Mapping the D/H of water on Mars using high-resolution spectroscopy

O at 9 slit-positions across the Mars’ disk. We extracted 43 spectra along the slit sampling a total of 8.6 arcsec North-South, and leading to a disk-map consisting of 387 points for each isotope (see Figures 1 and 2). At each footprint, we estimated the local atmospheric conditions by querying the Mars Climate Database v4.2 [1], a highly realistic general-circulation-model (GCM). These parameters were fed to a multi-layer planetary radiative transfer model (CODAT package [2]), and the Martian column densities were derived from the measured spectral line intensities (HDO, H