Evolution of the Far-infrared Cloud at Titan's South Pole

Donald E. Jennings, R. K. Achterberg, V. Cottini, C. M. Anderson, F. Michael Flasar, C. A. Nixon, G. L. Bjoraker, Virgil G. Kunde, Ronald C. Carlson, E. A. Guandique, M. S. Kaelberer, J. S. Tingley, S. A. Albright, M. E. Segura, R de Kok, A Coustenis, S Vinatier, G. Bampasidis, Nicholas A Teanby, SB Calcutt

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A condensate cloud on Titan identified by its 220 cm−1 far-infrared signature continues to undergo seasonal changes at both the north and south poles. In the north, the cloud, which extends from 55 N to the pole, has been gradually decreasing in emission intensity since the beginning of the Cassini mission with a half-life of 3.8 years. The cloud in the south did not appear until 2012 but its intensity has increased rapidly, doubling every year. The shape of the cloud at the south pole is very different from that in the north. Mapping in 2013 December showed that the condensate emission was confined to a ring with a maximum at 80 S. The ring was centered 4° from Titan's pole. The pattern of emission from stratospheric trace gases like nitriles and complex hydrocarbons (mapped in 2014 January) was also offset by 4°, but had a central peak at the pole and a secondary maximum in a ring at about 70 S with a minimum at 80 S. The shape of the gas emission distribution can be explained by abundances that are high at the atmospheric pole and diminish toward the equator, combined with correspondingly increasing temperatures. We discuss possible causes for the condensate ring. The present rapid build up of the condensate cloud at the south pole is likely to transition to a gradual decline from 2015 to 2016.

Original languageEnglish
Article numberL34
Number of pages5
JournalAstrophysical Journal Letters
Issue number2
Early online date8 May 2015
Publication statusPublished - 10 May 2015

Bibliographical note

Date of Acceptance: 17/04/2015


  • molecular processes
  • planets and satellites: atmospheres
  • planets and satellites: composition
  • planets and satellites: individual (Titan)
  • radiation mechanisms: thermal

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    Cite this

    Jennings, D. E., Achterberg, R. K., Cottini, V., Anderson, C. M., Flasar, F. M., Nixon, C. A., Bjoraker, G. L., Kunde, V. G., Carlson, R. C., Guandique, E. A., Kaelberer, M. S., Tingley, J. S., Albright, S. A., Segura, M. E., de Kok, R., Coustenis, A., Vinatier, S., Bampasidis, G., Teanby, N. A., & Calcutt, SB. (2015). Evolution of the Far-infrared Cloud at Titan's South Pole. Astrophysical Journal Letters, 804(2), [L34]. https://doi.org/10.1088/2041-8205/804/2/L34