One of the approaches to study interiors of planets is to carefully analyse the internally generated fields extending to the outer space i.e. gravitation and magnetic field. Whereas the gravitation is given by mass distribution within the body which is quite stable, the magnetic field of the planets is usually generated by some internal dynamic processes and, therefore, can change significantly with the time. Studying not only the current state of these fields but also the remnant signs from the past can give us a lot of clues about the global evolution of the planet.
Figure 1: Topographic relief and correlating gravity high (mascon) of the lunar Mare Smythii. Quelle: Martin Pauer.