Atmospheric chemistry on Uranus and Neptune
MOSES, Julianne, CAVALIÉ, T, FLETCHER, L, ROMAN, M
Abstract
Comparatively little is known about atmospheric chemistry on Uranus and\nNeptune, because remote spectral observations of these cold, distant ``Ice\nGiants'' are challenging, and each planet has only been visited by a single\nspacecraft during brief flybys in the 1980s. Thermochemical equilibrium is\nexpected to control the composition in the deeper, hotter regions of the\natmosphere on both planets, but disequilibrium chemical processes such as\ntransport-induced quenching and photochemistry alter the composition in the\nupper atmospheric regions that can be probed remotely. Surprising disparities\nin the abundance of disequilibrium chemical products between the two planets\npoint to significant differences in atmospheric transport. The atmospheric\ncomposition of Uranus and Neptune can provide critical clues for unravelling\ndetails of planet formation and evolution, but only if it is fully understood\nhow and why atmospheric constituents vary in a three-dimensional sense and how\nmaterial coming in from outside the planet affects observed abundances. Future\nmission planning should take into account the key outstanding questions that\nremain unanswered about atmospheric chemistry on Uranus and Neptune,\nparticularly those questions that pertain to planet formation and evolution,\nand those that address the complex, coupled atmospheric processes that operate\non Ice Giants within our solar system and beyond.