Introduction to Planetary Geology
There are many sub-fields of Geology involving a myriad of processes and rock types. One interesting discipline is the field of planetary geology. Planetary geologists study the makeup of the earth as well as the other planets and celestial bodies in the solar system. Part of this involves looking at processes that have occurred on Earth throughout its history in order to apply them to similar features on other planets. Likewise, we can study processes that have happened on other planets or moons and apply the interpretations to similar features on the earth.
One example is the process of meteor impacts. If you look at the moon it is pockmarked with craters caused by meteor impacts. Presumably the earth has undergone many impacts as well; however, the dynamic nature of the planet has largely erased the evidence. Because of this impact geologists often need to use creative and innovative techniques to determine sites of past craters.