Cometary Science Newsletter

November 2017
Michael S. P. Kelley (

Refereed Articles

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

The Main Belt Comets and Ice in the Solar System

  • Snodgrass, C. 1
  • Agarwal, J. 2
  • Combi, M. 3
  • Fitzsimmons, A. 4
  • Guilbert-Lepoutre, A. 5
  • Hsieh, H. H. 6,7
  • Hui, M.-T. 8
  • Jehin, E. 9
  • Kelley, M. S. P. 10
  • Knight, M. M. 10
  • Opitom, C. 11
  • Orosei, R. 12
  • de Val-Borro, M. 13
  • Yang, B. 11
  1. The Open University, UK
  2. Max Planck Institute for Solar System Research, Germany
  3. University of Michigan, US
  4. Queen's University Belfast, UK
  5. CNRS/UTINAM, France
  6. Planetary Science Institute, US
  7. Academia Sinica, Taiwan
  8. University of California Los Angeles, US
  9. Universite de Liege, Belgium
  10. University of Maryland, US
  11. European Southern Observatory, Chile
  12. Istituto Nazionale di Astrofisica, Italy
  13. NASA Goddard Space Flight Center, US

We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies.

The Astronomy and Astrophysics Review (In press)

DOI: 10.1007/s00159-017-0104-7 arXiv: 1709.05549

Water Production Activity of Nine Long-Period Comets from SOHO/SWAN Observations of Hydrogen Lyman-alpha: 2013-2016

  • M.R. Combi 1
  • T.T. Mäkinen 2
  • J.-L. Bertaux 3
  • E. Quémerais 3
  • S. Ferron 4
  • M. Avery 1
  • C. Wright 1
  1. Dept. of Climate and Space Sciences and Engineering, University of Michigan, USA
  2. Finnish Meteorological Institute, Finland
  3. LATMOS/IPSL, Université de Versailles Saint-Quentin, France
  4. ACRI-st, France

Nine recently discovered long-period comets were observed by the Solar Wind Anisotropies (SWAN) Lyman-alpha all-sky camera on board the Solar and Heliosphere Observatory (SOHO) satellite during the period of 2013 to 2016. These were C/2012 K1 (PanSTARRS), C/2013 US10 (Catalina), C/2013 V5 (Oukaimeden), C/2013 R1 (Lovejoy), C/2014 E2 (Jacques), C/2014 Q2 (Lovejoy), C/2015 G2 (MASTER), C/2014 Q1 (PanSTARRS) and C/2013 X1 (PanSTARRS). Of these 9 comets 6 were long-period comets and 3 were possibly dynamically new. Water production rates were calculated from each of the 885 images using our standard time-resolved model that accounts for the whole water photodissociation chain, exothermic velocities and collisional escape of H atoms. For most of these comets there were enough observations over a broad enough range of heliocentric distances to calculate power-law fits to the variation of production rate with heliocentric distances for pre- and post-perihelion portions of the orbits. Comet C/2014 Q1 (PanSTARRS), with a perihelion distance of only ~0.3 AU, showed the most unusual variation of water production rate with heliocentric distance and the resulting active area variation, indicating that when the comet was within 0.7 AU its activity was dominated by the continuous release of icy grains and chunks, greatly increasing the active sublimation area by more than a factor of 10 beyond what it had at larger heliocentric distances. A possible interpretation suggests that a large fraction of the comet's mass was lost during the apparition.

Icarus (Published)

DOI: 10.1016/j.icarus.2017.08.035 NASA ADS: 2018Icar..300...33C arXiv: 1709.00985

Evidence of sub-surface energy storage in comet 67P from the outburst of 3 July 2016

  • Agarwal, J. 1
  • Della Corte, V. 2,3
  • Feldman, P. D. 4
  • Geiger, B. 5
  • Merouane, S. 1
  • and 65 co-authorsnull
  1. MPS, Germany
  2. Universita degli Studi di Napoli, Italy
  3. Institute for Space Astrophysics and Planetology, Italy
  4. The Johns Hopkins University, USA
  5. European Space Astronomy Centre, Spain

On 2016 July 03, several instruments onboard ESA's Rosetta spacecraft detected signs of an outburst event on comet 67P, at a heliocentric distance of 3.32 au from the Sun, outbound from perihelion. We here report on the inferred properties of the ejected dust and the surface change at the site of the outburst. The activity coincided with the local sunrise and continued over a time interval of 14–68 min. It left a 10-m-sized icy patch on the surface. The ejected material comprised refractory grains of several hundred microns in size, and sub-micron-sized water ice grains. The high dust mass production rate is incompatible with the free sublimation of crystalline water ice under solar illumination as the only acceleration process. Additional energy stored near the surface must have increased the gas density. We suggest a pressurized sub-surface gas reservoir, or the crystallization of amorphous water ice as possible causes.

Monthly Notices of the Royal Astronomical Society (Published)

DOI: 10.1093/mnras/stx2386