New measurements of D/H on Mars using EXES aboard SOFIA

¹ LESIA, Observatoire de Paris, PSL University, CNRS, UPMC, Univ. Denis Diderot, 92195 Meudon, France
² Dept. of Physics, University of California Davis, CA 95616, USA
³ SwRI, Div. 15, San Antonio, TX 78228, USA
⁴ LATMOS, IPSL, 75252 Paris Cedex 05, France
⁵ Dept. of Climate and Space Sciences, University of Michigan, Ann Arbor, MI 48109-2143, USA
⁶ Belgium Institute for Space Aeronomy (BIRA-IASB), 1180 Brussels, and Fonds National de la Recherche Scientifique, 1000 Brussels, Belgium
⁷ Kyoto-Sangio University, Kyoto 603-8555, Japan

Received: 27 November 2017
Accepted: 21 January 2018

Abstract

The global D/H ratio on Mars is an important measurement for understanding the past history of water on Mars; locally, through condensation and sublimation processes, it is a possible tracer of the sources and sinks of water vapor on Mars. Measuring D/H as a function of longitude, latitude and season is necessary for determining the present averaged value of D/H on Mars. Following an earlier measurement in April 2014, we used the Echelon Cross Echelle Spectrograph (EXES) instrument on board the Stratospheric Observatory for Infrared Astronomy (SOFIA) facility to map D/H on Mars on two occasions, on March 24, 2016 (Ls = 127°), and January 24, 2017 (Ls = 304°), by measuring simultaneously the abundances of H₂O and HDO in the 1383–1391 cm⁻¹ range (7.2 μm). The D/H disk-integrated values are 4.0 (+0.8, −0.6) × Vienna Standard Mean Ocean Water (VSMOW) and 4.5 (+0.7, −0.6) × VSMOW, respectively, in agreement with our earlier result. The main result of this study is that there is no evidence of strong local variations in the D/H ratio nor for seasonal variations in the global D/H ratio between northern summer and southern summer.