Last updated June 22, 2018 at 3:56 pm
And that makes it hard to define a day.
Atmospheric waves could be slowing Venus’ rotation by a few minutes per day, possibly explaining why it is difficult to pin down exactly how long a day is, according to international researchers.
Venus rotates only once about every 243 Earth days, but its atmosphere moves much more quickly – taking four Earth days for a rotation.
Despite this, when Japan’s Akatsuki spacecraft recently observed a giant bow-shaped atmospheric structure appearing and disappearing, it noted that the structure remained stationary above a mountainous region.
It has been suggested that this structure was an atmospheric wave, caused by the lower atmosphere rising over mountain topography. If that is the case, the planet and its atmosphere might be more closely linked than originally thought.
To test this hypothesis, a US / French team led by UCLA’s Thomas Navarro simulated the circulation of the Venusian atmosphere. They found that the bow-shaped structure can indeed be explained by atmospheric waves forming over the mountains, with the waves only forming in the afternoon and vanishing by dusk.
They also found that the formation of these waves causes atmospheric pressure fluctuations that actually change the rotation rate of the solid planet, depending on the time of day.
This effect is small, but the interplay between the solid planet and its atmosphere may explain at least some of the discrepancies between past measurements of Venus’s rotation rate.
The Akatsuki spacecraft is orbiting Venus to study its climate and atmosphere.
The paper published in Nature Geoscience.