| Welcome to Planet
Earth, the third planet from a
star named the
Sun.
The Earth
is shaped like a sphere and
composed
mostly of rock.
Over 70 percent of the
Earth's surface is water.
The planet has a relatively thin
atmosphere composed mostly of
nitrogen and
oxygen.
This picture of Earth, dubbed
Blue Marble,
was taken from
Apollo 17
in 1972 and features Africa and Antarctica.
It is thought to be one of the most
widely distributed photographs
of any kind.
With its abundance of liquid
water,
Earth
supports a large variety of
life forms,
including potentially intelligent species such as
dolphins and humans.
Please
enjoy your stay on Planet Earth.
Credit:
Apollo 17 Crew,
NASA;
Photographic Mosaic & Digital Copyright:
Rob Stevenson
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