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http://hdl.handle.net/20.500.12386/27906
Titolo: | Stringent upper limit of CH4 on Mars based on SOFIA/EXES observations | Autori: | Aoki, S. Richter, M. J. DeWitt, C. Boogert, A. Encrenaz, T. Sagawa, H. Nakagawa, H. Vandaele, A. C. GIURANNA, MARCO Greathouse, T. K. Fouchet, T. Geminale, A. Sindoni, G. McKelvey, M. Case, M. Kasaba, Y. |
Data pubblicazione: | 2018 | Rivista: | ASTRONOMY & ASTROPHYSICS | Numero: | 610 | Da pagina:: | A78 | Abstract: | Discovery of CH<SUB>4</SUB> in the Martian atmosphere has led to much discussion since it could be a signature of biological and/or geological activities on Mars. However, the presence of CH<SUB>4</SUB> and its temporal and spatial variations are still under discussion because of the large uncertainties embedded in the previous observations. We performed sensitive measurements of Martian CH<SUB>4</SUB> 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<SUP>∘</SUP>) in the northern hemisphere on Mars. The high altitude of SOFIA ( 13.7 km) enables us to significantly reduce the effects of terrestrial atmosphere. Thanks to this, SOFIA/EXES improves our chances of detecting Martian CH<SUB>4</SUB> lines because it reduces the impact of telluric CH<SUB>4</SUB> on Martian CH<SUB>4</SUB>, and allows us to use CH<SUB>4</SUB> lines in the 7.5 μm band which has less contamination. However, our results show no unambiguous detection of Martian CH<SUB>4</SUB>. The Martian disk was spatially resolved into 3 × 3 areas, and the upper limits on the CH<SUB>4</SUB> volume mixing ratio range from 1 to 9 ppb across the Martian atmosphere, which is significantly less than detections in several other studies. These results emphasize that release of CH<SUB>4</SUB> on Mars is sporadic and/or localized if the process is present. | URI: | http://hdl.handle.net/20.500.12386/27906 | URL: | https://www.aanda.org/articles/aa/abs/2018/02/aa30903-17/aa30903-17.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/201730903 | Bibcode ADS: | 2018A&A...610A..78A | Fulltext: | open |
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