Towards a coupled activity-fallback model for comets I) 67P/Churyumov-Gerasimenko's water activity from a microphysics model with dynamic dust-depth

@misc{attree2026towards,
  title = {{Towards a coupled activity-fallback model for comets I) 67P/Churyumov-Gerasimenko's water activity from a microphysics model with dynamic dust-depth}},
  author = {Nicholas Attree and Yuri Skorov and Pedro Gutiérrez and Olivier Groussin and Abhinav Jindal and Raphael Marschall and Samuel P. D. Birch},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.13230},
  eprint = {2610.13230},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.13230},
}

TY  - UNPB
TI  - Towards a coupled activity-fallback model for comets I) 67P/Churyumov-Gerasimenko's water activity from a microphysics model with dynamic dust-depth
AU  - Nicholas Attree
AU  - Yuri Skorov
AU  - Pedro Gutiérrez
AU  - Olivier Groussin
AU  - Abhinav Jindal
AU  - Raphael Marschall
AU  - Samuel P. D. Birch
PY  - 2026
DA  - 2026/10/09
PB  - arXiv
DO  - 10.48550/arxiv.2610.13230
UR  - https://arxiv.org/abs/2610.13230
AB  - We apply a two-layer thermophysical model, with water sublimating from below a dust-crust with dynamically varying depth, to simulate the water outgassing rate, dust-ejections, and non-gravitational forces and torques of comet 67P/Churyumov-Gerasimenko. The dust-depth is determined at each time-step by the balance of dehydration and subsurface pressure, leading to alternating ejections and crust build-up. This model is the first stage of implementing a fully coupled activity-fallback model that self-consistently incorporates dust-fallback into the ejection depth calculation, but already a number of conclusions can be drawn from these results. The two-layer model with only dehydration and ejections is able to reproduce much of the Rosetta outgassing, dust-ejection data and non-gravitational dynamics, particularly in the comet's more primitive southern terrain. Best agreement is found for nucleus material made up of small aggregates (d_agg∼1 mm) with not-too-high dust-to-ice ratios (δ∼2−8) and low average strengths (≲1 Pa) that decreases with depth. Disagreements between the observations and model are greatest for the northern-facing and dust-covered terrains, suggesting the importance of surface modification by fallback and material processing here, which will be the subject of investigation in the next paper.
ER  -