The massive eruption at 40°N (planetographic latitude) in December 2010 has produced significant and long-lived changes in temperature and species abundances in Saturn's northern hemisphere (Fletcher et al., 2011). The northern storm region has been observed on many occasions in between January and August of 2011 by Cassini's Composite Infrared Spectrometer (CIRS). In this time period, temperatures in regions referred to as "beacons" (warm regions in the stratosphere at certain longitudes in the storm latitude) became significantly warmer than pre-storm values of 140K. These temperatures reached a peak of 220K near the 2-mbar region in May 2011 following the merger of two beacons. These are the highest temperatures ever observed at this altitude on Saturn. The temperatures in the storm region vary longitudinally by ~70K which is the largest variation in temperature ever seen on Saturn. These warm temperatures resulted in the detection of ethylene (C2H4) using CIRS. Early analysis of the May data indicates ethylene volume mixing ratios of 3x10-8 at 2 mbar. These beacon regions have also led to the identification of rare species such as diacetylene (C4H2), methylacetylene (CH3C2H), and carbon dioxide (CO2) in the stratosphere. These species were previously measured by the Infrared Space Observatory (de Graauw et al., 1997) and CIRS (Guerlet et al., 2010). However, mapping these species in longitude and latitude over the storm region using CIRS provides insight into the changes in the photochemistry induced by the storm. Ground-based observations were performed using the high-resolution spectrometer Celeste in May and July to confirm the CIRS detection of ethylene and to study its spectral signatures at higher spectral resolution than available with CIRS, and investigate the evolution of its abundance profile as the storm progresses. The time evolution of ethylene abundance in Saturn's northern storm region using CIRS and ground-based data from the McMath-Pierce Telescope (May 2011) and the United Kingdom Infrared Telescope (July 2011) will be presented. In addition, the abundance profiles, as measured by CIRS, of C4H2, CH3C2H, and CO2 will also be discussed including how their abundance profiles have changed throughout the storm period.
|Journal||American Geophysical Union, Fall Meeting 2011|
|Publication status||Published - 1 Dec 2011|
Hesman, B. E., Fletcher, L., Bjoraker, G. L., Sada, P. V., Achterberg, R. K., Jennings, D. E., ... Irwin, P. G. (2011). The Evolution of Trace Species and Temperature in Saturn's Northern Storm Region. American Geophysical Union, Fall Meeting 2011, 11.