Mars: Atmospheric Waves and Winds

What is it about?

Atmospheres are constantly evolving, and information about what is happening is carried by waves of all shapes and sizes, including: i) sound waves, ii) buoyancy waves, like the waves on a lake but inside the atmosphere, and most especially iii) vorticity waves (Rossby waves), for example the meandering of the jet stream. When the wind blows faster than a particular wave speed, it prevents the information carried by that wave from propagating upstream. This strongly affects the evolution of the atmosphere. The most recognizable examples are acoustic shocks for sound waves, hydraulic jumps or bores for buoyancy waves, and shear instability for vorticity waves. This study shows all three are important on Mars (only the latter is prevalent on Earth).

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Why is it important?

By examining vorticity-wind correlations, this article shows that a good way to view the atmosphere of Mars is to start with an atmosphere like Earth's, throw away the troposphere and the stratosphere, and place the mesosphere directly on the ground. Boots-on-the-ground astronauts will soon arrive at Mars, and will be living and working in what is essentially a mesosphere, without any of the buffers afforded by a troposphere or a stratosphere. Gaining an understanding of how un-Earth-like compressibility operates in the Martian atmosphere improves both the science return and the safety of Mars missions. Hydraulic jumps are likely to be common on Mars, and are associated with turbulence, which can pose hazards to astronauts and to scientific equipment, particularly to drones and balloons.

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