<P> The atmosphere of Uranus is composed primarily of hydrogen and helium . At depth it is significantly enriched in volatiles (dubbed "ices") such as water, ammonia and methane . The opposite is true for the upper atmosphere, which contains very few gases heavier than hydrogen and helium due to its low temperature . Uranus's atmosphere is the coldest of all the planets, with its temperature reaching as low as 49 K . </P> <P> The Uranian atmosphere can be divided into three main layers: the troposphere, between altitudes of − 300 and 50 km and pressures from 100 to 0.1 bar; the stratosphere, spanning altitudes between 50 and 4000 km and pressures of between 0.1 and 10 bar; and the hot thermosphere (and exosphere) extending from an altitude of 4,000 km to several Uranian radii from the nominal surface at 1 bar pressure . Unlike Earth's, Uranus's atmosphere has no mesosphere . </P>

What is uranus's atmosphere made out of
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