Cometary Science Newsletter

December 2015
Michael S. P. Kelley (

Conference Announcements

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

Workshop on ground-based observations of 67P/Churyumov-Gerasimenko

There will be a workshop on ground-based observations of 67P, and linking these observations with Rosetta results, at Schloss Seggau, near Graz, Austria, between the 20th and 22nd of June 2016. This meeting is sponsored by the EU Europlanet research infrastructure network, and limited funding is available to support participation by European researchers. Deadline for expressions of interest (and requesting travel funds) is December 15th, with a final registration and hotel booking deadline on January 31st.

See for more details and the registration form.

"From Giotto to Rosetta" 50th ESLAB Symposium

As part of the ESLAB series of symposia, ESA will host a comet science conference in Leiden, the Netherlands, 14-18 March 2016.

More details are available here:

Note the abstract deadline will be extended to 15 December 2015.

Cometary science after Rosetta

Results from the European Space Agency’s Rosetta mission to Comet 67P/Churyumov-Gerasimenko are leading to a revolution in our understanding of these ancient bodies, and hence the conditions prevalent in the early Solar System. This meeting will report on all aspects of the mission's ground-breaking discoveries, placing them in the context of cometary science as a whole. Invited speakers have been confirmed, however, there is the opportunity for a number of participants to present posters. This event is intended for researchers in relevant fields and is free to attend, but advance registration is essential:

Dates: June 14-15, 2016

Location: The Royal Society, London, 6-9 Carlton House Terrace, London, SW1Y 5AG

Organizers: Dr Geraint Jones, Dr Matthew Knight, Professor Alan Fitzsimmons, and Dr Matt Taylor

We are also planning a complementary workshop-style meeting to be held at the Royal Astronomical Society in London on June 16-17, 2016. Details will be announced in the near future.

Refereed Articles

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

Hubble and Keck Telescope Observations of Active Asteroid 288P/300163 (2006 VW139)

  • Agarwal, J. 1
  • Jewitt, D. 2,3
  • Weaver, H. 4
  • Mutchler, M. 5
  • Larson, S. 6
  1. Max Planck Institute for Solar System Research, Goettingen, Germany.
  2. Dept. Earth, Planetary and Space Sciences, UCLA, Los Angeles, USA.
  3. Dept. Physics and Astronomy, UCLA, Los Angeles, USA.
  4. The Johns Hopkins University Applied Physics Laboratory, Laurel, USA.
  5. Space Telescope Science Institut, Baltimore, USA.
  6. Lunar and Planetary Laboratory, University of Arizona, Tucson, USA.

We present Hubble Space Telescope and Keck 10 meter telescope observations of active asteroid 288P/300163 (2006 VW139) taken to examine ejected dust. The nucleus is a C-type object with absolute magnitude HV = 17.0±0.1 and estimated diameter ∼2.6 km (for assumed visual geometric albedo pV = 0.04). Variations in the brightness of the nucleus at the 10% to 15% level are significant in both 2011 December and 2012 October but we possess too few data to distinguish variations caused by activity from those caused by rotation. The dust scattering cross-section in 2011 December is ∼40 km2, corresponding to a dust mass ∼9×106 kg (88 μm mean particle radius assumed). The full width at half maximum of the debris sheet varies from ∼100 km near the nucleus to ∼1000 km 30arcsec (40,000 km) east of it. Dust dynamical models indicate ejection speeds between 0.06 and 0.3 m s−1, particle sizes between 10 and 300 μm and an inverse square-root relation between particle size and velocity. Overall, the data are most simply explained by prolonged, low velocity ejection of dust, starting in or before 2011 July and continuing until at least 2011 October. These properties are consistent with the sublimation of near-surface ice aided by centrifugal forces. The high spatial resolution of our HST images (52 km per pixel) reveals details that remained hidden in previous ground-based observations, such as the extraordinarily small vertical extent of the dust sheet, ejection speeds well below the nucleus escape speed, and the possibility of a binary nucleus.

Astronomical Journal (In press)

arXiv: 1510.07629


  • Morse A.D. 1
  • Mousis O. 2
  • Sheridan S. 1
  • Morgan G. 1
  • Andrews D. 1
  • Barber S. 1
  • Wright I. 1
  1. The Open University, UK
  2. Aix Marseille Universite, France

Comets are generally considered to contain the best-preserved material from the beginning of our planetary system, although the mechanism of their formation and subsequent evolution are still poorly understood. Here we report the direct in situ measurement of H2O, CO, and CO2 by the Ptolemy mass spectrometer onboard the Philae lander, part of the European Space Agency’s Rosetta mission, at the Abydos site of the Jupiter-family comet 67P/Churyumov-Gerasimenko. A CO/CO2 ratio of around 0.07 ± 0.04 is found at the surface of the comet, a value substantially lower than the one measured by ROSINA in the coma. Such a major difference is a potential indication of heterogeneity of the nucleus and not of changes in the CO/CO2 ratio of the coma with radial distance.

Astronomy and Astrophysics (Published)

DOI: 10.1051/0004-6361/201526624

Ultraviolet observations of the hydrogen coma of comet C/2013 A1 (Siding Spring) by MAVEN/IUVS

  • Matteo MJ Crismani 1
  • Nicholas M Schneider 1
  • Justin I Deighan 1
  • A Ian F Stewart 1
  • Michael Combi 2
  • Michael S Chaffin 1
  • Nicolas Fougere 2
  • Sonal K Jain 1
  • Arnaud Stiepen 1
  • Roger V Yelle 3
  • William E McClintock 1
  • John T Clarke 4
  • Gregory M Holsclaw 1
  • Frank Montmessin 5
  • Bruce M Jakosky 1
  1. Laboratory for Atmospheric and Space Sciences, University of Colorado Boulder, Boulder, Colorado, USA
  2. Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA
  3. Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
  4. Center for Space Physics, Boston University, Boston, Massachusetts, USA
  5. LATMOS/IPSL, Guyancourt, France

We used the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiting spacecraft to construct images of the hydrogen coma of comet C/2013 A1 (Siding Spring) days before its close encounter with Mars. We obtain a water production rate of 1.1 ± 0.5 × 1028 molecules/s and determine the total impacting fluence of atoms and molecules corresponding to the photodissociation of water and its daughter species to be 2.4 ± 1.2 × 104 kg. We use these observations to confirm predictions that the mass of delivered hydrogen is comparable to the existing reservoir above 150 km. Furthermore, we reconcile disparity between observations and predictions about the detectability of the hydrogen perturbation and thermospheric response.

Geophysical Research Letters (Published)

DOI: 10.1002/2015GL065290