Venus' thick atmosphere speeds up the planet's spin

[Judi Lynn]

The way the air flows over mountains changes the entire planet’s rotation speed
BY LISA GROSSMAN 3:44 PM, JUNE 18, 2018



PUSH AND PULL New research has shown that Venus’ thick atmosphere, shown here in an image from the Japanese space agency’s Akatsuki spacecraft, can speed up the planet’s rotation.

DAMIA BOUIC, DARTS, ISAS, JAXA

Time is out of joint on Venus. The planet’s thick air, which spins much faster than the solid globe, may push against the flanks of mountains and change Venus’ rotation rate.

Computer simulations show that the thick Venusian atmosphere, whipping around the planet at 100 meters per second, exerts enough push against a mountain on one side and suction on the other side to speed the planet’s rotation rate by about two minutes each Venus day, according to a study in Nature Geoscience June 18.

That’s not much, considering that the planet rotates just once every 243 Earth days. By comparison, Venus’ atmosphere rotates about once every four Earth days. Precise measurements of the planet’s rotation rate have varied by about seven minutes, however. The push and pull of the air over the mountains could help explain the mismatch, with some other force — possibly the gravitational influence of the sun — slowing the planet’s spin back down.

The simulations by UCLA planetary scientist Thomas Navarro and colleagues are the first to account for a 10,000-kilometer-long wave in Venus’ cloud tops, spotted in 2015 by the Japanese space agency’s Akatsuki spacecraft (SN: 2/18/17, p. 5). Similar waves are launched into the atmosphere on Earth when air flows over a mountain, but they normally dissipate quickly as opposing winds break them up. Venus’ atmosphere rotates so much faster than the planet and in such a uniform direction that the waves could persist for a long time.

More:
https://www.sciencenews.org/article/venus-thick-atmosphere-speeds-planets-spin?utm_source=email&utm_medium=email&utm_campaign=latest-newsletter-v2

[Judi Lynn]

1. Why Does Venus Spin So Weirdly?

By Chelsea Gohd, Space.com Staff Writer | June 18, 2018 04:47 pm ET

- click for image -

https://img.purch.com/h/1400/aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzA3NS83MDEvb3JpZ2luYWwvdmVudXMtY2xvdWRzLWpheGEuanBn

A composite image of Venus as seen by Japan's Akatsuki spacecraft. Venus' spin varies because of atmospheric waves over the planet's mountains, according to a new study.
Credit: JAXA


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

The planet Venus rotates very slowly, with a single revolution taking about 243 Earth days, and this rotation rate varies. Additionally, while the planet turns slowly, its atmosphere moves dramatically faster, making a complete rotation in only four Earth days, according to a statement about the new study. However, while we can follow the planet's changing rotation, until now, scientists weren't able to clearly explain why the rate changes.

Thanks to images from the Akatsuki spacecraft of JAXA, the Japanese space agency, researchers think that they have finally found 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 its surface, marked with volcanos and mountains, changes the speed of the planet's spin. [Japan at Venus: Akatsuki Photos of the Cloudy World]

Recently, Akatsuki spotted a huge, bow-shaped atmospheric structure on Venus. The spacecraft noticed that the structure kept disappearing and reappearing, yet it remained in the same location above mountains on the planet's surface. When researchers first studied images of the planet from Akatsuki's mission in 2015, they suggested that the strange structure was actually a fast-moving mountain wave. A mountain wave is a type of atmospheric gravity wave created by topographical elements like mountains and the way wind flows over them.

More:
https://www.space.com/40906-venus-mountains-change-planet-rotation.html?utm_source=sdc-newsletter&utm_medium=email&utm_campaign=20180619-sdc