Unlike the other planets (except Uranus), Venus rotates slowly in a clockwise direction, when viewed from an imaginary point high above the Earth's north pole.

Scientists speculate that Venus may have collided with another large object during its early formation. (Similar theories have been advanced for the formation of our Moon.) There are other theories involving the thick Venus atmosphere.

(Note: although the planet Uranus is also said to rotate clockwise -- as seen from above the Earth's north pole -- it still spins in the same direction as it did when it formed. But it is "tipped over onto its side" relative to its orbital plane by more than 90° -- possibly by a similar type of collision.)