标题： 类木行星科学与天王星的大气氙云 显示英文标题

标题： Noble Gas Planetology and the Xenon Clouds of Uranus

摘要： 稀有气体提供了可被未来天王星大气探测器使用的宇宙起源示踪剂。 相对于氢气（H$_2$）和氦气，氩气和氪气预计会在天王星上与之充分混合，尽管在冬季极地可能会发生凝结现象。 氩气与氢气（Ar/H$_2$）以及氩气与氪气（Ar/Kr）的比例可以揭示天王星所吸收的物质是否类似于木星大气层吸收的极端寒冷物质，或者它们是否更温暖，类似于彗星67P/楚留莫夫-格拉希门克，或者天王星两者都不是。 在天王星上层对流层，氙气会以冰的形式凝结，可能是在甲烷冰上。 凝结可能会使氙气与氢气（Xe/H$_2$）的比例解释变得复杂，但它也为收集浓缩的氙气样本提供了机会，这些样本可用于测量同位素。 太阳系中的氙气追踪到了三个不同的核合成氙气储库，一个在太阳和球粒陨石中明显可见，另一个存在于难熔的前太阳颗粒中，第三个则在彗星67P/楚留莫夫-格拉希门克和地球大气中显现。 第一和第三储库似乎是从不同气体云中捕获的。 这两种气体似乎没有很好地混合；此外，67P/楚留莫夫-格拉希门克中高$^{129}$Xe/$^{132}$Xe 比率表明，气体是在 15.7 百万年半衰期的$^{129}$I 初始核合成成分衰变之前被捕获的。 如果在天王星中观察到氙气的同位素特性，这将有助于我们理解行星起源。 氪气的同位素异常更为微妙，可能难以测量。 有一点可能性是，氖气和氦气的分馏可以用来约束天王星是如何获得其星云包层的。 显示英文摘要

摘要： Noble gases provide tracers of cosmic provenance that are accessible to a future Uranus Atmospheric Probe. Argon and krypton are expected to be well-mixed on Uranus with respect to H$_2$ and He, although condensation at the winter pole may be possible. The Ar/H$_2$ and Ar/Kr ratios address whether the materials accreted by Uranus resembled the extremely cold materials accreted by Jupiter's atmosphere, or whether they were warmer like comet 67P/Churyumov-Gerasimenko, or whether Uranus is like neither. Xenon condenses as an ice, probably on methane ice, in Uranus's upper troposphere. Condensation may complicate interpretation of Xe/H$_2$, but it also presents an opportunity to collect concentrated xenon samples suitable for measuring isotopes. Solar System Xe tracks three distinct nucleosynthetic xenon reservoirs, one evident in the Sun and in chondritic meteorites, a second in refractory presolar grains, and a third evident in comet 67P/C-G and in Earth's air. The first and third reservoirs appear to have been captured from different clouds of gas. The two gases do not appear to have been well-mixed; moreover, the high $^{129}$Xe/$^{132}$Xe ratio in 67P/C-G implies that the gas was captured before the initial nucleosynthetic complement of $^{129}$I (15.7 Myr half-life) had decayed. Xenon's isotopic peculiarities, if seen in Uranus, could usefully upset our understanding of planetary origins. Krypton's isotopic anomalies are more subtle and may prove hard to measure. There is a slight chance that neon and helium fractionations can be used to constrain how Uranus acquired its nebular envelope.