Identification of gaseous SO2 and new upper limits for other gases on Io

Pearl, J. C.; Hanel, Rudolf; Kunde, V. G.; Maguire, W. C.; Fox, Kenneth; Gupta, Satyandra K.; Ponnamperuma, Cyril; Raulin, F.

doi:10.1038/280755a0

Cited by 268 publications

(106 citation statements)

References 31 publications

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“…One of the primary pieces of evidence for lo's near-surface atmosphere is the detection of gaseous 802 above one hotspot (Loki Patera) by the Voyager infrared 19 spectrometer experiment (Pearl et al, 1979). The most simplistic interpretations imply a surface pressure of ",10-7 bar.…”

Section: Thick Atmosphere Modelsmentioning

confidence: 99%

Sodium in Io's Extended Atmosphere

Schneider¹

1988

PASP

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This dissertation combines several new observations of the Io sodium cloud to create a consistent picture of the extended Io atmosphere and its interaction with the Jovian plasma torus. I used the LPL echelle spectrograph to obtain three types of high-resolution spectra of the extended sodium cloud at the sodium D lines (5890 Â, 5896 Â). The first class of observations made use of the mutual satellite eclipses of 1985 to probe the density profile of the atmosphere in the range 1.4 to 10 Io radii, a previously unstudied region. The second type of observation examined the sodium emission in the immediate vicinity of Io, allowing an accurate measurement of the velocity structure around Io. The final method employed a high-sensitivity detector to study faint jets of high-speed sodium farther out in the extended cloud. The synthesis of these three data sets results in a better understanding of how sodium is distributed about Io as a function of position and velocity.The extended atmosphere of Io is composed of many kinematically distinct components. The distribution in space is linked to their characteristic velocities, with low-energy sodium confined near Io and faster atoms (10 to 100 km sec -1 ) prevalent beyond ~ 25 Io radii. The sodium density falls rapidly near Io and more slowly outside 5.6 Io radii, the effective limit of the gravity of Io.The data indicate that the atmosphere is collisionally thick near the surface but becomes thin by an altitude of ~ 700 km. The upper limit of the exobase location is derived from reliable sodium density measurements made during the satellite eclipses. The lower limit is indirectly inferred from the velocity distribution of sodium near Io and the nature of high-speed jets far from Io.The high-speed jets reveal a new type of close interaction between the corotating plasma and the atmosphere of Io. The morphology and brightness of the jets require a two-reaction process in which atmospheric sodium is ionized, accelerated to high speeds, and then charge-exchanges with other sodium atoms. These processes must occur near the atmospheric exobase, indicating that the atmosphere of Io is not completely protected from the plasma flow.

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Section: Thick Atmosphere Modelsmentioning

confidence: 99%

Sodium in Io's Extended Atmosphere

Schneider¹

1988

PASP

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“…The first atmospheric species, sulfur dioxide, was identified in Voyager IRIS spectra by Pearl et al (1979), and confirmed at millimeter and UV wavelengths by Lellouch et al (1990) and Ballester et al (1994) respectively. The observations and subsequent analysis posed two major questions about the atmosphere which are yet to be fully resolved.…”

Section: Introductionmentioning

confidence: 99%

Temporal behavior of the SO 1.707 μm ro-vibronic emission band in Io's atmosphere

Laver¹,

Pater²,

Roe³

et al. 2007

Icarus

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We report observations of the ro-vibronic a 1 ∆ → X 3 Σ − transition of SO at 1.707 µm on Io. These data were taken while Io was eclipsed by Jupiter, on four nights between July 2000 and March 2003. We analyze these results in conjunction with a previously published night to investigate the temporal behavior of these emissions. The observations were all conducted using the near-infrared spectrometer NIRSPEC on the W.M. Keck II telescope. The integrated emitted intensity for this band varies from 0.8 x 10 27 to 2.4 x 10 27 photons/sec, with a possible link to variations in Loki's infrared brightness. The band-shapes imply rotational temperatures of 550-1000K for the emitting gas, lending further evidence to a volcanic origin for sulfur monoxide. An attempt to detect the B 1 Σ → X 3 Σ − transition of SO at 0.97 µm was unsuccessful; simultaneous detection with the 1.707 µm band would permit determination of the SO column abundance.

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“…On Io, evaluations of this type were impossible until now. Only SO2 gas was detected in Io's volcanic plumes or local volcanic atmospheres by the Voyager spacecrat't [Pearl et al, 1979] and by the HST [Sartoretti et al 1994;Spencer, 1997b]. However recent analysis of 1996 HST observations led to the detection of SO2, monatomic sulfur vapor, and SO gas in the plume or volcanic atmosphere of Pele …”

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confidence: 99%