Venus Number of Moons

by Fraser Cain on August 6, 2009

Venus.  Credit: NASA

Venus. Credit: NASA


Earth has the Moon, Jupiter has more than 50 moons, even Pluto has 3 moons. So what about Venus? What number of moons does Venus have? Ready for this?

Venus: number of moons: 0.

That’s right, Venus has no moons at all; not even captured asteroids like Mars. Why doesn’t Venus have any moons?

There appears to be evidence that Venus did have moons in the ancient past. That’s because Venus is rotating backwards from the rest of the planets. Seen from above, all of the planets rotate counter-clockwise. From the surface of the planets, the Sun seems to rise in the east, travel across the sky and then set in the west. But on Venus, it’s backwards; the planet is rotating clockwise, so the Sun rises in the west and sets in the east.

Even stranger, a day on Venus lasts 243 days, while a year on Venus is only 224.7 days. In other words, a day on Venus lasts longer than a year on Venus.

This strange rotation is evidence that Venus was probably whacked hard in the past by a planetesimal; a similar event is believed to have happened to the Earth billions of years ago, forming the Moon. It’s possible that this collision threw up material that coalesced into a moon, or even moons. But the material wasn’t high enough in orbit to remain stable around Venus. Instead of orbiting the planet for billions of years, it would have crashed back into the planet. Perhaps the tidal forces from the Sun made the orbit unstable.

Unfortunately the evidence of any past moons of Venus has been completely wiped away. At some point in the last 300-500 millions years ago, the outer crust of Venus was completely resurfaced, removing all trace of impact craters, and ancient volcanism.

So we’ll never truly know the number of moons that Venus had. But today, it has no moons.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

About 

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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