A WORLD OF MYSTERY
Our knowledge of Pluto’s properties has grown a lot since 1930, but gaps remain
Pluto Pluto is the largest member of the Kuiper Belt and part of a group of objects known as Trans-Neptunian bodies. These objects will reveal a lot about conditions in the early Solar System. Pluto has five satellites, the largest being Charon, at just over half Pluto’s diameter. The other four are Nix, Hydra, Kerberos and Styx. Pluto’s orbit is more like a comet’s: it is inclined by 17º to the ecliptic. At times it is closer to the Sun than Neptune. Pluto’s thin atmosphere is composed of nitrogen, methane and carbon dioxide. Remarkably, there is some evidence of winds blowing in the atmosphere. Pluto’s surface varies greatly in brightness and colour. Patches of red, grey and white give Pluto’s surface as much contrast as the Saturnian moon Iapetus. It’s thought that Pluto’s atmosphere could collapse and freeze as the dwarf planet moves farther away from the Sun; it is not known whether there enough heat to prevent this. Between 1994 and 2002/2003 some of Pluto’s surface features appeared to change, with the northern polar region brightening up and the overall reddish hue of the surface increasing.
Hydra Nix Styx Charon Kerberos Pluto has five known moons, the latest – Styx – only discovered in 2012
2002/2003 Images from Hubble show surface features changing over eight years