Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star (called a supernova).
This explosion made waves in space which squeezed the cloud of gas and dust. Squeezing made the cloud start to collapse, as gravity pulled the gas and dust together, forming a solar nebula, the cloud began to spin as it collapsed. .
As the disk got thinner and thinner, particles began to stick together and form clumps. Some clumps got bigger, as particles and small clumps stuck to them, eventually forming planets or moon.
Venus- is the second planet from the Sun, and the sixth largest of all the nine planets.
Venus probably once had large amounts of water like Earth, but it all boiled away. The same thing would have happened to the Earth had it been just a little closer to the Sun. Because Venus is so similar to our Earth, we sometimes call it Earth's "sister planet."
Earth is the third planet from the Sun, and the fifth largest of the nine planets.
The Earth's surface is very young . This means that the Earth's surface has changed a lot from when it was first formed. Erosion and tectonic processes (like earthquakes) destroy, recreate and reshape most of the Earth's surface.
Saturn is the sixth planet from the Sun, and the second largest of the nine planets.
Saturn's rings, unlike the rings of the other gas planets, are very bright. Though they look "solid" or continuous from the Earth, the rings are actually composed of many, many small particles circling Saturn at their own speeds.
Uranus is the seventh planet from the Sun and the third largest of the nine planets.
Uranus' blue color is the result of a gas called "methane" found in the planet's upper atmosphere. Uranus may have colored bands like Jupiter's, but they are hidden from view by the overlaying methane layer.