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Io on the eve of the galileo mission
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Io, the innermost of Jupiter's large moons, is one of the most unusual objects in the Solar System as discussed by the authors, which produces a global heat flux 40 times the terrestrial value, producing intense volcanic activity and a global resurfacing rate averaging perhaps 1 cm yr−1.Abstract:
▪ Abstract Io, innermost of Jupiter's large moons, is one of the most unusual objects in the Solar System. Tidal heating of the interior produces a global heat flux 40 times the terrestrial value, producing intense volcanic activity and a global resurfacing rate averaging perhaps 1 cm yr−1. The volcanoes may erupt mostly silicate lavas, but the uppermost surface is dominated by sulfur compounds including SO2 frost. The volcanoes and frost support a thin, patchy SO2 atmosphere with peak pressure near 10−8 bars. Self-sustaining bombardment of the surface and atmosphere by Io-derived plasma trapped in Jupiter's magnetosphere causes escape of material from Io (predominantly sulfur, oxygen, and sodium atoms, ions, and molecules) at a rate of about 103 kg s−1. The resulting Jupiter-encircling torus of ionized sulfur and oxygen dominates the Jovian magnetosphere and, together with an extended cloud of neutral sodium, is readily observable from Earth.read more
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Journal ArticleDOI
Orogenic tectonism on Io
Windy L. Jaeger,Elizabeth P. Turtle,Laszlo P. Keszthelyi,Laszlo P. Keszthelyi,Jani Radebaugh,Alfred S. McEwen,Robert T. Pappalardo +6 more
Abstract: [1] We catalog 143 Ionian mountains (montes) and mountain-like features (mensae, tholi, plana, and small peaks) in order to investigate orogenic tectonism on Io. From this comprehensive list, we select 96 mountains for which there are sufficient coverage and resolution to discern spatial relationships with surrounding geologic features. Three of the 96 mountains are probably volcanoes, 92 appear to be tectonic massifs, and 1 is ambiguous. Of the 92 tectonic mountains, 38 abut paterae (volcanic or volcano-tectonic craters with irregular or scalloped margins). This juxtaposition is unlikely to be a coincidence as the probability of it occurring by chance is ∼0.1%. We propose instead that orogenic faults may act as conduits for magma ascent, thus fueling patera formation near mountains. As resurfacing buries a shell of material from Io's surface to the base of the lithosphere, its effective radius is reduced and it heats up. We calculate the lithospheric volume change due to subsidence and thermal expansion as a function of lithospheric thickness. Conservation of volume dictates that this material must be uplifted at Io's surface. By estimating the total volume of the mountains, we are able to place a lower limit of 12 km on Io's lithospheric thickness. We hypothesize that, in some cases, mountain formation may be facilitated by asthenospheric diapirs impinging on the base of the lithosphere. The resulting lithospheric swell could focus the compressive stresses that drive orogenic tectonism. This model is one of several possible mechanisms for uplifting isolated mountains such as are observed on Io.
Dynamics of the Jovian magnetosphere
TL;DR: In this article, a simple conceptual model for these periodic processes was presented, assuming (1) ion mass loading from internal plasma sources and (2) fast planetary rotation causing magnetotail field line stretching due to centrifugal forces.
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Galileo radio occultation measurements of Io's ionosphere and plasma wake
TL;DR: In this paper, radio occultation experiments were conducted with the Galileo orbiter in 1997, yielding detailed measurements of the distribution and motion of plasma surrounding Io, and the ionosphere is substantial, with the peak density exceeding 50,000 cm−3 at 9 out of 10 locations.
Journal ArticleDOI
Volcanic resurfacing of io : post-repair hst imaging
John R. Spencer,Alfred S. McEwen,Melissa A. McGrath,Paola Sartoretti,Douglas B. Nash,Keith S. Noll,Diane Gilmore +6 more
TL;DR: McEwen et al. as mentioned in this paper used the newly refurbished Hubble Space Telescope (HST) to obtain global imaging of Io at five wavelengths between 0.34 and 1.02 μm, with a spatial resolution of 160 km.
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Io after Galileo
TL;DR: Io's surface, atmosphere and space environment during the NASA Galileo mission was reviewed in this article, with a discussion of the types of future observations, from the ground and from space, that will be needed to address these issues.
References
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Journal ArticleDOI
Extreme ultraviolet observations from Voyager 1 encounter with Jupiter
A. L. Broadfoot,M. J. S. Belton,P. Z. Takacs,Bill R. Sandel,Donald E. Shemansky,Jay B. Holberg,Joseph M. Ajello,Sushil K. Atreya,Thomas M. Donahue,H. W. Moos,Jean-Loup Bertaux,J. E. Blamont,Darrell F. Strobel,John C. McConnell,Alexander Dalgarno,Richard Goody,Michael B. McElroy +16 more
TL;DR: The observed resonance scattering of solar hydrogen Lyman α by the atmosphere of Jupiter and the solar occultation experiment suggest a hot thermosphere (≥ 1000 K) wvith a large atomic hydrogen abundance.
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Melting of Io by Tidal Dissipation
TL;DR: The dissipation of tidal energy in Jupiter's satellite Io is likely to have melted a major fraction of the mass, and consequences of a largely molten interior may be evident in pictures of Io's surface returned by Voyager I.
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Inertial limit on corotation
TL;DR: In this article, the inertial corotation lag is calculated as a function of radial distance in the magnetosphere, the solution being parameterized in terms of the Pedersen conductivity of the atmosphere and the rate at which plasma mass is produced and transported outward.
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Physics of the Jovian Magnetosphere
TL;DR: In this paper, the authors considered the physics of magnetospheric radio emissions, plasma waves in the Jovian magnetosphere, theories of radio emissions and plasma waves, and magnetosphere models.