Cometary Science Newsletter

August 2018
Michael S. P. Kelley (

Rosetta Special Issue in A&A

Dear colleagues,

Please note that following the Rosetta meeting in Rhodes, we have organised a special issue in Astronomy and Astrophysics to capture the current state of play of Rosetta science. The broader small body community is invited to submit their Rosetta related science to the special issue. When submitting, please indicate that you are submitting to the Rosetta special issue #2 or “Rosetta mission full comet phase results.”

Submission deadline is end of November 2018.

The target date for having all papers accepted will be beginning of March 2019, so the publications should be ready soon after that.

Best regards,
Matt Taylor, on behalf of the Rosetta Science Working Team

Conference Announcements

Announcements for cometary conferences or workshops. Limited to 2000 characters.

Symposium in Celebration of Mike A'Hearn

We will be holding a symposium at the University of Maryland in College Park on August 6-8, 2019 in celebration of the contributions that Mike A'Hearn made to cometary science.

In Mike's honor, this symposium will focus on results from observations of comet 46P/Wirtanen (and the other recent bright comets) to allow the compilation of individual studies into a comprehensive understanding of the comet.

We encourage cometary scientists of all types as well as anyone who knew and worked with Mike in any capacity to come and participate in this event and reflect on his legacy.

For additional details on the Wirtanen Observing Campaign and for future updates on the symposium, please visit the campaign website:

Tony Farnham
for the Wirtanen Campaign

Refereed Articles

Abstracts of articles in press or recently published. Limited to 3000 characters.

Further investigation of changes in cometary rotation

  • Mueller, B. E. A. 1
  • Samarasinha, N. H. 1
  1. Planetary Science Institute

Samarasinha & Mueller (2013) related changes of cometary rotation to other physical parameters for four Jupiter family comets defining a parameter X, which is approximately constant within a factor of two irrespective of the active fraction of a comet. Two additional comets are added to this sample in this paper and the claim of a nearly constant parameter X for these six comets is confirmed, albeit with a larger scatter. Taking the geometric mean of X for all the comets above excluding 2P/Encke (as X for each comet was determined with respect to that of 2P/Encke), the expected changes in the rotation periods for a sample of 24 periodic comets are derived. We identify comets from this sample that are most likely to show observationally detectable changes in their rotation periods. Using this sample and including the six comets used to determine X, we find a correlation between the parameter ζ (i.e. the total water production per unit surface area per orbit approximated by that inside of 4 au) and the perihelion distance q; specifically we derive ζ proportional to q-0.8 and provide a theoretical basis for this in Appendix A. This relationship between ζ and q enables ready comparisons of activity due to insolation between comets. Additionally, a relationship between the nuclear radius R and the rotation period P is found. Specifically, we find that on average smaller nuclei have smaller rotation periods compared to the rotation periods of larger nuclei. This is consistent with expectations for rotational evolution and spin-up of comet nuclei, providing strong observational evidence for sublimation-driven rotational changes in comets.

Astronomical Journal (In press)

arXiv: 1806.11158

Icy Grains from the Nucleus of Comet C/2013 US10 (Catalina)

  • Protopapa, S. 1,2
  • Kelley, M.S.P. 1
  • Yang, B. 3
  • Bauer, J.M. 1
  • Kolokolova, L. 1
  • Woodward, C.E. 4
  • Keane, J.V. 5
  • Sunshine, J.M. 1
  1. Department of Astronomy, University of Maryland, College Park, MD, USA
  2. Southwest Research Institute, Boulder, CO 80302, USA
  3. European Southern Observatory, Santiago, Chile
  4. Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455, USA
  5. Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA

We present IRTF/SpeX and NEOWISE observations of the dynamically new comet C/2013 US10 (Catalina), hereafter US10, from 5.8 au inbound, to near perihelion at 1.3 au, and back to 5.0 au outbound. We detect water ice in the coma of US10, assess and monitor the physical properties of the ice as insolation varies with heliocentric distance, and investigate the relationship between water ice and CO2. This set of measurements is unique in orbital coverage and can be used to infer the physical evolution of the ice, and, potentially, the nucleus composition. We report (1) nearly identical near-infrared spectroscopic measurements of the coma at -5.8 au, -5.0 au, +3.9 au (where <0 au indicates pre-perihelion epochs), all presenting evidence of water-ice grains, (2) a dust-dominated coma at 1.3 au and 2.3 au and, (3) an increasing CO2/Afρ ratio from -4.9 au to 1.8 au. We propose that sublimation of the hyper-volatile CO2 is responsible for dragging water-ice grains into the coma throughout the orbit. Once in the coma, the observability of the water-ice grains is controlled by the ice grain sublimation lifetime, which seems to require some small dust contaminant (i.e., non-pure ice grains). At |Rh|>=3.9 au, the ice grains are long-lived and may be unchanged since leaving the comet nucleus. We find the nucleus of comet US10 is made of, among other components, ~1 μm water-ice grains containing up to 1% refractory materials.

The Astrophysical Journal Letters (In press)

NASA ADS: 2018arXiv180708215P arXiv: 1807.08215

Solar system science with the Wide-Field InfraRed Survey Telescope (WFIRST)

  • Holler, B. J. 1
  • Milam, S. N. 2
  • Bauer, J. M. 3,4
  • Alcock, C. 5
  • Bannister, M. T. 6
  • Bjoraker, G. L. 2
  • Bodewits, D. 3
  • Bosh, A. S. 7
  • Buie, M. W. 8
  • Farnham, T. L. 3
  • Haghighipour, N. 9
  • Hardersen, P. S. 10
  • Harris, A. W. 11
  • Hirata, C. M. 12
  • Hsieh, H. H. 13,14
  • Kelley, M. S. P. 3
  • Knight, M. M. 3
  • Kramer, E. A. 4
  • Longobardo, A. 15
  • Nixon, C. A. 2
  • Palomba, E. 15
  • Protopapa, S. 3,8
  • Quick, L. C. 16
  • Ragozzine, D. 17
  • Reddy, V. 18
  • Rhodes, J. D. 4
  • Rivkin, A. S. 19
  • Sarid, G. 20
  • Sickafoose, A. A. 21,7
  • Simon, A. A. 2
  • Thomas, C. A. 13
  • Trilling, D. E. 22
  • West, R. A. 4
  1. Space Telescope Science Institute, Baltimore, MD, USA
  2. NASA Goddard Space Flight Center, Greenbelt, MD, USA
  3. Department of Astronomy, University of Maryland, College Park, USA
  4. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  5. Harvard-Smithsonian Center for Astrophysics, Cambridge, USA
  6. Astrophysics Research Centre, Queen’s University Belfast, Belfast, UK
  7. Department of Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, MA, USA
  8. Southwest Research Institute, Boulder, CO, USA
  9. Institute for Astronomy, University of Hawaii-Manoa, Honolulu, HI, USA
  10. University of North Dakota, Department of Space Studies, Grand Forks, ND, USA
  11. MoreData! Inc., La Cañada, CA, USA
  12. Center for Cosmology and Astro Particle Physics (CCAPP), The Ohio State University, Columbus, OH, USA
  13. Planetary Science Institute, Tucson, USA
  14. Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
  15. INAF Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy
  16. Smithsonian Institution, National Air and Space Museum, Center for Earth and Planetary Studies, Washington, DC, USA
  17. Department of Physics and Astronomy, Brigham Young University, Provo, UT, USA
  18. Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
  19. Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
  20. Florida Space Institute, University of Central Florida, Orlando, FL, USA
  21. South African Astronomical Observatory, Cape Town, South Africa
  22. Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ, USA

We present a community-led assessment of the solar system investigations achievable with NASA’s next-generation space telescope, the Wide Field InfraRed Survey Telescope (WFIRST). WFIRST will provide imaging, spectroscopic, and coronagraphic capabilities from 0.43-2.0 μm and will be a potential contemporary and eventual successor to JWST. Surveys of irregular satellites and minor bodies are where WFIRST will excel with its 0.28 deg2 field of view Wide Field Instrument (WFI). Potential ground-breaking discoveries from WFIRST could include detection of the first minor bodies orbiting in the Inner Oort Cloud, identification of additional Earth Trojan asteroids, and the discovery and characterization of asteroid binary systems similar to Ida/Dactyl. Additional investigations into asteroids, giant planet satellites, Trojan asteroids, Centaurs, Kuiper Belt Objects, and comets are presented. Previous use of astrophysics assets for solar system science and synergies between WFIRST, LSST, JWST, and the proposed NEOCam mission are discussed. We also present the case for implementation of moving target tracking, a feature that will benefit from the heritage of JWST and enable a broader range of solar system observations.

Journal of Astronomical Telescopes, Instrumentation, and Systems (In press)

arXiv: 1709.02763