For years, scientists have been unable to agree on the duration of a day on Venus, but this new study, conducted by the planetologist Thomas Navarro of the University of California in Los Angeles and French colleagues, could put an end to this confusion.
The rotation of the planet of Venus is retrograde: it turns on itself in a clockwise direction, whereas the other planets of the solar system (with the exception of Uranus) turn in the other way. In addition, it turns very slowly, so a Venusian day is equivalent to 243 Earth days. Furthermore, being closer to the sun than the Earth, the planet revolves around it in 225 Earth days. Its years are shorter than its days.
The speed of rotation of Venus is difficult to measure because of the thick sheet of sulfuric acid that covers the planet, and the data we had so far was to say the least confusing. Indeed, data collected by the radar instruments during two orbital missions, that of NASA’s Magellan spacecraft (from 1990 to 2004) and that of Venus Express from Europe (from 2006 to 2014), showed differences of several minutes in rotation measurements. A phenomenon that researchers did not know how to explain.
“We have suspected that the rotation speed of Venus varied constantly, but the reasons for this reality remained unclear,” says Thomas Navarro, planetologist at the University of California at Los Angeles.
Recent computer simulations carried out by Navarro and his French colleagues confirm that the winds, which circulate around the planet at 100 meters per second, exert major surges on one of the steep slopes of Ovda Regio, a mountain of more than 4000 meters above sea level, and cause a suction effect on the other side.
These studies also show that the phenomenon, which takes the appearance of a wave of a length of 10 000 kilometers and a width of 70 kilometers, blows gusts at altitude which interact with the atmospheric winds, which causes, according to the researchers, the speed of rotation of Venus and a decrease in the duration of a day of the order of two minutes per day.
The wave extends practically to the whole planet and wave also was photographed in 2015 by the Akatsuki probe of the Japanese space agency (JAXA).