Distinguishing between Wet and Dry Atmospheres of TRAPPIST-1 e and f
Distinguishing between Wet and Dry Atmospheres of TRAPPIST-1 e and f
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DOI：
10.3847/1538-4357/aba59c
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发表时间：
2020-06
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影响因子：
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通讯作者：
F. Wunderlich;M. Scheucher;M. Godolt;J. Grenfell;Franz Schreier;P. Schneider;David J. Wilson;Alejandro S'anchez L'opez;Manuel L'opez Puertas;Heike Rauer
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作者：
F. Wunderlich;M. Scheucher;M. Godolt;J. Grenfell;Franz Schreier;P. Schneider;David J. Wilson;Alejandro S'anchez L'opez;Manuel L'opez Puertas;Heike Rauer
附近的 TRAPPIST-1 行星系统是描述类地行星大气特征的令人兴奋的目标。 e、f 和 g 行星位于星际宜居带内，其表面可能存在液态水。然而，在 TRAPPIST-1 延长的前主序阶段，行星可能经历了极度的水分流失，导致地幔干燥。使用当前和下一代望远镜很难确定海洋是否存在。因此，我们研究是否可以从对行星大气的观测中推断出海洋和/或生物圈的间接证据。我们引入了一种新开发的行星大气光化学模型，与辐射对流模型相结合，并针对现代地球、金星和火星对其进行了验证。耦合模型应用于 TRAPPIST-1 行星 e 和 f，假设不同的表面条件和大气中不同数量的 CO2。作为模型的输入，我们使用基于从 X 射线到光学波长的近同步数据构建的 TRAPPIST-1 光谱。我们计算行星大气的无云透射光谱，并使用极大望远镜 (ELT) 和詹姆斯·韦伯太空望远镜 (JWST) 确定分子特征的可探测性。我们发现，在某些条件下，通过将 K 波段内的 ELT 和 JWST 的 30 个凌日观测结果相结合，可以推断生物圈和/或海洋是否存在。未检测到 CO 可能表明海洋的存在，而大量 CH4 则暗示生物圈的存在。
The nearby TRAPPIST-1 planetary system is an exciting target for characterizing the atmospheres of terrestrial planets. The planets e, f, and g lie in the circumstellar habitable zone and could sustain liquid water on their surfaces. During the extended pre–main-sequence phase of TRAPPIST-1, however, the planets may have experienced extreme water loss, leading to a desiccated mantle. The presence or absence of an ocean is challenging to determine with current and next-generation telescopes. Therefore, we investigate whether indirect evidence of an ocean and/or a biosphere can be inferred from observations of the planetary atmosphere. We introduce a newly developed photochemical model for planetary atmospheres, coupled to a radiative-convective model, and validate it against modern Earth, Venus, and Mars. The coupled model is applied to the TRAPPIST-1 planets e and f, assuming different surface conditions and varying amounts of CO2 in the atmosphere. As input for the model we use a constructed spectrum of TRAPPIST-1, based on near-simultaneous data from X-ray to optical wavelengths. We compute cloud-free transmission spectra of the planetary atmospheres and determine the detectability of molecular features using the Extremely Large Telescope (ELT) and the James Webb Space Telescope (JWST). We find that under certain conditions the existence or nonexistence of a biosphere and/or an ocean can be inferred by combining 30 transit observations with ELT and JWST within the K band. A nondetection of CO could suggest the existence of an ocean, whereas significant CH4 hints at the presence of a biosphere.