The theory has little support among lunar experts, Space.com reported Tuesday. An older theory and one with more support is that the moon formed when a large body struck Earth early in its history.
Scientists who raised the Venus theory at the Royal Society conference suggested Earth's stronger gravity allowed it to capture the moon from its sister planet. Venus is close to the Earth in size but with a mass about 20 percent less.
While the impact theory also has some glitches, the similarity of the moon and Earth in chemical makeup suggests the planet gave birth to the satellite.
Neither Venus nor Mercury, the two inner-most planets, have any natural satellites, and the Earth only has one and Mars two. The outer planets have far more, with Jupiter the champion with 67, including one that is larger than Mercury.
The Royal Society is one of the oldest and most famous scientific bodies in the world. Its past presidents include Sir Isaac Newton, who worked out the theory of gravity.