Spectroscopic Links among Giant Planet Irregular Satellites and Trojans

Benjamin N.L. Sharkey, Vishnu Reddy, Olga Kuhn, Juan A. Sanchez, William F. Bottke

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


We collect near-infrared spectra (∼0.75-2.55 μm) of four Jovian irregular satellites and visible spectra (∼0.32-1.00 μm) of two Jovian irregular satellites, two Uranian irregular satellites, and four Neptune Trojans. We find close similarities between the observed Jovian irregular satellites and previously characterized Jovian Trojans. However, irregular satellites’ unique collisional histories complicate comparisons to other groups. Laboratory study of CM and CI chondrites shows that grain size and regolith packing conditions strongly affect spectra of dark, carbonaceous materials. We hypothesize that different activity histories of these objects, which may have originally contained volatile ices that subsequently sublimated, could cause differences in regolith grain size or packing properties and therefore drive spectral variation. The Uranian satellites Sycorax and Caliban appear similar to TNOs. However, we detect a feature near 0.7 μm on Sycorax, suggesting the presence of hydrated materials. While the sample of Neptune Trojans have more neutral spectra than the Uranian satellites we observe, they remain consistent with the broad color distribution of the Kuiper Belt. We detect a possible feature near 0.65-0.70 μm on Neptune Trojan 2006 RJ103, suggesting that hydrated material may also be present in this population. Characterizing hydrated materials in the outer solar system may provide critical context regarding the origins of hydrated CI and CM chondrite meteorites. We discuss how the hydration state(s) of the irregular satellites constrains the thermal histories of the interiors of their parent bodies, which may have formed among the primordial Kuiper Belt.

Original languageEnglish (US)
Article number223
JournalPlanetary Science Journal
Issue number11
StatePublished - Nov 1 2023

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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