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G.J. Veeder, D.L. Matson, A.G. Davies, T.V. Johnson, D.L. Blaney (JPL)
Night temperatures on Io are not a strong function of latitude or local time. Moreover, polar temperatures on Io are higher than expected from any passive surface. The implied low level, but large scale, thermal activity is not necessarily confined to the polar regions of Io. An alternative model features three units. The first is a global, dark, 'volcanic' unit. The second and third more conventional units are characterized by 'low albedo zero thermal inertia' and 'high albedo infinite thermal inertia'. These units have albedos of 0.2, 0.25, and 0.6 and uniform fractional surface coverage of 0.1, 0.1, and 0.8 respectively. The supported temperature of the 'volcanic' unit is ~90 K which then contributes an additional ~0.5 W m-2 to the heat flow budget similar to our previous 'polar' unit (Veeder et al., 2003, LPSC XXXIV, 1448). The total model value remains ~3 W m-2 for Io's average heat flow.
This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. The authors are supported by grants from the NASA Planetary Geology & Geophysics program.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.