Scientists have found carbon dioxide on Pluto’s largest moon – offering clues about how it formed

A composite of enhanced colour images of Pluto (lower right) and Charon (upper left). NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

In the outer reaches of our Solar System, 5.7 billion kilometres from the Sun, lies the dwarf planet Pluto. Smaller than Australia, it is an icy world of mountains, glaciers and craters where the average temperature is –232°C.

Five moons orbit Pluto – Styx, Nix, Kerberos, Hydra and Charon. Of these, Charon is the largest. Unlike most other planetary systems, it exists in a “binary system” with its parent body, meaning they both orbit a point in space between the two.