Model for Nitric oxide and its dayglow emission in the Martian upper atmosphere using NGIMS/MAVEN measured neutral and ion densities

TL;DR

This study develops a photochemical model using MAVEN NGIMS data to estimate nitric oxide densities and dayglow emissions in Mars' upper atmosphere, aligning well with observations and aiding in understanding NO distribution.

Contribution

The paper introduces a novel photochemical model that utilizes MAVEN NGIMS measurements to estimate NO densities and emissions in Mars' upper atmosphere, improving upon previous models.

Findings

Modelled NO densities agree with MAVEN IUVS observations.

NO dayglow intensity varies with CO2 and N2 densities by a factor of 2 to 5.

The approach can help constrain NO abundance in Mars' upper atmosphere.

Abstract

A comprehensive study of Nitric oxide (NO) chemistry in the Martian upper atmosphere is restricted due to the lack of requisite measurements. NO is an abundant form of odd nitrogen species in the Martian lower atmosphere and its density depends on several photochemical processes. We have developed a photochemical model to study the NO density in the dayside of Martian upper atmosphere by accounting for various production and loss mechanisms. By utilizing the Neutral Gas and Ion Mass Spectrometer (NGIMS) on-board Mars Atmosphere and Volatile Evolution (MAVEN) mission measured neutral and ion densities during deep dip 8 and 9 campaigns, we modelled NO number density in the Martian sunlit upper atmosphere for the altitudes between 120 and 200 km. The modelled NO densities are employed to calculate NO (1,0) gamma band emission intensity profiles in the dayside upper atmosphere of Mars. The calculated NO density and its gamma band intensity profiles are found to be consistent with Imaging Ultraviolet Spectrograph (IUVS) onboard MAVEN observations and also with other modelling studies. We found that the local CO2 and N2 density variations can lead to a change in NO density and consequently its dayglow intensity by a factor of 2 to 5. Since NO is a trace constituent and also its dayglow emissions are strongly obscured by CO Cameron band emissions, we suggest that the derivation of NO number density based on our approach can constrain its abundance in the dayside upper atmosphere of Mars. More observations of (1-0) gamma band emission along with modelling will help to study the global distribution of NO in the Martian atmosphere.