Deep in the cold and distant regions of the Solar System, beyond the orbit of Pluto, lie trans-Neptunian objects (TNOs), mysterious bodies that preserve crucial clues about the early history of our planetary system. The latest research, conducted using the James Webb Space Telescope (JWST), provides the most detailed insight yet into the composition, evolution, and interconnectedness of these icy worlds, revealing an extraordinary diversity of surface materials and chemical compounds.

Icy Worlds as Windows into the Past

Trans-Neptunian objects are small, icy bodies that have never formed into planets. Therefore, they act as time capsules that preserve molecular traces from the period of the formation of the Solar System. According to new data obtained by the JWST, scientists have for the first time been able to precisely determine the molecular compositions of the surfaces of these objects, including water ice, carbon dioxide, methanol, and complex organic molecules.

These compounds not only point to chemical processes in the early stages of the Solar System but also reveal how conditions such as temperature and distance from the Sun shaped their structure. Scientists have identified three main groups of TNOs, classified by the characteristics of their surface compositions, which they have named "Bowl," "Double Depression," and "Cliff."

Three Different Groups of TNOs

The first group, "Bowl," makes up about 25% of the observed objects and is characterized by a high concentration of crystalline water ice and dark, dusty surfaces. The second group, "Double Depression," which covers about 43% of the sample, shows distinct traces of carbon dioxide and organic molecules. The third group, called "Cliff," with 32% of the sample, contains complex organic molecules, methanol, and nitrogen-containing molecules.

These data provide crucial insight into the temperature boundaries within the protoplanetary disk of the Solar System, where different compounds could condense and persist. Each of these groups corresponds to specific conditions in certain regions of the disk, allowing scientists to recreate the scenario of the formation of these objects billions of years ago.

Centaur – A Bridge Between TNOs and the Inner Solar System

While TNOs remain in the distant parts of the Solar System, some of them, under the influence of gravitational interactions, migrate toward the inner regions, becoming so-called centaurs. These objects, located between Jupiter and Saturn, represent a transitional step between TNOs and comets. Research on centaurs conducted in parallel with TNO studies has revealed significant differences in their surface characteristics.

Centaurs show unique spectral signatures, including the presence of dusty regolith layers mixed with ice. These surfaces suggest that centaurs undergo significant changes during their journeys closer to the Sun, including heating, ice sublimation, and comet tail formation.

Unique Surface Features of Centaurs

Researchers have noted that two of the three classes of surface types of TNOs, "Bowl" and "Cliff," are also present among centaurs. However, a new category has emerged, called "Shallow Type," which is not present among TNOs. This new class is characterized by a high concentration of primitive cometary dust and a markedly low presence of volatile ices.

These discoveries suggest that centaurs are not a homogeneous group but represent dynamic objects that undergo different stages of evolution depending on their orbital paths and distance from the Sun. Their unique characteristics offer key clues about how TNOs migrate, evolve, and eventually become comets.

New Perspectives and Future Research

This research not only reveals new details about the chemical composition and surface evolution of TNOs and centaurs but also opens the door for future studies. Scientists now have a more precise insight into the molecular processes that shape these bodies, as well as their connections to the protoplanetary disk from which they originated.

The results suggest that carbon dioxide, rather than water ice, is the dominant compound on the surfaces of many TNOs, calling into question previous assumptions about the composition of the outer regions of the Solar System. Furthermore, the spectroscopic diversity of centaurs indicates the need for new models that can more accurately describe their evolutionary paths.

With ever more precise instruments like the James Webb Telescope, scientists will continue to study these distant worlds, seeking answers to questions about the formation, evolution, and future of our Solar System.

Source: University of Central Florida