The albedo spectrum of Europa from 2200 Å to 3300 Å

Abstract

We obtained a spectrum of Europa from 2224 to 3302 Å with high signal to noise and a resolution of 6.3 Å with the Hubble space telescope faint object spectrograph. We detect a broad absorption feature centered at 2800 Å, seen previously at lower signal to noise in International Ultraviolet Explorer spectra of Europa. No additional absorption features are detected. We compare the observed spectrum to laboratory spectra of sulfur ions in water ice and sulfur dioxide ice on water ice. The absorption in Europa is a closer match to sulfur dioxide ice. The poor fit of ice irradiated by sulfur ions may indicate that a direct source of SO₂ is required to explain the observed absorption.