Venus Moon Would Have Been Doomed From The Start, Says New Paper
Venus likely never had a moon and even if it did it would have soon been torn asunder by the planet’s own gravity, says prominent planetary astrophysicist.
A new study published in The Astrophysical Journal suggests that Venus would have been doomed to remain moonless from the very beginning. Researcher Stephen Kane, from the University of California, Riverside, and his colleagues used a computer model to track the gravitational tides between Venus, a hypothetical moon, and the Sun over billions of years.
The findings indicate that any moon Venus once had would have spiraled inward and been torn apart by the planet's gravity, likely within the first billion years of its formation. This outcome is a natural consequence of ordinary tidal physics, not evidence of an exotic catastrophe, according to Kane. The team's simulations varied Venus's initial spin, the moon's mass, Venus's orbital eccentricity, and the properties of Venus's interior.
The model shows that a moon would only survive under specific conditions, such as a fast-spinning early Venus and a moon no heavier than Earth. The Roche limit, the distance below which a moon would be pulled apart by a planet's tidal gravity, is about 2.85 Venus radii (roughly 17,000 km from the planet's center). Any moon that ventured past this boundary would be destroyed and rain down onto Venus.
However, large moons like our own can help stabilize a planet's tilt, preventing extreme climate fluctuations. Without a moon, Venus's lack of a gyroscopic stabilizer could have led to dramatic climate swings. The planned DAVINCI mission, set to launch to Venus by the end of the decade, could potentially find in situ atmospheric evidence of a long-destroyed Venus moon.
If such material had fallen onto Venus, it could have altered the chemistry of the surface and atmosphere. The DAVINCI mission aims to measure these noble gas abundances and isotopic ratios, which could carry a fingerprint of a disrupted moon. The study also predicts that rocky planets like Venus, orbiting close to their stars and spinning slowly, should generally be moonless. This finding could inform future searches for habitable exoplanets around other sunlike stars.
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