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Meteors & Meteorites

Meteors

Meteors are small rocks that enter Earth's atmosphere and heat up from compression of the air in front of them (not from friction), mostly between 75 and 120 km up. Millions of these enter Earth's atmosphere each day. Most disintegrate between 50 and 95 km up, in the mesosphere. Most are only the size of a grain of sand.

Before entry meteors are likely to be travelling at tens of thousands of kilometres per hour.

A fireball is a brighter than usual meteor.

A meteor shower occurs when Earth passes through a cloud of dust and small rocks left behind a comet. Many meteors a minute can be seen appearing to radiate from a point source in the sky.

A meteor storm is a particularly impressive meteor shower.

Historic meteors

Meteors were originally regarded as an atmospheric event, like lightning. This view was shaken up in 1807 (see historic meteorites below) and with the meteor storm of 1833.

In February 2013 the largest meteor strike in over a century resulted in about 1200 injuries in Chelyabinsk, Siberia, Russia. The meteor exploded high up in the sky (perhaps as much as 70km up), causing a large extended flash of light. Many people went to look at what had caused the flash and were injured by broken glass from windows blowing out when the shock wave arrived a couple of minutes later. Up to 3,000 buildings were damaged, and all schools have been closed due to broken windows. Temperatures in the city are below freezing. The event was significant enough to get its own Wikipedia listing.

Meteorites

Meteorites are rocks that are big enough to survive passing through Earth's atmosphere and strike the ground. They are likely to be cool and travelling at terminal velocity, having just passed through tens of kilometres of very cold air.

About 500 meteorites land on Earth every year, almost always smaller than a soccer ball, and about 1% of those get found.

There are different kinds of meteorites; about 5% are made of iron and iron-nickel alloys, and a further 1% are iron and rock mixes. Large meteorites are more likely to be iron-nickel because that sort of meteor is less likely to break up in the atmosphere than rock or rock/ice meteors.

Historic meteorites

Meteorites were ancient people's first source of iron. See that page for more meteorites used as a source of iron.

The Weston Meteorite fell on the morning of 14 December 1807. Wikipedia recounts: "The meteor fall was widely witnessed and reported in newspaper accounts at the time. Eyewitnesses reported three loud explosions, and stone fragments fell in at least six locations." The investigation of this meteorite by Yale University chemistry professor Benjamin Silliman and a colleague is said to have prompted the then President of the USA Thomas Jefferson to respond "I would more easily believe that two Yankee professors would lie than that stones would fall from heaven."

In February 2016 a bus driver in India was killed by a meteorite (NZ Herald article) that left a 60 cm crater. Forensics teams found no trace of chemicals from explosives. This page about meteors was posted in response to this sad news.