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Observational Characterization of Recurrently Active Main-Belt Comets and Near-Earth Main-Belt Comet Candidates

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Principle Investigator: Henry Hsieh, Planetary Science Institute

Program Summary:

We propose a multi-year optical observational campaign to characterize the activity and nuclei of a number of known main-belt comets (MBCs) and near-Earth MBC (NEMBC) candidates. MBCs are rare objects that are dynamically indistinguishable from main-belt asteroids, yet display cometary activity indicative of sublimating ice, while NEMBCs are Jupiter-family comets recently identified as potentially originating in the asteroid belt, and which therefore represent exciting potential opportunities to probe icy main-belt objects at close proximity. Our objectives are to monitor and analyze the activity of 10 MBCs expected to be active between 2019 and 2022 to constrain onset and termination times and monitor activity strength evolution, and conduct physical characterization observations of 11 inactive MBC nuclei and 6 inactive NEMBC candidate nuclei to determine phase functions and compositional properties. Results of our analyses will be used to study long-term activity attenuation in MBCs, improve our understanding of volatile preservation in asteroids and the likely total fraction of icy objects in the asteroid belt, and assess the likelihood that NEMBC candidates originated in the asteroid belt. This research is supported by a funded NASA Solar System Observations program (PI: H. Hsieh) for which Gemini observations constitute a central component.


  • Jana Chesley: Jet Propulsion Laboratory
  • Matthew Knight: University of Maryland
  • Scott Sheppard: Carnegie Institution for Science (Terrestrial Magn.)
  • Audrey Thirouin: Lowell Observatory
  • Chadwick Trujillo: Northern Arizona University
  • Masateru Ishiguro: Seoul National University
  • Nicholas Moskovitz: Lowell Observatory
  • Bin Yang: European Southern Observatory