Venus’ Atmosphere Rotates Far Faster Than Its Surface Because of Thermal Tides
Akatsuki: surveying lightning emission in Venus’ sea of clouds and observing cloud layers on the horizon (by Akihiro Ikeshita). A conceptual image of Akatsuki observing cloud layers with lightning.
By tracking the thick clouds of Venus’ rapidly rotating atmosphere, researchers have gained new insight into the dynamic forces that drive atmospheric super-rotation — a little-understood phenomenon in which an atmosphere rotates much faster than the solid planetary body below.
Based on observations from the Japan Aerospace Exploration Agency (JAXA) spacecraft Akatsuki, which has been orbiting Venus since 2015, the study suggests that super-rotation is maintained by a combination of solar heating-driven thermal tides, planetary waves and atmospheric turbulence.”
Among the intriguing mysteries that remain for planetary atmospheres, the phenomenon of super-rotation is still a teasing problem,” writes Sebastion Lebonnois in a related Perspective. Compared to Earth, the rotation of Venus is slow — its surface takes 243 Earth days to complete one rotation. However, the Venusian atmosphere spins nearly 60 times faster, whipping around the planet once every 96 hours.
For this phenomenon to occur, a continuous redistribution of angular momentum is needed to overcome friction with the planet’s surface, although neither the source of this momentum nor how it’s maintained are known.