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Publication - Dr Nick Teanby

    HCN ice in Titan's high-altitude southern polar cloud


    Kok, RJd, Teanby, NA, Maltagliati, L, Irwin, PGJ & Vinatier, S, 2014, ‘HCN ice in Titan's high-altitude southern polar cloud’. Nature, vol 514., pp. 65-67


    Titan's middle atmosphere is currently experiencing a rapid change of season after northern spring arrived in 2009 (refs 1, 2). A large cloud was observed for the first time above Titan's southern pole in May 2012, at an altitude of 300 kilometres. A temperature maximum was previously observed there, and condensation was not expected for any of Titan's atmospheric gases. Here we report that this cloud is composed of micrometre-sized particles of frozen hydrogen cyanide (HCN ice). The presence of HCN particles at this altitude, together with temperature determinations from mid-infrared observations, indicate a dramatic cooling of Titan's atmosphere inside the winter polar vortex in early 2012. Such cooling is in contrast to previously measured high-altitude warming in the polar vortex, and temperatures are a hundred degrees colder than predicted by circulation models. These results show that post-equinox cooling at the winter pole of Titan is much more efficient than previously thought.

    Full details in the University publications repository