Compositional diversity of small bodies in the outer Solar System revealed by JWST : clues to primordial and evolutionary processes

Since their discovery 30 years ago, our knowledge of the chemical composition of trans-Neptunian objects (TNOs), faraway icy asteroids, has been limited. Now, the capacities of the James Webb Space Telescope offer a new era for the chemical characterisation of trans-Neptunian surfaces. Using cycle 1 observations from the large programme “DiSCo-TNOs”, we found the existence of three distinct spectral and compositional groups of TNOs : some are dusty and water ice rich, some are rich in carbon dioxide ice while others show methanol and complex organics. I will present how these compositional differences are linked to their formation distance in the protoplanetary disk. The detection of CO ice on two groups of TNOs prompted investigations into its origin. I will present how ion irradiation experiments allowed to confirm the effect of space weathering on TNO surfaces by providing an efficient pathway for CO formation.