Issue |
A&A
Volume 677, September 2023
|
|
---|---|---|
Article Number | A181 | |
Number of page(s) | 16 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202245636 | |
Published online | 26 September 2023 |
Sublimation of refractory minerals in the gas envelopes of accreting rocky planets
1
Center for Star and Planet Formation, Globe Institute, University of Copenhagen,
Øster Volgade 5–7,
1350
Copenhagen, Denmark
e-mail: steinmeyer_ml@yahoo.com
2
Space Research Institute, Austrian Academy of Sciences,
Schmiedlstraße 6,
8042
Graz, Austria
3
Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University,
Box 43,
221 00
Lund, Sweden
Received:
7
December
2022
Accepted:
10
August
2023
Protoplanets growing within the protoplanetary disk by pebble accretion acquire hydrostatic gas envelopes. Due to accretion heating, the temperature in these envelopes can become high enough to sublimate refractory minerals which are the major components of the accreted pebbles. Here we study the sublimation of different mineral species and determine whether sublimation plays a role during the growth by pebble accretion. For each snapshot in the growth process, we calculate the envelope structure and the sublimation temperature of a set of mineral species representing different levels of volatility. Sublimation lines are determined using an equilibrium scheme for the chemical reactions responsible for destruction and formation of the relevant minerals. We find that the envelope of the growing planet reaches temperatures high enough to sublimate all considered mineral species when M ≳ 0.4 M⊕. The sublimation lines are located within the gravitationally bound envelope of the planet. We make a detailed analysis of the sublimation of FeS at around 720 K, beyond which the mineral is attacked by H2 to form gaseous H2S and solid Fe. We calculate the sulfur concentration in the planet under the assumption that all sulfur released as H2S is lost from the planet by diffusion back to the protoplanetary disk. Our calculated values are in good agreement with the slightly depleted sulfur abundance of Mars, while the model over predicts the extensive sulfur depletion of Earth by a factor of approximately 2. We show that a collision with a sulfur-rich body akin to Mars in the moon-forming giant impact lifts the Earth’s sulfur abundance to approximately 10% of the solar value for all impactor masses above 0.05 Earth masses.
Key words: planets and satellites: formation / planets and satellites: atmospheres / planets and satellites: terrestrial planets / planets and satellites: composition
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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