Cometary Science Newsletter

February 2021
Michael S. P. Kelley (

Postdoctoral Research Associate in Planetary Sciences - University of Maryland

The Small Bodies Group in the Department of Astronomy at the University of Maryland, College Park invites applications for up to two Postdoctoral Research Associate positions to work with Tony Farnham and Jessica Sunshine on studies involving the composition and evolution of small bodies in the Solar System. Specific topics of interest include:

  • Sublimation processes and modeling to investigate the evolution of cometary surfaces.
  • Modeling and/or simulation of granular flows in microgravity environments.
  • Mapping the distribution of organics on Ceres.

For more information:

A'Hearn Symposium papers

Papers published in response to "New Cometary Insights from the Close Approach of 46P/Wirtanen: A Symposium in Celebration of Mike A'Hearn" have begun to appear in the Focus Issue of the Planetary Sciences Journal. Currently, the following papers are available:

  • Michael F. A'Hearn (Tony L. Farnham et al.)
  • What Does It Mean to be a "Depleted" Comet? High Spectral Resolution Observations of the Prototypical Depleted Comet 21P/Giacobini–Zinner from the McDonald Observatory (Anita L. Cochran et al.)
  • Comet 41P/Tuttle–Giacobini–Kresak, 45P/Honda–Mrkos–Pajdusakova, and 46P/Wirtanen: Water Production Activity over 21 yr with SOHO/SWAN (M. R. Combi et al.)
  • Volatile-rich Asteroids in the Inner Solar System (Joseph A. Nuth III et al.)
  • Intensity Distribution in the Heads of Comets (L. Haser et al.)
  • Seeing the Bigger Picture: Rosetta Mission Amateur Observing Campaign and Lessons for the Future (Helen Usher et al.)
  • Narrowband Observations of Comet 46P/Wirtanen during Its Exceptional Apparition of 2018/19. I. Apparent Rotation Period and Outbursts (Tony L. Farnham et al.)
  • FUV Observations of the Inner Coma of 46P/Wirtanen (John W. Noonan et al.)

... with another 20 manuscripts working their way through the review process.

These papers are open access and can be obtained from

Postdoctoral Researcher in Solar System Science

Objectives of this Role: Analysis of ground- and space-based data of Pluto to quantify the spatial distribution and long-term evolution of Pluto's ices; the main goal is to further understand the mechanisms of interaction between Pluto's surface and its atmosphere. Be involved in the development of an optical constants database for quantitative spectral analysis of small bodies in the Solar System; this will be achieved through the synergy between laboratory measurements and computational analysis.

Daily and Monthly Responsibilities: Radiative transfer model of Pluto's spectroscopic measurements acquired from ground (e.g., IRTF) and space (New Horizons). Laboratory measurements of small bodies analog materials and software development to compute optical constants. Meet weekly with the project team/lead to discuss progress and develop project pathways. Assist with scientific publications, presentations at scientific meetings, PDS archiving, proposal writing to secure observing time and/or funding.

Requirements: Requires a PhD with a 3.00 GPA in Physics, Astronomy, or related disciplines. 0-1 years: skills in spectroscopic studies, laboratory measurements, and experience in Python and/or IDL. A valid/clear driver's license is required. This is a 2 year limited term assignment with possible extension. Work assignment is in Boulder, Colorado.

Attention To: Must Apply at


- Southwest Research Institute in Boulder, Colorado

Summary of Comet Narrowband Filter Discussion

A round-table discussion of comet narrowband filters was held in mid-January. Approximately 35 people attended during a lively 2.5 hour discussion. The highlights are summarized below. Anyone who would like more detailed notes or to be notified of future discussions should contact Matthew Knight (

  1. There is strong interest in new filters to be built for use on larger telescopes, public facilities, and in the southern hemisphere. A few people have funding to buy their own filters, and there is broad community interest in having filters for additional facilities should funding be available. Many people are only looking for a subset of filters (most commonly CN, continuum, possibly OH) while others would like full HB sets.
  2. Advancements in filter technology make it unlikely to exactly replicate the HB filters. Filters which can match the locations of the sharp edges of the HB filter bandpasses could probably utilize the existing HB calibrations in Farnham et al. (2000), but small differences will propagate and result in larger uncertainties. Less-well matched filters can probably only safely be used for morphological assessment.
  3. It is strongly desirable for the entire community to use the same filter specifications and reduction methods. Otherwise it becomes impossible to compare datasets.
  4. Designing and calibrating new filters would require a substantial effort. It is possible to develop a pipeline that could create custom calibrations from existing astronomical spectra and filter bandpasses, but there was disagreement amongst discussion participants about how reliable this would be.
  5. The cost of specially designed professional filters is likely not significantly higher than available off-the-shelf narrowband filters, especially if a modest bulk order (~10 filters) can be made. Long term reliability of astronomical filter manufacturers is probably better. Several people have experience with custom filter manufacturers.

Refereed Articles

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

Organic Matter in Cometary Environments

  • McKay, Adam J. 1
  • Roth, Nathan X. 2
  1. American University/NASA Goddard Space Flight Center
  2. Universities Space Research Association/NASA Goddard Space Flight Center

Comets contain primitive material leftover from the formation of the Solar System, making studies of their composition important for understanding the formation of volatile material in the early Solar System. This includes organic molecules, which, for the purpose of this review, we define as compounds with C–H and/or C–C bonds. In this review, we discuss the history and recent breakthroughs of the study of organic matter in comets, from simple organic molecules and photodissociation fragments to large macromolecular structures. We summarize results both from Earth-based studies as well as spacecraft missions to comets, highlighted by the Rosetta mission, which orbited comet 67P/Churyumov–Gerasimenko for two years, providing unprecedented insights into the nature of comets. We conclude with future prospects for the study of organic matter in comets.

Life (Published)

DOI: 10.3390/life11010037