Universe Today

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Earth has the Moon, Mars has two moons, and even tiny Pluto has 3 satellites. So how many satellites does Venus have? Well, Venus has no natural satellites today. However, it’s possible that Venus did have natural satellites in the past.

Perhaps the biggest evidence that Venus once had a natural satellite is its current rotation. Seen from above, all the rest of the planets in the Solar System rotate counter-clockwise. That’s why eastern countries have an earlier sunrise than western countries. But the rotation of Venus is very slow and backwards. Seen from above, Venus rotates clockwise. In fact, a day on Venus lasts 243 Earth days, while a year on Venus lasts almost 225 days.

With this slow, backwards rotation, it’s possible that Venus experienced a catastrophic impact in its early history, just like the impact that created the Earth’s moon. While our Moon formed out at a stable point where it’s been slowly drifting away, it’s possible that a moon around Venus formed at an unstable distance and just crashed down into the planet.

It’s also possible that Venus captured an asteroid or two in the past, as astronomers believe happened with the Martian moons Phobos and Deimos. And this might also help us figure out what happened to satellites around Venus. Phobos is in an unstable orbit, and is expected to crash into Mars in the next 10 million years or so. So it’s possible that Venus had unstable moons orbiting it in the past, and they crashed into the surface. Venus is also much closer to the Sun than Earth, so the solar tides might just be too powerful to allow Mercury or Venus to have moons.

Unfortunately, the entire surface of Venus was resurfaced between 300-500 million years ago, and any evidence of crashing asteroids or moons has been covered up by volcanic flows. So perhaps we’ll never know if Venus ever had satellites.

Of course, Venus does have artificial satellites. At the time this article was written, ESA’s Venus Express was in orbit around Venus, capturing images and gathering data about our twin planet. And there could be more missions in the future.

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.

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

References:
NASA StarChild: The Planet Venus
NASA Solar System Exploration: Planet Venus

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It’s been said that Venus is Earth’s twin planet, in terms of size and composition. So when you ask how big is Venus, you know it’s going to be pretty close to Earth. Of course, Venus has incredibly high temperatures, crushing pressure and a poisonous atmosphere, so it’s not exactly a twin of Earth.

Let’s start with the size of Venus. The diameter of Venus is 12,100 km. That’s about 95% of the diameter of Earth. If you put Earth and Venus side by side, it would be pretty hard to see which one was larger.

The volume of Venus is 9.38 x 10¹¹ km³, written out, that’s 938,000,000,000 cubic kilometers. Of course, since Venus isn’t as big as Earth, it actually has a smaller volume. Venus has only 86% the volume of Earth. In other words, you could fit 1.16 Venuses inside Earth.

The surface area of Venus is 4.6 x 10⁸ km². That works out to be 460,000,000 square kilometers. Again, that’s a little smaller than Earth. The surface area of Venus is only 90% the surface area of Earth.

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.

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

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For seventy-six years, ever since Pluto was discovered in 1930, we had 9 planets in our Solar System. This all changed in 2006 when Pluto was demoted to the category of dwarf planets.

Mercury was only the second smallest planet back when there were 9. Mercury is closer to Earth than a number of other planets, but we cannot get a very good look at it because of its proximity to the Sun. Astronomers cannot use the Hubble Space Telescope to look at the planet because the Sun’s light would permanently damage the piece of equipment.

Venus is the brightest of all 9 planets. The only objects brighter in the Solar System are the Sun and the Moon. Venus is so bright that it can actually cast shadows. If the Moon is not out one night, you may be able to find some shadows thrown by the planet.

Earth is the densest of all planets in our Solar System. Our planet is composed mostly of iron, silicon, magnesium, and oxygen. Almost one-third of the planet (32.1%) is iron. There is nearly as much oxygen in the planet – 30.1%. There are lesser amounts of silicon (15.1%) and magnesium (13.9%). The materials are not spread equally throughout the planet. For example, most of the iron is in the core of the planet.

Ever since astronomers spotted what looked like canals on Mars, they have been searching for water and signs of life. While life has not been discovered yet, scientists have found deposits of water underneath the surface of the planet.

Not only is Jupiter the largest and most massive planet in our Solar System, but it is also the fastest spinning planet. Jupiter completes a full rotation in about 10 hours. The planet has actually flattened slightly at both ends due to the speed at which it spins.

Saturn does not have the most moons of any planet in our Solar System – that distinction goes to Jupiter with 63 moons – but Saturn comes in a close second with 60 moons. When Galileo first saw Saturn with a telescope, he thought that the planet’s rings were moons. Astronomers were not able to determine what the rings were until they developed better telescopes.

Uranus is the only planet to rotate on its side. This planet has the greatest axial tilt of any planet in our Solar System – 98°. As a result of this extreme tilt, the north pole is in darkness for 42 years then it gets 42 years of light before repeating the cycle.

Neptune is quite a bit larger than Earth, but its gravity is very similar. If you could stand on Neptune – you cannot because it does not actually have a surface – then you would only experience approximately 17% more gravity than you would standing on Earth.

Pluto, which was discovered in 1930, was the ninth planet. Pluto was by far the smallest planet. In fact, Pluto is even smaller than the Earth’s moon. This tiny planet was also the coldest one. Although its temperatures can drop to -240°C, the average temperatures on Pluto are -219°C.

Universe Today has articles on all 9 planets of the solar system including list of the planets and planets in the Solar System.

If you’d like more info on the nine planets, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

Astronomy Cast has episodes on all the 9 planets of the Solar System including Mercury.