Why does Venus rotate in the opposite direction?

Our neighboring planet, Venus, is peculiar in many aspects. First and foremost, unlike all other planets, it rotates from east to west. In other words, on Venus, the Sun rises in the west. While it completes one rotation around its axis in 243 days, it completes a full orbit around the Sun in 224 days. Therefore, a day on Venus is longer than a year.

Many scientists believe that the strong gravitational pull of the Sun on the planet contributes to these extended days. However, scientists are still puzzled by Venus's backward rotation. The French research institute Astronomie et Systemes Dynamiques proposed a theory on this matter.

According to the current theory, Venus used to rotate in the same direction as other planets, just like it does now. In other words, the rotation direction of the planet has not changed; it simply appears to rotate in the opposite direction when observed in relation to other planets. Scientists discuss the possibility that the excessive gravitational force of the Sun on the planet could lead to strong atmospheric tides.

These tides, combined with the friction between Venus's crust and core, might have caused the backward rotation.

Alexander Correira and Jacques Laskar, on the other hand, argue that Venus did not originally rotate in the opposite direction. According to Correira and Laskar, the planet's rotation faced interruptions and changed direction. Taking into account the effects of tidal forces caused by other planets in addition to the mentioned influences, the team concluded that Venus's axis changed due to the evolutionary processes on the planet. Whether it spins backward or not, Venus is one of the four planets with retrograde rotation. The researchers also added that Venus might be more stable in its backward rotation compared to the two other backward-spinning planets.