IAstro draws up a more complete profile of the winds on Venus

A team of researchers from the Institute of Astrophysics and Space Sciences (IAstro), the Faculty of Sciences of the University of Lisbon (ULisboa Sciences) and the University of Seville published a study this month in the scientific journal Atmosphere presenting the most detailed and comprehensive set of measurements ever made of wind speeds on Venus parallel to the equator and at cloud base altitude. Some of the measurements taken were unprecedented and are expected to contribute to understanding the unique characteristics of the planet closest to Earth and very similar to it in terms of size.

The study, led by Pedro Machado, from IAstro and Ciências ULisboa, sought to study the movement of clouds in the atmosphere on the night side of Venus—the side that is not facing the Sun, equivalent to nighttime on Earth, which on Venus, because of the planet's long rotation time (243 Earth days), lasts much longer. The combination of observations from Earth, using the Telescopio Nazionale Galileo (TNG) in La Palma, in the Canary Islands, with data collected by the European Space Agency's (ESA) Venus Express probe, allowed the team to track the movement of clouds using a method developed by Javier Peralta of the University of Seville, co-author of the study, and indirectly calculate the wind speed that drives them at various different altitudes.

One of the unprecedented results was the simultaneous measurement of wind speeds at two separate altitudes 20 kilometers apart. The team found a difference in wind speed of about 150 kilometers per hour faster at the top of the clouds. It is known that Venus' atmosphere is peculiar, consisting of thick clouds that create a huge greenhouse effect, causing the temperature at ground level to reach 460ºC. The planet's surface continuously emits infrared radiation—called thermal emission—which heats the lower layers of the atmosphere. In the words of Pedro Machado, the team managed for the first time to "study the vertical component of the wind, that is, how energy is transported from the lower layers, which are warmer, to the top of the clouds, leading to the acceleration of the winds," helping to explain the relationship between the extremely hot surface and the cyclonic speeds of the clouds in the upper layers of Venus' atmosphere.

With the success of this approach, the team will now expand its research into the vertical component of winds with new observations using the probe currently orbiting Venus, coordinated with observations made from Earth which, as this study has shown, complement the study of the planet with data that probes are unable to obtain. In addition, the experience of IAstro and Portuguese researchers in understanding the dynamics of Venus' atmosphere will help to choose the wavelengths of light at which the EnVision mission, the European Space Agency's (ESA) next mission dedicated to Venus, will observe, as well as the most scientifically relevant layers of the atmosphere, thus contributing to the design and planning of the mission and its instruments. Portugal is involved in the development of this new mission, with the Portuguese consortium led by Pedro Machado, and it is hoped that this participation will mobilize Portuguese industry for another ESA international project, with the prospect of support from the Portuguese Space Agency, Portugal Space.

A more detailed article on the method and results of this study can be found on the IAstro website.