A Global collaboration of Amateur Astronomers has shed light on Venus' superrotation mystery.
A groundbreaking study has closely observed an enormous atmospheric ‘tsunami’ wave in the clouds of Venus for the first time, revealing its potential role in accelerating the planet’s fast-moving atmosphere. This discovery was made possible by an international collaboration of amateur astronomers who observed Venus for over 100 consecutive days.
In a first-of-its-kind study, a team led by Javier Peralta from the University of Seville observed a massive atmospheric wave, resembling a tsunami, that propagates through the deepest clouds of Venus. The findings, published in Astronomy & Astrophysics, suggest this discontinuity may play a significant role in accelerating Venus’s rapidly moving atmosphere. The uninterrupted observations, spanning more than 100 days, were made possible by a global network of amateur astronomers working in conjunction with the Japanese mission Akatsuki in 2022.
Discontinuity
The study unveils another surprising fact: ultraviolet images captured by the UVI camera aboard the Akatsuki mission in June showed that the discontinuity appeared to propagate to about 70 km above the surface of Venus for a few hours. “It is surprising because, until now, the discontinuity appeared ‘trapped’ in the deepest clouds and we had never observed it at such a height,” explains Peralta.
As an astrophysicist, Peralta designed the Venus observation strategy for the WISPR instrument during NASA’s Parker spacecraft approach and departure maneuvers in 2022, and contributed to the physical interpretation of the observations by comparing thermal emission images from Venus’s surface taken by WISPR and Akatsuki’s IR1 camera.
Venus’ upper clouds
The Akatsuki images not only suggest the discontinuity may have spread to Venus’s upper clouds, but also help researchers understand why this occurred. Generally, regions with winds matching a wave’s speed act as a physical barrier to the wave’s propagation. On Venus, winds increase gradually with altitude and move faster than the cloud-top discontinuity, preventing the discontinuity from propagating upward from the deep clouds. However, when researchers measured the winds in the high clouds using Akatsuki, they discovered that they were unusually slow in the first half of 2022, several times slower than the discontinuity itself. As a result, the discontinuity could propagate to higher altitudes.
“Measuring the winds on Venus is critical to trying to explain why the Venusian atmosphere spins 60 times faster than the surface. This atmospheric phenomenon is known as superrotation. It also occurs on Saturn’s moon Titan and on many exoplanets, but after more than half a century of research, we still cannot explain it satisfactorily,” Peralta explained.
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