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Seasonal evolution of Titan’s stratosphere during the Cassini mission

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)3079-3089
Number of pages11
JournalGeophysical Research Letters
Issue number6
Early online date18 Mar 2019
DateAccepted/In press - 20 Feb 2019
DateE-pub ahead of print - 18 Mar 2019
DatePublished (current) - 28 Mar 2019


Titan's stratosphere exhibits significant seasonal changes, including breakup and formation of polar vortices. Here we present the first analysis of midinfrared mapping observations from Cassini's Composite InfraRed Spectrometer to cover the entire mission (L s =293–93°, 2004–2017)—midnorthern winter to northern summer solstice. The north polar winter vortex persisted well after equinox, starting breakup around L s ∼60° and fully dissipating by L s ∼90°. Absence of enriched polar air spreading to lower latitudes suggests large-scale circulation changes and photochemistry control chemical evolution during vortex breakup. South polar vortex formation commenced soon after equinox and by L s ∼60° was more enriched in trace gases than the northern middle-winter vortex and had temperatures ∼20 K colder. This suggests that early-winter and middle-winter vortices are dominated by different processes—radiative cooling and subsidence-induced adiabatic heating respectively. By the end of the mission (L s =93°) south polar conditions were approaching those observed in the north at L s =293°, implying seasonal symmetry in Titan's vortices.

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