Cometary Science Newsletter

August 2019
Michael S. P. Kelley (

Conference Announcements

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

Rosetta SWT workshop

Registration and abstract submission is now open for the last Rosetta SWT and associated workshop. Details can be found here . The meeting will run from 23-27 September, at the ESA ESTEC site in the Netherlands.

Refereed Articles

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

The natural history of ‘Oumuamua

  • The ‘Oumuamua ISSI Team:
  • Bannister, M.T. 1
  • Bhandare, A. 2
  • Dybczyński, P.A. 3
  • Fitzsimmons, A. 1
  • Guilbert-Lepoutre, A. 4,5
  • Jedicke, R. 6
  • Knight, M.M. 7
  • Meech, K.J. 6
  • McNeill, A. 8
  • Pfalzner, S. 9,10,11
  • Raymond, S.R. 12
  • Snodgrass, C. 13
  • Trilling, D.E. 8
  • Ye, Q. 14,15
  1. Queen's University Belfast, UK
  2. Max-Planck-Institut für Astronomie, Germany
  3. A. Mickiewicz University, Poland
  4. Université de Bourgogne-Franche Comté, France
  5. Université de Lyon/Université Claude Bernard Lyon, France
  6. University of Hawaii, USA
  7. University of Maryland, USA
  8. Northern Arizona University, USA
  9. Max-Planck-Institut für Radioastronomie, Germany
  10. Jülich Supercomputing Center, Germany
  11. University of Cologne, Germany
  12. Université de Bordeaux, France
  13. University of Edinburgh, UK
  14. California Institute of Technology, USA
  15. Infrared Processing and Analysis Center, USA

The discovery of the first interstellar object passing through the Solar System, 1I/2017 U1 (‘Oumuamua), provoked intense and continuing interest from the scientific community and the general public. The faintness of ‘Oumuamua, together with the limited time window within which observations were possible, constrained the information available on its dynamics and physical state. Here we review our knowledge and find that in all cases, the observations are consistent with a purely natural origin for ‘Oumuamua. We discuss how the observed characteristics of ‘Oumuamua are explained by our extensive knowledge of natural minor bodies in our Solar System and our current knowledge of the evolution of planetary systems. We highlight several areas requiring further investigation.

Nature Astronomy (Published)

DOI: 10.1038/s41550-019-0816-x NASA ADS: 2019NatAs...3..594O arXiv: 1907.01910

The Peculiar Volatile Composition of CO-Dominated Comet C/2016 R2 (PanSTARRS)

  • McKay, A.J.1,2
  • DiSanti, M.A.1
  • Kelley, M.S.P.3
  • Knight, M.M.3
  • Womack, M.4
  • Wierzchos, K.5
  • Harrington-Pinto, O.5
  • Bonev, B.2
  • Villanueva, G.1
  • Dello Russo, N.6
  • Cochran, A.L.7
  • Biver, N.8
  • Bauer, J.3
  • Vervack, R.J.6
  • Gibb, E.9
  • Roth, N.9
  • Kawakita, H.10
  2. American University
  3. University of Maryland
  4. Florida Space Institute
  5. University of South Florida
  6. Johns Hopkins APL
  7. University of Texas at Austin/McDonald Observatory
  8. LESIA, Observatoire de Paris
  9. University of Missouri St. Louis
  10. Kyoto Sangyo University

Comet C/2016 R2 (PanSTARRS) has a peculiar volatile composition, with CO being the dominant volatile as opposed to H2O and one of the largest N2/CO ratios ever observed in a comet. Using observations obtained with the Spitzer Space Telescope, NASA's Infrared Telescope Facility, the 3.5-meter ARC telescope at Apache Point Observatory, the Discovery Channel Telescope at Lowell Observatory, and the Arizona Radio Observatory 10-m Submillimeter Telescope we quantified the abundances of 12 different species in the coma of R2 PanSTARRS: CO, CO2, H2O, CH4, C2H6, HCN, CH3OH, H2CO, OCS, C2H2, NH3, and N2. We confirm the high abundances of CO and N2 and heavy depletions of H2O, HCN, CH3OH, and H2CO compared to CO reported by previous studies. We provide the first measurements (or most sensitive measurements/constraints) on H2O, CO2, CH4, C2H6, OCS, C2H2, and NH3, all of which are depleted relative to CO by at least one to two orders of magnitude compared to values commonly observed in comets. The observed species also show strong enhancements relative to H2O, and even when compared to other species like CH4 or CH3OH most species show deviations from typical comets by at least a factor of two to three. The only mixing ratios found to be close to typical are CH3OH/CO2 and CH3OH/CH4. The CO2/CO ratio is within a factor of two of those observed for C/1995 O1 (Hale-Bopp) and C/2006 W3 (Christensen) at similar heliocentric distance, though it is at least an order of magnitude lower than many other comets observed with AKARI. While R2 PanSTARRS was located at a heliocentric distance of 2.8 AU at the time of our observations in January/February 2018, we argue, using sublimation models and comparison to other comets observed at similar heliocentric distance, that this alone cannot account for the peculiar observed composition of this comet and therefore must reflect its intrinsic composition. We discuss possible implications for this clear outlier in compositional studies of comets obtained to date, and encourage future dynamical and chemical modeling in order to better understand what the composition of R2 PanSTARRS tells us about the early Solar System.

Astronomical Journal (In press)

NASA ADS:  2019arXiv190707208M arXiv: 1907.07208

sbpy: A Python module for small-body planetary astronomy

  • Michael Mommert 1
  • Michael S. P. Kelley 2
  • Miguel de Val-Borro 3
  • Jian-Yang Li 3
  • Giannina Guzman 4
  • Brigitta Sipöcz 5
  • Josef Ďurech 6
  • Mikael Granvik 7
  • Will Grundy 1
  • Nick Moskovitz 1
  • Antti Penttilä 7
  • Nalin Samarasinha 3
  1. Lowell Observatory, US
  2. University of Maryland, US
  3. Planetary Science Institute, US
  4. Villanova University, US
  5. DIRAC Institute, Department of Astronomy, University of Washington, US
  6. Charles University, Prague, Czech Republic
  7. University of Helsinki, Finland

Planetary astronomy - the study of Solar System objects with telescopic observations from the ground or from space - utilizes a wide range of methods that are common in observational astronomy. However, some aspects, including the planning of observations, as well as the analysis and interpretation of the results, require tailored techniques and models that are unique and disparate from those used in most other fields of astronomy. Currently, there is no single open source software package available to support small-body planetary astronomers in their study of asteroids and comets in the same way in which Astropy supports the general astronomy community. sbpy is a community effort to build a Python package for small-body planetary astronomy in the form of an Astropy affiliated package. The goal is to collect and implement well-tested and well-documented code for the scientific study of asteroids and comets.

Journal of Open Source Software (Published)

DOI: 10.21105/joss.01426