PLUTO

MASS: 0.2% of Earth's
DIAMETER: 1,430 miles
ROTATION: 6 days, 9 hours
ORBIT AROUND SUN: 248 Earth years

Pluto is the smallest and coldest planet of the solar system. It is the ninth planet away from the Sun. Pluto's orbit is the most elliptical of all the planets. At one point it crosses over Neptune's orbit and is the eighth planet from the Sun. Since Pluto is so small some scientists believe it should be reclassified as an asteroid but since Pluto is round it will stay a planet for now.Some scientists believe that Pluto may have wandered into our solar system from the Kupier Belt. In the Kupier Belt, there are other Pluto-like objects that orbit the Sun. If this is true then Pluto isn't a planet at all. Other scientists believe that Pluto may have been an old moon of Neptune that escaped.Pluto is coated with a frozen sheet of methane, nitrogen, and carbon monoxide on the surface. As Pluto gets closer to the Sun the ice melts and the gases form a thin atmosphere then as it gets farther away from the Sun these gases freeze again. Scientists believe that Pluto has a rocky core with a mantle of water ice.Charon is the only known moon to orbit Pluto. Even their orbit is unusual because they are gravitationally locked. The same sides are always facing each other as Charon orbits around Pluto. Charon may be a chunk of Pluto that broke off in a collision with another large object.