Methane Ice Crystals

Explanation: During its 2006 flyby of Titan, the Cassini spacecraft captured some of the most detailed images of Saturn's largest moon. Some of the cloud formations over Titan's north pole bear a strong resemblance to those that are seen in Earth's own polar stratosphere. Given Titan's incredibly low temperatures – minus 185 °C (-300 °F) some methane ice crystals can exist in these clouds. Methane ice is one of the ices known to exist on the surface of Pluto.

Pluto

Image credit: NASA/JPL/U. of Ariz./LPGNantes.