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Hydrologic modelling with variable fluid properties : a liquid sulfur aquifer beneath the surface of Io

University of British Columbia

The return of the first Voyager images of Io in 1979 provoked a controversy over the importance of sulfur versus silicate volcanism in resurfacing the satellite. The debate involves both the strength of crustal material as well as the mode of mass and heat transport to the surface of Io. The dynamics of sulfur magma transport will depend upon the properties of liquid sulfur. Unlike the Newtonian behaviour of silicate magmas, molten sulfur has anomalies in the heat capacity (a A-like transistion at 432 K) and in the viscosity (a maximum at 460 K) due to a polymerization reaction. Numerical modelling of a pure liquid sulfur supply region at depth in a porous crust shows that the fluid supply rate from such a magma reservoir is about seven orders of magnitude less than the observed mass and heat fluxes at the surface of Io. This requires accumulation of magma in a reservoir prior to eruption at the surface, but the accumulation time on the order of tens of thousands of years is much longer than would be consistent with the level of volcanic activity observed on Io. Low sulfur magma supply rates suggest that sulfur is not the dominant resurfacing material for the satellite. This is consistent with calculations performed for the viscous relaxation of topography on Io. Surface features of a largely sulfur crust would disappear within months because of material weakness. Significant topographic highs and steep slopes on Io provide evidence for a crust with stronger mechanical properties. Sulfur convection in the crust can still provide a large fraction of the global heat flow, within certain conditions on the permeability. Previous estimates of resurfacing rates have equated the cooling of erupted material to the entire global energy budget. Significant convective transfer of heat by liquid sulfur may call for a downward revision of resurfacing rates.

Thesis/Dissertation

application/pdf

2009-02-06

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http://hdl.handle.net/2429/4224

Geophysics

University of British Columbia

UBCV

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