Magnetic anomalies on Io and their relationship to the spatial distribution of volcanic centers
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2017 Elsevier B.V. Forward modeling of planetary-scale magnetic anomalies due to induced crustal magnetization of Io is developed. The approach involves finite difference modeling of a temporally- and spatially-averaged steady state geotherm superimposed by the thermal evolution of an instantaneously emplaced volcanic pipe with and without an underlying magma chamber. A slight adjustment to previous studies results in a preferred steady state geotherm. The crustal magnetization is based on the calculated distribution of temperature, the strength of an idealized Jovian magnetic field, and a temperature-dependent susceptibility. Magnetite is assumed to be the dominant magnetic mineral. Synthetic satellite flyby data are generated along selected meridional swaths of Io's surface, based on observed locations of volcanic centers, hotspots, and accumulations of ejected volcanic material. This work produces a 1-D geotherm which remains at approximately the surface temperature to within a few kilometers of the thermal lithosphere/mantle boundary. This solution shows little dependence on porosity due to the depth at which rapid temperature change occurs. These conclusions hold for largely varying mantle temperatures. Silicate volcanic centers cool to the temperature of sulfur eruptions rapidly and become indistinguishable from sulfur volcanism within 10,000years. The magnetic anomaly due to temperature variation is smaller than detectable for nominal conditions. The modeling herein requires a flyby altitude of 25km and a pipe radius of 640m for detection, or, for a more reasonable flyby altitude of 100km, a pipe radius of 6000m. If a crustal anomaly is detected by future satellite missions, it would suggest different conditions at Io than modeled here.
