We obviously know most about the Earth. As a planet, it contains water in all three states: liquid, vapor, and ice.  It has a very thin atmosphere in comparison to some of the planets, but it is sufficient to protect the Earth from most meteorites, and to shield it from much of the sun's radiation.  Since it tilts on its axis about 23 degrees, it has "seasons" of temperature and weather variations.

It's the only planet known to have, or even to ever have had life.  Due to its atmosphere and the abundance of water on the planet, the Earth appears bluish from space, brushed with white clouds on closer viewing.  All of the outer planets have moons, as does Earth with its single one following it along on its journey around the sun.

More information on Earth??

http://pds.jpl.nasa.gov/planets/choices/earth1.htm

http://www.seds.org/nineplanets/nineplanets/earth.html

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Page by Francis Perry, April 2002