Titan’s temporal evolution in stratospheric trace gases near the poles

• Published in: Icarus
• Main Authors: Coustenis, Athena, Jennings, Donald E., Achterberg, Richard K., Bampasidis, Georgios, Lavvas, Panayotis, Nixon, Conor A., Teanby, Nicholas A., Anderson, Carrie M., Cottini, Valeria, Flasar, F. Michael
• Other Authors: 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), NASA Goddard Space Flight Center (GSFC), Department of Astronomy College Park, University of Maryland College Park, University of Maryland System-University of Maryland System, National and Kapodistrian University of Athens (NKUA), School of Earth Sciences Bristol, University of Bristol Bristol, Department of Atmospheric, Oceanic and Planetary Physics Oxford (AOPP), University of Oxford
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: atmosphere; Titan; Atmospheres; structure; composition; Satellites; evolution; [SDU]Sciences of the Universe [physics]; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; South pole
• Online Access: https://hal.sorbonne-universite.fr/hal-01198804; https://hal.sorbonne-universite.fr/hal-01198804/document; https://hal.sorbonne-universite.fr/hal-01198804/file/Coustenis_Titan%E2%80%99s_temporal.pdf; https://doi.org/10.1016/j.icarus.2015.08.027

International audience We analyze spectra acquired by the Cassini/Composite Infrared Spectrometer (CIRS) at high resolution from October 2010 until September 2014 in nadir mode. Up until mid 2012, Titan’s Northern atmosphere exhibited the enriched chemical content found since the Voyager days (November 1980), with a peak around the Northern Spring Equinox (NSE) in 2009. Since then, we have observed the appearance at Titan’s south pole of several trace species for the first time, such as HC3N and C6H6, observed only at high northern latitudes before equinox. We investigate here latitudes poleward of 50°S and 50°N from 2010 (after the Southern Autumnal Equinox) until 2014. For some of the most abundant and longest-lived hydrocarbons (C2H2, C2H6 and C3H8) and CO2, the evolution in the past 4 years at a given latitude is not very significant within error bars especially until mid-2013. In more recent dates, these molecules show a trend for increase in the south. This trend is dramatically more pronounced for the other trace species, especially in 2013–2014, and at 70°S relative to 50°S. These two regions then demonstrate that they are subject to different dynamical processes in and out of the polar vortex region. For most species, we find higher abundances at 50°N compared to 50°S, with the exception of C3H8, CO2, C6H6 and HC3N, which arrive at similar mixing ratios after mid-2013. While the 70°N data show generally no change with a trend rather to a small decrease for most species within 2014, the 70°S results indicate a strong enhancement in trace stratospheric gases after 2012. The 663 cm−1 HC3N and the C6H6 674 cm−1 emission bands appeared in late 2011/early 2012 in the south polar regions and have since then exhibited a dramatic increase in their abundances. At 70°S HC3N, HCN and C6H6 have increased by 3 orders of magnitude over the past 3–4 years while other molecules, including C2H4, C3H4 and C4H2, have increased less sharply (by 1–2 orders of magnitude). This is a strong indication of the rapid and sudden ...