Venus May Once Have Had a Moon

Venus has no moon today, but it may have been different long ago. Simulations suggest that, in the early Solar System, a huge collision could have made a moon around Venus, perhaps in a way similar to what likely happened to Earth.

Depending on the moon’s mass and Venus’s starting rotation speed, it might have orbited the planet for as long as about 1.7 billion years.

Eventually, tidal forces may have pulled the moon back toward Venus. Its orbit would slowly shrink until it came so close that tidal forces tore it apart, and its pieces eventually fell onto the surface. Interestingly, the more massive the hypothetical moon was, the sooner its end may have come. In some simulations, a satellite with twice the mass of Earth’s Moon lasted only about 30 million years.