The Solar System

554 PART 4^ |^ THE SOLAR SYSTEM

Chondrules are

small, glassy

spheres found

in chondrites.

d

c

a

A stony-iron meteorite cut

and polished reveals a

mixture of iron and rock.

b

Iron meteorites are very

heavy for their size and have

a dark, irregular surface.

Stony meteorites tend to have

a fusion crust caused by

melting in Earth’s atmosphere.

■ Figure 25-2

The three main types of meteorites—(a) irons, (b) stony-

irons, and (c) stones—have distinctive characteristics.

(d) Carbonaceous chondrite meteorites are a rare type of

stony meteorite that is rich in carbon, making the rock

very dark. (Lab photos courtesy of Russell Kempton, New England

Meteoritical)

■ Figure 25-3

Sliced, polished, and etched with acid, iron meteorites show what is called a

Widmanstätten pattern of large crystals, indicating that this material cooled

very slowly from a molten state and must have been inside a fairly large

object. (Photo courtesy of Russell Kempton, New England Meteoritical Services)

especially rich in water, other volatiles, and organic compounds.
Th ose substances all would have been lost if the meteoroid had
been heated even to room temperature.
One of the most important meteorites ever studied was a
carbonaceous chondrite seen falling in 1969 near the little Mexican
village of Allende (pronounced ah-yen-day). About 2 tons of frag-
ments were recovered. Studies of the Allende meteorite disclosed
that it contained chondrules, water, complex organic compounds
including amino acids, and a number of small, irregular inclusions

especially rich in water other volatiles and organic compounds

■ Table25-1 ❙ Proportions of Meteorites

Type Falls Finds

(%) (%)

Iron 6 66

Stony-iron 2 8

Stony 92 26