Measurements of trace gases in planetary atmospheres help us explore chemical conditions different to those on Earth. Our nearest neighbour, Venus, has cloud decks that are temperate but hyperacidic. Here we report the apparent presence of phosphine (PH₃) gas in Venus’s atmosphere, where any phosphorus should be in oxidized forms. Single-line millimetre-waveband spectral detections (quality up to ~15σ) from the JCMT and ALMA telescopes have no other plausible identification. Atmospheric PH₃ at ~20 ppb abundance is inferred. The presence of PH₃ is unexplained after exhaustive study of steady-state chemistry and photochemical pathways, with no currently known abiotic production routes in Venus’s atmosphere, clouds, surface and subsurface, or from lightning, volcanic or meteoritic delivery. PH₃ could originate from unknown photochemistry or geochemistry, or, by analogy with biological production of PH₃ on Earth, from the presence of life. Other PH₃ spectral features should be sought, while in situ cloud and surface sampling could examine sources of this gas.

对行星大气中痕量气体的测量有助于我们探索与地球化学条件不同的化学条件。我们最近的邻居维纳斯（Venus）具有温带但酸性过强的云层。在这里，我们报告金星大气中存在明显的磷化氢（PH ₃）气体，其中任何磷都应呈氧化态。单行毫米波段的光谱检测（质量达〜15 σ从JCMT和ALMA望远镜）没有其他合理的标识。推断出〜20 ppb丰度的大气PH ₃。PH ₃的存在在对稳态化学和光化学途径进行了详尽的研究之后，尚无法解释。目前尚无维纳斯大气，云，地表和地下的非生物生产途径，也没有来自闪电，火山或陨石的非生物生产途径。PH ₃可能源自未知的光化学或地球化学，或者类似于生命中地球上PH ₃在地球上的生物产生。应寻求其他PH ₃光谱特征，而原位云和地表采样可以检查这种气体的来源。