[P-PS04] Small Solar System Bodies: A New Insight from Hayabusa2, OSIRIS-REx and Other Space Missions

[PPS04-06] Internal structure of pebble-pile comets inferred from thermal and mechanical properties of dust aggregates

★Invited Papers

*Sota ARAKAWA¹ (1.National Astronomical Observatory of Japan)

Keywords:Comet, Thermal inertia, Dust growth

The Rosetta mission has provided new data to better understand what comets are made of. The weak tensile strength of the cometary surface materials suggests that comet 67P/Churyumov−Gerasimenko is a hierarchical dust aggregate formed through gravitational collapse of a bound clump of small dust aggregates so-called `pebbles' in the gaseous solar nebula. Recently, we calculated the thermal inertias and thermal skin depths as functions of the size of pebbles (Arakawa & Ohno 2020). We found that the thermal properties of the comet are consistent with the hierarchical aggregate of cm- to dm-sized pebbles. This estimate is also consistent with the mechanical strength of the nucleus. In addition, we reanalyzed the stickiness of icy dust particles using a viscoelastic contact model. Our results indicate that not only H₂O ice but also CO₂ ice particles could easily grow into cm-sized large pebbles in the solar nebula (Arakawa & Krijt 2021), and this size estimate may be consistent with that from thermal and mechanical analyses on comet 67P.