Achieving a comprehensive understanding of TNO formation and evolution hinges on investigating TNOs within the context of other related populations. In this presentation, we focus on the connections between TNOs, Centaurs, and comets.
Comets formed as planetesimals beyond the giant planets' orbits. During planetary migration, millions were scattered outward to the trans-Neptunian region and the Oort cloud. In the current epoch, some of the TNOs interact gravitationally with the outer planets and re-enter the middle Solar System, first as Centaurs, and then as active comets. Once they transition to cometary orbits, they lose material continuously, and undergo noticeable surface changes with every orbit until they disintegrate or reach dormancy.
The individual comet life-cycle stages have been studied extensively. However, the findings about the different populations are rarely combined and a complete model is missing. This gap in our knowledge motivated the work of the ISSI International team ("The Life Cycle of Comets”) and will be the presentation's focus. We will showcase the implications that recent observational and modeling evidence on the physical and surface evolution of comets has for TNOs and Centaurs. We will focus on the insights from our review on Centaur evolution processes for the upcoming IOP book “Centaurs”. Evolution in the giant-planet region is governed by orbital dynamics and is driven by three main mechanisms: thermal processing, close encounters and impacts. Different evolutionary processes leave distinct imprints onto the objects properties, and we will demonstrate how observables such as surface color and spectrum, albedo, phase function, rotation period and axis ratio can be used as diagnostics of evolution. Finally, we will highlight the key questions that should be addressed with current and upcoming facilities (especially LSST and JWST) in order to disentangle the primordial properties of TNOs and Centaurs from any evolutionary signatures.