As the closest planet to Earth, Venus is a relatively easy object to observe. However, many mysteries remain, not least the super-rotation of Venus’ atmosphere, which enables high altitude winds to circle the planet in only four days. Now images of cloud features sent back by ESA’s Venus Express orbiter have revealed that these remarkably rapid winds are becoming even faster.
Similar in size to Earth, Venus has an extremely dense, carbon-dioxide-rich atmosphere and the planet’s surface is completely hidden by a blanket of bland, yellowish cloud. Only at ultraviolet wavelengths (and to a lesser extent in the infrared) do striking cloud streaks and individual cells emerge, due to the presence of some unknown UV absorber in the cloud deck.
By tracking the movements of these distinct cloud features, observers have been able to measure the super-hurricane-force winds that sweep around the planet at the cloud tops, some 70 km above the scorching volcanic plains.
Despite decades of observation from the ground and from spacecraft, a number of mysteries remain. What causes the remarkable super-rotation of Venus’ atmosphere – so called because the upper winds travel 50 times faster than the planet’s rate of rotation? How do the winds vary with latitude and longitude? How much do they change over time?
The answers to some of these questions are being provided by instruments on board Venus Express, such as the Venus Monitoring Camera (VMC), which have been observing the atmosphere for 10 Venus years – equivalent to 6 Earth years.
The VMC acquires instantaneous snapshots of Venus at UV and near-infrared wavelengths. Simultaneous imaging in these wavebands makes it possible to detect and track cloud features, and thus derive wind data, at two different levels – approximately 70 km and 60 km above the surface.
Read more at: Phys.org