Exoplanets & Exomoons

Analysis of the Planetary Mass Uncertainties on the Atmospherical Retrieval Accuracy

By Keith Cowing
Press Release
November 7, 2022
Filed under , ,
Analysis of the Planetary Mass Uncertainties on the Atmospherical Retrieval Accuracy
Comparison between the normalised retrieved mass in the case of a hot-Jupiter around a G star when the mass is estimated with an uncertainty of 40% (in green), of 10% (in magenta) and when is totally unknown (in orange) as a function of clouds pressure. In the grey area we reported the results obtained for a Pclouds = 10−3 bar considering a noise decreased by a factor of two. The size of the box and the error bar represent the points within 1σ and 2σ of the median of the distribution (highlighted with solid-lines), respectively. The blue line is the real value. — astro-ph.EP

The properties of the atmospheres of the exoplanets depend on several interconnected parameters, making it difficult to determine them.

The mass of the planets plays a role in determining the scale height of atmospheres, similarly to that covered by the average molecular weight of the gas. We investigated the relevance of planetary mass knowledge in spectral retrievals, identifying in which cases a mass measurements is needed for clear or cloudy, primary or secondary atmospheres, and at which precision, in the context of the ESA M4 Ariel Mission.

We used TauREx to simulate the Ariel transmission spectra of representative targets of the Ariel mission reference sample assuming different scenarios: a primordial cloudy atmosphere of a hot-Jupiter and hot-Neptune and a secondary atmosphere of a super-Earth, also in presence of clouds. We extract information about various properties of the atmospheres for the cases of unknown mass, or mass with different uncertainty. We also test how the signal-to-noise impacts the atmospheric retrieval for different wavelength ranges. We accurately retrieved the primordial atmospheric composition independently from mass uncertainties for clear atmospheres, while the uncertainties increased for high altitude clouds.

We highlighted the importance of signal-to-noise ratio in the Rayleigh scattering region of the spectrum. For the secondary atmosphere cases a minimum mass uncertainty of 50% is sufficient to retrieve the atmospheric parameters, even in presence of clouds. Our analysis suggests that even in worst case scenarios a 50% mass precision level is enough for producing reliable retrievals, while an atmospheric retrieval without any knowledge of a planetary mass could lead to biases in cloudy primary atmosphere and in secondary atmosphere.

C. Di Maio, Q. Changeat, S. Benatti, G. Micela

Comments: 29 pages, 21 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2211.02897 [astro-ph.EP] (or arXiv:2211.02897v1 [astro-ph.EP] for this version)
Submission history
From: Claudia Di Maio
[v1] Sat, 5 Nov 2022 12:59:19 UTC (16,267 KB)
Astrobiology, Astrochemistry,

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) 🖖🏻