The Cosmic Shoreline: Modelling Bare-rock Surfaces and Atmospheres on Rocky M-dwarf Exoplanets

Stuitje, Karen (2025) The Cosmic Shoreline: Modelling Bare-rock Surfaces and Atmospheres on Rocky M-dwarf Exoplanets. Bachelor's Thesis, Physics.

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Abstract

Context. Rocky exoplanets around M-stars are promising targets for finding extraterrestrial life, but may not retain atmospheres. Degeneracies between bare surface and atmosphere observations complicate mapping the cosmic shoreline: the boundary between planets with and without atmospheres. Aims. This thesis characterises four M-star exoplanets (GJ 486b, GJ 367b, TRAPPIST-1b, TRAPPIST-1c) using JWST mid-infrared observations to distinguish bare-rock surfaces from atmosphere scenarios. Methods. I modelled compositions using the 1D radiative-convective model AGNI, incorporating heat transport. I applied a Bayesian model selection framework and simulated future JWST/MIRI broadband observations. Results. For GJ 486b, water atmospheres (0.01 – 100 bar) outperform surface models, although heat transport weakens the evidence. GJ 367b is most likely bare, but characterising its surface remains challenging. TRAPPIST-1b and 1c may lack thick atmospheres, although nitrogen-methane atmospheres (≤10 bar) with substantial heat transport remain viable. Conclusions. Heat transport significantly affects atmosphere characterisation. Observational degeneracies between atmospheric and surface emissions limit definitive atmosphere detection. Mapping the cosmic shoreline requires combining multiple JWST techniques.

Item Type:	Thesis (Bachelor's Thesis)
Supervisor name:	Lichtenberg, T.
Degree programme:	Physics
Thesis type:	Bachelor's Thesis
Language:	English
Date Deposited:	15 Jul 2025 06:20
Last Modified:	15 Jul 2025 06:20
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/36163

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