Cometary Science Newsletter

July 2017
Michael S. P. Kelley (

LSST Solar System Science Collaboration

Over its 10 year lifespan, the Large Synoptic Sky Survey Telescope (LSST) will catalog over 5 million Main Belt asteroids, almost 300,000 Jupiter Trojans, over 100,000 NEOs, over 40,000 KBOs, and over 10,000 comets. Many of these objects will receive 100s of observations in multiple bandpasses. The LSST Solar System Science Collaboration (SSSC) is preparing methods and tools to analyze this data, as well as understand optimum survey strategies for discovering moving objects throughout the Solar System.

The SSSC launched a new website. Check it out at, and please consider joining the collaboration if you're an eligible researcher. If you have any questions, please contact the SSSC Co-Chairs, Meg Schwamb ( and David Trilling (

Refereed Articles

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

The footprint of cometary dust analogs: I. Laboratory experiments of low-velocity impacts and comparison with Rosetta data

  • Ellerbroek, L. E. 1
  • Gundlach, B. 2
  • Landeck, A. 2
  • Dominik, C. 1
  • Blum, J. 2
  • Merouane, S. 3
  • Hilchenbach, M. 3
  • Bentley, M. S. 4
  • Mannel, T. 4,5
  • John, H. 3
  • van Veen, H. A. 6
  1. Astronomical Institute "Anton Pannekoek'', University of Amsterdam, The Netherlands
  2. Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Germany
  3. Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
  4. Space Research Institute, Austrian Academy of Sciences, Graz, Austria
  5. Physics institute, University of Graz, Graz, Austria
  6. Electron Microscopy Center Amsterdam, Academic Medical Center, Amsterdam, The Netherlands

Cometary dust provides a unique window on dust growth mechanisms during the onset of planet formation. Measurements by the Rosetta spacecraft show that the dust in the coma of comet 67P/Churyumov-Gerasimenko has a granular structure at size scales from sub-μm up to several hundreds of μm, indicating hierarchical growth took place across these size scales. However, these dust particles may have been modified during their collection by the spacecraft instruments. Here we present the results of laboratory experiments that simulate the impact of dust on the collection surfaces of COSIMA and MIDAS, instruments onboard the Rosetta spacecraft. We map the size and structure of the footprints left by the dust particles as a function of their initial size (up to several hundred μm) and velocity (up to 6 m/s). We find that in most collisions, only part of the dust particle is left on the target; velocity is the main driver of the appearance of these deposits. A boundary between sticking/bouncing and fragmentation as an outcome of the particle-target collision is found at v ∼ 2 m/s. For velocities below this value, particles either stick and leave a single deposit on the target plate, or bounce, leaving a shallow footprint of monomers. At velocities > 2 m/s and sizes > 80 μm, particles fragment upon collision, transferring up to 50 per cent of their mass in a rubble-pile-like deposit on the target plate. The amount of mass transferred increases with the impact velocity. The morphologies of the deposits are qualitatively similar to those found by the COSIMA instrument.

Monthly Notices of the Royal Astronomical Society (Published)

NASA ADS: 2017arXiv170507127E arXiv: 1705.07127

Cine: Line excitation by infrared fluorescence in cometary atmospheres

  • de Val-Borro, M. 1,2
  • Cordiner, M. A. 1,2
  • Milam, S. N. 1
  • Charnley, S. B. 1
  1. NASA Goddard Space Flight Center
  2. The Catholic University of America

CINE is a Python module for calculating infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. Excitation by solar radiation of vibrational bands followed by radiative decay to the ground vibrational state is one of the main mechanisms for molecular excitation in comets. This code calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Line transitions are queried from the latest version of the HITRAN spectroscopic repository using the astroquery affiliated package of astropy. Molecular data are obtained from the LAMDA database. These coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

Journal of Open Source Software (Published)

DOI: 10.21105/joss.00182 NASA ADS: 2017JOSS.2017..182D

  • Snodgrass, C. 1
  • Yang, B. 2
  • Fitzsimmons, A. 3
  1. The Open University, UK
  2. European Southern Observatory, Chile
  3. Queen's University Belfast

Main Belt Comets are a recently identified population of minor bodies with stable asteroid-like orbits but cometary appearances. Sublimation of water ice is the most likely mechanism for their recurrent activity (i.e. dust tails and dust comae), although there has been no direct detection of gas. These peculiar objects could hold the key to the origin of water on Earth. In this paper we present a search for the gas responsible for lifting dust from P/2012 T1 (Pan-STARRS), and review previous attempts at such measurements. To date such searches have mainly been indirect, looking for the common cometary gas CN rather than gasses related to water itself. We use the VLT and X-shooter to search for emission from OH in the UV, a direct dissociation product of water. We do not detect any emission lines, and place an upper limit on water production rate from P/2012 T1 of 8-9x1025 molecules s−1. This is similar to limits derived from observations using the Herschel space telescope. We conclude that the best current facilities are incapable of detecting water emission at the exceptionally low levels required to produce the observed activity in Main Belt Comets.

Astronomy & Astrophysics (In press)

arXiv: 1706.06760

Colour variations of Comet C/2013 UQ4 (Catalina)

  • Ivanova, O. 1,2
  • Zubko, E. 3
  • Videen, G. 4,5
  • Mommert, M. 6
  • Hora, J.L. 7
  • Seman Krišandová, Z. 1
  • Svoreň, J. 1
  • Novichonok, A. 8
  • Borysenko, S. 2
  • Shubina, O 2
  1. Astronomical Institute of the Slovak Academy of Sciences, Slovak Republic
  2. Main Astronomical Observatory of National Academy of Sciences, Ukraine
  3. School of Natural Sciences, Far Eastern Federal University, Russia
  4. Space Science Institute, USA
  5. U.S. Army Research Laboratory, USA
  6. Northern Arizona University, USA
  7. Harvard-Smithsonian Center for Astrophysics, USA
  8. Petrozavodsk State University, Russia

We report observations of color in the inner coma of Comet C/2013 UQ4 (Catalina) with the broadband B and R filters. We find significant temporal variations of the color slope, ranging from -12.67 ± 8.16% per 0.1 μm up to 35.09±11.7% per 0.1 μm. It is significant that the comet changes color from red to blue over only a two-day period. Such dispersion cannot be characterized with an average color slope. We also observe Comet C/2013 UQ4 (Catalina) in infrared using Spitzer and find no significant CO/CO2 gaseous species in its coma. Therefore, we classify Comet C/2013 UQ4 (Catalina) as a dust-rich comet and attribute the measured color slope to its dust. We analyze the color slope using the model of agglomerated debris particles and conclude that the C/2013 UQ4 coma was chemically heterogeneous, consisting of at least two components. The first component producing the bluest color is consistent with Mg-rich silicates. There are three different options for the second component producing the reddest color. This color is consistent with either Mg-Fe silicates, kerogen type II, or organic matter processed with a low dose of UV radiation.

Monthly Notices of the Royal Astronomical Society (Published)

DOI: 10.1093/mnras/stx1004 NASA ADS: 2017MNRAS.469.2695I arXiv: 1706.01228