Phosphine on Jupiter and Saturn from Cassini/CIRS
Phosphine on Jupiter and Saturn from Cassini/CIRS
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DOI：
10.1016/j.icarus.2009.03.023
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发表时间：
2009-08-01
期刊：
影响因子：
3.2
通讯作者：
Irwin, P. G. J.
中科院分区：
文献类型：
--
作者：
Fletcher, L. N.;Orton, G. S.;Irwin, P. G. J.
利用Cassini/CIRS 2.5cm（-1）光谱分辨率观测数据，得到了木星和土星上磷化氢（PH 3）的全球分布。我们扩展了对气态巨星的初步PH 3分析[欧文，P. G. J.，2004年，6名同事。Icarus 172，37-49;弗莱彻，L.N.，和9名同事，2007年a。Icarus 188，72-88]通过（a）纳入a.更广泛的Cassini/CIRS数据集和考虑更广泛的光谱范围：（B）直接纳入对流层气溶胶造成的热红外不透明，以及（c）使用共同的检索算法和光谱线数据库，以便直接比较这两个气体巨星。结果表明，在100-1000毫巴区域的巨行星对流层动力学之间存在惊人的相似之处：两者都表明在赤道的PH 3增强，在邻近的赤道带和中纬度带/带结构上的耗尽。土星的极地PH 3显示出在热气旋极地涡旋中的耗尽。木星气溶胶分布与以前的独立研究是一致的，在土星上，我们证明了CIRS光谱是最一致的薄雾在100-400毫巴的范围内，在10 μ m的平均光学深度为0.1。与木星不同的是，土星的对流层薄雾呈现半球形的不对称性，南半球的夏季比北半球更不透明。热红外薄雾不透明度在土星的赤道没有增强，因为它是在木星上。小尺度扰动的平均PH 3丰度进行了讨论，无论是在一个模型的湍流翻转和参数化涡混合。PH 3分布的大尺度结构可能与光化学寿命的变化和气溶胶不透明度造成的屏蔽有关。在土星上，增强的夏季不透明度导致PH 3的屏蔽和延长的光化学寿命，使土星夏季半球的PH 3水平升高。(C)2009 Elsevier Inc. All rights reserved.
The global distribution of phosphine (PH3) on Jupiter and Saturn is derived using 2.5 cm(-1) spectral resolution Cassini/CIRS observations. We extend the preliminary PH3 analyses on the gas giants [Irwin, P.G.J., and 6 colleagues, 2004. Icarus 172, 37-49; Fletcher, L.N., and 9 colleagues, 2007a. Icarus 188, 72-88] by (a) incorporating a. wider range of Cassini/CIRS datasets and by considering a broader spectral range: (b) direct incorporation of thermal infrared opacities due to tropospheric aerosols and (c) using a common retrieval algorithm and spectroscopic line database to allow direct comparison between these two gas giants.The results suggest striking similarities between the tropospheric dynamics in the 100-1000 mbar regions of the giant planets: both demonstrate enhanced PH3 at the equator, depletion over neighbouring equatorial belts and mid-latitude belt/zone structures. Saturn's polar PH3 shows depletion within the hot cyclonic polar vortices. Jovian aerosol distributions are consistent with previous independent Studies, and on Saturn we demonstrate that CIRS spectra are most consistent with a haze in the 100-400 mbar range with a mean optical depth of 0.1 at 10 mu m. Unlike Jupiter, Saturn's tropospheric haze shows a hemispherical asymmetry, being more opaque in the southern summer hemisphere than in the north. Thermal-IR haze opacity is not enhanced at Saturn's equator as it is on Jupiter. Small-scale perturbations to the mean PH3 abundance are discussed both in terms of a model of meridional overturning and parameterisation as eddy mixing. The large-scale structure of the PH3 distributions is likely to be related to changes in the photochemical lifetimes and the shielding due to aerosol opacities. On Saturn, the enhanced summer opacity results in shielding and extended photochemical lifetimes for PH3, permitting elevated PH3 levels over Saturn's summer hemisphere. (C) 2009 Elsevier Inc. All rights reserved.