Reduced greenhouse gases such as methane (CH₄) and hydrogen (H₂) might be the only tenable solution to explain warming of the ancient Martian climate, but direct geological evidence that a reduced atmosphere actually existed on Mars has been lacking. Here we report widespread, strong Fe loss in chemically weathered bedrock sections in the Mawrth Vallis region and other 3–4-billion-year-old terrains on Mars. The separation of Fe from Al in Martian palaeosols, which is comparable to trends observed in palaeosols before the Great Oxidation Event on Earth, suggests that the ancient Martian surface was chemically weathered under a reducing greenhouse atmosphere. Although for different reasons than on Earth, Mars underwent an oxidation event of its own in the late Noachian that forever changed the geological path of the planet.

减少温室气体，如甲烷 (CH ₄ ) 和氢气 (H ₂) 可能是解释古代火星气候变暖的唯一可行的解​​决方案，但缺乏直接的地质证据表明火星上确实存在减少的大气层。在这里，我们报告了 Mawrth Vallis 地区的化学风化基岩部分和火星上其他 3-40 亿年历史的地形中广泛的、强烈的 Fe 损失。火星古土壤中铁与铝的分离，这与地球上大氧化事件之前在古土壤中观察到的趋势相当，表明古代火星表面在减少的温室气氛下发生了化学风化。尽管出于与地球不同的原因，火星在晚期诺亚纪经历了自己的氧化事件，这永远改变了地球的地质路径。