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Why is Venus spin so strange?

A composite image of Venus as seen by Japan’s Akatsuki spacecraft. Venus’ spin varies because of atmospheric waves on the planet’s mountains, according to a new study.

(JAXA)

For years, scientists have been unable to agree on the length of a day on Venus, but a new study would put an end to this confusion.

The planet Venus rotates very slowly, with one revolution taking about 243 earth days, and this rotation speed varies. In addition, while the planet rotates slowly, the atmosphere moves much faster, making a full rotation in just four Earth days, according to a statement on the new study. However, while we can follow the planet to change rotation, until now, scientists were not able to clearly explain why the rate changes.

Thanks to the images of the Akatsuki spacecraft of JAXA, the Japanese space agency, researchers think they finally have the reason behind these variations. In a new study, published today (June 18) in the journal Nature Geoscience, researchers showed how the interaction between Venus’ fast-moving atmosphere and the surface, marked with volcanoes and mountains, changes the speed of the planet turning. [Japan Venus: Shinobi Pictures of the Murky World]

Recently, Shinobi, and saw a large, bow-shaped atmospheric structure on Venus. The spacecraft should be noted that the structure retained disappear and reappear, but it remained in the same location above the mountains on the surface of the planet. When researchers first studied images of the planet of the Shinobi’s mission in 2015, they suggested that the strange structure was actually a fast-moving mountain golf. A mountain wave is a type of atmospheric gravity wave by topographic elements like mountains and the way of the wind flow over them.

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Venus’ surface is hard to get a picture is not only the result of the planet have different rotation, but also because the surface is “hidden behind a solid, thick cloud cover,” Thomas Navarro, study author and researcher at the University of California, told Space.com in an e-mail. This made it extra difficult for researchers to understand this phenomenon.

However, through the use of photos at various wavelengths of Shinobi, the researchers in the new study were finally able to get a clear image of the arch-shaped structure and confirm the presence of a mountain wave. They also explained how mountain waves cause Venus to rotate at different speeds: Due to the different directions of the wind flow upstream and downstream at the mountain, “is Generally the net force exerted on the mountain, and the whole solid body follows,” Navarro said.

By learning about Venus’ mountain waves, scientists can better understand how angular momentum is transferred between the solid body [Venus] and the atmosphere,” Navarro said. In other words, because researchers have confirmed that the mysterious structure is a mountain wave, they are better able to study “how the atmosphere and the solid body influence each other, and why Venus is the way it is,” he said.

Original article on Space.com.

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