Astrochemistry

Effect of Different Stickiness Between Icy and Silicate Particles on Carbon Depletion in Protoplanetary Disks

By Keith Cowing

Status Report

astro-ph.EP

October 12, 2024

Filed under astorchemistry, astro-ph.EP, astrogeology, dust, Earth, geology, Habitable Zone, hydrocarbons, imaging, Interstellar, interstellar medium, organic chemistry, photosphere, rocky planet, silicates, snow line, Spectroscopy, white dwarf

Effect of Different Stickiness Between Icy and Silicate Particles on Carbon Depletion in Protoplanetary Disks — Overview of our models for gas disk and particles evolution in different disk regions. The blue and yellow particles represent silicates with and without refractory carbon. The light blue particles represent icy pebbles. The pink particles show the oxygen atoms which are formed by the destruction of oxygen molecules because of the FUV radiation which is described as red arrows. The light blue dashed line is the snow line. Icy pebbles enclosing many small silicates drift to the snow line (blue dashed line) from the outer region. Orange upper and lower layers are FUV-exposed regions, where oxygen atoms exist. — astro-ph.EP

Earth and other rocky bodies in the inner Solar System are significantly depleted in carbon compared to the Sun and interstellar medium (ISM) dust.

Observations indicate that over half of carbon in the ISM and comets is in refractory forms, like amorphous hydrocarbons and complex organics, which can be building blocks of rocky bodies. While amorphous hydrocarbons are destroyed by photolysis and oxidation, radial transport of solid particles can limit carbon depletion, except when complex organics, which are less refractory, are the main carbon source.

We aim to identify conditions for severe carbon depletion in the inner Solar System by introducing more realistic factors: differences in stickiness between icy and silicate particles, and high-temperature regions in the disk’s upper optically-thin layer, which were not considered in previous studies.

We perform a 3D Monte Carlo simulation of radial drift and turbulent diffusion in a steady accretion disk, incorporating ice evaporation/re-condensation, photolysis/oxidation of hydrocarbons in the upper layer, and pyrolysis of complex organics.

Our results show that the carbon fraction drops by two orders of magnitude inside the snow line under two conditions: i) silicate particles are much less sticky than icy particles, leading to a rapid decline in icy pebble flux while silicates accumulate inside the snow line, and ii) high-temperature regions in the disk’s upper layer stir silicate particles into UV-exposed areas.

These conditions reproduce carbon depletion patterns consistent with observations and allow for diverse carbon fractions in rocky bodies. This diversity may explain the wide variation of metals in white dwarf photospheres and suggest different surface environments for rocky planets in habitable zones.

Tamami Okamoto, Shigeru Ida

Comments: 17 pages, 17 figures, accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2410.07047 [astro-ph.EP] (or arXiv:2410.07047v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2410.07047
Focus to learn more
Submission history
From: Tamami Okamoto
[v1] Wed, 9 Oct 2024 16:38:20 UTC (9,904 KB)
https://arxiv.org/abs/2410.07047

Astrobiology, Astrochemistry,

Keith Cowing

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) 🖖🏻

Follow on Twitter