Martian Dayside Temperature Maps Derived from MAVEN IUVS Observations of O I 297.2 nm Emission

We present thermal contour maps for the upper mesosphere and lower thermosphere, from ~80-160 km, of Mars using limb observations from the Imaging Ultraviolet Spectrograph (IUVS) aboard NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Temperature profiles as a function of altitude are determined from retrieved CO2 number densities using the O I 297.2 nm double-peaked emission profile that is detectable by IUVS. The temperature profiles presented here span Mars years (MY) 32-36, since the inception of the MAVEN mission in 2014 through the fall of 2021, and are shown with respect to latitude, longitude, local solar time, season, dust activity, and solar activity. Our analysis (1) reveals a mesopause at approximately 120 km, (2) shows polar warming at both northern and southern latitudes (typically from 100 km to below the mesopause) for all Mars years and seasons, with equatorial warming (below the mesopause from 50° S to 50° N) present in most seasons from MY32 to MY36, (3) warm regions at the dawn and dusk terminators (from approximately 100 km upwards to the mesopause), and (4) longitudinal waves in both the upper mesosphere and lower thermosphere that are about 30° out of phase. This is the first study of its kind to use inbound and outbound segments of the MAVEN orbit in addition to periapse observations of O I 297.2 nm emission to retrieve CO2 number densities and temperatures with formally propagated errors. The results presented are the first to extend temperature calculations from the thermosphere to the upper mesosphere using O I 297.2 nm emission and thereby provide a pathway to understanding the coupling between the two regions of the atmosphere.