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Cervantes, S. and Saur, J. (2022). Constraining Europa's Subsolar Atmosphere With a Joint Analysis of HST Spectral Images and Galileo Magnetic Field Data. J. Geophys. Res-Space Phys., 127 (9). WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-9402

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Abstract

We constrain Europa's tenuous atmosphere on the subsolar hemisphere by combining two sets of observations: oxygen emissions at 1,304 and 1,356 angstrom 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 (O-2) 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 angstrom emissions from Roth (2021; ) and on magnetic field data allows us to derive constraints on the density and location of O-2 and H2O in Europa's atmosphere. We demonstrate that 50% of the O-2 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 x 10(16) 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 x 10(18) m(-2) for O-2, and 1.5 x 10(19) to 2.2 x 10(19) 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.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Cervantes, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Saur, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-661650
DOI:	10.1029/2022JA030472
Journal or Publication Title:	J. Geophys. Res-Space Phys.
Volume:	127
Number:	9
Date:	2022
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-9402
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language RADIATION MAGNETOHYDRODYNAMICS CODE; 2 SPACE DIMENSIONS; JOVIAN MAGNETOSPHERE; ASTROPHYSICAL FLOWS; OXYGEN ATMOSPHERE; SUBSURFACE OCEAN; CROSS-SECTIONS; ATOMIC OXYGEN; PLUME; ALGORITHMS Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/66165