Although no one knows exactly what Pluto is made of, most scientists agree that it is between 50 and 70 percent rock, with the remainder being composed of various ices. Pluto’s core is composed of dense rock, while the ices form the larger, but less dense, mantle. The very outer crust of Pluto is composed of methane and nitrogen frost.
According to Nine Planets, Pluto is very hard to study because it is so far from the Earth; it orbits the sun from a distance of over 3.67 billion miles. As a comparison, the Earth orbits the sun at a distance of only about 93 million miles. Pluto’s orbit is about 39 times as distant from the sun as Earth’s orbit is. Pluto is a part of the Kuiper Belt, which is a collection of millions of rocks, frozen blocks of ice and comets. The objects in the Kuiper Belt are the remnants that were left over from when the solar system was formed. Scientists suspect that if Pluto were to be knocked out of its orbit and approach the inner solar system, it would grow a tail as its surface ices sublimated.
Scientists have used Pluto’s largest moon, Charon, to learn more about the dwarf planet. By measuring the amount, color and intensity of the light that reflects from Pluto and then noting what happens when Charon obstructs the light, scientists have been able to figure out Pluto’s size and characteristics more accurately.