small bodies that were until then known as asteroids. Activation mechanisms have been proposed for these objects, including the sublimation of volatiles, rotational instability, and recent impacts; all these mechanisms provide strong constraints on the physical properties and evolution of these objects. The identification of more active asteroids will improve our understanding of the processes triggering activity as well the nature of asteroids in general. We present first results from our "Systematic Characterization and Monitoring of Potentially Active Asteroids" program, which obtains BVRI colors and performs V-band photometric monitoring of a sample of 103 dormant comet candidates and 10 near-Sun asteroids. The goal of this program is to find activity in and provide a spectrophotometric taxonomic classification for our targets in order to place limits on the volatile contents of these potentially active populations and improve our understanding of their evolution. We present the case of near-Earth asteroid (3552) Don Quixote in which we discovered activity in multiple wavelength regimes. In October 2017 we observed activity using Spitzer Space Telescope observations that agrees with findings by Mommert et al. (2014, ApJ 781), suggesting continuous activity from the sublimation of CO or CO2. While close in time optical observations did not reveal any dust activity, observations in March 2018 revealed for the first time episodic dust activity in this object (Mommert et al., 2018, CBET 4502). Follow-up observations in June 2018 with the 30m IRAM sub-millimeter telescope show a lack of emission from the CO(2-1) line and hence suggest that activity in this object is most likely triggered by the sublimation of CO2. Our observations suggest that Don Quixote is most likely a weakly active CO2-rich comet. The finding of faint activity in Don Quixote underscores the necessity of a systematic monitoring campaign to find activity. This program is based upon work supported by NASA under Grant No. NNX17AG88G.