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    Anatomy of Empirical Transit Spectra of Mars Based on TGO/NOMAD

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    Aoki(2026a).pdf (3.301Mb)
    Authors
    Aoki, S.
    Fujii, Y.
    Sagawa, H.
    Villanueva, G.L.
    Thomas, I.
    Ristic, B.
    Daerden, F.
    López-Valverde, M.A.
    Patel, M.R.
    Mason, J.
    Willame, Y.
    Bellucci, G.
    Vandaele, A.C.
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    Discipline
    Physical sciences
    Subject
    Exoplanet atmospheres
    Extrasolar rocky planets
    Habitable planets
    Interdisciplinary astronomy
    Exoplanet atmospheric dynamics
    Audience
    Scientific
    Date
    2026
    Metadata
    Show full item record
    Description
    Transit spectroscopy is a powerful tool for probing atmospheric structures of exoplanets. Accurately accounting for the effects of aerosols is key to reconstructing atmospheric properties from transit spectra, yet this remains a significant challenge. To advance this effort, it is invaluable to examine the spectral features of well-characterized planetary atmospheres. Here, we synthesize empirical transit spectra of Mars across different seasons based on data from the NOMAD’s Solar Occultation channel on board ExoMars/TGO, which operates at wavelengths of 0.2–0.65 and 2–4 μm. In the generated empirical transit spectra, the atmosphere below 25 km is found to be largely opaque due to the presence of micron-sized dust and H2O ice clouds, both of which substantially weaken spectral features. The spectra exhibit CO2 absorption features at 2.7–2.8 μm and signatures of submicron-sized mesospheric H2O ice clouds around 3.1 μm, accompanied by a continuum slope. The amplitudes of these spectral features are found to vary with the Martian seasons, where the dust storms weaken the CO2 signatures and strengthen the H2O ice features, which serve as potential indicators of a dusty planet like Mars. If TRAPPIST-1f possessed a Mars-like atmospheric structure, both CO2 and H2O ice features would be detectable at a noise level of 3 ppm, a level likely beyond current observational capabilities. Nevertheless, the 3.1 μm feature produced by submicron-sized mesospheric H2O ice clouds offers a novel avenue for characterizing the atmospheres of habitable-zone exoplanets.
    Citation
    Aoki, S.; Fujii, Y.; Sagawa, H.; Villanueva, G.L.; Thomas, I.; Ristic, B.; Daerden, F.; López-Valverde, M.A.; Patel, M.R.; Mason, J.; Willame, Y.; Bellucci, G.; Vandaele, A.C. (2026). Anatomy of Empirical Transit Spectra of Mars Based on TGO/NOMAD. , The Astronomical Journal, Vol. 171, Issue 3, A166, DOI: 10.3847/1538-3881/ae3da7.
    Identifiers
    uri: https://orfeo.belnet.be/handle/internal/14640
    doi: http://dx.doi.org/10.3847/1538-3881/ae3da7
    Type
    article
    Peer-Review
    Yes
    Language
    eng
    Links
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