Cometary Science Newsletter

October 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 November 2022 will be considered for visits in spring and summer 2023.

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

Refereed Articles

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

Amorphous ice in comets: evidence and consequences

  • Dina Prialnik 1
  • David Jewitt 2
  1. Tel Aviv University, Israel.
  2. University of California at Los Angeles, USA

Ice naturally forms in the disordered or “amorphous” state when accreted from vapor at temperatures and pressures found in the interstellar medium and in the frigid, low density outer regions of the Sun’s proto-planetary disk. It is therefore the expected form of ice in comets and other primitive bodies that have escaped substantial heating since formation. Despite expectations, however, the observational evidence for amorphous ice in comets remains largely indirect. This is both because the spectral features of amorphous ice are subtle and because the solar system objects for which we possess high quality data are mostly too close to the Sun and too hot for amorphous ice to survive near the surface, where it can be detected. This chapter reviews the properties of amorphous ice, the evidence for its existence and its consequences for the behavior of comets.

Comets III (In press)

NASA ADS: 2022arXiv220905907P arXiv: 2209.05907

A Survey of CO, CO2, and H2O in Comets and Centaurs

  • Harrington Pinto, O 1
  • Womack, M. 1,2
  • Fernandez, Y.R. 1
  • Bauer, J. 3
  1. Department of Physics, University of Central Florida
  2. National Science Foundation
  3. University of Maryland

CO and CO2 are the two dominant carbon-bearing molecules in comae and have major roles in driving activity. Their relative abundances also provide strong observational constraints to models of solar system formation and evolution but have never been studied together in a large sample of comets. We carefully compiled and analyzed published measurements of simultaneous CO and CO2 production rates for 25 comets. Approximately half of the comae have substantially more CO2 than CO, about a third are CO-dominated and about a tenth produce a comparable amount of both. There may be a heliocentric dependence to this ratio with CO dominating comae beyond 3.5 au. Eight out of nine of the Jupiter Family Comets in our study produce more CO2 than CO. The six dynamically new comets produce more CO2 relative to CO than the eight Oort Cloud comets that have made multiple passes through the inner solar system. This may be explained by long-term cosmic ray processing of a comet nucleus's outer layers. We find (QCO/QH2O)median = 3 ± 1% and (QCO2/QH2O)median = 12 ± 2%. The inorganic volatile carbon budget was estimated to be (QCO+QCO2)/QH2O ≈ 18% for most comets. Between 0.7 to 4.6 au, CO2 outgassing appears to be more intimately tied to the water production in a way that the CO is not. The volatile carbon/oxygen ratio for 18 comets is C/Omedian ≈ 13%, which is consistent with a comet formation environment that is well within the CO snow line.

The Planetary Science Journal (In press)

NASA ADS: 2022arXiv220909985H arXiv: 2209.09985