Probing for Evidence of Plumes on Europa with HST/STIS

TL;DR

This study uses HST FUV imaging to search for water plumes on Europa, finding potential evidence of activity at multiple locations, which could imply frequent outgassing similar to previous spectroscopic detections.

Contribution

It provides direct imaging evidence of possible water plumes on Europa, complementing prior spectroscopic findings and suggesting more frequent activity.

Findings

Potential plume activity detected in 3 out of 10 observations.

Detected features at latitudes similar to previous studies.

Indications of frequent outgassing comparable to earlier reports.

Abstract

Roth et al (2014a) reported evidence for plumes of water venting from a southern high latitude region on Europa - spectroscopic detection of off-limb line emission from the dissociation products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which plume activity could be implicated. Two show statistically significant features at latitudes similar to Roth et al, and the third, at a more equatorial location. We consider potential systematic effects that might influence the statistical analysis and create artifacts, and are unable to find any that can definitively explain the features, although there are reasons to be cautious. If the apparent absorption features are real, the magnitude of implied outgassing is similar to that of the Roth et al feature, however the apparent activity appears more frequently in our data.