Credit & Copyright: Apollo 17 Crew,
NASA
Explanation:
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.
The above 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.
Earth has a single large
Moon that is
about 1/4 of its diameter and, from the planet's surface,
is seen to have almost exactly the same angular size as the
Sun.
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.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day