Like gas giants, ice giants also lack a well defined solid surface. Uranus's atmosphere is similar to Jupiter's and Saturn's because of the hydrogen and helium, but it contains more "ices" like water, ammonia, and methane. It has the coldest atmosphere in the Solar System, with a minimum temperature of −371 degrees Fahrenheit, and a layered cloud structure with water that makes up the lowest clouds and methane the uppermost layer of clouds. The interior of Uranus is mainly made of ices and rock.