Universität zu Köln

Saur, Joachim ORCID: 0000-0003-1413-1231, Feldman, Paul D., Roth, Lorenz ORCID: 0000-0003-0554-4691, Nimmo, Francis, Strobel, Darrell F., Retherford, Kurt D., McGrath, Melissa A., Schilling, Nico, Gerard, Jean-Claude and Grodent, Denis (2011). HUBBLE SPACE TELESCOPE/ADVANCED CAMERA FOR SURVEYS OBSERVATIONS OF EUROPA'S ATMOSPHERIC ULTRAVIOLET EMISSION AT EASTERN ELONGATION. Astrophys. J., 738 (2). BRISTOL: IOP PUBLISHING LTD. ISSN 1538-4357

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Abstract

We report results of a Hubble Space Telescope (HST) campaign with the Advanced Camera for Surveys to observe Europa at eastern elongation, i.e., Europa's leading side, on 2008 June 29. With five consecutive HST orbits, we constrain Europa's atmospheric OI 1304 angstrom and OI 1356 angstrom emissions using the prism PR130L. The total emissions of both oxygen multiplets range between 132 +/- 14 and 226 +/- 14 Rayleigh. An additional systematic error with values on the same order as the statistical errors may be due to uncertainties in modeling the reflected light from Europa's surface. The total emission also shows a clear dependence of Europa's position with respect to Jupiter's magnetospheric plasma sheet. We derive a lower limit for the O-2 column density of 6 x 10(18) m(-2). Previous observations of Europa's atmosphere with the Space Telescope Imaging Spectrograph in 1999 of Europa's trailing side show an enigmatic surplus of radiation on the anti-Jovian side within the disk of Europa. With emission from a radially symmetric atmosphere as a reference, we searched for an anti-Jovian versus sub-Jovian asymmetry with respect to the central meridian on the leading side and found none. Likewise, we searched for departures from a radially symmetric atmospheric emission and found an emission surplus centered around 90 degrees west longitude, for which plausible mechanisms exist. Previous work about the possibility of plumes on Europa due to tidally driven shear heating found longitudes with strongest local strain rates which might be consistent with the longitudes of maximum UV emissions. Alternatively, asymmetries in Europa's UV emission can also be caused by inhomogeneous surface properties, an optically thick atmospheric contribution of atomic oxygen, and/or by Europa's complex plasma interaction with Jupiter's magnetosphere.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Saur, Joachim UNSPECIFIED orcid.org/0000-0003-1413-1231 UNSPECIFIED Feldman, Paul D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Roth, Lorenz UNSPECIFIED orcid.org/0000-0003-0554-4691 UNSPECIFIED Nimmo, Francis UNSPECIFIED UNSPECIFIED UNSPECIFIED Strobel, Darrell F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Retherford, Kurt D. UNSPECIFIED UNSPECIFIED UNSPECIFIED McGrath, Melissa A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schilling, Nico UNSPECIFIED UNSPECIFIED UNSPECIFIED Gerard, Jean-Claude UNSPECIFIED UNSPECIFIED UNSPECIFIED Grodent, Denis UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-489127
DOI:	10.1088/0004-637X/738/2/153
Journal or Publication Title:	Astrophys. J.
Volume:	738
Number:	2
Date:	2011
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	1538-4357
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language JOVIAN MAGNETOSPHERE; GALILEAN SATELLITES; OXYGEN ATMOSPHERE; SUBSURFACE OCEANS; ICE SHELL; ENCELADUS; CONSTRAINTS; ION; JUPITER; FLUX Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/48912