MNRAS pre-print on ArXiv today: [2410.03251] Localised ejection of dust and chunks on comet 67P/Churyumov-Gerasimenko: testing how comets work (arxiv.org)

 

Localised ejection of dust and chunks on comet 67P/Churyumov-Gerasimenko: testing how comets work

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

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

 

 

Another paper of interest (which I also posted to NEMETODE) is:

[2410.02883] How Meteor Showers Can Guide the Search for Long Period Comets (arxiv.org)

How Meteor Showers Can Guide the Search for Long Period Comets

Samantha Hemmelgarn, Nicholas Moskovitz, Stuart Pilorz, Peter Jenniskens

With orbital periods longer than 200 years, most long-period comets (LPCs) remain undiscovered until they are in-bound towards perihelion. The comets that pass close to Earth's orbit are Potentially Hazardous Objects (PHOs). Those with orbital periods up to ~4000 years tend to have passed close to Earth's orbit in a previous orbit and produced a meteoroid stream dense enough to be detected at Earth as a meteor shower. In anticipation of Rubin Observatory's Legacy Survey of Space and Time (LSST), we investigate how these meteor showers can guide dedicated searches for their parent comets. Assuming search parameters informed by LSST, we calculated where the 17 known parent bodies of long-period comet meteor showers would have been discovered based on a cloud of synthetic comets generated from the shower properties as measured at Earth. We find that the synthetic comets predict the on-sky location of the parent comets at the time of their discovery. The parent comet's location on average would have been 1.51 ±1.19° from a line fit through the synthetic comet cloud. The difference between the heliocentric distance of the parent and mean heliocentric distance of synthetic comets on the line was 2.09 ±1.89 au for comets with unknown absolute nuclear magnitudes and 0.96 ±0.80 au for comets with known absolute nuclear magnitudes. We applied this method to the σ-Hydrids, the proposed meteor shower of Comet Nishimura, and found that it successfully matched the pre-covery location of this comet 8 months prior to Nishimura's discovery