Mars north polar deposits: stratigraphy, age, and geodynamical response

R.J. Phillips; M.T. Zuber; S.E. Smrekar; M. T. Mellon; J.W. Head; K. L. Tanaka; N.E. Putzig; S.M. Milkovich; B.A. Campbell; J.J. Plaut; A. Safaeinili; R. Seu; D. Biccari; L.M. Carter; G. Picardi; R. Orosei; Mohit P. Surdas; E. Heggy; R.W. Zurek; A.F. Egan; E. Giacomoni; F. Russo; M. Cutigni; E. Pettinelli; J.W. Holt; C.J. Leuschen; L. Marinangeli

doi:10.1126/science.1157546

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Mars north polar deposits: stratigraphy, age, and geodynamical response

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Abstract

The Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter has imaged the internal stratigraphy of the north polar layered deposits of Mars. Radar reflections within the deposits reveal a laterally continuous deposition of layers, which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice. The packet/interpacket structure can be explained by approximately million-year periodicities in Mars' obliquity or orbital eccentricity. The observed ???100-meter maximum deflection of the underlying substrate in response to the ice load implies that the present-day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers. Alternatively, the response to the load may be in a transient state controlled by mantle viscosity. Both scenarios probably require that Mars has a subchondritic abundance of heat-producing elements.

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R.J. Phillips, M.T. Zuber, S.E. Smrekar, M. T. Mellon, J.W. Head, K. L. Tanaka, N.E. Putzig, S.M. Milkovich, B.A. Campbell, J.J. Plaut, A. Safaeinili, R. Seu, D. Biccari, L.M. Carter, G. Picardi, R. Orosei, Mohit P. Surdas, E. Heggy, R.W. Zurek, A.F. Egan, E. Giacomoni, F. Russo, M. Cutigni, E. Pettinelli, J.W. Holt, C.J. Leuschen, L. Marinangeli. 2008. Mars north polar deposits: stratigraphy, age, and geodynamical response. https://doi.org/10.1126/science.1157546

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