IRTF/CSHELL mapping of atmospheric HDO, H2O and D/H on Mars during northern summer

Abstract Mapping the D/H isotopic ratio across Mars provides unique insights into the evolution and climatology of its atmosphere, and may help to identify the sources and sinks of atmospheric water vapor on the planet. We present new spatially-resolved measurements of atmospheric H 2 O, HDO and D/H on Mars during its northern summer at L s  = 126°, on March 21, 2016. High-resolution spectra were acquired at ν /Δ ν ~40,000 using CSHELL, the Cryogenic Near-IR Facility Spectrograph at the 3 m NASA Infrared Telescope Facility (IRTF) on top of Maunakea, Hawaii. We targeted the 2ν 2 spectral band of H 2 O around 2990 cm −1 (3.3 μm), and its deuterated form HDO at its ν 1 fundamental band around 2720 cm −1 (3.7 μm). The water vapor and HDO show increased mixing ratios in the northern hemisphere, reaching peak values of 400 ppmv for H 2 O, 170 ppbv–450 ppbv for HDO, as compared to the southern hemisphere where depleted values of 2 O and