Vapor equilibrium models of accreting rocky planets demonstrate direct core growth by pebble accretion
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Vapor equilibrium models of accreting rocky planets demonstrate direct core growth by pebble accretion. / Steinmeyer, Marie-Luise; Johansen, Anders.
In: Astronomy and Astrophysics, Vol. 683, A217, 2024.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Vapor equilibrium models of accreting rocky planets demonstrate direct core growth by pebble accretion
AU - Steinmeyer, Marie-Luise
AU - Johansen, Anders
N1 - Publisher Copyright: © The Author(s) 2024
PY - 2024
Y1 - 2024
N2 - The gaseous envelope of an accreting rocky planet becomes hot enough to sublimate silicates and other refractory minerals. For this work, we studied the effect of the resulting envelope enrichment with a heavy vapor species on the composition and temperature of the envelope. For simplification, we used the gas-phase molecule SiO to represent the sublimation of silicate material. We solved the equilibrium structure equations in 1D for planets in the mass range of 0.1 to 3 M⊙. The convective stability criterion was extended to take the stabilizing effect of the condensation of SiO clouds into account. We assumed that the envelope is both in hydrostatic equilibrium and in vapor equilibrium with the underlying magma ocean. This means that pebbles do not undergo sublimation in the envelope and therefore survive until they plunge into the magma ocean. We find that the emergence of an inner radiative region, where SiO condensation suppresses convection, increases the pressure and temperature in the inner envelope compared to pure H2/He envelopes once Mpl ≥ 0.3 M⊙. For Mpl > 0.75 M⊙, the temperature and pressure close to the surface reach the supercritical point of SiO. The amount of SiO stored in the envelope is lower than the total planet mass for low mass planets. However, for Mpl > 2.0 M⊙, all accreted pebble material must contribute to maintain the vapor equilibrium in the envelope. Therefore, the non-vapor mass of the planet ceases to increase beyond this threshold. Overall, our vapor equilibrium model of the planetary envelope allows for direct core growth by pebble accretion up to much higher masses than previously thought.
AB - The gaseous envelope of an accreting rocky planet becomes hot enough to sublimate silicates and other refractory minerals. For this work, we studied the effect of the resulting envelope enrichment with a heavy vapor species on the composition and temperature of the envelope. For simplification, we used the gas-phase molecule SiO to represent the sublimation of silicate material. We solved the equilibrium structure equations in 1D for planets in the mass range of 0.1 to 3 M⊙. The convective stability criterion was extended to take the stabilizing effect of the condensation of SiO clouds into account. We assumed that the envelope is both in hydrostatic equilibrium and in vapor equilibrium with the underlying magma ocean. This means that pebbles do not undergo sublimation in the envelope and therefore survive until they plunge into the magma ocean. We find that the emergence of an inner radiative region, where SiO condensation suppresses convection, increases the pressure and temperature in the inner envelope compared to pure H2/He envelopes once Mpl ≥ 0.3 M⊙. For Mpl > 0.75 M⊙, the temperature and pressure close to the surface reach the supercritical point of SiO. The amount of SiO stored in the envelope is lower than the total planet mass for low mass planets. However, for Mpl > 2.0 M⊙, all accreted pebble material must contribute to maintain the vapor equilibrium in the envelope. Therefore, the non-vapor mass of the planet ceases to increase beyond this threshold. Overall, our vapor equilibrium model of the planetary envelope allows for direct core growth by pebble accretion up to much higher masses than previously thought.
KW - Planets and satellites: atmospheres
KW - Planets and satellites: composition
KW - Planets and satellites: formation
KW - Planets and satellites: terrestrial planets
U2 - 10.1051/0004-6361/202349052
DO - 10.1051/0004-6361/202349052
M3 - Journal article
AN - SCOPUS:85188701457
VL - 683
JO - Astronomy & Astrophysics
JF - Astronomy & Astrophysics
SN - 0004-6361
M1 - A217
ER -
ID: 389365143