Venus is the only planet that spins clockwise. In many ways, you can say that Venus is Earth’s twin. How? Well, it has a similar size, mass, density, and chemical composition.
But then what makes Earth livable but not Venus? Venus has a high temperature and extreme pressure and both these conditions make it difficult for life to survive on this planet.
The Solar System
An interesting fact about the solar system is that all the planets, with one exception, rotate counterclockwise. The reason behind their consistent behavior is fairly simple.
The direction of the planets rotate in the same direction the sun rotates, and the sun rotates counterclockwise because the material from which it formed happened to do so as well.
To clear things up, after the sun was formed from a cloud of dust and gas inside the proto-planetary disk surrounding it, which rotated counterclockwise, the planets that are now present in our solar system eventually formed.
This resulted in a consistent pattern of spinning among all planets except Venus. Earth’s nearest planetary neighbor, Venus, rotates clockwise. Why does Venus rotate the “wrong” way?
The Planet venus
Our neighboring planet Venus is an oddball in many ways. For starters, it spins in the opposite direction from most other planets, including Earth, so that on Venus the sun rises in the west.
Not that it happens often: a day there lasts a little more than 243 Earth days, actually making it longer than a Venusian year, which is only about 224 Earth days long.
Many scientists believe that the long days are a result of the sun’s strong pull on the planet. (Mercury, which is even closer to Sol, has fairly long days as well: three for every two Mercury years). But scientists are still puzzled by Venus’s retrograde, or backward, rotation.
Now a team of scientists from the French research institute Astronomie et Systemes Dynamiques have proposed a new explanation, published in this week’s issue of Nature.
The Nature of Venus
Current theory holds that Venus initially spun in the same direction as most other planets and, in a way, still does: it simply flipped its axis 180 degrees at some point. In other words, it spins in the same direction it always has, just upside down, so that looking at it from other planets makes the spin seem backward.
Scientists have argued that the sun’s gravitational pull on the planet’s very dense atmosphere could have caused strong atmospheric tides. Such tides, combined with friction between Venus’s mantle and core, could have caused the flip in the first place.
Now Alexandre Correira and Jacques Laskar suggest that Venus may not have flipped at all. 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 states¿two 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.
Why Does Venus Rotate Clockwise?
After it formed, Venus likely rotated counterclockwise like all the other planets. It simply would not have been possible for Venus to rotate clockwise after its formation, given the rotation of the protoplanetary disk it formed in.
Instead, something must have caused Venus to start spinning the other way. Shortly after the sun was born, the planets began to form as well. Although the solar system has eight planets today, that has not always been the case. There were likely as many as a hundred planets forming in the early solar system.
The early solar system was chaotic, and none of the current planets had found themselves in a stable orbit. The gravitational pull of the forming planets tugged on one another and brought each other closer together.
Collisions between entire planets were commonplace, and every planet in the solar system is believed to have undergone one or more crashes in the past. Venus was no exception, and it likely experienced at least one major collision with another planet.
A collision between Venus and another planet could explain why Venus rotates counterclockwise. Another planet colliding with Venus at just the right angle could have reversed its rotation.
Other Facts to Know about Venus
- Venus spins clockwise on its axis.
- Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BC.
- We tend to say ‘Venusian’ not ‘Venerian’.
- A day on Venus is longer than a year.
- Venus is the second brightest natural object in the night sky after the Moon.
- Venus is named after the Roman goddess of love and beauty.
- Venus has 90 times the atmospheric pressure of Earth.
- Venus is hotter than Mercury – despite being further away from the Sun.
