How Many Moons Does Venus Have?

by Jerry Coffey on October 10, 2008

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Venus.  From the Pioneer Venus Orbiter

Venus. From the Pioneer Venus Orbiter

There are 166 recognized moons in our Solar System. The Earth only has one. Jupiter has the most with 63 moons confirmed as of 2009. So, how many moons does Venus have? Zero. Venus and Mercury are the only two planets that do not have a single moon in orbit about them.

If Venus and Mercury do not have moons and other planets have so many, how does a planet get a moon? Scientist think that there are three ways that a planet obtains a moon:

  • During the early period of the Solar System, planets accreted matter to gain mass. Some astronomers think that regular moons are simply matter that was not accreted, but remained within a planet’s gravitational influence.
  • Other moons, called irregular moons, were captured later. They were most likely asteroids or comets that ended up trapped by a planet’s gravity. Some of them may have even accreted smaller particles n their path as the orbited their primary.
  • The last way, is when a body impacted a planet. Many astronomers think that is how the Earth obtained its moon. A body nearly the size of Mars is thought to have impacted our planet several billion years ago. The moon is the ejecta that could not escape Earth’s gravity and eventually accreted into the object we call the Moon.

So, where does that leave Venus? Two scenario’s are plausible. One is that it had a moon in the early years of the Solar System. It could have been in a deteriorating orbit and impacted the surface or been lost to the Sun’s gravitational pull. The Martian moon Phobos is currently spiraling towards the surface(it should impact in about 25 million years) for this reason. A more widely held believe is that after a colossal impact, Venus began to spin in retrograde and a moon was formed, but did not reach a distance where it would be in stable orbit, so impacted the surface again.

Now you know the answer to ‘how many moon does Venus have?’ along with some trivia about the formation of moons in our Solar System. Can you imagine how strange it would be to look into the night sky and not see a moon or to see several at once? Stranger still would have been standing on the Moon and seeing your home planet on the horizon.

Other planets in the Solar System have moons. For example, here’s how many moons Jupiter has, and here’s how many moons Saturn has.

Here’s the official entry on this question from NASA. Seriously, click the link, you’ll laugh.

We have recorded an episode of Astronomy Cast all about Venus. Check it out here: Episode 50: Venus.

References:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/981026b.html
http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question38.html

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