A new model suite to determine the influence of cosmic rays on (exo)planetary atmospheric biosignatures
A new model suite to determine the influence of cosmic rays on (exo)planetary atmospheric biosignatures
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DOI：
10.1051/0004-6361/201935888
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发表时间：
2019-09
影响因子：
6.5
通讯作者：
K. Herbst;J. Grenfell;M. Sinnhuber;H. Rauer;B. Heber;S. Banjac;M. Scheucher;V. Schmidt;S. Gebau
中科院分区：
文献类型：
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作者：
K. Herbst;J. Grenfell;M. Sinnhuber;H. Rauer;B. Heber;S. Banjac;M. Scheucher;V. Schmidt;S. Gebau
上下文探测太阳系外生命迹象的第一次机会可能在未来十年内已经提供，即将进行的飞行任务包括詹姆斯·韦伯空间望远镜、欧洲超大望远镜和大气遥感红外系外行星大型巡天使命，这些任务将在冷K星和M星的可居住区寻找行星上的大气生物特征。然而，它们恶劣的恒星辐射和粒子环境可能导致大气生物特征的光化学损失。目标。我们的目标是研究宇宙射线对行星外大气生物特征和辐射环境的影响，同时考虑高能粒子沉淀，气候，大气电离，中性和离子化学以及二次粒子生成之间的反馈。方法.我们描述了新结合的最先进的建模工具，研究辐射和粒子环境的影响，特别是宇宙射线，对大气粒子相互作用，大气化学和气候化学耦合在一个自洽的模型套件。为此，大气辐射相互作用模拟器（AtRIS），系外行星地球离子化学模型（ExoTIC）和更新的耦合气候化学模型等模型被结合起来。结果除了将我们的结果与地球上的测量结果进行比较外，我们还研究了臭氧的产生和损失周期以及太阳静止期和1956年2月23日强太阳高能粒子事件期间的大气辐射剂量分布。此外，由JWST机载的NIR-Spec红外光谱仪所看到的依赖于地球表面的过境光谱被建模。其中，我们发现，相对较弱的太阳事件大大增加了HNO 3的光谱信号，而显着抑制臭氧的光谱特征。由于此类事件后的缓慢恢复，后者表明臭氧可能不是一个很好的生物标志物，为行星轨道恒星与高耀斑率。
Context. The first opportunity to detect indications for life outside of the Solar System may be provided already within the next decade with upcoming missions such as the James Webb Space Telescope (JWST), the European Extremely Large Telescope (E-ELT) and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL) mission, searching for atmospheric biosignatures on planets in the habitable zone of cool K- and M-stars. Nevertheless, their harsh stellar radiation and particle environment could lead to photochemical loss of atmospheric biosignatures. Aims. We aim to study the influence of cosmic rays on exoplanetary atmospheric biosignatures and the radiation environment considering feedbacks between energetic particle precipitation, climate, atmospheric ionization, neutral and ion chemistry, and secondary particle generation. Methods. We describe newly combined state-of-the-art modeling tools to study the impact of the radiation and particle environment, in particular of cosmic rays, on atmospheric particle interaction, atmospheric chemistry, and the climate-chemistry coupling in a self-consistent model suite. To this end, models like the Atmospheric Radiation Interaction Simulator (AtRIS), the Exoplanetary Terrestrial Ion Chemistry model (ExoTIC), and the updated coupled climate-chemistry model are combined. Results. In addition to comparing our results to Earth-bound measurements, we investigate the ozone production and -loss cycles as well as the atmospheric radiation dose profiles during quiescent solar periods and during the strong solar energetic particle event of February 23, 1956. Further, the scenario-dependent terrestrial transit spectra, as seen by the NIR-Spec infrared spectrometer onboard the JWST, are modeled. Amongst others, we find that the comparatively weak solar event drastically increases the spectral signal of HNO3, while significantly suppressing the spectral feature of ozone. Because of the slow recovery after such events, the latter indicates that ozone might not be a good biomarker for planets orbiting stars with high flaring rates.