Venus is notorious for extreme weather. Its dense atmosphere carries clouds around the planet at speeds above 100 metres per second — about 60 times faster than the planet's slow rotation. In fact, the atmosphere circles Venus in just four Earth days, even though the planet itself spins once every 243 days. For years, the origin of this super-rotating atmosphere remained unclear. Now researchers say they have identified a key driving force behind these runaway winds.
Daily thermal tide identified as key wind driver
According to the new study, most momentum driving Venus's fast cloud-top winds comes from a once-per-day (diurnal) thermal tide powered by solar heating. The researchers analysed two decades of data from ESA's Venus Express and JAXA's Akatsuki orbiters, which tracked atmospheric conditions via radio signals, and ran numerical simulations of Venus's circulation.
They found that "diurnal tides play a primary role in transporting momentum toward the tops of Venus's thick clouds," overturning earlier ideas that twice-daily tides dominated. The work includes the first analysis of Venus's Southern Hemisphere, strengthening the case that daily solar heating drives the atmosphere's extraordinary superrotation.
Long-standing mystery
For decades, Venus's violent winds have puzzled scientists. Early spacecraft data in the 1960s showed the atmosphere racing around the planet in just days, giving rise to the term “superrotation,” but its cause remained elusive. As one review observes, "Although Venus's atmospheric superrotation was discovered in the 1960s, the cause is still debated".
Numerous theories — from gravity waves to circulation cells — were proposed, but none fully solved the mystery. The new study builds on a long history of research into Venus's atmospheric quirks.
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