Star stuff

meteorites

 

brilliant fiery streaks-

burning debris from solar

system formation.

truth is, falling stars aren’t stars

but lost cousins coming home.

 

 

Meteorites are natural objects composed of stone, metal, or a combination of the two that have survived their fall from space through our atmosphere. Most meteorites come from asteroids, a small percentage from Mars and the moon, a very few may even originate from comets.

 

Those that come from asteroids are the oldest objects that are available for direct study. (As opposed to the light from ancient stars, which we can see but not touch…) They date back about 4.5 billion years, to the first stages of the creation of the solar system. So they can give scientists insight into the processes that made our sun and its planets.

 

(FYI- Asteroids are not exploded planets, they’re the bits that never made it into planets, possibly because Jupiter’s gravitational pull was too strong for them to coalesce.)

Stone meteorites are mostly silicate rock very much like Earth’s crust. Iron meteorites are actually iron with different percentages of nickel. The stony-iron meteorites are just that. Though what’s really neat is that some have crystals of the gemstone peridot (or olivine) in them. So when you see a sample it’s this literally space age slice of metal with green gems embedded in it.

 

Just to confuse things–meteors–the ones you see in showers and normally are associated with the orbits of comets–don’t generally become meteorites. It’s very rare for there to be enough material to be recovered, the norm is complete vaporization.

 

Meteorites start as larger objects, called meteoroids. One would be travelling at around 67,500 mph when it hits our atmosphere and is slowed by the friction. The outer part melts off and the droplets are carried away–at this point, though slowed by the atmosphere it is still moving fast enough to create shock waves. As it cools and falls the melted surface forms a glassy coating known as a fusion crust. Once it (or its pieces if it explodes in the air) hit the ground it’s officially a meteorite.

 

Factoids:

 

40,000-60,000 tons of ‘extraterrestrial material’ fall to Earth every year. Most are almost dust grains, smaller than 1 mm.

 

Around a thousand meteorites bigger than a soccer ball strike the Earth’s atmosphere every day.

 

Yes, people have been hit by meteorites… I wonder if insurance covers that?

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1 Comment

Filed under Gems, Natural Science

One response to “Star stuff

  1. Pingback: And Rocks Falling… « Magpie's Miscellany

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