GEOLOGY Neptune is a gas giant without a solid surface. Its interior comprises a dense core of rock, metal, and ice surrounded by layers of hydrogen, helium, and other gases. Deep within, extreme pressure and temperatures likely create exotic states of matter. Despite lacking a defined surface, Neptune's atmosphere transitions gradually into its interior, with the atmosphere blending into layers of gas and ice. Magnetic field fluctuations hint at complex internal processes, but due to its distance and the challenges of observation, detailed understanding of Neptune's geology remains elusive.