<P> The rings of Saturn are the most extensive planetary ring system of any planet in the Solar System . They consist of countless small particles, ranging from μm to m in size, that orbit about Saturn . The ring particles are made almost entirely of water ice, with a trace component of rocky material . There is still no consensus as to their mechanism of formation; some features of the rings suggest a relatively recent origin, but theoretical models indicate they are likely to have formed early in the Solar System's history . </P> <P> Although reflection from the rings increases Saturn's brightness, they are not visible from Earth with unaided vision . In 1610, the year after Galileo Galilei turned a telescope to the sky, he became the first person to observe Saturn's rings, though he could not see them well enough to discern their true nature . In 1655, Christiaan Huygens was the first person to describe them as a disk surrounding Saturn . Although many people think of Saturn's rings as being made up of a series of tiny ringlets (a concept that goes back to Laplace), true gaps are few . It is more correct to think of the rings as an annular disk with concentric local maxima and minima in density and brightness . On the scale of the clumps within the rings there is much empty space . </P>

What are saturn's rings mostly made of