Cometary Science Newsletter

January 2019
Michael S. P. Kelley (

Conference Announcements

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

Centaur Exploration Workshop: The Roots of Activity

March 6-8, 2019, Florida Space Institute, University of Central Florida, Orlando, FL.

A workshop addressing the scientific importance and space exploration relevance of active centaurs, with a specific focus on mapping knowledge gaps and paths forward.


  • Workshop URL:
  • Registration and Abstract Submission Deadline: January 7, 2019.
  • In-situ participation will be capped – Consider registering early and submitting an abstract.
  • Online participation will be available – Will require registration and notice of acceptance.

The workshop’s impetus is two-fold: Advance our understanding of how small bodies originate, evolve and become active beyond Jupiter’s orbit; Planning of exploration strategies – Both Earth-based observations and Space-based measurements – aimed at representative objects of the Centaur population. We will include forward-looking presentations and free discussions to allow for streaming of ideas and encourage inclusive participation.

We strongly encourage the participation of early career researchers (including graduate students and postdoctoral researchers). We aim for the workshop to result in a white paper and a plan for a multi-wavelength observing campaign.

Questions? Please contact the organizers:
Gal Sarid (
Maria Womack (

ABSCICON 2019 Session: Have Comet, Will Travel!

We are pleased to announce that AbSciCon 2019 (June 24-28, 2019, Bellevue, WA) will feature a session focused on the role small bodies play in promoting habitability.


  • Topic Area: Star-planet-planetary system interactions and habitability
  • Session Title: Have Comet, Will Travel – How small bodies promote habitable conditions across the solar system?
  • Session ID: 66054
  • Abstract submission deadline: Wednesday, January 23, 2019 23:59 EST.

Small bodies in the solar system (and other planetary systems) may play a significant role in the promotion, proliferation, dissemination and the cessation of life and its related building blocks.

This session will combine recent insights from experimental, observational and theoretical studies of ice and organic-rich environments of comets and carbonaceous asteroids. We invite contributions aimed at revealing how the physics and chemistry of small bodies help catalyze and distribute life’s building blocks, across the planetary system, from early to late stages of planetary formation. We focus on how small bodies:

  1. Serve as reservoirs or catalytic surfaces that promote the production of more complex prebiotically relevant chemistries.
  2. Dynamically distribute prebiotic material across different regions of the proto-planetary disk.
  3. Alter the volatile and isotopic inventories of planetary atmospheres and surfaces.
  4. Enable local variations of habitable niches on planetary surfaces (e.g., Earth, Mars, Icy Moons).

For more details and abstract submission go to:

Gal Sarid & Chris Bennett
University of Central Florida, FSI & Physics

Refereed Articles

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

Monitoring of the activity and composition of comets 41P/Tuttle–Giacobini–Kresak and 45P/Honda–Mrkos–Pajdusakova

  • Y. Moulane 1,2
  • E. Jehin 1
  • C. Opitom 3
  • F. J. Pozuelos 1
  • J. Manfroid 1
  • Z. Benkhaldoun 2
  • A. Daassou 2
  • M. Gillon 1
  1. Space Sciences, Technologies and Astrophysics Research (STAR) Institute, University of Liège, Liège, Belgium
  2. Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco
  3. European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile

We report on photometry and imaging of the Jupiter family comets 41P/Tuttle–Giacobini–Kresak and 45P/Honda–Mrkos–Pajdusakova with the TRAPPIST-North (TRAnsiting Planets and PlanetesImals Small Telescope) telescope. We observed 41P on 34 nights from February 16 to July 27, 2017, pre- and post-perihelion (rh = 1.04 au), and collected data for comet 45P after perihelion (rh = 0.53 au) from February 10 to March 30, 2017. We computed the production rates of the daughter species OH, NH, CN, C3 and C2 and we measured the dust proxy, Afρ, for both comets. The peak of water-production rate of 41P was (3.46 ± 0.20) × 1027 molecules s−1 on April 3, 2017, when the comet was at 1.05 au from the Sun. We have shown that the activity of 41P is decreasing by about 30–40% from one apparition to the next. We measured a mean water-production rate for 45P of (1.43 ± 0.62) × 1027 molecules s−1 during a month after perihelion. Our results show that these Jupiter family comets had low gas and dust activity and no outburst was detected. Relative abundances, expressed as ratios of production rates and the Afρ parameter with respect to OH and to CN, were compared to those measured in other comets. We found that 41P and 45P have a typical composition in terms of carbon-bearing species. The study of coma features exhibited by the CN gas species allowed the measurement of the rotation period of 41P, showing a surprisingly large increase of the rotation period from (30 ± 5) h at the end of March to (50 ± 10) h at the end of April, 2017, in agreement with recent observations by other teams.

Astronomy and Astrophysics (Published)

DOI: 10.1051/0004-6361/201833582

Reactive collision of electrons with CO+ in cometary coma

  • Y. Moulane 1,2,3
  • J. Zs. Mezei 3,4,5,6
  • V. Laporta 3,7
  • E. Jehin 2
  • Z. Benkhaldoun 1
  • I. F. Schneider 3,6
  1. Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco
  2. Space sciences, Technologies & Astrophysics Research (STAR) Institute, University of Liège, Liège, Belgium
  3. Laboratoire Ondes et Milieux Complexes, CNRS-UMR-6294, Université du Havre, Le Havre, France
  4. Laboratoire des Sciences des Procédés et des Matériaux, CNRS-UPR-3407, Université Paris 13, Paris, France
  5. Institute for Nuclear Research, Hungarian Academy of Sciences, Debrecen, Hungary
  6. Laboratoire Aimé Cotton, CNRS-UMR-9188, Université Paris Sud, ENS Cachen et Université Paris Saclay, Paris, France
  7. Department of Physics and Astronomy, University College London, London WC1E 6BT, UK

Context. In order to improve our understanding of the kinetics of the cometary coma, theoretical studies of the major reactive collisions in these environments are needed. Deep in the collisional coma, inelastic collisions between thermal electrons and molecular ions result in recombination and vibrational excitation, the rates of these processes being particularly elevated due to the high charged particle densities in the inner region.

Aims. This work addresses the dissociative recombination, vibrational excitation, and vibrational de-excitation of electrons with CO+ molecular cations. The aim of this study is to understand the importance of these reactive collisions in producing carbon and oxygen atoms in cometary activity.

Methods. The cross-section calculations were based on multichannel quantum defect theory. The molecular data sets, used here to take into account the nuclear dynamics, were based on ab initio R-matrix approach.

Results. The cross-sections for the dissociative recombination, vibrational excitation, and vibrational de-excitation processes, for the six lowest vibrational levels of CO+ – relevant for the electronic temperatures observed in comets – are computed, as well as their corresponding Maxwell rate coefficients. Moreover, final state distributions for different dissociation pathways are presented.

Conclusions. Among all reactive collisions taking place between low-energy electrons and CO+, the dissociative recombination is the most important process at electronic temperatures characterizing the comets. We have shown that this process can be a major source of O(3P), O(1D), O(1S), C(3P) and C(1D) produced in the cometary coma at small cometocentric distances.

Astronomy and Astrophysics (Published)

DOI: 10.1051/0004-6361/201832912

Active Asteroid P/2017 S5 (ATLAS)

  • Jewitt, D. 1
  • Kim, Y. 2
  • Rajagopal, J. 3
  • Ridgway, S. 3
  • Kotulla, R. 4
  • Liu, W. 3
  • Mutchler, M. 5
  • Li, J. 1
  • Weaver, H. 6
  1. UCLA
  2. Max Planck Institute for Solar System
  3. NOAO
  4. University Wisconsin-Madison
  5. STSCI
  6. Johns Hopkins Applied Physics Laboratory

Observations of active asteroid P/2017 S5 when near perihelion reveal the ejection of large (0.1 to 10 mm) particles at 0.2 to 2 m/s speeds, with estimated mass-loss rates of a few kg/s. The protracted nature of the mass loss (continuous over 150 days) is compatible with a sublimation origin, meaning that this object is likely an ice-bearing main-belt comet. Equilibrium sublimation of exposed water ice covering as little as 0.1 sq. km can match the data. Observations a year after perihelion show the object in an inactive state from which we deduce a nucleus effective radius 450+100/-60 m (albedo 0.06+/-0.02 assumed). The gravitational escape speed from a body of this size is just 0.3 m /s, comparable to the inferred ejection speed of the dust. Time-series photometry provides tentative evidence for rapid rotation (lightcurve period 1.4 hour) that may also play a role in the loss of mass and which, if real, is a likely consequence of spin-up by sublimation torques. P/2017 S5 shares both physical and orbital similarities with the split active asteroid pair P/2016 J1-A and J1-B, and all three objects are likely members of the 7 Myr old, collisionally produced, Theobalda family.

The Astronomical Journal (In press)

NASA ADS: 2018arXiv181200060J arXiv: 1812.00060