A comparison of the four Smallest Planets. EARTH, VENUS, MARS, and MERCURY. Pluto, the Dwarf Planet, does not meet the requirements.................In order to be classified as a planet, it must be massive enough that gravity will keep it round while it's rotating. Pluto consists of mostly methane and hydrogen gas, which doesn't give it the required mass. It must also rotate around the sun. The MOON is the only natural satellite of EARTH. Diameter = 2,160 miles. Mean distance, Moon to Earth = 238, 712 miles. Note: a dollar bill, end to end from Earth to the Moon, is One Billion Dollars. Mean surface Temp. during day is 107 degrees C. Mean Temp at night = minus 153 degrees C. 180 lbs on Earth = 30 lbs. on Moon. Gravity is 1/6th that of Earth.
First visited by Soviet spacecraft Luna 2 in 1959. Neil Armstong first man on moon 7/20/69 with Edwin Aldrin, both on Apollo 11. Last visit was Dec. 1972. It is the only extraterrestrial body visited by humans. The Moon's gravitational force causes low and high tides. There is no atmosphere, but spacecraft Clmentine suggests there may be water ice in some deep craters near the Moon's South Pole. Look for NASA'S Lunar Orbiter for 2008 to further shed light on this determination.