Simplified Relations for the Martian Nighttime Hydroxyl Layer Suitable for Interpretation of Observations

Observations of excited hydroxyl (OH^*) emissions are broadly used for inferring information about atmospheric dynamics and composition. It plays an important role in the photochemical balance and is affected by transport and mixing processes. We present several analytical approximations for characterizing the hydroxyl layer in the Martian atmosphere. They include OH^* number density at the maximum and the height of the peak, along with the relations for assessing different impacts on the OH^* layer at nighttime conditions. These characteristics are determined by the ambient temperature, atomic oxygen concentration and their vertical gradients. The derived relations can be used for analysis of airglow measurements and interpretation of its variations.