Jupiter

Jupiter probably has a core of rocky material amounting to something like Earth masses. Above the core lies the main bulk of the planet in the form of liquid metallic hydrogen. This exotic form of the most common of elements is possible only at pressures exceeding million bars, as is the case in the interior of Jupiter and Saturn. Liquid metallic hydrogen consists of ionized protons and electrons like the interior of the Sun but at a far lower temperature. At the temperature and pressure of Jupiter's interior hydrogen is a liquid, not a gas. It is an electrical conductor and the source of Jupiter's magnetic field. This layer probably also contains some helium and traces of various ices.

The outermost layer is composed primarily of ordinary molecular hydrogen and helium which is liquid in the interior and gaseous further out. The atmosphere we see is just the very top of this deep layer. Water, carbon dioxide, methane and other simple molecules are also present in tiny amounts. Recent experiments have shown that hydrogen does not change phase suddenly. Therefore the interiors of the jovian planets probably have indistinct boundaries between their various interior layers.

Three distinct layers of clouds are believed to exist consisting of ammonia ice, ammonium hydrosulfide and a mixture of ice and water. However, the preliminary results from the Galileo probe show only faint indications of clouds one instrument seems to have detected the topmost layer while another may have seen the second. But the probe's entry point left was unusual Earth based telescopic observations and more recent observations by the Galileo orbiter suggest that the probe entry site may well have been one of the warmest and least cloudy areas on Jupiter at that time.

Data from the Galileo atmospheric probe also indicate that there is much less water than expected. The expectation was that Jupiter's atmosphere would contain about twice the amount of oxygen combined with the abundant hydrogen to make water as the Sun. But it now appears that the actual concentration much less than the Sun's. Also surprising was the high temperature and density of the uppermost parts of the atmosphere.