June 27, 2013
After monitoring cloud motion in the Venusian atmosphere for six years, using European Space Agency's Venus Express, scientists have discovered that planet's winds have been getting faster year after year.
Winds on Venus increased a lot over the last six years.
Venus is already known by its harsh atmosphere conditions, high pressure and temperatures. Its atmosphere rotates around the planet in four Earth days, while the Venus itself rotates only once every 243 Earth days. This makes Venuvian atmosphere rotation extremely fast compared to planet rotation itself.
The Venus Express has been in planet's orbit since May 2006, at which time the speed of winds between 50º north and 50º south latitude was about 300 km/h on avarage. Today, the speed of winds is clocked at 400 km/h, as confirmed by two separate studies.
"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," said Igor Khatuntsev from the Space Research Institute, Moscow, Russia. Dr Khatuntsev leads a team that measured wind speeds by tracking almost 400 000 cloud features moving between image frames, 45 000 of which was measured manualy, the rest by using a computer software.
In another study, a Japanese team used independant cloud tracking method to come to the same result, which will be published in the Journal of Geophysical Research. "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," said Toru Kouyama, Information Technology Research Institute, Ibaraki, Japan.
Beside the increase in speed over the years, both studies have also found variations of wind speeds at lower latitudes, taking anywhere from 3.9 days to 5.3 days to complete the rotation around the planet. Neither of the two teams offered an explanation for long-term increase in wind speed or these short-term variations.