Titan's Seasonal Changes Observed in the Thermal Infrared (Invited)

• Main Authors: Jennings, Donald E., Anderson, Carrie M., Nixon, Conor A., Bjoraker, Gordon L., Achterberg, Richard K., Flasar, Michael, Cottini, Valeria, Coustenis, Athéna, Vinatier, Sandrine, Teanby, Nicholas A., Bampasidis, Georgios
• Other Authors: NASA Goddard Space Flight Center (GSFC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), University of Bristol Bristol, National and Kapodistrian University of Athens (NKUA)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2013
• Subjects: [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]; Saturn; South Pole; Titan; South pole
• Online Access: https://hal.science/hal-03733664

International audience A central goal of the Cassini Mission is the detection and tracking of seasonal variations on Titan. Cassini arrived in the Saturn system in late northern winter and has so far observed for almost four Titan months, enough time to see significant changes as solar warming has moved northward. In the thermal infrared the shift has been apparent both in emission from the atmosphere and temperatures at the surface. Gases, clouds and aerosols in the atmosphere warm and cool with the seasons, accumulate and dissipate, and undergo transport on a global scale. Warming of the surface helps drive the exchange of heat and volatiles with the atmosphere, which contributes to weather. Seasonal activity in the north can be expected to be repeated in the south over the course of a year, so that it may be possible by the end of the Cassini Mission to combine winter-spring data from the north and summer-autumn data from the south to build up a picture that covers almost a full annual cycle. The Composite Infrared Spectrometer (CIRS) on Cassini records thermal infrared spectra in the 7-1000 micron range. CIRS has found that surface temperatures at Titan's poles are about 2.5 K lower than near the equator and that the temperatures moved from peaking south of the equator in 2005 to being approximately centered at the equator in 2011. As Titan passed through equinox in 2009, CIRS watched as atmospheric patterns that had been associated with northern winter began to emerge in the south. Emission from stratospheric gases and condensates varied dramatically as temperatures, chemistry and transport configurations adjusted to the season. Complex nitriles that had only been present at high northern latitudes began to appear near the South Pole while a polar ice cloud, originally identified in the north by its spectral emission, made an abrupt debut in the south. We expect much more evidence of seasonal evolution in the thermal infrared as CIRS continues to study Titan through the remainder of the Cassini mission.