The Sun is at the center of
the planets. Close to it are the inner planets - Mercury, Venus,
Earth and Mars.
Mercury the planet closest
to the Sun, is a cratered rock not much bigger than our
Moon. It is incredibly hot and unable to support any kind of
life. The atmosphere contains sodium and potassium.
Venus is the next planet
from the Sun and is about the same size as the Earth. The
atmosphere is made up of mainly carbon dioxide. The surface
temperature can be as high as 480 degrees Celsius. There is
no life of any kind on the planet Venus.
Earth is the only planet
that has the conditions to support life. The surface is
neither very cold nor very hot. Water can exist in all its
three forms - as gas, liquid, and solid. These conditions
allow plants and animals to live and reproduce.
Mars, the first planet
beyond Earth is smaller than the Earth. The atmosphere is
made up mostly of carbon dioxide. Water exists on this
planet, but only in the form of ice. The whole planet is a
red, lifeless desert.
The outer planets, Jupiter,
Saturn, Uranus, and Neptune are called the gas giants. They
are much larger than the Earth. The outermost planet, Pluto, is no
longer classified as a planet. It is now called a dwarf
Planet. It is so far away, it is a mystery.