Glossary term: 地外生命
Description: 地外生命或外星生命是指可能出现在地球之外且未在地球上起源的生命形式。
尽管迄今为止尚未发现简单形式的地外生命，但在我们银河系的数十亿颗系外行星上，生命的产生是可能的。据天文学家估计，在我们银河系中的平均每颗恒星都有一个以上的行星。其中一些系外行星可能能提供与地球上生命出现时相似的条件，特别是液态水。
正如在地球上一样，某些种类生命的存在可能会显著改变这种行星大气的化学成分，因此天文学在未来几十年的一个主要目标就是通过研究遥远行星的大气来探测生命的存在。另一方面，寻找地外智慧生命（SETI）项目长期以来一直在寻找其他世界上智慧生命可能发出的无线电信号。在我们的太阳系中，木星的卫星木卫二和土星的卫星土卫二的冰封海洋中可能存在生命。
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
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