Japan Geoscience Union Meeting 2016

Presentation information


Symbol P (Space and Planetary Sciences) » P-PS Planetary Sciences

[P-PS15] New developments of planetary sciences with ALMA

Sun. May 22, 2016 3:30 PM - 5:00 PM A02 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Munetake Momose(The College of Science, Ibaraki University), Satoshi Okuzumi(Graduate School of Science, Tokyo Institute of Technology), Hiroshi Kobayashi(Department of Physics, Nagoya University), Hideo Sagawa(Faculty of Science, Kyoto Sangyo University), Tetsuo Hasegawa(National Astronomical Observatory of Japan, National Institutes of Natural Sciences), Chair:Satoshi Okuzumi(Graduate School of Science, Tokyo Institute of Technology)

4:45 PM - 5:00 PM

[PPS15-06] The vertical distribution of CH3CN in Titan's atmosphere by the ALMA archive data analysis

*Satoru Nakamoto1, Yasuhiro Hirahara1, Takahiro IINO2, Yuma Nakayama3 (1.Graduate School of Environmental Studies, Nagoya University, 2.Nature and Science Museum, Tokyo University of Agriculture and Technology, 3.Department of Earth and Planetary Sciences, School of Science, Nagoya University)

Keywords:ALMA, Titan

We report the analysis of CH3CN (metyl cyanide) in Titan’s atmosphere using the Atacama Large Millimeter/submillimeter Array (ALMA) archive data ranging from 275 to 350 GHz. We developed a radiative transfer code for the multiple emission lines of CH3CN in spherically symmetric distribution within the synthetic beamshape of ALMA, and derived the optimized vertical abundance profile for CH3CN by the fittings of spectral line shapes. It was found that the abundance of CH3CN readily increases around 200 km altitude, and then decreases along with the higher altitude. This result disagrees with various photochemical calculations for Titan’s atmosphere, showing that the mole fraction of CH3CN has a peak around 1000 km altitude. In contrast, our result is in reasonable accordance with that observed by the Cassini/Composite Infrared Spectrometer (CIRS) for the vertical distribution of HCN, which is as stable as CH3CN from a chemical point of view. Our results also suggest the effect of Titan’s atmospheric dynamics and seasonal change on the vertical profile of CH3CN.