Fan Siteng, Gao Peter, Zhang Xi, Adams Danica J, Kutsop Nicholas W, Bierson Carver J, Liu Chao, Yang Jiani, Young Leslie A, Cheng Andrew F, Yung Yuk L
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA.
LMD/IPSL, Sorbonne Université, PSL Research University, École Normale Supérieure, École Polytechnique, CNRS, Paris, 75005, France.
Nat Commun. 2022 Jan 11;13(1):240. doi: 10.1038/s41467-021-27811-6.
Pluto, Titan, and Triton make up a unique class of solar system bodies, with icy surfaces and chemically reducing atmospheres rich in organic photochemistry and haze formation. Hazes play important roles in these atmospheres, with physical and chemical processes highly dependent on particle sizes, but the haze size distribution in reducing atmospheres is currently poorly understood. Here we report observational evidence that Pluto's haze particles are bimodally distributed, which successfully reproduces the full phase scattering observations from New Horizons. Combined with previous simulations of Titan's haze, this result suggests that haze particles in reducing atmospheres undergo rapid shape change near pressure levels ~0.5 Pa and favors a photochemical rather than a dynamical origin for the formation of Titan's detached haze. It also demonstrates that both oxidizing and reducing atmospheres can produce multi-modal hazes, and encourages reanalysis of observations of hazes on Titan and Triton.
冥王星、土卫六和海卫一构成了一类独特的太阳系天体，它们具有冰冷的表面以及富含有机光化学和霾形成的化学还原大气层。霾在这些大气层中起着重要作用，其物理和化学过程高度依赖于颗粒大小，但目前对还原大气层中霾的粒径分布了解甚少。在此，我们报告观测证据表明，冥王星的霾粒子呈双峰分布，这成功再现了“新视野号”的全相位散射观测结果。结合之前对土卫六霾的模拟，这一结果表明，还原大气层中的霾粒子在压力水平约0.5帕附近会迅速发生形状变化，并且更倾向于土卫六分离霾的形成源于光化学而非动力学。这也表明，氧化和还原大气层都能产生多峰霾，并促使对土卫六和海卫一上霾的观测进行重新分析。
