Stringent upper limit of CH4 on Mars based on SOFIA/EXES observations S. Aoki, M.J. Richter, C. DeWitt, A. Boogert, T. Encrenaz, H. Sagawa, H. Nakagawa, A. C. Vandaele, M. Giuranna, T. K. Greathouse et al. (6 more) A&A, 610 (2018) A78 Published online: 07 March 2018 DOI: 10.1051/0004-6361/201730903