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Project Progress

This large-scale volcanism early in martian history is estimated to have released enough water to produce a 120-m-thick global layer and enough CO₂ to produce a 1.5 bar atmosphere (Phillips et al., 2001). The release of volatiles would have had a major effect on climate and habitability. (Objective 1.1 in the Roadmap)

Previous studies of the Martian interior have highlighted the difficulty in maintaining plumes throughout the history of the planet and predict a very brief existence of a magnetic field. A deep stable mantle layer could provide a plume-source and therefore a source of long-lasting, localized volcanism. We have created a series of 1D numerical models to determine which classes of evolutionary models for the Martian interior can explain the history of crustal thickness, magnetic field, magma flux, and elastic plate thickness. In particular, we focused our efforts on the effects of a layered mantle on the compositional, thermal, and melting history of the planet. Our 1D model (similar to that of Hauck and Phillips (2002); Breuer and Spohn (2003)) solves for average core and mantle potential temperature, surface heat flux, core heat flux, melt generation, and crustal thickness as a function of time. Unlike previous 1D models of the thermal evolution of Martian mantle, our model also considers a layered mantle and the influence of plumes on melt generation. A dense layer in the deep mantle seems to provide a robust mechanism for the generation of plumes and melting late in the planet’s history (Zaranek et al., to be submitted).

In earlier work, we (Wenzel et al., 2004) argued on the basis of laboratory experiments that if the martian mantle were compositionally layered, a single large upwelling might have been formed under the Southern Highlands. We have now tested the hypothesis with a 3D computational model of layered convection (figure 1). We find that an internal heating rate similar to that on early Mars was probably too large to allow a single strong plume to form (Wenzel et al. 2006 to be submitted).

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The thermal history of a planet’s interior affects the hydrosphere (e.g., Clifford and Parker, 2001) and the release of volatile elements to the atmosphere. The thermal history can therefore be related to the hydrologic history of Mars ( e.g., Bibring et al. 2006). We have started coupling thermal histories with models for water release (Wang et al., 2006 in review). We are also developing numerical models for hydrothermal circulation near magma intrusions in order to determine the volume and rate at which liquid water can be released at volcanic centers (figure 2).

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