Final answer:
Crater cracks are typically detected by visual examination, with the study of their patterns and characteristics helping to understand the age and geological history of a planetary surface.
Step-by-step explanation:
Crater cracks are most commonly detected by visual examination. Understanding the formation and the age of craters involves observing various features, such as mudcracks which are wider at the top and become narrower towards the bottom, serving as a way-up indicator in a cross-section view. Additionally, crater counts can deduce the relative age of planetary surfaces, as areas with more craters are typically older, indicating a longer period since the surface was last 'swept clean' by geological events like lava flows or large impacts. The observation and documentation of craters and their characteristics, such as the famous lunar craters observed by Grove K. Gilbert, contribute to the field of lunar geology and the broader study of planetary science.