Impact of Mars GDS 2018 on the Chemistry of Water, Nitrogenated and Deuterated Cluster Ions: NOMAD Observations

Abstract

The ExoMars Trace Gas Orbiter instruments, Nadir and Occultation for Mars Discovery and Atmospheric Chemistry Suite have provided vertical profiles of H2O and HDO mixing ratios in the presence and absence of Global Dust Storm 2018. These observations are carried out in the lower atmosphere at SZA ∼ 71° of northern mid latitude (∼55°N, 130°E). Using NOMAD observations, we developed chemical models 1 and 2 for dust and non‐dust storm conditions, respectively. The production/loss rates of H2O, HDO and D2O and the densities of water, nitrogenated and deuterated cluster ions (H2O+, D2O+, HDO+, H+(H2O)n, D+(D2O)n, H+(HDO)n, CO4−, CO3−, CO3−(H2O)n, CO3−(D2O)n, CO3−(HDO)n, NO2−(H2O), NO2−(HDO), and NO2−(D2O) (for n = 1 to 5)) are estimated from these models between 10 and 70 km. We have used two ionization sources: (a) Galactic Cosmic Rays (GCR) and (b) hard X‐ray in both models. The D peak density produced by GCR is lower by a factor of ∼5 than that produced by the hard X‐rays. In model 1, the electron densities were increased by a factor of ∼2–3 than that produced by model 2. The estimated production/loss rates of H2O, HDO, and D2O are also larger by an order of magnitude in model 1 than that estimated by model 2.