Although the evolution, composition, and interiors of terrestrial planets have some features in common, such as iron-rich cores, slowly convecting silicate mantles, and rigid crustal layers – they are entirely different in many other respects.
Comparing the Earth with the other terrestrial planets, the most striking difference at first glance is the state of the surface (including the crust) and the way heat is transported. The surfaces of other planets are not segmented but consist of single plates, the so called stagnant lids, beneath which the mantle convects. Heat flow through the surface is mainly transported by conduction, with some minor contribution by volcanic heat transport through this stagnant lid. The difference in the heat transport mechanism for the planets is also reflected in their thermo-chemical evolution.
For instance a strong diversity in crustal evolution has been identified: Mercury and the Moon show highly cratered surfaces indicating an average crust older than about 4 Ga (the age of the terrestrial planets is assumed to be ~ 4.5 Ga) with only minor volcanic activity in the subsequent evolution. Mars shows a distinct dichotomy of the surface consisting of the old southern highlands and the superficially younger northern lowlands.
Similar to crustal evolution, magnetic field evolution differs among the terrestrial planets and the Moon. Mercury is the only terrestrial planet, except the Earth, that has a magnetic field – although a weak one – that is generated in the iron core. Venus, Mars and the Moon on the other hand have no present global magnetic fields but at least in the case of the Moon and Mars the remanent magnetization of part of their crust indicates that they once had dynamo action in their cores.
The diversity in the thermo-chemical evolution of the various planetary bodies is not fully understood. The subject of our research aims for a better understanding of the processes involved - not only for the planets of our solar system but also for exoplanets.