IAstro draws the most complete profile of Venus' winds

A team formed by researchers from the Institute of Astrophysics and Space Sciences (IAstro), the Faculty of Sciences of the University of Lisbon (Ciências 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 the cloud base. Some of the measurements carried out 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 terms of size.

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

One of the unprecedented results was the simultaneous measurement of wind speeds at two altitudes 20 kilometers apart. The team found a difference in wind speeds of about 150 kilometers per hour faster at the cloud tops. It is known that the atmosphere of Venus is peculiar, consisting of thick clouds that create an enormous greenhouse effect, and that causes the temperature near the ground to reach 460ºC. The planet's surface continuously emits infrared radiation – so-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 lowest 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 highest layers of the atmosphere of Venus.

With the success of this approach, the team will now expand the research into the vertical component of the winds with new observations using the probe currently orbiting Venus, coordinated with observations made from Earth which, as this study has shown, allow the study of the planet to be complemented with data that probes cannot obtain. Furthermore, the experience of IAstro and Portuguese researchers in understanding the dynamics of Venus' atmosphere will help to choose the wavelengths of light in which the EnVision mission, the next one from 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 yet another international ESA project, with the prospect of support from the Portuguese Space Agency, Portugal Space.

On the IAstro website there is a more detailed article about the method and results of this study.