Unformatted text preview: electrical conductivity, is sometimes called a water-ammonia ocean.  At a depth of 7000 km, the conditions may be such that methane decomposes into diamond crystals that then precipitate toward the core.  The mantle may consist of a layer of ionic water where the water molecules break down into a soup of hydrogen and oxygen ions, and deeper down superionic water in which the oxygen crystallises but the hydrogen ions float around freely within the oxygen lattice.  The core of Neptune is composed of iron , nickel and silicates , with an interior model giving a mass about 1.2 times that of the Earth.  The pressure at the centre is 7 Mbar (700 GPa), millions of times more than that on the surface of the Earth, and the temperature may be 5,400 K...
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- Fall '10
- Astronomy, Planet, Mantle, internal structure