Planetary geology: an historical and philosophical overview

The use of geological interpretations to better understand features that are observed outside the Earth defines what is known as planetary geology. It is a highly multi-disciplinary field, using concepts from many areas of human knowledge to better understand the many objects of the Universe. Interpretations tend to be based on analogue models, created from observations made on the Earth and extrapolated to the many geological contexts of other celestial bodies. It is assumed that these models can always be used, as long as corrections considering differences in properties such as temperature, mass, atmospheric, crustal and mantel composition, amongst others, are made. In most cases, such correlations are possible, requiring minor to no significant modifications. However, a reasonable number of extra-terrestrial features cannot be explained using the Earth as the unique comparison ground, requiring the use of other analogues as a basis, or even the creation of models and theories from scratch. Here, we present an overview of planetary geology: what it is, the limits of its application, the current state of the art and the meaning of this line of research in the era in which we live, where the exploration of other objects of the Solar System is a reality.