Simultaneous mapping of H 2O and H 2O 2 on Mars from infrared high-resolution imaging spectroscopy

Abstract

New maps of martian water vapor and hydrogen peroxide have been obtained in November–December 2005, using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infra Red Telescope facility (IRTF) at Mauna Kea Observatory. The solar longitude L s was 332° (end of southern summer). Data have been obtained at 1235–1243 cm −1, with a spectral resolution of 0.016 cm −1 ( R = 8 × 10 4 ). The mean water vapor mixing ratio in the region [0°–55° S; 345°–45° W], at the evening limb, is 150 ± 50 ppm (corresponding to a column density of 8.3 ± 2.8 pr-μm ). The mean water vapor abundance derived from our measurements is in global overall agreement with the TES and Mars Express results, as well as the GCM models, however its spatial distribution looks different from the GCM predictions, with evidence for an enhancement at low latitudes toward the evening side. The inferred mean H 2O 2 abundance is 15 ± 10 ppb , which is significantly lower than the June 2003 result [Encrenaz, T., Bézard, B., Greathouse, T.K., Richter, M.J., Lacy, J.H., Atreya, S.K., Wong, A.S., Lebonnois, S., Lefèvre, F., Forget, F., 2004. Icarus 170, 424–429] and lower than expected from the photochemical models, taking in account the change in season. Its spatial distribution shows some similarities with the map predicted by the GCM but the discrepancy in the H 2O 2 abundance remains to be understood and modeled.