For Trans-Neptunian Objects, The Past Is Written On Their Surface

The formation of our solar system is complex, but two key facts are well-established. Icy giants like Neptune and Uranus formed beyond the snow line, while Earth and Venus formed near the Sun, where solar winds stripped their atmospheres. Planets like Jupiter and Saturn migrated inward, and this realignment triggered the Late Heavy Bombardment, when Earth was hit by many impacts. It was thought that planetary bodies maintain their original composition, but small bodies can change due to gravitational interactions. Two new studies on Trans-Neptunian Objects (TNOs) challenge this idea. The first study examines the surface colors and luminosities of TNOs, while the second uses JWST and Hubble data to study their size distribution. TNOs are faint and difficult to study, but the studies found that the distinction between cold and hot TNOs remains true even for the smallest ones. Cold TNOs have reddish surfaces, while warm TNOs have a broader color distribution. The studies also found that the size distributions of hot and cold TNOs are similar, suggesting they have experienced similar collision rates. The process of driving hot TNOs to the outer solar system wasn't violent. Another discovery is that there are fewer small TNOs than predicted by models, which could explain why the two TNO types retain their history. This research opens the door to more discoveries about the formation and evolution of small bodies in the solar system.

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