TY - JOUR A1 - Attree, Nicholas A1 - Gutiérrez, Pedro A1 - Groussin, Olivier A1 - Bürger, Johanna A1 - Keller, Horst Uwe A1 - Kramer, Tobias A1 - LASAGNI MANGHI, RICCARDO A1 - Läuter, Matthias A1 - Lemos, Pablo A1 - Markkanen, Johannes A1 - Marschall, Raphael A1 - Schuckart, Christian T1 - Varying water activity and momentum transfer on comet 67P/Churyumov-Gerasimenko from its non-gravitational forces and torques JF - Astronomy and Astrophysics N2 - Aims. We investigate the ability of a simultaneous fitting of comet 67P/Churyumov-Gerasimenko’s non-gravitational forces, torques, and total water-outgassing rate, as observed by Rosetta, to constrain complex thermophysical models of cometary material. Methods. We extend the previous work of fitting geographically defined surface outgassing models to the Rosetta observations by testing the effects of a more detailed geomorphological mapping, the resolution of the shape-model used, self-heating by neighbouring facets on the shape-model, thermal inertia in the outgassing solution, and the variation in the momentum coupling between the gas and the nucleus. We also directly compare the non-gravitational acceleration curves available in the literature. Results. We correct an error in the calculation of pole-orientation in the previous paper. We find that, under the assumptions of the model, non-gravitational forces and torques are driven by water sublimation from the nucleus, thermal inertia and self-heating have only minor effects, spatially uniform activity cannot explain 67P’s non-gravitational dynamics, spatially uniform momentum transfer cannot explain 67P’s non-gravitational dynamics, and different terrain types have different instantaneous responses to insolation. Conclusions. Consolidated terrain facing south on 67P/Churyumov-Gerasimenko has a high outgassing flux, a steep response to insolation, and a large gas momentum transfer coefficient. Instead, that facing north behaves differently, producing little to no water outgassing, and with a lower momentum transfer efficiency. Dusty terrain also has a lower outgassing rate and momentum transfer efficiency, and either depletes its volatile component or is buried in fall-back as the comet approaches the Sun. Momentum transfer appears correlated with insolation, likely due to an increased enhancement in the gas temperature as the dust it flows through is heated. Y1 - 2024 U6 - https://doi.org/10.1051/0004-6361/202450728 VL - 690 SP - A82 ER - TY - CHAP A1 - Attree, Nicholas A1 - Gutiérrez, Pedro A1 - Groussin, Olivier A1 - Bürger, Johanna A1 - Keller, Horst Uwe A1 - Kramer, Tobias A1 - Lasagni Manghi, Riccardo A1 - Läuter, Matthias A1 - Lemos, Pablo A1 - Markkanen, Johannes A1 - Marschall, Raphael A1 - Schuckart, Christian T1 - The Results of ISSI Team #547: Understanding the Activity of Comets Through 67P's Dynamics T2 - EPSC Abstracts N2 - Understanding cometary activity gives us an insight into the materials properties, and therefore formation and evolution processes of these relatively pristine protoplanetary objects. We will present the results of an International Space Science Institute project to investigate the phenomenon through the effects of the outgassing activity on the orbit and spin-state of comet 67P/Churymov-Gerasimenko, e.g. its non-gravitational dynamics. This International Team gathered experts in orbital dynamics and trajectory reconstruction together with thermophysical modellers and comet observationalists, in order to compare the available extractions of 67P’s non-gravitational acceleration (NGA) from its trajectory. The team then fitted a combination of the NGA, the non-gravitational torque (NGT), and the total water-outgassing rate with a thermophysical activity model. The results of this model will be presented. In particular, it was found that: non-gravitational forces and torques are driven by water sublimation from the nucleus; thermal inertia and self-heating have only minor effects; spatially uniform activity cannot explain 67P's non-gravitational dynamics; spatially uniform momentum transfer cannot explain 67P's non-gravitational dynamics; and different terrain types have different instantaneous responses to insolation. The implications of these findings for the modelling of cometary material and the variety of surface types seen on 67P will be discussed. Y1 - 2024 U6 - https://doi.org/10.5194/epsc2024-82 VL - 17 ER -