Paris, September 19 : The European Space Agency's (ESA's) Venus Express has for the first time, put together a 3-D picture of the Venusian winds for an entire planetary hemisphere, which would help estimate how windy is it on Venus.
The most powerful atmospheric investigator ever sent to Venus, Venus Express has an advantageous orbit around the planet and a unique set of instruments.
The spacecraft has the ability to peer through Venus's thick atmospheric layers and obtain a truly global picture.
The spacecraft has continuously monitored the planet since observations began in 2006, and scientists now have enough data to start building a complete picture of the planet's atmospheric phenomena.
The Venus Express Visual and Infrared Thermal Imaging Spectrometer, VIRTIS, has been studying the thick blanket of clouds that surround Venus, gathering data on the winds.
The area studied spans altitudes of 45 to 70 km above the surface and covers the entire southern hemisphere, up to the equator.
It is above the southern hemisphere that Venus Express reaches its highest point in orbit (about 66 000 km), allowing the instruments to obtain a global view.
Agustin Sanchez-Lavega, from the Universidad del Pais Vasco in Bilbao, Spain, led the research on 3-D wind mapping with data from the first year of VIRTIS observations.
"We focused on the clouds and their movement. Tracking them for long periods of time gives us a precise idea of the speed of the winds that make the clouds move and of the variation in the winds," he said.
According to Ricardo Hueso, also from the Universidad del Pais Vasco, co-author of the results, "We studied three atmospheric layers and followed the movement of hundreds of clouds in each. This has never been done before at such large temporal and spatial scales, and with multi-wavelength coverage."
In total, the team tracked 625 clouds at about 66 km altitude, 662 at around 61 km altitude, and 932 at about 45-47 km altitude, on the day and night sides of the planet.
The individual cloud layers were imaged over several months for about 1-2 hours each time.
"We have learnt that between the equator and 50-55 degrees latitude south, the speed of the winds varies a lot, from about 370 km/h at a height of 66 km down to about 210 km/h at 45-47 km", said Sanchez-Lavega.
Sanchez-Lavega and colleagues observed that the speed of the zonal winds (which blow parallel to the lines of latitude) strongly depend on the local time.
The difference in the Sun's heat reaching Venus in the mornings and in the evenings - called the solar tide effect - influences the atmospheric dynamics greatly, making winds blow more strongly in the evenings.