Introduction to Planetary Interiors

In the context of this volume, planetary interiors provide a testing ground for fundamental physics (theory and laboratory) under "extreme" conditions. For example, much of the interest in metallic hydrogen stems from its inferred presence in Jupiter (and the implication that it is the most common metal in the Universe). The melting properties of iron at megabar pressures are likewise "tested" in the deepest Earth through their relevance to the presence of a solid inner core. There are also a small number of people who study planetary interiors for reasons that are not primarily motivated by the desire w understand materials under extreme conditions. They do so for three reasons: 1) An explanatory basis for many phenomena that arise within a planet (but have external manifestation). You cannot understand why certain planets have volcanoes, why some planets have magnetic fields (and others do not), and why Jupiter emits as much heat as it does without an understanding of the insides of these bodies. 2) An essential part of the understanding of phenomena and processes that are not intrinsically internal to the planet. For example, you cannot claim any understanding of the history of Mars' atmosphere if you are ignorant of likely outgassing rates or of how the sputtering of the atmosphere is affected by a magnetic field that varies through geologic time. 3) The search for a unifying story. If you want to build a story of how the planet formed and evolved to the present state, this will depend mainly on understanding the interior