You should all know that the Solar System consists of 9 planets, which all orbit around the Sun!
Below, I have listed the planets in order from the Sun, and have got some information about each of them.
Mercury
Mercury is a very hot planet, mostly because it is the closest planet to the Sun orbiting at around 60 million kms away from the Sun. The temperatures on Mercury can reach up to 430ºC in the daytime. (800ºF) That is over four times as hot as boiling water! But at night, it is very different, the temperature can sometimes drop to -180ºC! (-300ºF)
Mercury is a very rocky, cratered planet as well.
Mercury is a small planet in relation to some of the others in our Solar System, it is the second smallest planet in the Solar System, only 4,800km (3000 miles) in diameter.
Mercury takes 88 days to do a complete orbit around the Sun, so a year on Mercury is only 88 Earth days.
Mercury's days are very long though because it has a very slow rotation. 1 Mercury day is equal to 59 Earth days, which means there are less than two days in Mercury's year!
Venus
Even though Venus orbits the Sun at a distance of around 110 million kms, about 50 million kms further away than Mercury, Venus actually hotter than Mercury! Why? Because Venus has a very thick atmosphere and cloud cover over itself, and most of the heat gets reflected away from the planet. But what heat does end up getting through Venus' thick clouds, gets trapped in there and can't get out, so it gets very hot in there! On the surface of Venus, temperatures can reach up to about 480ºC! (around 900ºF) This is what makes it the hottest planet in the Solar System. Mercury has no atmosphere or cloud cover etc to keep any heat in, so even though it is the closest planet to the Sun, it still isn't the hottest planet!
Venus is also a very rocky planet, a bit like a desert.
Venus takes longer to rotate, than it does to orbit the Sun. So a day on Venus, is actually longer than the year!
Venus also rotates in the opposite direction to the other planets! Venus is 12,100km in diameter.
Earth
Well, you should know enough about this planet, you live on it!
Earth takes 365 days to orbit the Sun, and it takes 24 hours to complete a rotation. Now I bet you never knew any of that!
Earth is only a little bit bigger than Venus, 12,700km in diameter, and orbits the Sun from a distance of around 150 million km. (around 93 million miles)
Mars
Mars orbits the Sun at a distance of about 225 million km (140 million miles).
Mars take nearly 687 days to orbit the Sun. So 2 years on Earth, is roughly only 1 year on Mars. Mars is also only about half the size of planet Earth, about 6,500 km in diameter.
Mars' surface has lots of rocks scattered all over it, and it is also very red. But why? Because Mars' surface has lots of iron in it, which has rusted away over millions of years, and rusty iron is obviously red!
Scientists also think that Mars could support life on it. They hope to have people on Mars by the year 2015. A rover called Sojourner has already been on Mars. It was a little 6 wheeled buggy, powered by solar panels, and was remote-controlled from here on Earth by scientists. It has been on the surface of Mars since 1997. Scientists have lost contact with the rover now though.
Mars also has the largest volcano in the Solar System on it's surface, Olympus Mons. It rises 24km above the surface, and is 550 km across. The biggest volcano on Earth, Mauna Loa, in Hawaii is only 9 km high, and 120 km across. Although this volcano is big for here on Earth, it is pretty small in comparison with Olympus Mons!
Mars also has some big canyons on it's surface. Some of them are as wide, as the Grand Canyon is long!
Jupiter
Jupiter, the king of the planets, orbits the Sun at a distance of 778 million km (483 million miles), and is 142,800 km in diameter, making it the biggest planet in our Solar System. Thats so big that more than 1000 planets the size of Earth could fit inside it!
Jupiter is the first of the Gas Giant planets. (Gas Giants are four of the outer planets, Jupiter, Saturn, Uranus and Neptune that are made up mostly of gas.)
This means that you couldn't really land on Jupiter, you would just fall straight through it, because there is no solid land to land on! Jupiter has a very strong gravitational pull, and small objects (i.e. asteroids, meteoroids etc) that go too near it, get sucked into it.
Jupiter also has a big storm raging across it's surface. This storm is commonly known as The Great Red Spot, because it looks just like a red spot on Jupiter's surface! The Great Red Spot is about 8 km (5 miles) high, around 40,000 km (25,000 miles) long, and about 14,000 km (8,700 miles) wide, and it's winds blow at about 500 km per hour (310 miles per hour). As it moves across the surface of Jupiter, it swallows up other smaller storms. But even though it does this, it is still shrinking. Now, it is only about half of the size it was 100 hundred years ago.
Jupiter also has a ring around it, like Saturn. It is very small though, in comparison to Saturn's, which you can easily see from Earth. These rings cannot be seen from Earth, they were discovered by one of the Voyager probes.
>Saturn
Saturn is the second largest planet in the Solar System, about 119,300 km (74,100 miles) across. Saturn orbits the Sun at a distance of around 1,425 million km (890 million miles)!
Saturn rotates very quickly, taking just 10 hours to complete a rotation. Because of this, some of the gases that Saturn is made up of are flung towards it's equator.
This make Saturn "bulge", making it fatter in the middle of the planet.
Saturn is also a Gas Giant, like Jupiter. The planet itself is made up mostly of hydrogen. The atmosphere of Saturn is made up of lots of helium though, so Saturn is a very light planet in relation to the others. It is so light in fact, that if there was ever an ocean big enough that Saturn could fit in, it would float.
Saturn also has a big ring system. Saturn's rings are much bigger than Jupiter's though, and they are easily visible from Earth through a telescope.
They are made up from lots of rocks, ranging in size from about 1 foot across to some the size of a car.
Uranus
Now we're getting a bit further out into the Solar System!
Uranus is the third gas giant in the Solar System and is about 2,900 million km (1,800 million miles) away from the Sun. It is 50,800 km in diameter, and takes just over 84 years to do a complete orbit around the Sun.
The atmosphere is made up mostly of hydrogen. It does have some helium and small amounts of other gases in it as well.
Uranus has a strange spin, it rotates on it's side.
This could have been caused by a collision with another large, planet-sized object millions of years ago, which tipped it over.
Uranus spins a bit slower than Earth, it takes 18 hours to do a complete rotation. (And of course Earth takes 24 hours!)
Uranus moves through space at about 7 km (4 ¼ miles) per second. In comparison, Earth moves at nearly 30 km (19 miles) a second.
Uranus also has a ring system, but not as big and easily visible as Saturn's. They were discovered from Earth in 1977, then the Voyager probe gathered more information on them in 1986. The rings are made up mostly from dust.
Neptune
Neptune is the fourth and last Gas Giant in the Solar System.
Neptune is over 4,500 million km (more than 2,800 million miles) away from the Sun, and takes nearly 165 years to do a complete orbit around the Sun. Neptune takes 16 hours to do a complete rotation, so a day on Neptune is 8 hours shorter than here on Earth.
Astronomers thought that Neptune would be pretty plain, and dull looking because they hadn't seen much of it, mostly because it was to hard to see much of, because of its distance from Earth. The space probe Voyager 2 proved them wrong though - Neptune is just like the other Gas Giant planets.
Neptune has storms raging across it's surface, ones similar to the Great Red spot on Jupiter. Astronomers have seen a few dark spots on Neptune. The largest spot on Neptune, called the Great Dark Spot, is about the same size as the Earth. It is probably a huge storm like the Great Red Spot.
This Great Dark Spot was seen by the Voyager 2 probe in 1989, but when astronomers searched for it using the Hubble Space Telescope in the 1990s, they could not find it! No one is certain as to why the spot disappeared, and no one can say if it will re-appear.
Neptune is blue in colour because of the methane gas in it's atmosphere, which obviously is blue! In Neptunes atmosphere, there is also some hydrogen, helium, and water.
Big clouds race around Neptune as well. They are pushed around by the fastest winds that have been found on any planet in the Solar System. Near the Great Dark Spot, winds blew at speeds of up to 2000 km per hour (1,200 miles per hour)! One of the clouds on Neptune goes around the planet every 16 hours! Astronomers have nicknamed this cloud Scooter, because of the speed it goes around Neptune at.
Pluto
Now we've got to the last planet of the Solar System: Pluto.
Pluto is very far away from the Sun. It's distance from the Sun changes a lot though, due to the difference in it's orbit.
At it's closest to the Sun, Pluto is 4,425 million km, and at its furthest, it is 7,375 million km away!
At times Pluto is the 8th planet from the Sun, and other times it is the 9th planet from the Sun. (See this image for an illustration of why this happens) Because of Pluto's great distance from the Sun, it takes a very long time to orbit the Sun. (The further a planet is away from the Sun, the slower it orbits the Sun) Pluto takes 249 years to orbit the Sun!
Pluto takes 6 days to complete a rotation.
Pluto's diameter is only around 2,300 km (1,429 miles, which makes it the smallest planet in the Solar System.
Pluto is also a very cold planet, because of its distance from the Sun. This is the only planet that a space probe hasn't visited yet. Scientists are working on sending one to Pluto sometime though, called the Pluto/Kupier Express, but even if it does go, it will be quite a while before it gets launched. I have heard that they have put the idea off all together, so they might not even send one there at all!
Some astronomers think that Pluto may not even be a planet, because it is so far away from the Sun, and because it is so small.
Click here to learn about other things in the Solar System, like comets and asteroids.
