Istro profiles Venus' winds more completely

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

The study, led by Pedro Machado, from IAstro e Ciências ULisboa, sought to study the movement of clouds in the atmosphere on the nocturnal side of Venus - the side that is not facing the Sun, equivalent to the period of night on Earth, which on Venus, because of the planet's long rotation time (243 Earth days), lasts much longer. The combination of observation from Earth, with the Telescopio Nazionale Galileo (TNG), in La Palma, in the Canary Islands, with data collected by the Venus Express probe, of the European Space Agency (ESA), allowed the team to follow the movement of clouds, using a method developed by Javier Peralta, from 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 first results was the simultaneous measurement of wind speed at two altitudes 20 kilometers apart. The team found a difference in wind speed 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, and that causes the temperature near the ground to reach 460°C. The planet's surface continuously emits infrared radiation - the so-called thermal emission - which heats up the lower layers of the atmosphere. In Pedro Machado's words, 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, and which will lead 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 the research of the vertical component of the winds with new observations through the probe currently orbiting Venus, coordinated with observations made from Earth, which, as this study proved, allow the study of the planet to be complemented with data that the probes cannot obtain. In addition, IAstro's and Portuguese researchers' experience in understanding the dynamics of Venus' atmosphere will help choose the wavelengths of light that the EnVision mission, the next of the European Space Agency (ESA) dedicated to Venus, will observe, as well as the layers of the atmosphere that are most relevant from a scientific point of view, 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 expected that this participation will mobilize Portuguese industry for another ESA international project, with the perspective 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.