Mars' Middle Atmosphere Appears Driven By Gravity Waves

A new study published in the Journal of Geophysical Research Planets reveals that atmospheric gravity waves play a crucial role in driving latitudinal air currents on Mars, particularly at high altitudes. Phys.Org reports: The study applied methods developed to explore Earth's atmosphere to quantitatively estimate the influence of gravity waves on Mars' planetary circulation. 'On Earth, large-scale atmospheric waves caused by the planet's rotation, known as Rossby waves, are the primary influence on the way air circulates in the stratosphere, or the lower part of the middle atmosphere. But our study shows that on Mars, gravity waves (GWs) have a dominant effect at the mid and high latitudes of the middle atmosphere,' said Professor Kaoru Sato from the Department of Earth and Planetary Science. 'Rossby waves are large-scale atmospheric waves, or resolved waves, whereas GWs are unresolved waves, meaning they are too fine to be directly measured or modeled and must be estimated by more indirect means.'

Not to be confused with gravitational waves from massive stellar bodies, GWs are an atmospheric phenomenon when a packet of air rises and falls due to variations in buoyancy. That oscillating motion is what gives rise to GWs. Due to the small-scale nature of them and the limitations of observational data, researchers have previously found it challenging to quantify their significance in the Martian atmosphere. So Sato and her team turned to the Ensemble Mars Atmosphere Reanalysis System (EMARS) dataset, produced by a range of space-based observations over many years, to analyze seasonal variations up there.

'We found something interesting, that GWs facilitate the rapid vertical transfer of angular momentum, significantly influencing the meridional, or north-south, in the middle atmosphere circulations on Mars,' said graduate student Anzu Asumi. 'It's interesting because it more closely resembles the behavior seen in Earth's mesosphere rather than in our stratosphere. This suggests existing Martian atmospheric circulation models may need to be refined to better incorporate these wave effects, potentially improving future climate and weather simulations.'

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