The fast winds of Venus are getting faster
ESA PRESS RELEASE
Posted: 24 June 2013
The most detailed record of cloud motion in the atmosphere of Venus chronicled by ESA's Venus Express has revealed that the planet's winds have steadily been getting faster over the last six years.
By tracking the movements of distinct cloud features in the cloud tops some 70 km above the planet's surface over a period of 10 venusian years (6 Earth years), scientists have been able to monitor patterns in the long-term global wind speeds.
When Venus Express arrived at the planet in 2006, average cloud-top wind speeds between latitudes 50º on either side of the equator were clocked at roughly 300 km/h. The results of two separate studies have revealed that these already remarkably rapid winds are becoming even faster, increasing to 400 km/h over the course of the mission.
"This is an enormous increase in the already high wind speeds known in the atmosphere. Such a large variation has never before been observed on Venus, and we do not yet understand why this occurred," says Igor Khatuntsev from the Space Research Institute in Moscow and lead author of the Russian-led paper to be published in the journal Icarus.
On top of this long-term increase in the average wind speed, however, both studies have also revealed regular variations linked to the local time of day and the altitude of the Sun above the horizon, and to the rotation period of Venus.
One regular oscillation occurs roughly every 4.8 days near the equator and is thought to be connected to atmospheric waves at lower altitudes.
But the research also unveiled some harder-to-explain curiosities.
"Our analysis of cloud motions at low latitudes in the southern hemisphere showed that over the six years of study the velocity of the winds changed by up 70 km/h over a time scale of 255 Earth days - slightly longer than a year on Venus," says Toru Kouyama from the Information Technology Research Institute in Ibaraki, Japan.