@article{AttreeGutierrezGroussinetal.2024, author = {Attree, Nicholas and Guti{\´e}rrez, Pedro and Groussin, Olivier and B{\"u}rger, Johanna and Keller, Horst Uwe and Kramer, Tobias and LASAGNI MANGHI, RICCARDO and L{\"a}uter, Matthias and Lemos, Pablo and Markkanen, Johannes and Marschall, Raphael and Schuckart, Christian}, title = {Varying water activity and momentum transfer on comet 67P/Churyumov-Gerasimenko from its non-gravitational forces and torques}, volume = {690}, journal = {Astronomy and Astrophysics}, arxiv = {http://arxiv.org/abs/2408.10877}, doi = {10.1051/0004-6361/202450728}, pages = {A82}, year = {2024}, abstract = {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.}, language = {en} } @inproceedings{AttreeGutierrezGroussinetal.2024, author = {Attree, Nicholas and Guti{\´e}rrez, Pedro and Groussin, Olivier and B{\"u}rger, Johanna and Keller, Horst Uwe and Kramer, Tobias and Lasagni Manghi, Riccardo and L{\"a}uter, Matthias and Lemos, Pablo and Markkanen, Johannes and Marschall, Raphael and Schuckart, Christian}, title = {The Results of ISSI Team \#547: Understanding the Activity of Comets Through 67P's Dynamics}, volume = {17}, booktitle = {EPSC Abstracts}, doi = {10.5194/epsc2024-82}, year = {2024}, abstract = {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.}, language = {en} }