Venus may have swallowed its own moon, study suggests

New research published in The Astrophysical Journal suggests that Venus may have once possessed a moon that was eventually consumed by the planet. Led by astrophysicist Stephen Kane of the University of California, Riverside, the study utilizes gravitational simulations to propose that Venus did not necessarily require a catastrophic collision to lose a satellite.

The theory centers on tidal mechanics and the difference in rotational speeds between Earth and Venus. While Earth’s rapid rotation transfers energy to the Moon, pushing it away, Venus’s sluggish rotation—taking 242 Earth days to complete one turn—would have the opposite effect. In this scenario, the planet’s gravity and slow spin would cause an orbiting moon to undergo orbital decay, spiraling inward until it collapsed onto the planet.

While the study does not confirm that Venus definitely had a moon, it demonstrates that if one had formed, the planet’s specific rotational characteristics would have made it extremely difficult to retain. These findings provide new insights into the evolution of rocky exoplanets and the divergent histories of Earth and its planetary neighbor.