Japanese mission studies the mystery of Venus in collaboration with Portuguese researchers
2018 December 07

Composition of a Venus image in the infrared, with the Milky Way on the background.
Credits: Venus - ISAS/JAXA (modified), background - John Colosimo (
Examples of images acquired with the IR2 infrared camera on board of Akatsuki probe during the year 2016. Credits: ISAS/JAXA
One of the mysteries of the Solar System is the fact that the atmosphere of Venus circles the planet sixty times faster than its rotation period, generating permanent winds with hurricane-like speeds. The quest for the mechanisms that sustain this “super-rotation” motivated one of the most complete and detailed studies1 about the nocturnal winds on Venus close to its surface. This work, published today, had the important contribution of Pedro Machado, of Instituto de Astrofísica e Ciências do Espaço (IA2) and Faculdade de Ciências da Universidade de Lisboa (FCUL), and was led by Javier Peralta, of the Japanese mission Akatsuki.

In order to create an ever more comprehensive picture of what is happening in the atmospheric circulation of Venus, one needs to know the winds, in detail and over time, in the several layers of its atmosphere. The Akatsuki mission, of the Japanese space agency JAXA, observed for one full year the night side of Venus, enabling the analysis of the clouds between 48 and 70 kilometres of altitude. One of the most important revelations, according to Pedro Machado, was the discovery of the acceleration of the winds, at those altitudes, in the dusk zone, in the transition between the day side and the night side of the planet.

This is the first time it is detected, and will help understand the processes at the origin of the dramatic acceleration of the Venus atmosphere,” says Pedro Machado. These winds at low altitude are totally different from those already being studied on the layers above3. They can only be investigated through the analysis of the infrared light emitted by the planet itself, domain in which the research group at IA gave an important contribution to the paper published today.

Due to the greenhouse effect produced by the atmosphere, the zone below 48 kilometres of altitude is so hot, so hot, that it emits a large quantity of thermal radiation, in the infrared,” says Pedro Machado. “This radiation, once it hits the cloud layer, and being some of these clouds denser and others less, it traces their contour on the images obtained in the infrared. This way we can follow the cloud formations and build the wind map over time.

IA's Solar System research group collaborates directly with the Akatsuki mission because it developed a method that is complementary to the Japanese probe in the measuring of the winds in the infrared from telescopes based on Earth. As, throughout its orbit, the probe is not always over the night side, Pedro Machado used this method with the Telescopio Nazionale Galileo, in Canary Islands, in coordination with the Japanese mission, in order to guarantee a global observation, and as continuous as possible, of the planet Venus.

This method is a great leap in terms of the precision in this domain, being now as competitive as the data from the infrared camera of the space probe,” highlights Pedro Machado. For this reason, the Akatsuki mission is interested in this collaboration, in which the IA research group has also access to the images obtained with the probe.

One of the team's next steps is to understand the relationship between the lower layers of the atmosphere and the features on the surface of Venus, such as mountains, and how this relationship might contribute to the mechanisms that trigger and sustain the “super-rotation” of the atmosphere of the planet. 

  1. The article “Nightside winds at the middle-to-low clouds of Venus with Akatsuki/IR2”, by Javier Peralta et al., was published online on the 7th of December, 2018, in the Astrophysical Journal Supplement Series, Volume 239 (DOI: 10.3847/1538-4365/aae844).
  2. The Instituto de Astrofísica e Ciências do Espaço (Institute of Astrophysics and Space Sciences – IA) is the reference Portuguese research unit in space sciences and integrates researchers from the University of Porto and the University of Lisbon. The institute encompasses most of the field’s national scientific output and it was evaluated as Excellent in the last evaluation Fundação para a Ciência e Tecnologia (FCT) commissioned from the European Science Foundation (ESF). IA's activity is funded by national and international funds, including Fundação para a Ciência e a Tecnologia (UID/FIS/04434/2013), POPH/FSE and FEDER through COMPETE 2020.
  3. See for instance the following IA press-releases: “A preview of the Venus atmosphere in 3D” (23rd of May, 2017) and “Meridional wind on Venus was detected for the first time in both hemispheres” (15th of March, 2017).

Pedro Machado

Science Communication Group
Sérgio Pereira
Ricardo Cardoso Reis

Daniel Folha (Coordenação, Porto)
João Retrê (Coordenação, Lisboa)

Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia