[astro-ph.EP]. The characterization of terrestrial exoplanets with thick, CO2-dominated atmospheres via transmission and emission spectroscopy is limited by degeneracies between atmospheric composition, cloud structure, and surface conditions.
These degeneracies are particularly acute for planets in or near the Venus Zone, where sulfuric acid aerosol layers and deep-atmosphere opacity render the lower atmosphere and surface spectroscopically inaccessible via many optical/IR wavelengths. Venus provides the only accessible analog to such worlds, yet current knowledge of its full atmospheric profile relies on decades-old in situ data with known limitations.
Here we demonstrate that the forthcoming DAVINCI (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) mission will provide the comprehensive, high-fidelity atmospheric profile data necessary to resolve many of these degeneracies.
We quantify how atmospheric profile uncertainties translate into uncertainties in modeled transmission and thermal emission spectra of CO2-dominated terrestrial worlds, and show that the spread in the modeled Venus benchmark spectrum arising from current atmospheric profile uncertainties will decrease by factors of ∼4–5 for transmission and ∼5–15× for thermal emission after DAVINCI, providing a correspondingly improved benchmark and prior for the modeling of exoplanets with Venus-like atmospheres.
We further demonstrate that these improvement factors are larger for the cloud-free atmospheric case, where the opacity floor is set by gas-phase processes rather than aerosols, because the pre-DAVINCI data are most discrepant in the sub-cloud region.
Our results highlight the importance of Venus for the atmospheric characterization of rocky exoplanets in the JWST and HWO era, and demonstrate how DAVINCI measurements will directly improve exoplanet atmospheric modeling.
Schematic of the Venus atmospheric structure and its implications for exoplanet spectroscopic characterization. Shown altitude-dependent regions are as follows: the deep atmosphere (0–12 km, dark orange), the sub-cloud region (12–48 km, medium orange), the H2SO4 cloud deck (48–70 km, gold), the upper haze (70–90 km, pale yellow), and the upper atmosphere (>90 km, pale blue). Atmospheric boundaries are from the Venus International Reference Atmosphere (Seiff et al. 1985) and the cloud structure of Knollenberg & Gilland (1980). The red line at ∼70 km marks the transmission spectroscopy opacity floor set by the H2SO4 haze layer (Ehrenreich et al. 2012; Barstow et al. 2016). This corresponds to a pressure of ∼0.03 bar, meaning that less than 0.03% of the total atmospheric mass is spectroscopically accessible. The blue arrow indicates the DAVINCI descent sphere trajectory from the upper cloud deck to the near-surface. The four labeled boxes identify the degeneracies described in Section 2.3, located at the altitudes where each degeneracy originates. The approximate pressure scale on the right axis is derived from the VIRA profile (Seiff et al. 1985; Taylor et al. 2018). — [astro-ph.EP]
Stephen R. Kane, David S. Alexander, Shahid Aslam, Giada N. Arney, James B. Garvin, Stephanie A. Getty, Amy E. Hofmann, Noam R. Izenberg, Natasha M. Johnson, Erika Kohler, Emma L. Miles
Comments: 17 pages, 4 figures, 2 tables, accepted for publication in the Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2609.00147 [astro-ph.EP] (or arXiv:2609.00147v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2609.00147
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From: Stephen Kane
[v1] Mon, 31 Aug 2026 18:00:06 UTC (63 KB)
https://arxiv.org/abs/2609.00147
Astrobiology,
