Comparatively little is known about atmospheric chemistry on Uranus and Neptune, because remote spectral observations of these cold, distant ‘Ice Giants’ are challenging, and each planet has only been visited by a single spacecraft during brief flybys in the 1980s. Thermochemical equilibrium is expected to control the composition in the deeper, hotter regions of the atmosphere on both planets, but disequilibrium chemical processes such as transport-induced quenching and photochemistry alter the composition in the upper atmospheric regions that can be probed remotely. Surprising disparities in the abundance of disequilibrium chemical products between the two planets point to significant differences in atmospheric transport. The atmospheric composition of Uranus and Neptune can provide critical clues for unravelling details of planet formation and evolution, but only if it is fully understood how and why atmospheric constituents vary in a three-dimensional sense and how material coming in from outside the planet affects observed abundances. Future mission planning should take into account the key outstanding questions that remain unanswered about atmospheric chemistry on Uranus and Neptune, particularly those questions that pertain to planet formation and evolution, and those that address the complex, coupled atmospheric processes that operate on Ice Giants within our solar system and beyond. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.

中文翻译：

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天王星和海王星的大气化学

人们对天王星和海王星的大气化学知之甚少，因为对这些寒冷、遥远的“冰巨星”进行远程光谱观测具有挑战性，而且在 20 世纪 80 年代，只有一艘航天器曾短暂飞越过每颗行星。热化学平衡预计将控制两个行星上更深、更热的大气区域的成分，但不平衡的化学过程，如传输引起的猝灭和光化学，会改变可以远程探测的高层大气区域的成分。两颗行星之间不平衡化学产品的丰度存在惊人的差异，这表明大气输送存在显着差异。天王星和海王星的大气成分可以为揭示行星形成和演化的细节提供关键线索，但前提是充分了解大气成分在三维意义上如何以及为何变化，以及来自行星外部的物质如何影响观测到的结果。丰富。未来的任务规划应考虑到天王星和海王星大气化学方面尚未解答的关键悬而未决的问题，特别是那些与行星形成和演化有关的问题，以及那些解决在我们的冰巨星上运行的复杂、耦合的大气过程的问题。太阳系及更远的地方。本文是“冰巨系统的未来探索”讨论会议问题的一部分。