How many moons does Venus have?

Apr 23, 2014 by Elizabeth Howell, Universe Today
A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL

There are dozens upon dozens of moons in the Solar System, ranging from airless worlds like Earth's Moon to those with an atmosphere (most notably, Saturn's Titan). Jupiter and Saturn have many moons each, and even Mars has a couple of small asteroid-like ones. But what about Venus, the planet that for a while, astronomers thought about as Earth's twin?

The answer is no moons at all. That's right, Venus (and the planet Mercury) are the only two that don't have a single natural moon orbiting them. Figuring out why is one question keeping busy as they study the Solar System.

Astronomers have three explanations about how planets get a moon or moons. Perhaps the moon was "captured" as it drifted by the planet, which is what some scientists think happened to Phobos and Deimos (near Mars). Maybe an object smashed into the planet and the fragments eventually coalesced into a moon, which is the leading theory for how Earth's Moon came together. Or maybe moons arose from general accretion of matter as the solar system was formed, similar to how planets came together.

Considering the amount of stuff flying around the Solar System early in its history, it's quite surprising to some astronomers that Venus does not have a moon today. Perhaps, though, it had one in the distant past. In 2006, California Institute of Technology researchers Alex Alemi and David Stevenson presented at the American Astronomical Society's division of planetary sciences meeting and said Venus could have been smacked by a large rock at least twice. (You can read the abstract here.)

The International Space Station captured as it passed in front of the Moon on Dec. 6, 2013, as seen from Puerto Rico. Credit: Juan Gonzalez-Alicea.

"Most likely, Venus was slammed early on and gained a moon from the resulting debris. The satellite slowly spiraled away from the planet, due to tidal interactions, much the way our Moon is still slowly creeping away from Earth," Sky and Telescope wrote of the research.

"However, after only about 10 million years Venus suffered another tremendous blow, according to the models. The second impact was opposite from the first in that it 'reversed the planet's spin,' says Alemi. Venus's new direction of rotation caused the body of the planet to absorb the moon's orbital energy via tides, rather than adding to the moon's orbital energy as before. So the spiraled inward until it collided and merged with Venus in a dramatic, fatal encounter."

Venus as photographed by the Pioneer spacecraft in 1978. Some exoplanets may suffer the same fate as this scorched world. Credit: NASA/JPL/Caltech

There could be other explanations as well, however, which is part of why astronomers are so interested in revisiting this world. Figuring out the answer could teach us more about the solar system's formation.

Explore further: Radar guards against space debris

More information: To learn more about Venus, check out these links:

Venus (NASA)
Venus Express (European Space Agency spacecraft currently at the planet)Venus (Astronomy Cast))
Magellan Mission to Venus (NASA)
Chasing Venus (Smithsonian)

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User comments : 5

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Apr 23, 2014
This comment has been removed by a moderator.
1 / 5 (4) Apr 23, 2014
if this article is about Moons, then why nothing was mentioned about mercury ? Or is this article only about Venus ?
3 / 5 (4) Apr 23, 2014
Mercury was mentioned.
1 / 5 (1) Apr 25, 2014
Mercury was mentioned.

I know its here
The answer is no moons at all. That's right, Venus (and the planet Mercury)

but why no detailed discussion is what my question was
not rated yet Jun 13, 2014
Mercury was mentioned.
I know its here
The answer is no moons at all. That's right, Venus (and the planet Mercury)

but why no detailed discussion is what my question was
Because it was an article about Venus, not about Mercury or moons in general, just the possibility of a past Venusian moon.
Captain Stumpy
5 / 5 (1) Jun 14, 2014
(You can read the abstract here.)

Yep. Stupid copy-pasters can't include a link, because they'd get it wrong.
IMHO - it is a lot more likely that this is an automatic submission that occurs over time through a process set up by a site and, which would explain some of the other copy/paste problems like translation or spelling in some articles...

The abstract is found here: http://adsabs.har...38.0703A
the full paper is paywalled as far as I know...
(if anyone else finds it I would appreciate a link here... Thanks in advance)

and another article about it is here: http://www.skyand...-a-moon/
which was linked in her original article (from April 22, 2014) at universe today which is found here

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