Thermal structure of Mars' middle and upper atmospheres: Understanding the impacts of dynamics and solar forcing

We report six years of observations of dayside temperatures of the middle and upper atmospheres of Mars made by the Imaging Ultraviolet Spectrograph instrument aboard the MAVEN spacecraft. Thermospheric temperatures show strong long-term variability associated with Martian season and solar cycle. Temperatures from both the Martian thermosphere and mesosphere show strong short-term variability indicating coupling from the lower atmosphere. The observed local time effect is strong in both upper and middle atmosphere temperatures. The thermosphere tends to be colder in the morning compared to the evening when temperatures are higher. Middle atmospheric temperatures show cooling during the dawn and dusk hours. Our analysis shows strong tidal activity during aphelion, whereas non-migrating tides are suppressed during perihelion, possibly due to increased dust activity. Observations during the deep minimum of solar cycle 24 reveal that thermospheric temperatures are highly variable with respect to local time if solar forcing, Mars-Sun distance, and spatial effects are removed.

Automated summary

We present six years of temperature observations of Mars' middle and upper atmospheres during the day, obtained using the Imaging Ultraviolet Spectrograph instrument aboard the MAVEN spacecraft. Our results reveal strong long-term variability in thermospheric temperatures, which is linked to Martian seasons and the solar cycle. Both the thermosphere and mesosphere exhibit pronounced short-term variations, indicating a coupling with the lower atmosphere. Additionally, we identify a significant local time effect, with the thermosphere being colder in the morning and warmer in the evening.