Ices On Pebbles In Protoplanetary Discs

By Keith Cowing
Status Report
March 6, 2024
Filed under , , , , , , , ,
Ices On Pebbles In Protoplanetary Discs
Evolution of the azimuthally averaged radial distributions of gas and dust parameters. The panels show (a) surface density of gas, (b) grown dust (including pebbles), (c) small dust, (d) maximum dust size, (e) dust-to-gas mass ratio, (f) surface density of pebbles, (g) maximum dust size relative to the fragmentation barrier, (h) Stokes number, (i) minimum pebble size. The solid blue line in panels (a) and (g) indicates the approximate disc boundary at Σg = 1g cm−2 , the dashed cyan line in panels (c)–(f), (h), and (i) shows the position of the water snowline. — astro-ph.EP

The formation of solid macroscopic grains (pebbles) in protoplanetary discs is the first step toward planet formation. We aim to study the distribution of pebbles and the chemical composition of their ice mantles in a young protoplanetary disc.

We use the two-dimensional hydrodynamical code FEOSAD in the thin-disc approximation, which is designed to model the global evolution of a self-gravitating viscous protoplanetary disc taking into account dust coagulation and fragmentation, thermal balance, and phase transitions and transport of the main volatiles (H2O, CO2, CH4 and CO), which can reside in the gas, on small dust (<1 μm), on grown dust (>1 μm) and on pebbles.

We model the dynamics of the protoplanetary disc from the cloud collapse to the 500 kyr moment. We determine the spatial distribution of pebbles and composition of their ice mantles and estimate the mass of volatiles on pebbles, grown dust and small dust. We show that pebbles form as early as 50 kyr after the disc formation and exist until the end of simulation (500 kyr), providing prerequisites for planet formation. All pebbles formed in the model are covered by icy mantles.

Using a model considering accretion and desorption of volatiles onto dust/pebbles, we find that the ice mantles on pebbles consist mainly of H2O and CO2, and are carbon-depleted compared to gas and ices on small and grown dust, which contain more CO and CH4. This suggests a possible dominance of oxygen in the composition of planets formed from pebbles under these conditions.

A. Topchieva, T. Molyarova, V. Akimkin, L. Maksimova, E. Vorobyov

Comments: 18 pages, 9 figures, 1 table, accepted to MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2403.02895 [astro-ph.EP] (or arXiv:2403.02895v1 [astro-ph.EP] for this version)
Submission history
From: Anastasiia Topchieva
[v1] Tue, 5 Mar 2024 12:01:34 UTC (19,731 KB)

Astrobiology, Astrochemistry, Astrogeology,

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻