Pluto Pluto is the farthest from the sun. It is also the ninth planet from the sun. And is the smallest planet-less then half the size of Mercury. Another reason Pluto is unusual is that its moon, Charon is more than half its size! In fact, Charon is the largest satellite relative to its planet in the solar system. On average, Pluto's orbit is 5.9 billion kilometers (3 2/3 billion miles) away from the sun. All the planets …showed first 75 words of 314 total…

…showed last 75 words of 314 total…hundred twenty degrees Celsius (negative three hundred sixty degrees Fahrenheit) at the planet. From calculations of Pluto's density, it must be made of rock and ice. A very thin atmosphere of methane has been detected. While Pluto is covered by nitrogen ice, Charon is covered by water ice. Pluto is the only planet that has not been visited by a NASA mission, but plans are underway to finally visit this world and its moon in 2010.