TY - JOUR

T1 - Sublimation of refractory minerals in the gas envelopes of accreting rocky planets

AU - Steinmeyer, Marie-Luise

AU - Woitke, Peter

AU - Johansen, Anders

N1 - Publisher Copyright: © 2023 EDP Sciences. All rights reserved.

PY - 2023

Y1 - 2023

N2 - 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.

AB - 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.

KW - Planets and satellites: atmospheres

KW - Planets and satellites: composition

KW - Planets and satellites: formation

KW - Planets and satellites: terrestrial planets

U2 - 10.1051/0004-6361/202245636

DO - 10.1051/0004-6361/202245636

M3 - Journal article

AN - SCOPUS:85174203808

VL - 677

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - A181

ER -