Meridional variations of temperature, C 2 H 2 and C 2 H 6 abundances in Saturn's stratosphere at southern summer solstice

• Published in: Icarus
• Main Authors: Greathouse, Thomas K., Lacy, John H., Bézard, Bruno, Moses, Julianne I., Griffith, Caitlin A., Richter, Matthew J.
• Other Authors: Lunar and Planetary Institute, Houston, Department of Astronomy, University of Texas, Observatoire de Paris, Université Paris sciences et lettres (PSL), 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), Lunar and Planetary Laboratory University of Arizona (LPL), University of Arizona, University of California Davis (UC Davis), University of California (UC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2005
• Subjects: [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]; South pole
• Online Access: https://hal.science/hal-03797074; https://doi.org/10.1016/j.icarus.2005.02.016

International audience Measurements of the vertical and latitudinal variations of temperature and C 2 H 2 and C 2 H 6 abundances in the stratosphere of Saturn can be used as stringent constraints on seasonal climate models, photochemical models, and dynamics. The summertime photochemical loss timescale for C 2 H 6 in Saturn's middle and lower stratosphere ( ˜40-10,000 years, depending on altitude and latitude) is much greater than the atmospheric transport timescale; ethane observations may therefore be used to trace stratospheric dynamics. The shorter chemical lifetime for C 2 H 2 ( ˜1-7 years depending on altitude and latitude) makes the acetylene abundance less sensitive to transport effects and more sensitive to insolation and seasonal effects. To obtain information on the temperature and hydrocarbon abundance distributions in Saturn's stratosphere, high-resolution spectral observations were obtained on September 13-14, 2002 UT at NASA's IRTF using the mid-infrared TEXES grating spectrograph. At the time of the observations, Saturn was at a L≈270°, corresponding to Saturn's southern summer solstice. The observed spectra exhibit a strong increase in the strength of methane emission at 1230 cm -1 with increasing southern latitude. Line-by-line radiative transfer calculations indicate that a temperature increase in the stratosphere of ≈10 K from the equator to the south pole between 10 and 0.01 mbar is implied. Similar observations of acetylene and ethane were also recorded. We find the 1.16 mbar mixing ratio of C 2 H 2 at -1° and -83° planetocentric latitude to be 9.2-3.8+6.4×10 and 2.5-1.0+1.8×10, respectively. The C 2 H 2 mixing ratio at 0.12 mbar is found to be 1.0-0.3+0.5×10 at -1° planetocentric latitude and 2.6-0.9+1.3×10 at -83° planetocentric latitude. The 2.3 mbar mixing ratio of C 2 H 6 inferred from the data is 7.5-1.7+2.3×10 and 1.0-0.2+0.3×10 at -1° and -83° planetocentric latitude, respectively. Further observations, creating a time baseline, will be required to completely resolve the question ...