Astrophysics study suggests Venus may have once possessed a moon

A new study published in The Astrophysical Journal proposes that Venus may have once possessed a moon that was eventually consumed by the planet. While previous scientific theories suggested that Venus either never formed a moon or lost one due to a massive external impact, this research suggests the planet’s own physical characteristics were responsible for the satellite's disappearance.

The study, led by astrophysicist Stephen Kane of the University of California, Riverside, utilizes computer models to simulate the gravitational mechanics of hypothetical moons orbiting Venus. The findings indicate that the planet's extremely slow rotation on its axis would have prevented it from maintaining a stable satellite. Unlike Earth, which rotates rapidly enough to transfer energy to its moon and push it further away, Venus lacks the rotational speed necessary to sustain a lunar orbit.

According to the research, any moon orbiting Venus would have been pulled gradually closer to the planet due to gravitational forces. Over time, this orbital decay would have resulted in the moon spiraling inward and ultimately crashing into the planet’s surface. The study suggests this cataclysmic event likely occurred within the first billion years of the solar system’s 4.5-billion-year history.

This explanation marks a departure from traditional hypotheses regarding the absence of a Venusian moon. While earlier models relied on the necessity of a dramatic, external collision to explain the current state of the planet, this research posits that the collapse was a natural consequence of planetary physics. By modeling various moon sizes, the researchers concluded that all hypothetical satellites would have met the same fate, eventually being absorbed by the planet.

The mechanics of this process are contrasted with the current behavior of Earth's moon, which is measured to be drifting away from our planet at a rate of approximately four centimeters per year. This outward movement is supported by the energy transferred from Earth's 24-hour rotation. Because Venus rotates much more slowly, it is unable to exert the same influence, rendering it incapable of keeping a moon in a stable, long-term orbit.