When the Solar System was still just
a rotating disk of gas and dust, the gentle clumping together
of dust particles began the process that ultimately created
the planets: accretion. Chondrite meteorites are actual mixtures
of this 4.6-billion-year-old dust! When these rocks land on
Earth, they give us an invaluable look at how the accretion
process worked so long ago.
About 85 percent of the meteorites
that fall to Earth are chondrites. Three major varieties have
been recognized, and each has several subcategories distinguished
by chemical composition.