Significant chemical cycles exist on Jupiter's moons. Recent evidence points to Europa possessing several active cycles, most notably a water cycle.[20] Other studies suggest an oxygen[21] and radiation induced carbon dioxide[3] cycle. Io and Europa, appear to have radiolytic sulphur cycles involving their lithospheres.[22] In addition, Europa is thought to have a sulfur dioxide cycle.[18] In addition, the Io plasma torus contributes to a sulphur cycle on Jupiter and Ganymede.[23] Studies also imply active oxygen cycles on Ganymede[24] and oxygen and radiolytic carbon dioxide cycles on Callisto.[18]