Cometary Science Newsletter

May 2019
Michael S. P. Kelley (

Postdoctoral Research Fellowship in Studies of Solar System Minor Planets

Applications are invited for a Postdoctoral Research Fellowship position in the study of the Solar System minor planets, funded by the UK Science and Technology Facilities Council (STFC). The post, available up to 31st March 2021 in the first instance with the possibility of renewal depending on performance and availability of funding, is located in the Astrophysics Research Centre (ARC) of the School of Mathematics and Physics at Queen’s University Belfast. The nominal starting date is October 1, 2019 or as soon thereafter as possible. The Postdoctoral Research Fellow will work with Dr. Meg Schwamb to develop and exploit next-generation tools for analysing and interpreting future observations and Solar System moving object detections from the Large Synoptic Survey Telescope (LSST).

To read the full details and to apply, visit:

Application Deadline: Monday, June 3, 2019

Informal enquiries may be directed to Dr Meg Schwamb, email:

Conference Announcements

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

First Announcement of the Final Rosetta Science Working Team Meeting and Science Workshop

Dear Colleagues,

A quick announcement so you can fix the dates. The final Rosetta SWT and Science workshop will be held from 23-27 September 2019 at ESA's ESTEC site in Noordwijk, Netherlands. The SWT meeting webpage will gradually have more information on it in the next months. The aim is to have a full week of science presentations, with one part of the meeting dedicated to the final SWT meeting. All members of the scientific community are welcome. Abstract submission and registration will open in June/July.

Warm Regards,
Matt Taylor
on behalf of the science and local organisation committee

LSST Solar System Readiness Sprint

The Large Synoptic Survey Telescope (LSST) will catalog millions of Solar System objects. The LSST Solar System Science Collaboration (SSSC) is hosting a sprint June 4-6, 2019 at Adler Planetarium to continue the work that the planetary community needs to do to prepare for the deluge of LSST data. This includes laying the infrastructure groundwork for joint computational tools drafting user-contributed data products, discussing funding proposals and new collaborations, brainstorming possible citizen science and machine learning applications to LSST Solar System data, and others issues to be identified by June 2019.

We have a few spots were are opening to non-SSSC members. Due to its interactive nature, we are limiting the sprint to approximately 20-25 attendees. Please fill out this form to register in order to be considered to attend the sprint by 9 pm PST on May 9, 2019. There is no registration fee. Selection of attendees will be focused on ensuring a wide variety of career stages, skill sets, perspectives, research expertise, backgrounds, and experiences are represented at the sprint.

Refereed Articles

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

C/2010 U3 (Boattini): A Bizarre Comet Active at Record Heliocentric Distance

  • Hui, Man-To 1
  • Farnocchia, Davide 2
  • Micheli, Marco 3,4
  1. UCLA, USA
  2. JPL, USA
  3. ESA NEO Coordination Centre, Italy
  4. INAF—Osservatorio Astronomico di Roma, Italy

We present a photometric and dynamical study of comet C/2010 U3 (Boattini), which was seen active in prediscovery data as early as 2005 November at a new inbound record heliocentric distance of rH = 25.8 au. Two outburst events around 2009 and 2017 were observed. The coma and tail of the comet consist of dust grains of ~10 μm in radius, ejected protractedly at speeds ≲ 50 m s−1 near the subsolar point, and are subjected to the Lorentz force, solar gravitation, and radiation pressure force all together. The prolonged activity indicates that sublimation of supervolatiles (e.g., CO, CO2) is at play, causing a net mass-loss rate ≳1 kg s−1. To sustain the mass loss, the nucleus radius has to be ≳0.1 km. The color of the cometary dust, similar to other long-period comets, is redder than the solar colors, but we also observed potential color variations when the comet was at 10 < rH < 15 au, concurrent with the onset of crystallization of amorphous water ice, if at all. Using publicly available and our refined astrometric measurements, we estimated the precise trajectory of the comet and propagated it backward to its previous perihelion. We found that the comet visited the planetary region 1.96 ± 0.04 Myr ago, with barycentric perihelion distance q = 8.364 ± 0.004 au. Thus, C/2010 U3 (Boattini) is almost certainly a dynamically old comet from the Oort cloud, and the observed activity cannot be caused by retained heat from the previous apparition.

The Astronomical Journal (Published)

DOI: 10.3847/1538-3881/ab0e09 NASA ADS: 2019AJ....157..162H arXiv: 1903.02260

The footprint of cometary dust analogues: II. Morphology as a tracer of tensile strength and application to dust collection by the Rosetta spacecraft

  • Ellerbroek, L. E. 1
  • Gundlach, B. 2
  • Landeck, A. 2
  • Dominik, C. 1
  • Blum, J. 2
  • Merouane, S. 3
  • Hilchenbach, M. 3
  • John, H. 3
  • van Veen, H. A. 4
  1. Anton Pannekoek Institute for Astronomy, University of Amsterdam, The Netherlands
  2. Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig
  3. Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
  4. Electron Microscopy Center Amsterdam, Academic Medical Center, Amsterdam, The Netherlands

The structure of cometary dust is a tracer of growth processes in the formation of planetesimals. Instrumentation on board the Rosetta mission to comet 67P/Churyumov- Gerasimenko captured dust particles and analysed them in situ. However, these deposits are a product of a collision within the instrument. We conducted laboratory experiments with cometary dust analogues, simulating the collection process by Rosetta instruments (specifically COSIMA, MIDAS). In Paper I we reported that velocity is a key driver in determining the appearance of deposits. Here in Paper II we use materials with different monomer sizes, and study the effect of tensile strength on the appearance of deposits. We find that mass transfer efficiency increases from ~1 up to ~10% with increasing monomer diameter from 0.3 μm to 1.5 μm (i.e. tensile strength decreasing from ~12 to ~3 kPa), and velocities increasing from 0.5 to 6 m/s. Also, the relative abundance of small fragments after impact is higher for material with higher tensile strength. The degeneracy between the effects of velocity and material strength may be lifted by performing a closer study of the deposits. This experimental method makes it possible to estimate the mass transfer efficiency in the COSIMA instrument. Extrapolating these results implies that more than half of the dust collected during the Rosetta mission has not been imaged. We analysed two COSIMA targets containing deposits from single collisions. The collision that occurred closest to perihelion passage led to more small fragments on the target.

Monthly Notices of the Royal Astronomical Society (Published)

DOI: 10.1093/mnras/stz1101 NASA ADS: 2019arXiv190407543E arXiv: 1904.07543

Stellar Occultation by Comet 67P/Churyumov–Gerasimenko Observed with Rosettaʼs Alice Far-ultraviolet Spectrograph

  • Brian A. Keeney 1
  • S. Alan Stern 1
  • Paul D. Feldman 2
  • Michael F. A’Hearn 3,10
  • Jean-Loup Bertaux 4
  • Lori M. Feaga 3
  • Matthew M. Knight 3
  • Richard A. Medina 1
  • John Noonan 5
  • Joel Wm. Parker 1
  • Jon P. Pineau 6
  • Rebecca N. Schindhelm 1,7
  • Andrew J. Steffl 1
  • M. Versteeg 8
  • Ronald J. Vervack, Jr. 9
  • Harold A. Weaver 9
  1. Southwest Research Institute, Boulder, CO USA
  2. Johns Hopkins University, Baltimore, MD USA
  3. University of Maryland, College Park, MD USA
  5. University of Arizona, Tucson, AZ USA
  6. Stellar Solutions, Inc., Palo Alto, CA USA
  7. Ball Aerospace and Technology Corp., Boulder, CO USA
  8. Southwest Research Institute, San Antonio, TX USA
  9. Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
  10. Deceased

Following our previous detection of ubiquitous H2O and O2 absorption against the far-ultraviolet continuum of stars located near the nucleus of Comet 67P/Churyumov–Gerasimenko, we present a serendipitously observed stellar occultation that occurred on 2015 September 13, approximately one month after the comet’s perihelion passage. The occultation appears in two consecutive 10-minute spectral images obtained by Alice, Rosetta’s ultraviolet (700–2100 Å) spectrograph, both of which show H2O absorption with column density >1017.5 cm−2 and significant O2 absorption (O2/H2O ≈ 5%–10%). Because the projected distance from the star to the nucleus changes between exposures, our ability to study the H2O column density profile near the nucleus (impact parameters <1 km) is unmatched by our previous observations. We find that the H2O and O2 column densities decrease with increasing impact parameter, in accordance with expectations, but the O2 column decreases ∼3 times more quickly than H2O. When combined with previously published results from stellar appulses, we conclude that the O2 and H2O column densities are highly correlated, and O2/H2O decreases with the increasing H2O column.

The Astronomical Journal (Published)

DOI: 10.3847/1538-3881/ab1097 NASA ADS: 2019AJ....157..173K arXiv: 1903.06793