Issue |
A&A
Volume 691, November 2024
|
|
---|---|---|
Article Number | A183 | |
Number of page(s) | 11 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202451114 | |
Published online | 11 November 2024 |
Evolution of gas envelopes and outgassed atmospheres of rocky planets that formed via pebble accretion
1
Center for Star and Planet Formation, Globe institute, University of Copenhagen,
Øster Voldgade 5–7,
1350
Copenhagen,
Denmark
2
Lund Observatory, Institute of Astronomy and Theoretical Physics, Lund University,
Box 43,
221 00
Lund,
Sweden
★ Corresponding author; piiamaria.tomberg@sund.ku.dk
Received:
14
June
2024
Accepted:
11
September
2024
In this work, we present results of numerical simulations of the formation and early evolution of rocky planets through pebble accretion, with an emphasis on hydrogen envelope longevity and the composition of the outgassed atmosphere. We modelled planets with a range in mass from 0.1 to 5 Earth masses that orbit between 0.7 and 1.7 AU. The composition of the outgassed atmosphere was calculated with the partial pressure of free oxygen fit to geophysical models of magma ocean self-oxidation. The combined X-ray and UV (XUV) radiation-powered photoevaporation is considered as the main driver of atmospheric escape. We modelled planets that remain below the pebble isolation mass and hence accrete tenuous envelopes only. We considered slow, medium, or fast initial stellar rotation for the temporal evolution of the XUV flux. The loss of the envelope is a key event that allows the magma ocean to crystallise and outgas its bulk volatiles. The atmospheric composition of the majority of our simulated planets is dominated by CO2. Our planets accrete a total of 11.6 Earth oceans of water, the majority of which enters the core. The hydrospheres of planets lighter than the Earth reach several times the mass of the Earth’s modern oceans, while the hydrospheres of planets ranging from 1 to 3.5 Earth masses are comparable to those of our planet. However, planets of 4–5 Earth masses have smaller hydrospheres due to the trapping of volatiles in their massive mantles. Overall, our simulations demonstrate that hydrogen envelopes are easily lost from rocky planets and that this envelope loss triggers the most primordial partitioning of volatiles between the solid mantle and the atmosphere.
Key words: planets and satellites: atmospheres / planets and satellites: formation / planets and satellites: terrestrial planets
© The Authors 2024
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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