New Horizons probe approaching the dwarf planet Pluto and its moon Charon. These objects lie in the Kuiper Belt, some 40 times further from the Sun than Earth is. Pluto has a surface with regions of dark, light and orange land, which change with the seasons. It is thought these regions are made up of nitrogen and methane ices, overlying a rocky core. Charon, by contrast, is largely made of water ices and rock. Pluto and Charon orbit each other closely, with a separation of less than 20, 000 kilometres. The centre of their mutual rotation lies outside the body of Pluto, and they are sometimes considered a double dwarf planet, rather than a planet and moon. Each is tidally locked to the other, presenting the same face and remaining fixed in the other's sky. New Horizons will arrive at this system in July 2015, becoming the first spacecraft to do so.