High Spatial and Spectral Resolution Observations of the Forbidden 1.707 μm Rovibronic SO Emissions on Io: Evidence for Widespread Stealth Volcanism
Abstract
We present observations obtained with the 10 m Keck telescopes of the forbidden SO a¹Δ → X³Σ⁻ rovibronic transition at 1.707 μm on Io while in eclipse. We show its spatial distribution at a resolution of ~0."12 and a spectral resolution of R ~ 2500, as well as disk-integrated spectra at a high spectral resolution (R ~ 15,000). Both the spatial distribution and the spectral shape of the SO emission band vary considerably across Io and over time. In some cases the SO emissions either in the core or the wings of the emission band can be identified with volcanoes, but the largest areas of SO emissions usually do not coincide with known volcanoes. We suggest that the emissions are caused by a large number of stealth plumes, produced through the interaction of silicate melts with superheated SO₂ vapor at depth. The spectra, in particular the elevated wing of the emission band near 1.69 μm, and their spatial distribution strongly suggest the presence of nonlocal thermodynamic equilibrium processes in addition to the direct ejection of excited SO from the (stealth and other) volcanic vents.
Additional Information
© 2020 The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2019 November 24; revised 2020 June 17; accepted 2020 June 18; published 2020 July 20. We thank Darrell Strobel for fruitful discussions regarding the interpretation of our observations. We appreciate Peter Bernath's communication pointing out his recent paper on new line lists of SO. We thank Emmanuel Lellouch and an anonymous referee for careful and detailed reviews of our manuscript, which helped improve the paper substantially. We further thank Edward Molter for reducing the NIRC2 data from 2019 April 15. Our research was supported by the National Science Foundation, NSF grant AST-1313485 to UC Berkeley. The data presented in this paper were obtained at the W.M. Keck Observatory. The Keck Telescopes are operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations of Ionian volcanoes from this Hawaiian volcano.Errata
Imke de Pater et al 2021 Planet. Sci. J. 2 42Attached Files
Published - de_Pater_2020_Planet._Sci._J._1_29.pdf
Accepted Version - 2101.01789.pdf
Erratum - de_Pater_2021_Planet._Sci._J._2_42.pdf
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Additional details
- Alternative title
- High Spatial and Spectral Resolution Observations of the Forbidden 1.707 micron Rovibronic SO Emissions on Io: Evidence for Widespread Stealth Volcanism
- Eprint ID
- 104475
- Resolver ID
- CaltechAUTHORS:20200721-101801680
- AST-1313485
- NSF
- W. M. Keck Foundation
- Created
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2020-07-21Created from EPrint's datestamp field
- Updated
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2023-06-01Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department