Venus 'Ate' Its Moon 2 Billion Years Ago
Researchers suggest Venus may have had a moon for nearly 2 billion years before it was consumed by the planet, with the moon's fate depending on factors such as its mass and Venus's spin speed
Venus, often referred to as Earth's twin due to its similar size and density, may have had a moon for nearly 2 billion years before it was consumed by the planet. A recent study suggests that the moon's fate depended heavily on factors such as its mass and Venus's spin speed.
The study's findings indicate that under some conditions, a moon could have survived for 4.5 billion years, while under others it would have been destroyed. The team suggests that the moon was most likely destroyed after spiraling back toward Venus, with the destruction occurring anywhere from 30 million years to 1.7 billion years after the moon formed.
The researchers found that a moon about half the mass of our own could have survived around Venus for 1.7 billion years. In contrast, a moon twice the mass of our moon would have survived just 30 million years due to the stronger tidal effect. The Roche limit, at about 15,000 kilometres, is where Venus's gravity would rip the moon apart and consumption would occur.
## Why it matters The study's findings could help explain why Earth and Venus, despite their similarities, have distinct differences. Understanding the history of Venus's moon could also provide insights into the planet's previous habitability. The lack of a moon on Venus is unusual, and the study suggests that it is likely that Venus did have a moon-forming impact, similar to the giant impact that is thought to have formed Earth's moon.
The study's lead author, Stephen R. Kane, notes that Venus's strange rotation, completing a rotation once every 243 days, compared with its orbit of 225 days, may have contributed to the moon's demise. The opposite effect of Earth's faster spin, which transfers angular momentum to our moon, would have caused the moon's orbit to catastrophically collapse.
The research provides a compelling scenario for how a moon could have existed and been destroyed, and could help scientists better understand the history of our solar system.
