What is a meteor?
Meteors are particles of debris in the solar system ranging in size from a grain of sand to a boulder. Meteors are also known as shooting stars and can be spotted as sudden streaks of light passing across the night sky. They are chunks of rock that have chipped off larger pieces following collisions in the asteroid belt, located between Mars and Jupiter. Many meteors seen together are called a meteor shower.
What is a meteorite?
A meteorite is the part of a meteor that survives its passage through the Earth’s atmosphere and impact with the ground without being destroyed. When meteors enter the atmosphere, they slow down and release energy in the form of heat. Most of the meteor then evaporates. With large meteors it is unlikely that all of the meteor will be evaporated. The outer layers are burnt away but the centre hurtles down towards the ground and hits it at around 500km per hour.
Impact craters
Holes made in the ground by meteorites are called impact craters. One of the most well known is the Barringer Crater in Arizona, USA. It was formed around 50,000 years ago when a 250,000 tonne iron meteorite with a diameter of 70 metres hit Earth at nearly 60,000km per hour.
What are meteorites made of?
Meteorites are mostly made of minerals and are classified into three main groups: stony, iron and stony-iron meteorites.
Stony meteorites are sub-divided into chondrites, carbonaceous chondrites and achondrites. Chondrites make up 90% of the meteorites that reach Earth and contain iron-nickel metal and small, stony minerals called chondrules.
Carbonaceous chondrites occur only rarely and contain chondrules and clay containing water. Importantly, they contain carbon, hydrogen, oxygen and nitrogen, the main building blocks of living cells.
Achondrites are composed of similar minerals to igneous rocks and contain little or no metal.
Iron meteorites are mainly composed of iron and nickel. The largest iron meteorite found weighs 60 tonnes. It is the Hoba meteorite in Namibia.
Stony-iron meteorites are rare types of meteorites and fall into two main types: pallasites and mesosiderites.
How do you know if you’ve found a meteorite?
Meteorites tend to be heavy for their size and the surface often has a dark brown or black crust, formed when the rock became charred during its journey to Earth. Check whether a magnet sticks to the rock as almost all meteorites contain a mixture of iron and nickel. If your rock is magnetic, scratch the rock on a piece of un-glazed tile. Magnetite, a magnetic mineral found on Earth will leave a grey powder streak. A meteorite won't leave a powder streak.
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