Universe Today

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

Venus is often called Earth’s twin planet. And when it comes to the composition, Venus is very similar to Earth. But it does have a few significant differences.

The diameter of Venus is just 650 km less than the Earth’s, and its mass is 81.5% of planet Earth.

Looking inside Venus is much harder. Here on Earth, scientists probe the structure of the Earth’s core by studying how seismic waves from earthquakes bounce off the interior of the planet. Only a few landers have reached the surface of Venus, and they didn’t last long.

Since Earth and Venus have similar size and density, scientists assume that Venus has a similar internal structure to Venus, with a core, mantle, and crust. The interior of Venus is probably at least partially liquid.

One big difference between Earth and Venus; however, is the fact that Venus has no plate tectonics. This is probably because the surface and atmosphere of Venus are so dry and hot. This reduces the amount of heat lost from the interior of the planet, and prevents it from cooling. This might also explain why Venus doesn’t have an internally magnetic field; such as the one generated by Earth.

Venus orbits closer to the Sun than Earth, so explaining how to find Venus in the sky is pretty easy. It will be fairly close to the Sun. Venus orbits the Sun faster than the Earth so it will either appear in the sky in the West in the evening or rise before the Sun in the East.

To pinpoint the location of Venus you can use some form of planetarium software like Starry Nights or you can do it the old fashioned way and train your telescope yourself. There are a few things to consider when doing that. The first is to understand what ecliptic plane is. When you trace the path of the Sun across the sky, its path is a line called the ecliptic. The ecliptic changes slightly throughout the year. It actually rises and falls. The highest point occurs at the summer solstice, while the lowest position happens six months later at winter solstice.

Most celestial bodies are most easily observed during an elongation. An elongation occurs when an inferior(closer to the Sun) planet’s position in its orbital path is at tangent to the view from Earth. Because they are inside the Earth’s orbits their positions are never very far from the position of the Sun. When a planet is at elongation, it is furthest from the Sun as viewed from Earth, so it’s view is best at that point. There are two kinds of elongations. The Eastern Elongation occurs when the planet is in the evening sky and the Western Elongation occurs when a planet is in the morning sky. This paragraph assumes that we are talking about viewing from Earth. The apparent motion of objects in the sky due to the rotation of the Earth is 15 degrees per hour. Venus is not visible against the Sun’s background light until it is 5 degrees from the Sun, so it can not be seen until 20 minutes after sunset or before sunrise. At its greatest eastern and western elongations, Venus is between 45 to 47 degrees from the Sun and moves 3 hours 8 minutes behind or in front of the Sun. That only leaves about 2 hours and 48 minutes of observation in a given day.

Once you know how to find Venus in the sky, you will need a telescope to see anything other than a light in the sky. Also, you should have a planetary filter or off-axis mask. Still, it might be best to invest in a telescope with an automatic tracking system so that you can focus all of your attention on observing and not be constantly adjusting your scope. Good luck on your quest to observe Venus.

We have written many articles about Venus for Universe Today. Here’s are facts about 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:
http://planet-venus.net/index.php?document_id=100
http://www-istp.gsfc.nasa.gov/stargaze/Secliptc.htm

Venus is the virtual twin of Earth in many ways. Similar size, mass and density. But what is the gravity on Venus? According to our friends over at NASA, the answer is 8.87 m/s². To translate that a little more, it is about 90% of the gravity here on Earth. A person who measures 100 kg when they leave home would tip the scales on the Venusian surface at 90 kg.

The surface gravity of Venus is not the only characteristic of the planet that nearly mirrors Earth. Venus has 86% of the volume that Earth has along with 82% of the mass. The planet’s density is nearly identical at 5.243 g/cm³.

In order to shed that ten kilos you would have to spend a couple of months in space. Once you arrived the real trouble would begin. Science has not been able to develop a spacesuit that could survive more than a few minutes in the harsh environment of Venus. To start with there is the 470C surface temperature. That is 9 times the temperatures in the hottest deserts here on Earth. The heat would not destroy your suit though. The atmosphere is 96% carbon dioxide and full of sulfuric acid clouds and droplets and ash from the volcanoes that dot the surface. The atmosphere is so thick that most meteors could not penetrate it, burning up before impact instead.

While there have been many large volcanoes here on Earth, there is no real comparison to the number, size, and extent of the volcanic activity on Venus. The Venusian surface is dominated by the more than 1,000 volcanoes or volcanic centers that are larger than 20 km. Lava flows are thought to have completely resurfaced the planet between 300 and 500 million years ago.

The reflective nature of the sulfuric acid in the atmosphere has made visual observation of the surface impossible. It was early in the 20th century, when astronomers were able to make spectroscopic, ultraviolet, and radar observations, before much was known about the planet. Surface features went undetected until radar observations were made in the 1970s.

Fifty years ago no one could have accurately told you much about Venus gravity. It was still a mystery at the beginning of the 20th century. In many ways it can be considered the Earth’s near twin, but the planet is still a host of mysteries that need to be solved. The Venus Express spacecraft has contributed a great deal of data. BepiColumbo and Akatsuki may be able to add a great deal more in 2014 and 2016, respectively. All we can do is wait and see.

We have written many articles about Venus for Universe Today. Here are some interesting facts about Venus, and here’s an article about the color of 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 Venus Facts
NASA Solar System Exploration on Venus