Water vapor map of Mars near summer solstice using ground-based infrared spectroscopy

Abstract

Ground-based spatial mapping of Mars provides a unique way to retrieve the global distribution of minor atmospheric species and to study transient phenomena or possible variations with the local hour. We have obtained an instantaneous map of water vapor on Mars near summer solstice (Ls = 80 • ) using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF) at Mauna Kea Observatory. Data have been obtained in the 1230-1245 cm −1 range (λ = 8.1 μm), with a spatial resolution of 1.1 arcsec (after convolution) and a spectral resolution of 0.012 cm −1 (R = 10 5 ). The map has been retrieved from the line depth of a weak HDO transition, compared with the line depth of a weak CO 2 nearby transition. The TEXES map exhibits a strong maximum around the northern pole, as expected from previous observations and from climate model predictions. More interestingly, it shows longitudinal variations, both at high northern latitudes and at mid-latitudes, in close agreement with the predictions of the Global Climate Model developed at the Laboratoire de Meteorologie Dynamique (LMD GCM). The inferred water vapor mixing ratio is also in good agreement with the model predictions. The longitudinal variations at mid latitudes show a general enhancement toward the east. They do not seem to be due to the effect of local hour, but can be explained by dynamical effects generated by the topography. The map of surface temperatures, inferred from the continuum flux, is surprisingly different from the map expected from the climate models; the source of this discrepancy is still unclear.

High-resolution imaging spectroscopy of planetary atmospheres

“…4 for Ls = 808, just before the northern summer solstice, when water vapor is expected to be maximum. There is a very good agreement between the data and the model (Encrenaz et al, 2010).…”

Seasonal variation of the HDO/H2O ratio in the atmosphere of Mars at the middle of northern spring and beginning of northern summer

“…Very low HDO/H 2 O ratio (1-3 wrt VSMOW) at the winter hemisphere reported by Villanueva et al (2015) might be related to subsurface-atmosphere interaction. In order to increase data set, we plan to investigate the HDO/H 2 O ratio by comparing between the HDO map observed by IRTF/TEXES (e.g., Encrenaz et al, 2010) and the H 2 O map retrieved from MEX/PFS. In addition, Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (Vandaele et al, 2011) will perform to measure maps of HDO/H 2 O ratio and its vertical profile are obtained from the Mars Orbiter.…”

A stringent upper limit to SO2in the Martian atmosphere

“…Since 2001, we have mapped the Martian disk with the TEXES instrument at the IRTF, with the prime objective of detecting and mapping hydrogen peroxide (Encrenaz et al , 2008. In addition, we have been using weak transitions of HDO to monitor the water vapor simultaneously (Encrenaz et al 2005(Encrenaz et al , 2008(Encrenaz et al , 2010). The observing run described in this paper was performed on October 11-15, 2009.…”