2007 Annual Science Report
University of California, Berkeley Reporting | JUL 2006 – JUN 2007
Evolution of the Interior and Its Consequences for Water on Mars
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). The history and availability of water on Mars may thus be intimately connected to its volcanic history and interior thermal evolution.
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 solves for average core and mantle potential temperature, surface heat flux, core heat flux, melt generation, and crustal thickness as 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.
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. In Wang et al. (2006) we show how cooling of the interior can pressurize water in sub-cryosphere aquifers. The water pressure can become large enough to crack the cryosphere and cause large amounts of water to erupt on the surface. This process may have operated throughout Martian history
We have also developed 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. We find that for plausible ranges of permeability, hydrothermal circulation does not significantly affect the subsurface temperature distribution. However, large amounts of water can be forced to circulate through the shallow crust.
PROJECT INVESTIGATORS:Michael Manga
PROJECT MEMBERS:Yoshiko Ogawa
RELATED OBJECTIVES:Objective 1.1
Models of formation and evolution of habitable planets