Data - Apps - AI - Cybernetics

ExoLyn: A Golden Mean Approach To Multi-species Cloud Modelling In Atmospheric Retrieval

By Keith Cowing

Status Report

astro-ph.EP

October 1, 2024

Filed under astro-ph.EP, atmosphere, Clouds, data, ExoLyn, exoplanet, modeling, RADTRANS, Spectroscopy, thermodynamics

ExoLyn: A Golden Mean Approach To Multi-species Cloud Modelling In Atmospheric Retrieval — The cloud structure and transmission spectrum of a sub-Neptune planet with physical properties similar to GJ 1214 b. The condensate species considered here is NaCl, KCl and ZnS. In the left panel, the meaning of each line is the same as Figure 8. The cloud is dominated by Na2S (upper part) and NaCl (cloud bottom). The right panel shows the synthetic spectrum and the blue line shows one set of parameters that leads to flat spectrum in 1 to 2 µm range, consistent with observation (Kreidberg et al. 2014). — astro-ph.EP

Context. Clouds are ubiquitous in exoplanets’ atmospheres and play an important role in setting the opacity and chemical inventory of the atmosphere. Understanding clouds is a critical step in interpreting exoplanets’ spectroscopic data.

Aims. The aim is to model the multi-species nature of clouds in atmospheric retrieval studies. To this end, we develop ExoLyn – a 1D cloud model that balances physical consistency with computational efficiency.

Methods. ExoLyn solves the transport equation of cloud particles and vapor under cloud condensation rates that are self-consistently calculated from thermodynamics. ExoLyn is a standalone, open source package capable to be combined with optool to calculate solid opacities and with RADTRANS to generate transmission or emission spectra.

Results. With ExoLyn we find that the compositional structure of clouds in hot Jupiter planets’ atmospheres is layered with a cloud dominated by magnesium-silicates on top of an iron cloud. This finding is consistent with more complex cloud formation models but can be obtained with ExoLyn in only a few seconds.

The composition of the cloud particles can be constrained from the spectrum, for example, MgSiO₃ and Mg₂SiO₄ components give rise to an absorption feature at 8 – 10 um. We investigate the dependence of the cloud structure on the bulk elemental composition of the planet and find that SiO₂-dominated clouds forms on metal-rich planet and Fe clouds with strong extinction effect forms on C-rich planet. Conclusions.

Designed towards maximum flexibility, ExoLyn can also be used in retrieval analysis of sub-Neptunes and self-luminous planets. The efficiency of ExoLyn opens the possibility of joint retrieval of exoplanets’ gas and cloud components.

Helong Huang, Chris W. Ormel, Michiel Min

Comments: 17 pages, 12 figures, accepted by A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2409.18181 [astro-ph.EP] (or arXiv:2409.18181v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2409.18181
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Submission history
From: Helong Huang
[v1] Thu, 26 Sep 2024 18:00:05 UTC (1,375 KB)
https://arxiv.org/abs/2409.18181

Astrobiology

Keith Cowing

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) 🖖🏻

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