Small bodies (i.e., asteroids and comets) play an important role in our understanding of the Solar System. They are composed of the same planetesimal material that was incorporated into the planets, but their smaller size kept them from experiencing extensive processing (such as differentiation or atmosphere-related surface erosion). Therefore, their primitive nature allows us to probe the composition of the early Solar System and its subsequent evolution. Even though comets and asteroids are expected to contain material characteristic of their formation region, they have undoubtedly undergone some degree of processing since they were formed. The overarching motivation for small-body science is to disentangle primordial characteristics from evolutionary characteristics developed since formation with the goal of better understanding how our Solar System came to be. This work seeks to tackle a small piece of this goal by studying the objects of two extreme populations: the most and least thermally processed bodies.

This thesis uses ground-based broadband optical photometry to investigate the differences between different small body populations and how thermal processing alters the characteristics of objects over time. First, we investigate the optical colors of near-Sun asteroids that experience extreme temperatures of > 1000 K to better understand the dominant processes that affect their surface properties and could potentially lead to their disruption. Next, we characterize the long-term brightness evolution of long-period comets using two distinct datasets: 1) an observing campaign that conducts long-term monitoring of long-period comets that are active beyond the region where water-ice sublimation is efficient, and 2) photometric magnitudes of long-period comets with well-characterized orbits that were collected and reported by amateur observers. We assess our ability to improve brightness predictions for comets discovered at large heliocentric distances and establish if brightness behavior can be used as a diagnostic of dynamical age.