TY  - JOUR
A1  - Cervantes, S.
A1  - Saur, J.
T1  - Constraining Europa's Subsolar Atmosphere With a Joint Analysis of HST Spectral Images and Galileo Magnetic Field Data
Y1  - 2022-09-06
VL  - 127
IS  - 9
JF  - Journal of Geophysical Research: Space Physics
DO  - 10.1029/2022JA030472
PB  - 
N2  - We constrain Europa's tenuous atmosphere on the subsolar hemisphere by combining two sets of observations: oxygen emissions at 1,304 and 1,356 Å from Hubble Space Telescope (HST) spectral images and Galileo magnetic field measurements from its closest encounter, the E12 flyby. We describe Europa's atmosphere with three neutral gas species: global molecular (O2) and atomic oxygen (O), and localized water (H2O) present as a near‐equatorial plume and as a stable distribution concentrated around the subsolar point on the moon's trailing hemisphere. Our combined modeling based on the ratio of OI 1,356 to OI 1,304 Å emissions from Roth (2021; https://doi.org/10.1029/2021gl094289) and on magnetic field data allows us to derive constraints on the density and location of O2 and H2O in Europa's atmosphere. We demonstrate that 50% of the O2 and between 50% and 75% of the H2O abundances from Roth (2021; https://doi.org/10.1029/2021gl094289) are required to jointly explain the HST and Galileo measurements. These values are conditioned on a column density of O close to the upper limit of 6 × 1016 m−2 derived by Roth (2021; https://doi.org/10.1029/2021gl094289), and on a strongly confined stable H2O atmosphere around the subsolar point. Our analysis yields column densities of 1.2 × 1018 m−2 for O2, and 1.5 × 1019 to 2.2 × 1019 m−2 at the subsolar point for H2O. Both column densities, however, still lie within the uncertainties of Roth (2021; https://doi.org/10.1029/2021gl094289). Our results provide additional evidence for the existence of a stable H2O atmosphere at Europa.
N2  - Key Points: We combine Hubble Space Telescope spectral images and Galileo magnetometer data to constrain the density and location of water vapor in Europa's atmosphere. We simulate the plasma interaction for the Galileo E12 flyby with a three‐component atmosphere: global O2, stable confined H2O, and a plume. Using 50% of O2 and from 50% to 75% of H2O column densities from Roth (2021) yields magnetic field signatures consistent with both observations.
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/10421
ER  -