Triton

Triton

. A mosaic of the south polar cap of Triton, the largest satellite of Neptune, taken in August 1989 from the Voyager 2 spacecraft. At the time of this flyby, Triton was the coldest measured object in the solar system with a surface temperate of 38 degrees kelvin. It is so cold that most of Tritonís nitrogen atmosphere is condensed as frost, making it the only satellite in the solar system known to have a surface made mainly of nitrogen ice. Highly reflective methane ice has been colored pink by the action of energetic radiation. (Courtesy of NASA and JPL.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University