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APOD
Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
Welcome to Planet Earth
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 . 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.
| Date | February 4, 2001 |
|---|---|
| Credit | Credit: Apollo 17 Crew , NASA |
| Authors & editors: | Robert Nemiroff (MTU) & Jerry Bonnell (UMCP) |
| A service of: |
ASD at NASA / GSFC, NASA Science Activation & Michigan Tech. U. |