Infrared imaging spectroscopy of Mars: H2O mapping and determination of CO2 isotopic ratios

High-resolution infrared imaging spectroscopy of Mars has been achieved at the NASA Infrared Telescope Facility (IRTF) on June 19–21, 2003, using the Texas Echelon Cross Echelle Spectrograph (TEXES). The areocentric longitude was 206°. Following the detection and mapping of hydrogen peroxide H2O2 [Encrenaz et al., 2004. Icarus 170, 424–429], we have derived, using the same data set, a map of the water vapor abundance. The results appear in good overall agreement with the TES results and with the predictions of the Global Circulation Model (GCM) developed at the Laboratory of Dynamical Meteorology (LMD), with a maximum abundance of water vapor of 3±1.5×10−4 (17±9pr-μm). We have searched for CH4 over the martian disk, but were unable to detect it. Our upper limits are consistent with earlier reports on the methane abundance on Mars. Finally, we have obtained new measurements of CO2 isotopic ratios in Mars. As compared to the terrestrial values, these values are: (18O/17O)[M/E]=1.03±0.09; (13C/12C)[M/E]=1.00±0.11. In conclusion, in contrast with the analysis of Krasnopolsky et al. [1996. Icarus 124, 553–568], we conclude that the derived martian isotopic ratios do not show evidence for a departure from their terrestrial values.