Localised Ejection Of Dust and Chunks on Comet 67P/Churyumov-Gerasimenko: Testing How Comets Work

We extend an existing thermophysical activity model of comet 67P/Churyumov-Gerasimenko to include pressure buildup inside the pebbles making up the nucleus.

We test various quantities of H₂O and CO₂, in order to simulate the material inside and outside of proposed water enriched bodies (WEBs). We find that WEBs can reproduce the peak water flux observed by Rosetta, but that the addition of a time-resolved heat-flow reduces the water fluxes away from perihelion as compared to the previously assumed equilibrium model.

Our modelled WEBs eject dust continuously but with a rate that is much higher than the observed erosion and mass-loss, thus requiring an active area smaller than the total comet surface area or very large quantities of dust fallback.

When simulating the CO₂-rich non-WEB material, we only find the ejection of large chunks under specific conditions (e.g.~low diffusivities between the pebbles or intense insolation at southern summer), whilst we also find CO₂ outgassing rates that are much greater than observed. This is a general problem in models where CO₂ drives erosion, alongside difficulties in simultaneously ejecting chunks from deep whilst eroding the surface layer.

We therefore conclude that ejection of chunks by CO₂ must be a localised phenomenon, occurring separately in space or time from surface erosion and water emission. Simulating the global production rates of gas, dust, and chunks from a comet thus remains challenging, while the activity mechanism is shown to be very sensitive to the material structure (i.e.~porosity and diffusivity) at various scales.

Nicholas Attree, Christian Schuckart, Dorothea Bischoff, Bastian Gundlach, Jürgen Blum

Comments: Accepted for publication in MNRAS, 14 pages, 9 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2410.03251 [astro-ph.EP] (or arXiv:2410.03251v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2410.03251
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Submission history
From: Nicholas Attree
[v1] Fri, 4 Oct 2024 09:15:32 UTC (2,947 KB)
https://arxiv.org/abs/2410.03251

Astrobiology