Issue |
A&A
Volume 685, May 2024
|
|
---|---|---|
Article Number | A136 | |
Number of page(s) | 30 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202346380 | |
Published online | 17 May 2024 |
Dynamics and potential origins of decimeter-sized particles around comet 67P/Churyumov-Gerasimenko
1
Max Planck Institute for Solar System Research,
Justus-von-Liebig-Weg 3,
37077
Göttingen,
Germany
e-mail: pfeifer@mps.mpg.de
2
Institute for Geophysics and Extraterrestrial Physics, TU Braunschweig,
Mendelssohnstraße 3,
38106
Braunschweig,
Germany
3
CNRS, Laboratoire J.-L. Lagrange,
Observatoire de la Côte d’Azur,
06304
Nice,
France
4
Aurora Technology B.V. for ESA, ESAC,
Madrid,
Spain
Received:
10
March
2023
Accepted:
16
February
2024
Context. One of the primary goals of the European Space Agency’s Rosetta mission to comet 67P/Churyumov-Gerasimenko was to investigate the mechanisms responsible for cometary activity.
Aims. Our aim is to learn more about the ejection process of large refractory material by studying the dynamics of decimeter-sized dust particles in the coma of 67P and estimating their potential source regions.
Methods. We algorithmically tracked thousands of individual particles through four OSIRIS/NAC image sequences of 67P’s near-nucleus coma. We then traced concentrated particle groups back to the nucleus surface, and estimated their potential source regions, size distributions, and projected dynamical parameters. Finally, we compared the observed activity to dust coma simulations.
Results. We traced back 409 decimeter-sized particles to four suspected source regions. The regions strongly overlap and are mostly confined to the Khonsu-Atum-Anubis area. The activity may be linked to rugged terrain, and the erosion of fine dust and the ejection of large boulders may be mutually exclusive. Power-law indices fitted to the particle size–frequency distributions range from 3.4 ± 0.3 to 3.8 ± 0.4. Gas drag fits to the radial particle accelerations provide an estimate for the local gas production rates (Qg = 3.6 × 10−5 kg s−1 m−2), which is several times higher than our model predictions based on purely insolation-driven water ice sublimation. Our observational results and our modeling results both reveal that our particles were likely ejected with substantial nonzero initial velocities of around 0.5–0.6 m s−1.
Conclusions. Our findings strongly suggest that the observed ejection of decimeter-sized particles cannot be explained by water ice sublimation and favorable illumination conditions alone. Instead, the local structures and compositions of the source regions likely play a major role. In line with current ejection models of decimeter-sized particles, we deem an overabundance of CO2 ice and its sublimation to be the most probable driver. In addition, because of the significant initial velocities, we suspect the ejection events to be considerably more energetic than gradual liftoffs.
Key words: comets: general / zodiacal dust / comets: individual: 67P/Churyumov / Gerasimenko
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model.
Open Access funding provided by Max Planck Society.
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