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

Remco J. de Kok*, Nick A Teanby, Luca Maltagliati, Patrick G. J. Irwin, Sandrine Vinatier

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

42 Citations (Scopus)
271 Downloads (Pure)

Abstract

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.

Original languageEnglish
Pages (from-to)65-67
Number of pages3
JournalNature
Volume514
Issue number7520
Early online date1 Oct 2014
DOIs
Publication statusPublished - 1 Oct 2014

Keywords

  • OPTICAL-CONSTANTS
  • INFRARED-SPECTRA
  • STRATOSPHERIC AEROSOLS
  • ATMOSPHERE
  • CASSINI
  • CONDENSATION
  • WINTER

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