The atmospheric signature of Io's Prometheus plume and anti-jovian hemisphere: evidence for a sublimation atmosphere☆

Jessup, Kandis Lea; Spencer, J. R.; Ballester, G. E.; Howell, R. R.; Roesler, F. L.; Vigel, M.; Yelle, R. V.

doi:10.1016/j.icarus.2003.11.015

Cited by 76 publications

(149 citation statements)

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“…Even the mean gas temperature remains uncertain, although recent HST and mm data tend to suggest low (< 250 K) temperatures , Jessup et al 2004. For this reason and for simplicity, we only considered isothermal atmospheres.…”

Section: Non-lte Vibrational Temperature Modelsmentioning

confidence: 99%

“…SO 2 column density appears to be modestly enhanced over at least some volcanos. Voyager IRIS observations of the ν 3 vibrational band at 7.4 µm implied 9 × 10 16 cm -2 -2 × 10 18 cm -2 of SO 2 at Loki (Pearl et al 1979, reinterpreted by Lellouch et al 1992), and UV absorption over Pele implied an SO 2 abundance of 3 × 10 16 cm -2 and 7 × 10 16 cm -2 (Spencer et al 2000a), while abundance over Prometheus reached 1.8 x 10 17 cm -2 (Jessup et al 2004). Disk-integrated mm-wave observations of SO 2 emission lines require local concentrations of a few × 10 17 cm -2 of SO 2 at temperatures > 600 K to match observed line widths, if the atmosphere is static (Lellouch et al 1992): such high temperatures are difficult to explain .…”

Section: Introductionmentioning

confidence: 95%

“…Lower temperatures, and local abundances of about 1 × 10 17 cm -2 , more consistent with the UV results, are possible if mm line widths are due to rapid motions associated with plumes or supersonic winds ( (Ballester et al 1994, Lellouch 1996. In addition to SO 2 , lesser amounts of SO , NaCl (Lellouch et al 2003) and S 2 (Spencer et al 2000a) have also been detected, as have neutral atomic emissions from S, O, and Na (Ballester et al 1987, Geissler et al 1999a, 2001a, Feaga et al 2002, Roesler et al 1999, Bouchez et al 2000, and molecular emissions from SO (dePater et al 2002) and, probably, SO 2 and/or S 2 (Geissler et al 1999a, 2001a, Jessup et al 2004). The emission data are more difficult to interpret in terms of bulk atmospheric properties than the absorption data, as emission strength depends on excitation and dissociation mechanisms as well as atomic or molecular abundances.…”

Section: Introductionmentioning

confidence: 98%

“…HST diskintegrated observations of 0.20 -0.23 µm SO 2 gas absorption bands give subsolar densities of a few x 10 16 cm -2 (Ballester et al 1994, Jessup et al 2002 to ~10 17 cm -2 (Trafton et al 1996) if the atmosphere is assumed to be concentrated over a few tens of percent of the surface at low latitudes, as suggested by the Lyman-α images. Disk-resolved 0.20 -0.23 µm spectroscopy away from plume sources gives low-latitude SO 2 densities of 1.5 x 10 16 cm -2 at longitude 318 W ) and 1.3 x 10 17 cm -2 at 160 W (Jessup et al 2004). High column densities up to 10 19 cm -2 have been inferred from Galileo UVS data (Hendrix et al 1999), but are dependent on assumptions about the surface albedo, as UVS did not resolve individual SO 2 gaseous absorption bands.…”

Section: Introductionmentioning

confidence: 99%

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Mid-infrared detection of large longitudinal asymmetries in Io's SO atmosphere

Spencer¹,

Lellouch²,

Richter³

et al. 2005

Icarus

103

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We have observed about 16 absorption lines of the ν 2 SO 2 vibrational band on Io, in disk-integrated 19 µm spectra taken with the TEXES high spectral resolution mid-infrared spectrograph at the NASA Infrared Telescope Facility in November 2001, December 2002, and January 2004 These are the first ground-based infrared observations of Io's sunlit atmosphere, and provide a new window on the atmosphere that allows better longitudinal and temporal monitoring than previous techniques. Dramatic variations in band strength with longitude are seen that are stable over at least a 2 year period. The depth of the strongest feature, a blend of lines centered at 530.42 cm -1 , varies from about 7% near longitude 180 to about 1% near longitude 315 W, as measured at a spectral resolution of 57,000. Interpretation of the spectra requires modeling of surface temperatures and atmospheric density across Io's disk, and the variation in non-LTE ν 2 vibrational temperature with altitude, and depends on the assumed atmospheric and surface temperature structure. About half of Io's 19µm radiation comes from the sun-heated surface, and half from volcanic hot spots with temperatures primarily between 150 and 200 K, which occupy about 8% of the surface. The observations are thus weighted towards the atmosphere over these lowtemperature hot spots. If we assume that the atmosphere over the hot spots is representative of the atmosphere elsewhere, and that the atmospheric density is a function of latitude, the most plausible interpretation of the data is that the equatorial atmospheric column density varies from about 1.5 x 10 17 cm -2 near longitude 180 W to about 1.5 x 10 16 cm -2 near longitude 300 W, roughly consistent with HST UV spectroscopy and Lyman-α imaging. The inferred atmospheric kinetic temperature is less than about 150 K, at least on the anti-Jupiter hemisphere where the bands are strongest, somewhat colder than inferred from HST UV spectroscopy and millimeter-wavelength spectroscopy. This longitudinal variability in atmospheric density correlates with the longitudinal variability in the abundance of optically thick, near-UV bright SO 2 frost. However it is not clear whether the correlation results from volcanic control (regions of large frost abundance result from greater condensation of atmospheric gases supported by more vigorous volcanic activity in these regions) or sublimation control (regions of large frost abundance produce a more extensive atmosphere due to more extensive sublimation). Comparison of data taken in 2001, 2002, and 2004 shows that with the possible exception of longitudes near 180 W between 2001 and 2002, Io's atmospheric density does not appear to decrease as Io recedes from the sun, as would be expected if the atmosphere were supported by the sublimation of surface frost, suggesting that the atmosphere is dominantly supported by direct volcanic supply rather than by frost sublimation. However, other evidence such as the smooth variation in atmospheric abundance with latitude, and atmospheric ch...

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Section: Non-lte Vibrational Temperature Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mid-infrared detection of large longitudinal asymmetries in Io's SO atmosphere

Spencer¹,

Lellouch²,

Richter³

et al. 2005

Icarus

103

View full text Add to dashboard Cite

show abstract

“…2-D computational work on Io's atmosphere has modeled Io's steady-state atmosphere including crude plasma heating [5] and plasma chemistry models that have found a dayside SO/SO 2 ratio of 3-7% [6], consistent with an observed ratio of 1-10% [7]. More recent 3-D DSMC simulations of Io's atmosphere [8] improved on previous simulations by using a complex surface temperature and frost fraction model but still used a simple plasma heating model without chemistry.…”

Section: Introductionmentioning

confidence: 74%

Simulation of Plasma Interaction with Io’s Atmosphere

Moore¹,

Deng²,

Goldstein³

et al. 2011

AIP Conference Proceedings

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Articles you may be interested inDevelopment of a chemistry model for DSMC simulation of the atmosphere of Io using molecular dynamics AIP Conf. Proc. 1501, 579 (2012) Abstract. One dimensional Direct Simulation Monte Carlo (DSMC) simulations are used to examine the interaction of the jovian plasma torus with Io's sublimation atmosphere. The hot plasma sweeps past Io at ~57 km/s due to the external Jovian magnetic and corotational electric fields and the resultant energetic collisions both heat and dissociate the neutral gas creating an inflated, mixed atmosphere of SO 2 and its daughter products. The vertical structure and composition of the atmosphere is important for understanding Io's mass loading of the plasma torus, electron excited aurora, and Io's global gas dynamics. Our 1D simulations above a fixed location on the surface of Io allows the O + and S + ions to drift down into the domain where they then undergo elastic and charge exchange collisions with the neutral gas. Each electron's position is determined by the motion of a corresponding ion; however, the electrons retain their own velocity components which are then used during elastic, ionization, and excitation collisions with the neutral gas. Charge exchange creates fast neutral O and S atoms. Molecular Dynamic/QuasiClassical Trajectory (MD/QCT) calculations are used to generate total and reaction cross sections for energetic O+SO 2 collisions [1] as well as for O+O 2 collisions. In addition, the model accounts for photo-dissociation assuming the atmosphere is optically thin. Our previous plasma heating model (without chemistry) agrees well with the vertical structure of the current model at lower altitudes where the gas is collisional; however, at high altitudes (>100 km) significant differences among the models appear. The current model's constant E and B fields results in reacceleration of the ions and electrons to a constant E×B drift velocity towards the surface after collisions with the neutral gas and, while the results are an upper limit on the plasma interaction strength, the results indicate that joule heating is significant, causing large changes in the vertical structure of the atmosphere. Plasma heating of, not momentum transfer to, the atmosphere dominates even for radially inward plasma flows resulting in a hot, inflated atmosphere. The scale heights for the various species were found to be a competition between the hydrodynamic scale height based on the gas constant (for the mixture if collisional) and the production rate from dissociation of SO 2 which depends on the local SO 2 density and available plasma energy at that altitude.

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Solar control of sodium escape from Io

et al. 2014

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We report ground-based spectroscopic observations of the Io sodium cloud before and after eclipse by Jupiter, in a search for possible effects of sunlight on the total atomic sodium content in Io's exosphere. These observations test the importance of the Sun in maintaining the supply of atoms from the thicker atmosphere, which lies close to the surface, to the thinner, more extended, sodium cloud. We performed ground-based spectroscopy of the sodium doublet at 589 nm with a high-resolution échelle spectrograph on the Italian National Telescope Galileo on La Palma Island. We find that the total atomic sodium content immediately after eclipse falls by a factor of~4 during eclipse and recovers to preeclipse values on a timescale of~5 h. We evaluate potential causes of the precipitous drop including condensation of the atmosphere, collapse of the ionosphere, and changes in atmospheric chemistry. We conclude that most plausible cause of the drop in atomic sodium production is the interruption of photodissociation of sodium-bearing molecules during eclipse. We discuss further implications of this change in atmospheric chemistry.

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The atmospheric signature of Io's Prometheus plume and anti-jovian hemisphere: evidence for a sublimation atmosphere☆

Cited by 76 publications

References 57 publications

Mid-infrared detection of large longitudinal asymmetries in Io's SO atmosphere

Mid-infrared detection of large longitudinal asymmetries in Io's SO atmosphere

Simulation of Plasma Interaction with Io’s Atmosphere

Solar control of sodium escape from Io

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