Venus is differentiated, meaning that it has layers like the Earth does: a core, a mantle and a crust. As the planet rotates, the core and mantle can experience friction where they meet. This hypothesis says that the core-mantle friction and those atmospheric tides could both put some torque on the planet and that instability could have flipped Venus over.
Some models suggest this might work only if Venus formed with an initial tilt of about 90 degrees, but others show that it might work with less initial tilt. Either way, the idea is pretty weird and thinking about an entire planet flipping is kind of mind-boggling.
But we have other ideas, too. Another one, first suggested in , is that Venus may have gradually slowed down and then reversed direction. Then, that may have provided the rest of the force necessary to get the whole planet going backwards. But there is no clear winner between these two hypotheses yet.
According to a paper published in Nature, the axis-flip mechanism is most likely if Venus had a rapid initial rotation rate. They propose instead that its rotation slowed to a standstill and then reversed direction. Taking into account the factors mentioned above, as well as tidal effects from other planets, the team concluded that Venus's axis could have shifted to a variety of positions throughout the planet's evolution.
Regardless of whether it flipped or not, it is bound to settle into one of four stable rotation statestwo in either direction. The researchers add that Venus would be more stable in one of the two retrograde rotational states. So in essence, it was just a question of time before Venus started spinning the wrong way. Already a subscriber? Sign in. Thanks for reading Scientific American. Visit us on the web at DaysOfAstronomy. This year we celebrate cosmic light as light is our info messenger in the universe.
Join us and share your story to celebrate the International Year of Light. Until tomorrow! Does that mean that both these planets came from out side our solar system?
Impact with another body earlier during the formation era change their spin. But Uranus is an Icy planet and thus should it be affected by another Solid object. This site uses Akismet to reduce spam.
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Join in! Avivah Yamani on May 22, at am. How does that happen to a planet? Astronomers think that the Sun's strong gravitational pull on the dense atmosphere of Venus; the atmospheric tides that would create; and the tidal pulls from other planets, could all have combined to reverse the planet's spin. This idea of tidal torques — where the dense atmosphere on the warm, Sun-drenched side of a planet is pulled away from the cold side — is one of the most well-established explanations for Venus' retrograde rotation, along with a planetary collision.
For now though, no one's percent sure what makes Venus and Uranus the odd ones out in our Solar System's family of planets. Our next close look at Venus should come from a flyby with the BepiColombo probe , which is eventually headed for Mercury and launching in
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