The Trojan asteroids, orbiting the Sun in Jupiter’s stable Lagrange points, provide a unique perspective on the history of our solar system. As a large population of small bodies, they record important gravitational interactions in the dynamical evolution of the solar system. As primitive bodies, their compositions and physical properties provide windows into the conditions in the solar nebula in the region in which they formed. In the past decade, significant advances have been made in understanding their physical properties, and there has been a revolution in thinking about the origin of Trojans. The ice and organics generally presumed to be a significant part of Trojan composition have yet to be detected directly, although the low density of the binary system Patroclus (and possibly low density of the binary/moonlet system Hektor) is consistent with an interior ice component. By contrast, fine-grained silicates that appear to be similar to cometary silicates in composition have been detected, and a color bimodality may indicate distinct compositional groups among the Trojans. Whereas Trojans had traditionally been thought to have formed near 5 AU, a new paradigm has developed in which the Trojans formed in the proto-Kuiper belt, and were scattered inward and captured in the Trojan swarms as a result of resonant interactions of the giant planets. Whereas the orbital and population distributions of current Trojans are consistent with this origin scenario, there are significant differences between current physical properties of Trojans and those of Kuiper belt objects. These differences may be indicative of surface modification due to the inward migration of objects that became the Trojans, but understanding of appropriate modification mechanisms is poor and would benefit from additional laboratory studies. Many open questions about this intriguing population remain, and the future promises significant strides in our understanding of Trojans. The time is ripe for a spacecraft mission to the Trojans, to transform these objects into geologic worlds that can be studied in detail to unravel their complex history.
|Original language||English (US)|
|Title of host publication||Asteroids IV|
|Publisher||University of Arizona Press|
|Number of pages||18|
|State||Published - Jan 1 2015|
ASJC Scopus subject areas
- Physics and Astronomy(all)