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Title: EXPLORING IO'S ATMOSPHERIC COMPOSITION WITH APEX: FIRST MEASUREMENT OF {sup 34}SO{sub 2} AND TENTATIVE DETECTION OF KCl

The composition of Io's tenuous atmosphere is poorly constrained. Only the major species SO{sub 2} and a handful of minor species have been positively identified, but a variety of other molecular species should be present, based on thermochemical equilibrium models of volcanic gas chemistry and the composition of Io's environment. This paper focuses on the spectral search for expected yet undetected molecular species (KCl, SiO, S{sub 2}O) and isotopes ({sup 34}SO{sub 2}). We analyze a disk-averaged spectrum of a potentially line-rich spectral window around 345 GHz, obtained in 2010 at the APEX 12 m antenna. Using different models assuming either extended atmospheric distributions or a purely volcanically sustained atmosphere, we tentatively measure the KCl relative abundance with respect to SO{sub 2} and derive a range of 4 × 10{sup –4}-8 × 10{sup –3}. We do not detect SiO or S{sub 2}O and present new upper limits on their abundances. We also present the first measurement of the {sup 34}S/{sup 32}S isotopic ratio in gas phase on Io, which appears to be twice as high as the Earth and interstellar medium reference values. Strong lines of SO{sub 2} and SO are also analyzed to check for longitudinal variations of column densitymore » and relative abundance. Our models show that, based on their predicted relative abundance with respect to SO{sub 2} in volcanic plumes, both the tentative KCl detection and SiO upper limit are compatible with a purely volcanic origin for these species.« less
Authors:
 [1] ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. National Radio Astronomy Observatory, Charlottesville, VA-22902 (United States)
  2. LESIA-Observatoire de Paris, 5 place J. Janssen, F-92195 Meudon CEDEX (France)
  3. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA-02138 (United States)
  4. Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala (Sweden)
  5. National Radio Astronomy Observatory, Socorro, NM-87801 (United States)
Publication Date:
OSTI Identifier:
22270716
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 776; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANTENNAS; ASTRONOMY; ASTROPHYSICS; DETECTION; GHZ RANGE; ISOTOPE RATIO; PLANETS; POTASSIUM CHLORIDES; SATELLITE ATMOSPHERES; SILICON OXIDES; SULFUR 32; SULFUR 34; SULFUR DIOXIDE