- Venus's atmosphere rotates about 60 times faster than its surface in a superrotation phenomenon
- The planet's atmosphere completes one orbit in four Earth days, while Venus rotates in 243 days
- Study analysed data from ESA's Venus Express and JAXA's Akatsuki satellites from 2006 to 2022
Imagine winds stronger than a category 5 hurricane, racing at more than 100 meters per second and circling the planet with no end in sight. While this would be catastrophic on Earth, it is a normal feature on Venus, reported Space.com.
At cloud level, Venus's atmosphere rotates about 60 times faster than the planet itself, a phenomenon known as superrotation. On Earth, by contrast, the atmosphere moves roughly at the same speed as the planet's surface.
Previous studies have attempted to understand why Venus's atmosphere rotates so rapidly, but the reasons behind it were not fully understood. A new study by Lai and his colleagues shows that the daily atmospheric tidal cycle, driven by solar heat, plays a more significant role in Venus's extreme winds than previously thought.
Superrotation is common on rocky planets that orbit their stars and rotate slowly. Venus completes one full rotation in 243 Earth days, while its atmosphere orbits the planet in just four Earth days.
To understand this fast-moving atmosphere, researchers analysed data obtained from the European Space Agency's Venus Express and the Japan Aerospace Agency's Akatsuki satellites between 2006 and 2022. Both satellites studied Venus's atmosphere by measuring the bending of radio waves. The research team also used numerical models to simulate superrotation.
The study focused primarily on thermal tides (solar tidal waves), which generate wind speeds in the atmosphere from the Sun's heat. Along with other processes like meridional circulation and planetary waves, thermal tides help maintain Venus's superrotation by transmitting motion. There are two major types of Venusian thermal tides: diurnal tides, which complete one cycle each Venusian day, and semidiurnal tides, which complete two cycles a day.
New findings suggest that diurnal tides, driven by solar heat, are a major contributor to the extreme speeds of Venus's winds. Understanding these tidal waves could help scientists better understand why Venus's atmosphere rotates so rapidly, even though the planet itself rotates very slowly.
