When people think of geology, they often imagine fieldwork on Earth—rock outcrops, fault lines, and stratigraphic layers exposed by erosion. For me, however, geology represents something broader: a way to reconstruct the history of worlds we cannot directly visit. One of the clearest examples of this idea comes from the Opportunity rover mission to Mars. Opportunity was not sent to Mars to drill deep cores or collect samples by hand. Instead, it explored the planet by observi