The planet Pluto has yet to be visited by a spacecraft. However, NASA is hoping that the New Horizons craft will reach the planet on July 14th, 2015. We do know that Pluto is a dwarf planet made up mostly of ice. Like its atmosphere, this icy surface is composed of Nitrogen, Methane and Carbon Monoxide. Pluto is 4.34 billion km from earth and has a diameter of 2,301 km, making it roughly 400 times smaller than Earth and only 70% the mass of the Moon. Pluto itself has one moon, Charon. Pluto's unusual 90,613 day orbit causes an anti-greenhouse effect through freezing and sublimation. Unusually, it's orbit sometimes brings it closer to the sun than Neptune. This occured in 1989 and it then remained ahead of Neptune for 10 years. It won't happen again until 2226.