Pluto is thought to be made of mostly ice. It probably also has a small rocky core which might contain some metals. The ice on the surface of Pluto is made of frozen nitrogen, methane and carbon monoxide.The ice covering Pluto reflects a lot of sunlight making it appear brighter than it would if it had been covered with a darker rocky material. 1  Javascript must be enabled to use Cool Cosmos.t probably also has a small rocky core which might contain some metals. The ice on the surface of Pluto is made of frozen nitrogen, methane and carbon monoxide. The ice covering Pluto reflects a lot of sunlight making it appear brighter than it would if it had been covered with a darker rocky material.