New Views of Europa's Atmosphere from Hubble: Water Vapor Plume Campaigns and Other Species
Abstract
Numerous advances in our understanding of Europa's atmosphere and auroral features have been accomplished in the last several years as a result of robust Hubble Space Telescope (HST) observing campaigns dedicated to searches for water vapor plumes. The most recent sets of observations started on March 28, 2018 as part of Hubble's Mid-Cycle 25 Europa Campaigns. In addition to continued Space Telescope Imaging Spectrograph (STIS) instrument long-slit far-UV auroral Lyman-alpha and oxygen line emission and Lyman-alpha Jupiter transit spectral data sets reported previously, we will describe our observations using three new modes: i) STIS/NUV G230L spectroscopy, off-limb, ii) STIS/CCD G750M spectroscopy in eclipse, and iii) WFC3/UVIS imaging in eclipse. Improved constraints to the relative abundance of molecular and atomic oxygen have been provided using the far-UV emission datasets. Exospheric atomic hydrogen is detected by absorption in the Lyman-alpha transit spectral data set, when Europa is silhouetted by Jupiter's bright Lyman-alpha dayglow. A confirmation of the initial detection using the technique of H and O auroral emissions released by electron impact dissociation of water vapor has not yet been achieved. The current HST campaign program led by our group has another 1/3rd of the program yet to come, with these observations deferred until the next Jupiter opposition period in 2019. We'll discuss our early assessments of the successfulness of the various techniques used to search for plumes and how this informs our plans for Europa Clipper and JUICE mission ultraviolet spectrograph observations.
- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #50
- Pub Date:
- October 2018
- Bibcode:
- 2018DPS....5040305R