Observations of Titan's Stratosphere During Northern Summer: Temperatures, CH3CN and CH3D Abundances
arxiv(2024)
摘要
Titan's atmospheric composition and dynamical state have previously been
studied over numerous epochs by both ground- and space-based facilities.
However, stratospheric measurements remain sparse during Titan's northern
summer and fall. The lack of seasonal symmetry in observations of Titan's
temperature field and chemical abundances raises questions about the nature of
the middle atmosphere's meridional circulation and evolution over Titan's 29-yr
seasonal cycle that can only be answered through long-term monitoring
campaigns. Here, we present maps of Titan's stratospheric temperature,
acetonitrile (or methyl cyanide; CH_3CN), and monodeuterated methane
(CH_3D) abundances following Titan's northern summer solstice obtained with
Band 9 (∼0.43 mm) ALMA observations. We find that increasing temperatures
towards high-southern latitudes, currently in winter, resemble those observed
during Titan's northern winter by the Cassini mission. Acetonitrile abundances
have changed significantly since previous (sub)millimeter observations, and we
find that the species is now highly concentrated at high-southern latitudes.
The stratospheric CH_3D content is found to range between 4-8 ppm in these
observations, and we infer the CH_4 abundance to vary between ∼0.9-1.6%
through conversion with previously measured D/H values. A global value of
CH_4=1.15% was retrieved, lending further evidence to the temporal and
spatial variability of Titan's stratospheric methane when compared with
previous measurements. Additional observations are required to determine the
cause and magnitude of stratospheric enhancements in methane during these
poorly understood seasons on Titan.
更多查看译文
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络
Chat Paper
正在生成论文摘要