AI 中文总结
该研究通过实验室证据论证，以氦为主的大气是岩质系外行星上可行的生命环境，还能增强生物特征的光谱可探测性。
AI 中文摘要
氦是宇宙中丰度第二高的元素，但以氦为主的大气却很少被视为生命的潜在环境。这种忽视源于两个假设：一是氦会随氢一起从岩质行星逃逸，二是地球本身不存在大量的氦包层。近期观测与大气演化模型表明，岩质系外行星可以保留以氦为主的大气。本文通过综合大量被忽视的关于氦大气中生命的实验室研究，论证这类环境中存在生命的可能性。研究涉及的所有生物，包括细菌、真菌、原生动物、微藻、植物和动物，在获得必需代谢物质的情况下均能耐受以氦为主的大气。在一定压力范围内，氦未表现出毒性，也未对代谢、细胞分裂、光合作用、固氮作用或包括人类在内的多细胞协调活动构成根本性障碍。因此，以氦为主的大气是一种可行但未被充分认识的行星生命环境。此外，氦具有化学惰性且光谱上不显眼，其主体大气既不会对生物特征气体造成化学破坏，也不会强烈掩盖其光谱特征；同时，以氦为主的大气平均分子量低、标高较大，可增强透射光谱特征，提升远程探测能力。
英文摘要
Helium is the second most abundant element in the Universe, yet helium-dominated atmospheres are rarely considered as environments for life. Two assumptions have contributed to this neglect: helium is expected to escape from rocky planets together with hydrogen, and Earth itself lacks a substantial helium envelope. Recent observations and atmospheric evolution models, indicate that rocky exoplanets can retain helium-dominated atmospheres. Here we make the case for life in such environments by synthesizing a largely overlooked body of laboratory research on life in helium-dominated atmospheres. Every organism studied, including bacteria, fungi, protozoa, microalgae, plants, and animals tolerates helium-dominated atmospheres when supplied with essential metabolic requirements. Across a range of pressures, helium has shown no demonstrated toxicity and no fundamental barrier to metabolism, cell division, photosynthesis, nitrogen fixation, or coordinated multicellular activity, including in humans. Helium-dominated atmospheres therefore constitute a viable and underrecognized planetary environment for life. Helium is chemically inert and spectroscopically unobtrusive, so the bulk atmosphere would neither contribute to the chemical destruction of biosignature gases nor strongly obscure their spectral features. Helium-dominated atmospheres also have low mean molecular weights and large scale heights, strengthening spectral features in transmission and improving remote detectability.
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