The discovery of potentially habitable planets around the ultracool dwarf star Trappist-1 naturally poses the question: could Trappist-1 planets be home to life? These planets orbit very close to the host star and are most susceptible to the UV radiation emitted by the intense and frequent flares of Trappist-1. Here, we calculate the UV spectra (100–450 nm) of a superflare observed on Trappist-1 with the K2 mission. We couple radiative transfer models to this spectra to estimate the UV surface flux on planets in the habitable zone of Trappist-1 (planets e, f, and g), assuming atmospheric scenarios based on a prebiotic and an oxygenic atmosphere. We quantify the impact of the UV radiation on living organisms on the surface and on a hypothetical planet ocean. Finally, we find that for non-oxygenic planets, UV-resistant life-forms would survive on the surface of planets f and g. Nevertheless, more fragile organisms (i.e., Escherichia coli) could be protected from the hazardous UV effects at ocean depths greater than 8 m. If the planets have an ozone layer, any life-forms studied here would survive in the habitable zone planets.

中文翻译：

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Trappist-1行星在耀斑影响下的表面和海洋宜居性

在超冷矮星 Trappist-1 周围发现了潜在的宜居行星，这自然提出了一个问题：Trappist-1 行星能否成为生命的家园？这些行星的轨道非常靠近主恒星，并且最容易受到 Trappist-1 强烈而频繁的耀斑发出的紫外线辐射的影响。在这里，我们计算了使用 K2 任务在 Trappist-1 上观察到的超级耀斑的紫外光谱（100-450 nm）。我们将辐射传输模型与该光谱相结合，以估计 Trappist-1 宜居带中行星（行星e、f和g)，假设基于益生元和含氧大气的大气情景。我们量化了紫外线辐射对地表生物和假设的海洋行星的影响。最后，我们发现对于非含氧行星，抗紫外线的生命形式将在行星 f 和 g 的表面上生存。然而，更脆弱的生物（即大肠杆菌）可以在大于 8 m 的海洋深处免受有害的紫外线影响。如果行星有臭氧层，这里研究的任何生命形式都会在宜居带行星中生存。