Cometary Science Newsletter

March 2022
Michael S. P. Kelley (

ESA Archival Research Visitor Programme

To increase the scientific return from its space science missions, the European Space Agency (ESA) welcomes applications from scientists interested in pursuing research projects based on data publicly available in the ESA Space Science Archives (

The ESA Archival Research Visitor Programme is open to scientists, at all career levels, affiliated with institutes in ESA Member States and Collaborating States. Early-career scientists (within 10 years of the PhD) are particularly encouraged to apply. Applications by PhD students are also welcome.

During their stay, visiting scientists will have access to archives and mission specialists for help with the retrieval, calibration, and analysis of archival data. In principle, all areas of space research covered by ESA science missions can be supported.

Residence lasts typically between one and three months, also distributed over multiple visits. Research projects can be carried out at ESAC (Madrid, Spain) and at ESTEC (Noordwijk, Netherlands). To offset the expenses incurred by visitors, ESA covers travel costs from and to the home institution and provides support for lodging expenses and meals.

Applications received before 1 May 2022 will be considered for visits in autumn 2022 and winter 2023.

For further details, including areas of research and contact information, please refer to, or write to the programme coordinators at

Conference Announcements

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

Pro-AM Comet Community (Hybrid) Workshop

First Announcement and Call for Applications and Abstracts: Pro-Am Comet Community (Hybrid) Workshop

10 June 2022 – 12 June 2022, Prague/Online

We are pleased to announce that a Pro-Am Workshop, bringing together professional and amateur members of the Cometary Science and Observational Community, will be held in hybrid format from 10-12 June 2022. The Workshop is being organised in cooperation with Europlanet, the British Astronomical Association, Planetum Prague, and the Czech cometary community SMPH. The Workshop will last for two and a half days, starting Friday morning, and be in English.

We are delighted that the face-to-face meeting will be hosted by colleagues from Czechia in the Stefanik Observatory in Prague. Given some covid restrictions, the venue capacity will be around 40 people. We will also make all the sessions available online, and ensure that virtual attendees can also take a full part in formal and informal discussions. Sponsorship by Europlanet and BAA means that there will be no registration fee, and in person participants may apply for assistance with travel costs.

The workshop will be a mix of invited and contributed talks and round-table discussions, addressing a broad range of cometary science areas and how Pro-Am observations can contribute to these.

For more details and a link to the application form see the workshop website

Deadline for application to attend in person and/or submit abstract is 19th March 2022. Registration for online attendance will remain open until 13 May 2022.

Helen Usher ( on behalf of the organising committee

Refereed Articles

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

Repeating Gas Ejection Events from Comet 45P/Honda-Mrkos-Pajdusakova

  • Alessondra Springmann 1
  • Walter M. Harris 1
  • Erin L. Ryan 2
  • Cassandra Lejoly 1
  • Ellen S. Howell 1
  • Beatrice E. A. Mueller 3
  • Nalin H. Samarasinha 3
  • Laura M. Woodney 4
  • Jordan K. Steckloff 3
  1. University of Arizona, USA
  2. SETI Institute, USA
  3. Planetary Science Institute
  4. California State University San Bernardino, USA

Studying materials released from Jupiter-family comets (JFCs)—as seen in their inner comae, the envelope of gas and dust that forms as the comet approaches the Sun—improves the understanding of their origin and evolutionary history. As part of a coordinated, multiwavelength observing campaign, we observed comet 45P/Honda–Mrkos–Pajdušáková during its close approach to Earth in 2017 February. Narrowband observations were taken using the Bok 90'' telescope at Kitt Peak National Observatory on February 16 and 17 UT, revealing gas and dust structures. We observed different jet directions for different volatile species, implying source region heterogeneity, consistent with other ground-based and in situ observations of other comet nuclei. A repeating feature visible in CN and C2 images on February 16 was also observed on February 17 with an interval of 7.6 ± 0.1 hr, consistent with the rotation period of the comet derived from Arecibo Observatory radar observations. The repeating feature's projected gas velocity away from the nucleus is 0.8 km s−1, with an outflow velocity of 0.5 km s−1. A bright compact spot adjacent to the nucleus provides a lower limit of the amount of material released in one cycle of ∼9.2 kg, depending on composition—a quantity small enough to be produced by repeated exposure of nucleus ices to sunlight. This repeating CN jet, forming within 400 km of the nucleus, may be typical of inner-coma behavior in JFCs; however, similar features could be obscured by other processes and daughter product species when viewed from distances further than the scale length of CN molecules.

The Planetary Science Journal (Published)

DOI: 10.3847/PSJ/ac3e66

Radial Distribution of the Dust Comae of Comets 45P/Honda-Mrkos-Pajdus̆áková and 46P/Wirtanen

  • Lejoly, C. 1
  • Harris, W. 1
  • Samarasinha, N. 2
  • Mueller, B.E.A. 2
  • Howell, E. 1
  • and 19 co-authors
  1. Lunar and Planetary Observatory, 1629 E University Boulevard, Tucson, AZ 85721-0092, USA
  2. Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA

There was an unprecedented opportunity to study the inner dust coma environments, where the dust and gas are not entirely decoupled, of comets 45P/Honda-Mrkos-Pajdus̆áková (45P/HMP) from 2016 December 26 to 2017 March 15, and 46P/Wirtanen from 2018 November 10 to 2019 February 13, both in visible wavelengths. The radial profile slopes of these comets were measured in the R and HB-BC filters most representative of dust, and deviations from a radially expanding coma were identified as significant. The azimuthally averaged radial profile slope of comet 45P/HMP gradually changes from -1.81 ± 0.20 at 5.24 days preperihelion to -0.35 ± 0.16 at 74.41 days postperihelion. Contrastingly, the radial profile slope of 46P/Wirtanen stays fairly constant over the observed time period at -1.05 ± 0.05. Additionally, we find that the radial profile of 46P/Wirtanen is azimuthally dependent on the sky-plane-projected solar position angle, while that of 45P/HMP is not. These results suggest that comets 45P/HMP and 46P/Wirtanen have vastly different coma dust environments and that their dust expansion properties are distinct. As evident from these two comets, well-resolved inner comae are vital for detailed characterization of dust environments.

The Planetary Science Journal (Published)

DOI: 10.3847/PSJ/ac4501 NASA ADS:  2022PSJ.....3...17L arXiv: 2112.10808