Atmospheres & Climate

Surface Pressure Impact On Nitrogen-dominated USP Super-Earth Atmospheres

By Keith Cowing
Status Report
April 18, 2023
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Surface Pressure Impact On Nitrogen-dominated USP Super-Earth Atmospheres
Mass–radius for USP planets, with mass–radius measurements better than 25 per cent from and for our USP TESS candidates (see Table 1), colour coded by their equilibrium temperature. Two-layer models from Zeng et al. (2016) are displayed with different lines and colours. ‘Earth-like’ here means a composition of 30 per cent Fe and 70 per cent MgSiO3, whereas ‘100 per cent Rock’ means a composition of 100 per cent MgSiO3. Earth and Venus are identified in this plot as pale blue and orange circles, respectively — astro-ph.EP

In this paper, we compare the chemistry and the emission spectra of nitrogen-dominated cool, warm, and hot ultra-short-period (USP) super-Earth atmospheres in and out of chemical equilibrium at various surface pressure scenarios ranging from 0.1 to 10 bar.

We link the one-dimensional VULCAN chemical kinetic code, in which thermochemical kinetic and vertical transport and photochemistry are taken into account, to the one-dimensional radiative transfer model, PETITRADTRANS, to predict the emission spectra of these planets. The radiative-convective temperature-pressure profiles were computed with the HELIOS code.

Then, using PANDEXO noise simulator, we explore the observability of the differences produced by disequilibrium processes with the JWST. Our grids show how different surface pressures can significantly affect the temperature profiles, the atmospheric abundances, and consequently the emission spectra of these planets.

We find that the divergences due to disequilibrium processes would be possible to observe in cooler planets by targeting HCN, C2H4, and CO, and in warmer planets by targeting CH4 with HCN, using the NIRSpec and MIRI LRS JWST instruments. These species are also found to be sensitive indicators of the existence of surfaces on nitrogen-dominated USP super-Earths, providing information regarding the thickness of these atmospheres.

VMRs of major chemical species in a nitrogen-dominated atmosphere for each of the USP super-Earths considered in this work. Each row represents a different surface pressure. The VMRs are calculated using chemical kinetic with radiative–convective temperature profiles (see Fig. 2). The dotted profiles are the thermochemical equilibrium abundances. The solid profiles are the disequilibrium chemical abundances calculated with vertical mixing (Kzz = 108 cm2 s−1) and photochemistry — astro-ph.EP

Jamila Chouqar, Jacob Lustig-Yaeger, Zouhair Benkhaldoun, Andrew Szentgyorgyi, Abdelhadi Jabiri, Abderahmane Soubkiou

Comments: 12 pages
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2304.08690 [astro-ph.EP] (or arXiv:2304.08690v1 [astro-ph.EP] for this version)
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Journal reference: Monthly Notices of the Royal Astronomical Society, Volume 522, June 2023, Pages 648-659
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Submission history
From: Jamila Chouqar
[v1] Tue, 18 Apr 2023 01:53:58 UTC (1,912 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻