Transcript: Neptune is a close twin of Uranus with similar size and structure. Its bluish tinge is visible even through a small telescope. At its center is a rocky, silicate core with trace metals surrounded by a mantel of water, ammonia, and methane in both liquid and ice forms. The pressure is insufficient to create hydrogen in its metallic form. The outer atmosphere consists primarily of hydrogen and helium in roughly the solar abundance. Like Jupiter, Uranus and Neptune have large storm systems. Neptune has a great dark spot that has persisted for many years analogous to Jupiter's great red spot.