Universität zu Köln

Roth, Lorenz ORCID: 0000-0003-0554-4691, Retherford, Kurt D., Saur, Joachim ORCID: 0000-0003-1413-1231, Strobel, Darrell F., Feldman, Paul D., McGrath, Melissa A. and Nimmo, Francis (2014). Orbital apocenter is not a sufficient condition for HST/STIS detection of Europa's water vapor aurora. Proc. Natl. Acad. Sci. U. S. A., 111 (48). S. E5123 - 10. WASHINGTON: NATL ACAD SCIENCES. ISSN 0027-8424

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Abstract

We report far-ultraviolet observations of Jupiter's moon Europa taken by Space Telescope Imaging Spectrograph (STIS) of the Hubble Space Telescope (HST) in January and February 2014 to test the hypothesis that the discovery of a water vapor aurora in December 2012 by local hydrogen (H) and oxygen (O) emissions with the STIS originated from plume activity possibly correlated with Europa's distance from Jupiter through tidal stress variations. The 2014 observations were scheduled with Europa near the apocenter similar to the orbital position of its previous detection. Tensile stresses on south polar fractures are expected to be highest in this orbital phase, potentially maximizing the probability for plume activity. No local H and O emissions were detected in the new STIS images. In the south polar region where the emission surpluses were observed in 2012, the brightnesses are sufficiently low in the 2014 images to be consistent with any H2O abundance from(0-5)x10(15) cm(-2). Large high-latitude plumes should have been detectable by the STIS, independent of the observing conditions and geometry. Because electron excitation of water vapor remains the only viable explanation for the 2012 detection, the new observations indicate that although the same orbital position of Europa for plume activity may be a necessary condition, it is not a sufficient condition. However, the December 2012 detection of coincident HI Lyman-alpha and OI 1304-angstrom emission surpluses in an similar to 200-km high region well separated above Europa's limb is a firm result and not invalidated by our 2014 STIS observations.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Roth, Lorenz UNSPECIFIED orcid.org/0000-0003-0554-4691 UNSPECIFIED Retherford, Kurt D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Saur, Joachim UNSPECIFIED orcid.org/0000-0003-1413-1231 UNSPECIFIED Strobel, Darrell F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Feldman, Paul D. UNSPECIFIED UNSPECIFIED UNSPECIFIED McGrath, Melissa A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Nimmo, Francis UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-420975
DOI:	10.1073/pnas.1416671111
Journal or Publication Title:	Proc. Natl. Acad. Sci. U. S. A.
Volume:	111
Number:	48
Page Range:	S. E5123 - 10
Date:	2014
Publisher:	NATL ACAD SCIENCES
Place of Publication:	WASHINGTON
ISSN:	0027-8424
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language EXCITATION CROSS-SECTIONS; GALILEAN SATELLITES; JOVIAN MAGNETOSPHERE; IOS ATMOSPHERE; ATOMIC OXYGEN; ULTRAVIOLET; CONSTRAINTS; DISSOCIATION; ERUPTIONS; EMISSION Multiple languages Multidisciplinary Sciences Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/42097