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Washington DC. [USA], April 25 (ANI): Images from the Akatsuki spacecraft reveal what makes Venus’ atmosphere spin much faster than the planet itself.
An international research team led by Takeshi Horinouchi from Hokkaido University has revealed that this ‘super rotation’ is held close to the equator by atmospheric tidal waves formed by solar warming on the day side of the planet and cooling on its side. night. However, closer to the poles, atmospheric turbulence and other types of waves have a more pronounced effect. The study was published online in Science.
Venus rotates very slowly, taking 243 Earth days to rotate once around its axis. Despite this very slow rotation, the atmosphere of Venus turns west 60 times faster than its planetary rotation. This super rotation increases with altitude, taking only four Earth days to circulate across the planet to the top of the cloud layer.
The fast-moving atmosphere transports heat from the day side of the planet to the night side, reducing temperature differences between the two hemispheres.
“However, ever since super rotation was discovered in the 1960s, the mechanism behind its formation and maintenance has been a long-standing mystery,” Horinouchi said.
Horinouchi and colleagues at the Institute for Space Science and Astronautics (ISAS, JAXA) and other institutes developed a highly accurate new method for tracking clouds and deriving wind speeds from images provided by ultraviolet and infrared cameras on the Akatsuki spacecraft , which began its orbit of Venus in December 2015. This allowed them to estimate the contributions of atmospheric waves and turbulence to super rotation.
The group noted for the first time that atmospheric temperature differences between low and high latitudes are as small as cannot be explained without circulation through the latitudes.
“Since such circulation should alter the wind distribution and weaken the superrotation peak, it also implies that there is another mechanism that reinforces and maintains the observed wind distribution,” Horinouchi explained. Other analyzes revealed that maintenance is sustained by the thermal tide, an atmospheric wave excited by the contrast of solar heating between the day and night sides, which provides acceleration at low latitudes.
Previous studies proposed that atmospheric turbulence and waves other than the thermal tide can provide acceleration. However, the current study showed that they work in the opposite way to weakly slow super rotation at low latitudes, despite the fact that they play an important role in mid and high latitudes.
Their findings uncovered the factors that maintain super rotation while suggesting a dual circulation system that effectively transports heat across the globe: the southern circulation that slowly transports heat to the poles and the super rotation that rapidly transports heat to the poles. the night side of the planet.
“Our study could help to better understand atmospheric systems on tidal-blocked exoplanets whose side is always facing the central stars, which is similar to Venus having a very long solar day,” Horinouchi added. (AND ME)
