New studies offer a clearer picture of how the outer solar system formed and evolved based on analyses of trans-Neptunian objects (TNOs) and centaurs. The findings reveal the distribution of ices in the early solar system and how TNOs evolve when they travel inward into the region of the giant planets between Jupiter and Saturn, becoming centaurs. TNOs are small bodies, or ‘planetesimals,’ orbiting the sun beyond Pluto. They never accreted into planets, and serve as pristine time capsules, preserving crucial evidence of the molecular processes and planetary migrations that shaped the solar system billions of years ago. These solar system objects are like icy asteroids and have orbits comparable to or larger than Neptune’s orbit. Prior to the new UCF-led study, TNOs were known to be a diverse population based on their orbital properties and surface colors, but the molecular composition of these objects remained poorly understood. For decades, this lack of detailed knowledge hindered interpretation of their color and dynamical diversity. Now, the new results unlock the long-standing question of the interpretation of color diversity by providing compositional information.