| Find a Meteorite:
Explore Meteorites |
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When
asteroids became hot enough to melt the rock and metal
portions found in the chondritic type, material separated
to form different types of meteorites. The rock portion
of the bodies became a type of stony meteorite called
the achondrites (meteorites
without chondrules). These are actually igneous rocks
from magmas that formed on asteroids. These asteroids
became hot enough to melt from radioactive elements just
after the Solar System formed
(4.6 billion years ago).
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| The Johnstown diogenite, possibly a sample from
asteroid 4 Vesta, one of the targets of the Dawn
mission. |
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This eucrite sample, from the Australian meteorite Camel Donga, is also a meteorite type that may be a fragment from Vesta.
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| The Dora pallasite,
a sample of the core-mantle boundary from an asteroid
that melted. |
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| The Hoba iron meteorite
in Namibia. A portion of the core of an asteroid
that melted. |
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| The Gibeon iron meteorite.
This sample of the core of an asteroid has been polished
and lightly etched with acid to show the crystalline
structure formed by different iron-nickel crystals. |
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During melting, the denser metal
separated in these asteroids to form iron meteorites.
The Iron meteorites are composed mainly of iron alloyed
with nickel and they often contain a sulfide mineral
called troilite (FeS) (something like fools gold or
pyrite found on the Earth). Irons are the meteorites
that are most easy to identify because they are heavier
than most rocks, are magnetic, and are made of iron
and nickel metal. Just like the Earth which has an
iron-nickel core, the composition of irons indicates
that they represent the cores of their parent asteroids.
The stony-iron meteorites or stony-irons
are composed of both rocky material that formed
from a magma and metallic iron-nickel. If an
asteroid, contains a core, mantle,
and crust,
like the Earth does; then, the irons would be from the core, the stones
from the crust or mantle, and the stony-irons
from in-between the core and mantle. The asteroid
Vesta is thought to have melted and may contain
achondrite materials. The optical and infrared
spectral signatures of the rocks on Vesta observed
by telescopes match some of the achondrite meteorites,
which suggests that some of these meteorite types
(Howardites, Eucrites, and Diogenites) might come
from Vesta!
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accountability report