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Biomarker Response to Galactic Cosmic Ray-Induced NO_x and the Methane Greenhouse Effect in the Atmosphere of an Earth-Like Planet Orbiting an M Dwarf Star

机译:生物标记响应银河系宇宙射线诱发的NO_x和M矮星绕地球飞行的大气中的甲烷温室效应

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Planets orbiting in the habitable zone of M dwarf stars are subject to high levels of galactic cosmic rays (GCRs), which produce nitrogen oxides (NO_x) in Earth-like atmospheres. We investigate to what extent these NO_x species may modify biomarker compounds such as ozone (O_3) and nitrous oxide (N_2O), as well as related compounds such as water (H_2O) (essential for life) and methane (CH_4) (which has both abiotic and biotic sources). Our model results suggest that such signals are robust, changing in the M star world atmospheric column due to GCR NO_x effects by up to 20% compared to an M star run without GCR effects, and can therefore survive at least the effects of GCRs. We have not, however, investigated stellar cosmic rays here. CH_4 levels are about 10 times higher on M star worlds than on Earth because of a lowering in hydroxyl (OH) in response to changes in the ultraviolet. The higher levels of CH_4 are less than reported in previous studies. This difference arose partly because we used different biogenic input. For example, we employed 23% lower CH_4 fluxes compared to those studies. Unlike on Earth, relatively modest changes in these fluxes can lead to larger changes in the concentrations of biomarker and related species on the M star world. We calculate a CH_4 greenhouse heating effect of up to 4K. O_3 photochemistry in terms of the smog mechanism and the catalytic loss cycles on the M star world differs considerably compared with that of Earth.
机译:在M矮星的宜居带中运行的行星受到高水平的银河系宇宙射线(GCR)的影响,在类似地球的大气层中会产生氮氧化物(NO_x)。我们调查了这些NO_x物种在多大程度上可以修饰生物标志物化合物,例如臭氧(O_3)和一氧化二氮(N_2O),以及相关的化合物,例如水(H_2O)(对生命至关重要)和甲烷(CH_4)(非生物和生物来源)。我们的模型结果表明,此类信号很健壮,与没有GCR效应的M星运行相比,由于GCR NO_x效应在M星世界大气柱中变化高达20%,因此至少可以幸免于GCR的影响。但是,我们尚未在这里研究恒星宇宙射线。在M星世界中,CH_4的水平比地球上高约10倍,这是由于响应紫外线变化而降低了羟基(OH)含量。 CH_4的较高水平低于以前的研究报告。之所以出现这种差异,部分原因是因为我们使用了不同的生物输入。例如,与这些研究相比,我们使用的CH_4通量降低了23%。与地球不同,这些通量的相对适度的变化会导致M恒星世界上生物标志物和相关物种的浓度发生较大变化。我们计算出的CH_4温室加热效应最高为4K。与地球相比,O_3光化学在烟雾机制和M星界的催化损失循环方面有很大差异。

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