[P-CG24] [EJ] Planetary Magnetosphere, Ionosphere, and Atmosphere

[PCG24-05] Search of CH4 on Mars by SOFIA/EXES

Shohei Aoki², *Hiromu Nakagawa¹, Yasumasa Kasaba¹, Hideo Sagawa³, Matthew Richter⁴, Curtis DeWitt⁴ (1.Planetary Atmosphere Physics Laboratory, Department of Geophysics, Graduate School of Science, Tohoku University, 2.Institut d'Aéronomie Spatiale de Belgique, 3.Kyoto Sangyo University, 4.Physics Department, UC Davis)

Keywords:Mars, Methane, SOFIA

Discovery of CH4 in the Martian atmosphere has led to much discussion since it could be a signature of biological/geological activities on Mars. However, the presence of CH4 and its temporal and spatial variations are still under discussion. We performed sensitive measurements of Martian CH4 by using the Echelon-Cross-Echelle Spectrograph (EXES) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) on 16 March 2016, which corresponds to summer (Ls = 123.2°) in the northern hemisphere on Mars. The high altitude of SOFIA telescope (~13.7 km) enables us to significantly reduce the effects of terrestrial atmosphere, and the high spectral resolution of EXES (R~90,000) enables us to detect the intrinsically narrow lines of Martian CH4 at the 7.5 μm band. . Mars disk was spatially resolved into 3 x 3 areas, none of the observed region showed the unambiguous detections of CH4. The upper limits on the CH4 volume mixing ratio ranges from 1 to 6 ppb.