Buried Mass Anomalies Along the Hemispheric Dichotomy in Eastern Mars: Implications for the Origin and Evolution of the Dichotomy

Walter S. Kiefer (Lunar and Planetary Institute)

Geophy. Res. Lett. 32, L22201, doi:10.1029/2005GL024260, 2005.

Abstract: Gravity observations indicate the presence of buried, high-density material along the hemispheric dichotomy in eastern Mars. This material is unrelated to present-day topography and is probably the result of localized thinning of the crust. This thinning may be the result of an epoch of edge-driven convection that occurred shortly after the dichotomy formed. Initiation of edge-driven convection requires that lateral variations in lithospheric structure be created on a timescale that is shorter than the conductive cooling time for the lithosphere, a few tens of million years at most. This timescale cannot be achieved if the dichotomy boundary is created solely by large-scale convective flow. Formation or modification of the boundary by large impact basins such as Utopia can create the required lithospheric structure in a geologic instant. This suggests that large impacts were important in shaping the dichotomy, at least on a regional scale.

Text of paper (on AGU's website)

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Walter S. Kiefer,   kiefer@lpi.usra.edu