Although deuterium (D) on Mars has received substantial attention, the; deuterated ionosphere remains relatively unstudied. This means that we; also know very little about non-thermal D escape from Mars, since it is; primarily driven by excess energy imparted to atoms produced in; ion-neutral reactions. Most D escape from Mars is expected to be; non-thermal, highlighting a gap in our understanding of water loss from; Mars. In this work, we set out to fill this knowledge gap. To accomplish; our goals, we use an upgraded 1D photochemical model that fully couples; ions and neutrals and does not assume photochemical equilibrium. To our; knowledge, such a model has not been applied to Mars previously. We; model the atmosphere during solar minimum, mean, and maximum, and find; that the deuterated ionosphere behaves similarly to the H-bearing; ionosphere, but that non-thermal escape on the order of 8000-9000; cm-2s-1 dominates atomic D loss under all solar conditions. The total; fractionation factor, f, is 0.04–0.07, and integrated water loss is; 147–158 m GEL. This is still less than geomorphological estimates.; Deuterated ions at Mars are likely difficult to measure with current; techniques due to low densities and mass degeneracies with more abundant; H ions. Future missions wishing to measure the deuterated ionosphere in; situ will need to develop innovative techniques to do so.
