This is a proposal for 98 hours of NIRSPEC/PRISM observations of 59 trans-Neptunian objects and Centaurs (hereafter, TNOs). Our targets cover a diverse range of orbital characteristics, sizes, albedos, and surface compositions complementary to the GTO targets. The TNO population includes some of the most primitive bodies in the Solar System and preserves a record of the significant dynamical dispersal of the protoplanetesimal folowing the era of planet formation.

Spectroscopy of TNOs is a powerfull tool to study their surface composition but has reached its limits from ground-based facilites and there is no instrumentation available, or planned for the next 10 years, capable of significantly increasing that existing sample with sufficient quality for compositional analysis.

NIRSpec will be able to provide high-quality data, even in its low resolving power mode, that will surpass the quality of the data available by orders of magnitude. The goal of this proposal is to asses the relative ratio of water ice, complex organics, silicates, and volatiles on the surface of a large sample of TNOs. This information is vital to improving models of the formation of our Solar System and other planetary systems and relates to disciplines such as astrochemistry, cosmochemistry, and astrobiology, being relevant to our understanding of the origin of water and life on Earth and possibly elsewhere.

This is the time to provide such critical information to the scientific community and JWST is the optimal avant-garde tool to face that challenge.