کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1781921 1523969 2009 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Storm clouds on Saturn: Lightning-induced chemistry and associated materials consistent with Cassini/VIMS spectra
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فیزیک زمین (ژئو فیزیک)
پیش نمایش صفحه اول مقاله
Storm clouds on Saturn: Lightning-induced chemistry and associated materials consistent with Cassini/VIMS spectra
چکیده انگلیسی

Thunderstorm activity on Saturn is associated with optically detectable clouds that are atypically dark throughout the near-infrared. As observed by Cassini/VIMS, these clouds are ~20% less reflective than typical neighboring clouds throughout the spectral range from 0.8 μm to at least 4.1 μm. We propose that active thunderstorms originating in the 10–20 bar water-condensation region vertically transport dark materials at depth to the ~1 bar level where they can be observed. These materials in part may be produced by chemical processes associated with lightning, likely within the water clouds near the ~10 bar freezing level of water, as detected by the electrostatic discharge of lightning flashes observed by Cassini/RPWS (e.g., Fischer et al. 2008, Space Sci. Rev., 137, 271–285). We review lightning-induced pyrolytic chemistry involving a variety of Saturnian constituents, including hydrogen, methane, ammonia, hydrogen sulfide, phosphine, and water. We find that the lack of absorption in the 1–2 μm spectral region by lightning-generated sulfuric and phosphorous condensates renders these constituents as minor players in determining the color of the dark storm clouds. Relatively small particulates of elemental carbon, formed by lightning-induced dissociation of methane and subsequently upwelled from depth – perhaps embedded within and on the surface of spectrally bright condensates such as ammonium hydrosulfide or ammonia – may be a dominant optical material within the dark thunderstorm-related clouds of Saturn.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Planetary and Space Science - Volume 57, Issues 14–15, December 2009, Pages 1650–1658
نویسندگان
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