Types of space rock Space is full of rocky debris left over from the formation of The very biggest space rocks are known Dwarf planets are massive enough to be shaped by their the Solar System. What they are called depends on what as dwarf planets. They are usually own gravity, but do not have enough gravity to have they are made of, how big there are, and where they are. found beyond the orbit of Neptune. cleared the space around them. Pluto is a dwarf planet.

Some meteoroids come from the debris left Asteroids Comets behind by comets Asteroids are large chunks of rock, or metallic Comets differ from asteroids because they Gas tail: rock, left over from the formation of the Solar are made up of mostly ice. Sometimes Charged gas System. Most are located in the Asteroid Belt called ‘dirty snowballs’, most comets particles between Mars and Jupiter. It is thought that come from an icy region beyond Neptune pushed from Jupiter’s gravity prevented them from coming called the Kuiper Belt. the comet together to form a planet. by the solar wind Asteroids range in size from as little as a metre to When their orbit thousands of metres. The largest asteroids are brings them close to Dust tail: the Sun, comets heat known as planetoids. Asteroid Larger dust and other up and vent gases particles trail and water vapour behind the that form a huge comet SPACE glowing cloud called meteoroids the ‘coma’. The dust Any chunk of rocky or metallic Most meteoroids and gas form tails material that travels through come from the that stretch away for Coma: space could be called a asteroid belt – millions of A hazy cloud meteoroid, but the name is either knocked kilometres. of dust and usually reserved for rocks clear by asteroid vapour that The Solar System is full of that are much smaller than collisions or surrounds asteroids. Meteoroids can disturbed by the the nucleus lumps of rock and ice. Some are range in size from that of gravity of larger as small as grains of sand, small pebble to a huge objects, such as boulder weighing several planets. Nucleus: others are the size of mountains. tonnes. ‘Dirty snowball’, or Sometimes they come to visit us ‘icy dirtball’ made up Meteors get their name from the Greek of rock, dust, water here on Earth. meteōros, which means ‘high in the air’. ice and frozen gases*

*The nucleus in this diagram is not to scale. Meteor, oid, or ite? Meteor showers The coma is many times larger than the nucleus. Whether a space rock is called a meteoroid, meteor, or Lots of meteors appearing in the same part of the During a meteor shower, the meteorite, depends on where it is at any given time. sky over a period of time is called a meteor shower. meteors appear to radiate from Most meteor showers are associated with comets. the same point in the night sky – astronomers call this the ‘radiant’. Meteoroid While it is floating around in space, a space rock is called a meteoroid. Really small space rocks (space dust) are called micrometeoroids. Debris trail Meteor When a meteoroid enters the Earth’s atmosphere, friction heats it up and it begins to Earth passes burn. The trail of light left behind by a burning through meteoroid is called a meteor, or ‘shooting star’. comet debris

Earth orbit of meteoroids travel through the Millions Earth’s atmosphere each day.

Fireball Comet Some meteoroids create more light when they burn up. These extra-bright meteors are called fireballs and they 24% can even be seen during the day. of meteoroids As a comet passes survive the through the Solar Meteorite journey System, it leaves behind Not all meteor Sometimes a meteoroid doesn’t through the a trail of dusty debris. showers are caused completely burn up as it travels through When the Earth’s orbit by comets. There Meteor showers get their name from the the Earth’s atmosphere. If it makes it to Earth’s carries us through the are two showers constellation from which they appear to radiate. the ground, it is called a meteorite. atmosphere comet’s debris, these every year that are The Orionid meteor shower, for example, appears to become micrometeoroids burn created by debris to radiate from the constellation of Orion. meteorites. up in the atmosphere. shed by asteroids. www.stfc.ac.uk Copyright: Ben Gilliland, STFC Meteorites that are spotted as they fall through The journey to the surface Types of meteorites the Earth’s atmosphere and then recovered are About 15,000 tonnes of meteoroids, micrometeoroids Meteorites come from many different parts of the Scientists classify meteorites by splitting them into called ‘falls’, all others are called ‘finds’. and space dust enter the Earth’s atmosphere ever year. Solar System and are formed in many different ways. three main groups: stony, iron and stony-iron. So why are meteorites so hard to find?

1. When a meteoroid Iron Stony-iron Stony enters the Earth’s atmosphere it can be Iron meteorites are made of about 90-95% iron with the rest Stony-Iron meteorites are made of a mix of both metallic and Stony meteorites are the most common type of meteorite. travelling at many made up of mostly nickel and some trace elements. It is rocky material. They probably formed when the metal cores They are made of rock, but can also contain small amounts 1 thought that they come from the metallic cores of asteroids. and the rocky magmas inside asteroids mixed together, which of iron. There are two types of stony meteorites: thousands of miles per hour. Compression of Iron meteorites are rarer than stony meteorites but their makes them extremely rare. There are two types of chondrites and achondrites. Achondrite meteorites were the air molecules in magnetism makes them easier to find. stony-iron meteorites: pallasites and mesosiderites. once part of the outer crust of a planet or asteroid. the atmosphere Pallasite Chondrite causes the meteoroid Iron-nickel Long before to heat up. crystals humans Pallasites have solid bodies of Chondrites contain rock that has discovered how nickel and iron but also contain changed little since the large translucent crystals of formation of the Solar System. 2. The surface of the to extract olivine. Pallasites come from the They are made up of small meteoroid melts, metals from the area between the metallic core mineral blobs called chondrules vapourises and small ground, ancient of an asteroid and the that formed in space billions of particles break away cultures used surrounding rocky magma. years ago and became clumped and burn up. together. Most meteors are metal from iron very small and so meteorites to Olivine Chrondules burn up completely make tools and crystals long before they 2 jewellery. reach the ground. Mesosiderite Achondrite Achondrites are much younger Meteors burn with different colours depending on the Mesosiderites differ from 3. In larger meteors, pallasites in that their crystals than chrondrites. They contain the surface layers are chemicals they are made up of. are smaller and made of silicate minerals which have been melted and burned minerals. It is thought that melted, changed and altered away, but some mesosiderites form when magma since they were formed. material survives. As mixes with the core during a Achondrites formed on bodies collision between two asteroids. that were large enough to it melts and shrinks, a support a molten interior – meteor can be 3 such as large asteroids, the sculpted into all sorts Nitrogen/ Iron Calcium Sodium Magnesium Small silicate Moon and even Mars. of interesting shapes. oxygen crystals

4. As it slows down, Killer space rocks! What can meteorites teach us? the meteor cools down, the melted Not all meteorites are harmless. Sometimes a space rock Meteorites contain rocks, metals and minerals so ancient surface solidifies and, 4 usually, turns black. pays us a visit that is so large it has the potential to that studying them can help us to understand the origins This layer is called the destroy a city or even wipe out most of the life on Earth. of the Earth, the Solar System and even life itself. fusion crust. 65 million years ago a 10 kilometre-wide asteroid Star birth smashed into the planet in modern-day Mexico. It Some meteorites contain grains 5 formed a crater 180 kilometres wide and caused a of dust produced by stars before 5. Most meteorites the formation of the Solar are lost at sea, but global climate shift that helped to kill off 75% of System. Studying them can help some do strike land the life on Earth – including the dinosaurs. us understand how stars form and can be found if and evolve. you know what to look for and are Big rocks don’t often hit Solar system very lucky. the Earth, but when they do the results can be Meteorites are the left over building blocks of the Sun and catastrophic. its planets and moons. Studying their composition helps us to understand how the Solar System was formed. This meteorite tumbled as it fell and has melted with thumbprint-like 50m 160m 700m 1.7km THE MOON Life on Earth indentations called (These strike (About Large meteorite Early in Earth’s history, regmaglypts. and other about once in once every impacts have shaped meteorites may have been every 190,000 1.5 million the face of the Earth responsible for delivering and Moon. A particularly the organic compounds that years) years) large impact (with a are the building blocks of Empire SPACE space rock the size of life. Studying meteorites State Mars) is thought to have may help us to understand Building created the Moon. how life first evolved. This meteorite Most disintegrate Land impact would destroy an area didn’t tumble and in the upper the size of Yorkshire. Ocean impact You don’t have to be scientist to examine meteorites. 50m has developed a atmosphere. 700m would create huge tsunamis. The STFC runs the only ‘Lunar Loans’ scheme that conical nose a bit allows schools and scientific organisations to borrow like a spacecraft’s Iron meteorites will leave Land impact would destroy heat shield. craters. Stone meteorites an area the size of France meteorites and samples of Lunar material. produce violent airburst and create a global 160m explosions. 1.7km climate-cooling dust cloud. www.stfc.ac.uk Copyright: Ben Gilliland, STFC