English: Atlas Images of Uranus, Neptune, and their moons. Uranus and Neptune were observed serendipitously by the 2MASS Southern Facility, during routine operations on 1998 June 7 and June 11 UT, respectively. Both planets appear very blue, i.e., they are not nearly as bright in the Ks band as in the shorter wavelength bands, due to more reflection of sunlight at short wavelengths and to absorption of light by methane gas in their atmospheres. The moons, or satellites, of both planets have icy surfaces with no (or very little) atmospheres. They simply reflect sunlight by various amounts, depending on the albedo, or reflectivity, of each moon's surface. Umbriel has a surprisingly dark, icy surface. Miranda is the innermost and smallest of the five large Uranian moons. Triton is odd, in that it is in a highly-inclined retrograde orbit around Neptune, leading planetary scientists to infer that Triton was captured by Neptune's gravity. For more information about these and other planets, see NASA/JPL's Welcome to the Planets and NASA/GSFC's Planetary Fact Sheets. Moon identification in and further analysis of these 2MASS images by B. Nelson (IPAC).