HCN Ice in Titan’s High-altitude Southern Polar Cloud
Titan’s middle atmosphere is currently experiencing a rapid change of season after northern spring arrived in 2009. A large cloud was observed for the first time above Titan’s southern pole in May 2012, at an altitude of 300 km. This altitude previously showed a temperature maximum and condensation was not expected for any of Titan’s atmospheric gases.
Here we show that this cloud is composed of micron-sized hydrogen cyanide (HCN) ice particles. The presence of HCN particles at this altitude, together with new temperature determinations from mid-infrared observations, indicate a very dramatic cooling of Titan’s atmosphere inside the winter polar vortex in early 2012. Such a cooling is completely contrary to previously measured high-altitude warming in the polar vortex, and temperatures are a hundred degrees colder than predicted by circulation models.
Besides elucidating the nature of Titan’s mysterious polar cloud, these results thus show that post-equinox cooling at the winter pole is much more efficient than previously thought.
Remco J. de Kok, Nicholas A. Teanby, Luca Maltagliati, Patrick G. J. Irwin, Sandrine Vinatier
(Submitted on 21 Oct 2014)
Comments: Published in Nature on 2 October 2014. This is the author version, before final editing by Nature
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference: Nature, Volume 514, Issue 7520, pp. 65-67 (2014)
Cite as: arXiv:1410.5563 [astro-ph.EP] (or arXiv:1410.5563v1 [astro-ph.EP] for this version)
Submission history
From: Remco de Kok
[v1] Tue, 21 Oct 2014 07:55:12 GMT (2107kb,D)
