Mars North Polar Deposits: Stratigraphy, Age, and Geodynamical Response

• DOI: 10.1126/science.1157546
• Publication Date: 2008-05-16T01:39:41Z
• Authors: Roger J. Phillips; Maria T. Zuber; Suzanne E. Smrekar; Michael T. Mellon; James W. Head; Kenneth L. Tanaka; Nathaniel E. Putzig; Sarah M. Milkovich; Bruce A. Campbell; Jeffrey J. Plaut; Ali Safaeinili; Roberto Seu; Daniela Biccari; Lynn M. Carter; Giovanni Picardi; Roberto Orosei; P. Surdas Mohit; Essam Heggy; Richard W. Zurek; Anthony F. Egan; Emanuele Giacomoni; Federica Russo; Marco Cutigni; Elena Pettinelli; John W. Holt; Carl J. Leuschen; Lucia Marinangeli
• Keywords: 13. Climate action; 01 natural sciences; 0105 earth and related environmental sciences

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.