Jupiter's Core 

To understand the interior of Jupiter is currently very hard to determine and is very indirect. This is due to the fact that atmospheric space probes can only go a depth of 150 km below the surface. Jupiter probably has a rocky core deep in the planet amounting to around 10 to 15 Earth-masses. This core is surrounded by a large quantity of hydrogen. However, unlike on the surface, this hydrogen is liquid, not gas. This is because at great depths in the planet where pressure exceeds 4 million bars, hydrogen atoms ionize, resulting in elements consisting only of protons. This process converts hydrogen into a metallic state and is then able to conduct electricity and produce magnetic fields. Thus Jupiter has one of the largest magnetospheres in the solar system, extending beyond the scope of Jupiter and into other planets.