A Search for Magnesium in Europa's Atmosphere

TL;DR

This study searched for magnesium in Europa's atmosphere using Hubble data but found none, suggesting magnesium is either depleted on the surface or less efficiently sputtered into the atmosphere.

Contribution

First to set an upper limit on magnesium abundance in Europa's atmosphere using archival Hubble spectra.

Findings

Magnesium was not detected in Europa's atmosphere.

The upper limit suggests magnesium is depleted or less sputtered.

Europa's surface may have lower magnesium content.

Abstract

Europa's tenuous atmosphere results from sputtering of the surface. The trace element composition of its atmosphere is therefore related to the composition of Europa's surface. Magnesium salts are often invoked to explain Galileo Near Infrared Mapping Spectrometer spectra of Europa's surface, thus magnesium may be present in Europa's atmosphere. We have searched for magnesium emission in Hubble Space Telescope Faint Object Spectrograph archival spectra of Europa's atmosphere. Magnesium was not detected and we calculate an upper limit on the magnesium column abundance. This upper limit indicates that either Europa's surface is depleted in magnesium relative to sodium and potassium, or magnesium is not sputtered as efficiently resulting in a relative depletion in its atmosphere.