Retrograde Rotation of Venus

Of all the planets in the Solar System, Venus has a unique rotation. Seen from above, all of the planets rotate in a counter-clockwise direction. And this is what you would expect if all the planets formed from the same planetary nebular billions of years ago.

And yet, the rotation of Venus is clockwise, what astronomers call “retrograde”. Venus rotates backwards. Of course, since the length of a day on Venus is longer than a year, this rotation happens very slowly.

Why does Venus rotate backwards? One possibility is that Venus rotated normally when it first formed from the solar nebula, and then the tidal effects from its dense atmosphere might have slowed its rotation down.

Another theory is that a series of gigantic impacts early on in Venus’ history might have stopped or even reversed its rotation altogether. A similar impact happened to Earth billions of years ago, which formed the Moon.