Constraining Europa’s Subsolar Atmosphere With A Joint Analysis Of HST Spectral Images And Galileo Magnetic Field Data

We constrain Europa’s tenuous atmosphere on the subsolar hemisphere by combining two sets of observations: oxygen emissions at 1304 Å and 1356 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 modelling based on the ratio of OI 1356 Å to OI 1304 Å emissions from Roth (2021) 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) 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), 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 m−2 to 2.2×1019 m−2 at the subsolar point for H2O. Both column densities however still lie within the uncertainties of Roth (2021). Our results provide additional evidence for the existence of a stable H2O atmosphere at Europa.

Sebastian Cervantes, Joachim Saur

Subjects: Space Physics (physics.space-ph); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2208.13650 [physics.space-ph] (or arXiv:2208.13650v1 [physics.space-ph] for this version)
Submission history
From: Juan Sebastian Cervantes Villa Dr.
[v1] Mon, 29 Aug 2022 14:52:55 UTC (2,392 KB)
Full paper https://arxiv.org/abs/2208.13650
Astrobiology