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“A Post Galileo view of Io’s Interior”

“A Post Galileo view of Io’s Interior”. Keszthelyi et al. Icarus 169 (2004) Raquel Fraga-Encinas Dec 7 , 2004 UMD TERPS Conference. View right after Voyager flybys. Completely molten interior (Peale 1979) Thin lithosphere flexed by tidal forces causes tidal heating

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“A Post Galileo view of Io’s Interior”

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  1. “A Post Galileo view of Io’s Interior” Keszthelyi et al. Icarus 169 (2004) Raquel Fraga-Encinas Dec 7 , 2004 UMD TERPS Conference

  2. View right after Voyager flybys • Completely molten interior (Peale 1979) • Thin lithosphere flexed by tidal forces causes tidal heating • Underlying basaltic magmas drive up sulfur eruptions

  3. View right before Galileo flybys • Thick cold lithosphere (> 30km) • Aesthenospheric heating model (Ross et al. 1990) • Io’s interior considered largely solid (Nash et al. 1986)

  4. Galileo Mission Observations • SSI (0.4–1 um) , NIMS (0.7-5.2 um), PPR (visible-100 um) Timeline:1995-2003 • Pillan Patera eruption T = 1870 +/- 25 K • SSI color data – hottest spots were darkest near 1 micron : presence of “enstatite” • Limits: superheating due to rapid ascent or tidal heating of materials

  5. Modeling • MELTS numerical thermodynamic model from published data • Assume Pressure ~ 100Mbar • Upper mantle ~ 50% molten , core boundary 10-20%

  6. Post-Galileo View Io & Implications • Core: molten Fe-S mix , size = 550-900 km • Mantle: molten ~ 10% base to ~ 50% upper (enstatite composition) • Crust: at least 13km thick (continually recycled into mantle) • Can explain features like paterae & plumes

  7. Concluding remarks • This latter model is closer to what was proposed on the 70’s than prior to the Galileo mission • Uncertainties on lava temperatures? Need more data

  8. RIGHT: Si magma (red) rises thru rock, not buoyant enough to reach volatiles (navy). Heat melts S (yellow) and SO2 (light blue) when it vaporizes erupts into surface. Depression forms and can be unroofed forming the patera. LEFT: Orange (warm S) black spot (Si unroofed)

  9. L/LL-chondrites have low Fe content, have olivine & pyroxene IO INFO Mass = 8.94E25 g Radius = 1821 km Av. Density = 3.53 g/cc

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