The first detailed study of the “tsunami” in the clouds of Venus surprises scientists!
Examples of discontinuity events during 2022. The discontinuation was visible on lower clouds on the night side in images taken on February 4, and in middle clouds on the day side as observed in images taken by amateur observers from May to July 2022. During June 14 , Akatsuki/UVI images at 365 nm indicate that the discontinuity was propagating simultaneously at the upper and middle clouds (last image in the top row).
(Peralta, J. et al. (2023) “Venus Cloud Outage in 2022,” Astronomy & Astrophysics, 672. DOI: https://doi.org/10.1051/0004-6361/202244822.)
Venus, Earth’s closest neighbor, has seen a lot of events lately. Scientists recently found the first direct evidence of volcanic activity on our sister planet using three-decade-old images from the Magellan mission. Archival data then revealed the possibility of the formation of tectonic plates on Venus. Images taken by NASA’s Curiosity mission this week indicated what looked like the skeletal remains of an ancient fish!
And the barrage of studies continues to flow! Earlier this month, another interesting study looked at “tsunamis” in the deepest clouds of Venus, which could help the planet’s fast-moving atmosphere!
Unexpected meteorological pattern
Venus is often called Earth’s sister planet due to their similarity in size, mass, density, and scale; However, this is where the similarity ends. Venus’ atmosphere is toxic, full of carbon dioxide that traps heat. Furthermore, the planet is always surrounded by thick, yellow clouds of sulfuric acid, making it the hottest planet in our solar system.
In addition to all these special characteristics, the Venusian clouds also host massive and rapidly spreading atmospheric turbulence – an atmospheric phenomenon not yet seen anywhere else in the solar system! This giant, tsunami-like cloud pattern is believed to play an important role in accelerating the planet’s fast-moving atmosphere.
An international research team has attempted to understand the evolution of this discontinuity in Venus’ clouds in detail for the first time. After observing this phenomenon non-stop for more than 100 days using the ultraviolet imaging (UVI) camera on board the Akatsuki mission, scientists were in for a surprise!
And after remaining unnoticed for at least 35 years, it looked as if a giant atmospheric outage had freed itself from the deep clouds. In fact, it was observed for several hours to spread about 70 kilometers above the surface of the planet.
Javier Peralta explained: “This is surprising because until now, this outage seemed to be ‘confined’ to the deepest clouds, and we had never observed it before at such a high altitude.” These disturbances were first discovered in 2020, when they periodically swept across the solid ball of Venus over the course of five days, at a speed of about 330 kilometers per hour.
Why the sudden change?
On Venus, wind speed increases as we move upward. It reaches its peak at the top of the clouds, where the wind speed is higher than the atmospheric cut-off speed.
Therefore, there is a constant struggle between the wind and the cutoff, which is trying to reach height by overcoming the obstacle of high-speed winds. Such attempts usually fail as these “tsunamis” dissipate when encountering faster winds as they rise.
However, during the first half of 2022, when the Akatsuki mission made these observations, Venus’ atmospheric winds were unusually slow. In fact, they were several times slower than the outage.
The slower winds meant that the atmospheric break saw no obstacles in its path as it rose higher. Hence, tsunami waves continued to propagate to higher altitudes for a longer period during these observations.
Until now, it was a mystery why Venus’ atmosphere moved about sixty times faster than its surface. This atmospheric phenomenon, known as superrotation, has been observed on Saturn’s moon Titan and several other exoplanets as well.
But now, researchers hope that analyzing Venus’ winds and further studying the “tsunami waves” that propagate above Venus’ deep clouds can finally help them solve the mystery.
This study was published in the journal Astronomy and astrophysics This month and can be accessed here.
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