Does Venus Have Moons?

by Jerry Coffey on May 12, 2008

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The quick and simple answer to ”does Venus have moons?” is No. There are no Venusian moons lurking in hidden orbits waiting to be found. Venus and Mercury are the only planets that do not have moons. There are even a few asteroids that have moons. Venus; however, may not have always been moonless.

There are a few different theories floating around to explain why Venus does not have a moon. The first is based on a series of large impacts. Some scientists think that , like Earth, Venus was impacted by a large mass asteroid or planetesimal in the early part of the history of our Solar System. The first impact would have cast a large amount of ejecta into orbit around the planet. That ejecta would have coalesced into a moon over millenia. The second stage of the theory holds that another large impact caused the planet to go into retrograde spin. The new direction of the planet’s rotation destabilized the moon’s orbit, causing it to eventually impact the surface. A similar situation is in action on Mars’s moon Phobos as we speak. That moon will impact the Martian surface in about 25 million years. This theory may have been substantiated by a 2006 study done by Alex Alemi and David Stevenson at the California Institute of Technology.

A second hypothesis holds that Venus has had moons at several points in history. Each moon would have been of varying size, but all had one thing in common: they were stolen away by the Sun. This theory is also applied to Mercury. The theory proposes that the Solar gravity is too strong and strips each planet of any moons that may have been in orbit. The solar tides destabilize the orbits of the moons and they are slowly drawn into impact courses with our star.

Asteroid 2002 VE 68 is in a quasi-orbital resonance with Venus. It is not a true moon because, while it orbits in the same time period(1:1 resonance) as Venus it has a much more elliptical orbit to the Sun, lies outside of the planet’s Hill sphere, and its orbit is unstable.

After all of the facts are in evidence, the answer to ”does Venus have moons?” is still no. The answer leaves room for the mysteries of the past to be explored. Perhaps future missions to the planet will be able to find more evidence of what happened to ancient moons around the planet.

We have written many articles about Venus for Universe Today. Here’s an article about how long it takes to get to Venus, and here’s an article about the distance from Earth to Venus.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We’ve also recorded an entire episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.

References:
NASA Solar System Exploration on Venus
Wikipedia

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