The 3 $\mu$m Spectrum of Jupiter's Irregular Satellite Himalia

TL;DR

This study provides a medium resolution 3 μm spectrum of Jupiter's irregular satellite Himalia, revealing a composition similar to certain outer asteroid belt asteroids, challenging existing satellite origin models.

Contribution

First detailed 3 μm spectral analysis of Himalia, showing its similarity to outer asteroid belt asteroids and questioning current satellite formation theories.

Findings

No evidence for aqueously altered minerals on Himalia.

Spectral similarity between Himalia and asteroid 52 Europa.

Challenges existing models of irregular satellite origins.

Abstract

We present a medium resolution spectrum of Jupiter's irregular satellite Himalia covering the critical 3 $\mu$m spectral region. The spectrum shows no evidence for aqueously altered phyllosilicates, as had been suggested from the tentative detection of a 0.7 $\mu$m absorption, but instead shows a spectrum strikingly similar to the C/CF type asteroid 52 Europa. 52 Europa is the prototype of a class of asteroids generally situated in the outer asteroid belt between less distant asteroids which show evidence for aqueous alteration and more distant asteroids which show evidence for water ice. The spectral match between Himalia and this group of asteroids is surprising and difficult to reconcile with models of the origin of the irregular satellites.