structure of planets

• an asteroid is a rocky object orbiting the sun left over from the formation of the solar system
• a meteorite is a lump of rock from outer space that has landed on earth. (usually from the asteroid belt)
• 6% of meteorites are made of iron and nickel. they represent the core of a planet
• 93% of meteorites are stony. they are made of silicate minerals. they represent the mantle of a planet
• carbonaceous chondrites are the rarest type of meteorite. they are a special type of stony meteorite which includes water and organic compounds. they represent the overall composition of earth.
• meteorites are useful because scientists assume all material in the solar system came from the same source
• there is no type of meteorite representing the crust because the earths crust has changed due to precesses like weathering
• most meteorites are dated around 4.5 billion years ago. believed to be the age of the solar system
• lithophile elements like to combine to oxygen and oxidise easily. eg lithium and sodium
• chalcophile elements like to combine with sulphur. eg silver and copper
• atmophile elements occur as liquids or gas. eg oxygen and hydrogen
• siderophile elements like to combine with iron. eg gold
• gravity pulled the denser compounds towards the core and the lighter formed the mantle
• lithosphere - rigid and brittle
• asthenosphere- ductile where areas of magma are created