Small grains of chemically-produced solid material accreted by gravitational forces, first into small bodies known as planetesimals and then, more slowly, into larger planets. Comets and some types of meteorites are probably remains of the original planetesimals. The chemical composition of the Earth was governed by the types of minerals that were able to condense and become solids at the temperature of the accreting Earth. This led to a rocky, silicate composition, as for the other inner planets and moons. Much research work remains to be done to interpret the detailed chemistry of the planets.
Classification schemes are in common use for the interior and atmosphere of the Earth.
The interior scheme has been derived from seimological measurements. The atmospheric scheme is derived from temperature measurements. Take the Self-Test for this lecture. Links Send feedback to the Global Change Webmaster .