Venus May Have Swallowed Its Moon, Study Suggests

A California-based astrophysicist proposed a new theory on September 14 to explain why Venus, Earth's twin in size and structure, does not have its own moon. This celestial cannibalism theory suggests a slow rotation speed of Venus would have caused any potential moon to spiral closer and be consumed. Stephen Krane, the lead author of the study published in The Astrophysical Journal, stated that if Venus once had a moon, it would have been crushed into its parent planet relatively quickly.

Computer models based on planetary physics showed all hypothetical Venusian moons eventually meeting this fate. This event likely occurred within the first billion years of Venus's existence, which spans about 4.5 billion years. Previously, it was believed Venus either never had a moon or had one obliterated during an impact with another celestial body.

The study focused on Earth-moon dynamics, finding that a planet's rotational speed is a crucial factor. In contrast to Venus, Earth completes a rotation in just 24 hours, a pace 200 times faster than Venus. This difference in rotation speeds causes the Moon to move away from Earth at a rate of four centimeters per year. Venus, the third brightest object in the night sky, is enveloped in a thick, toxic atmosphere causing a runaway greenhouse effect that heats its surface to 471 C. Despite no proof of a Venusian moon, it is unlikely that Venus avoided a world-shattering collision with another proto-planet that formed Earth's moon.

Two NASA missions, DAVINCI+ and VERITAS, are set to launch in the late 2020s or early 2030s to study Venus' atmosphere and geologic features.