Program: GN-2013A-Q-102

Main-belt comets (MBCs) exhibit cometary activity yet are dynamically indistinguishable from main-belt asteroids and likely formed in situ. Studies of these apparently icy inner-solar-system objects have significant implications for understanding the distribution of volatiles in our solar system as well as the origin of Earth’s water. We propose to use Gemini to obtain sparsely-sampled observations of 6 MBCs to determine their phase functions or characterize their activity profiles. This program will substantially increase the fraction of MBCs with well-determined phase functions, and also provide valuable information about the active behavior and nature of MBCs 133P and 259P. Characterization of MBC nuclei via phase functions will improve our characterization of the MBC population as a whole, giving insights into its origin and nature, while activity monitoring observations in 2013A will permit direct comparison of activity levels from different orbit passages for 133P, and definitively confirm the cometary nature of 259P.