Phillips Roger J, Zuber Maria T, Smrekar Suzanne E, Mellon Michael T, Head James W, Tanaka Kenneth L, Putzig Nathaniel E, Milkovich Sarah M, Campbell Bruce A, Plaut Jeffrey J, Safaeinili Ali, Seu Roberto, Biccari Daniela, Carter Lynn M, Picardi Giovanni, Orosei Roberto, Mohit P Surdas, Heggy Essam, Zurek Richard W, Egan Anthony F, Giacomoni Emanuele, Russo Federica, Cutigni Marco, Pettinelli Elena, Holt John W, Leuschen Carl J, Marinangeli Lucia
Southwest Research Institute, Boulder, CO 80302, USA.
Science. 2008 May 30;320(5880):1182-5. doi: 10.1126/science.1157546. Epub 2008 May 15.
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 approximately 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.
火星勘测轨道飞行器上的浅地层雷达（SHARAD）对火星北极层状沉积物的内部地层进行了成像。沉积物中的雷达反射显示出地层在横向是连续沉积的，这些地层通常由四组间隔细密的反射体组成，中间被几乎纯净的冰构成的均匀层间区域隔开。这种层组/层间结构可以用火星倾角或轨道偏心率大约每百万年的周期性变化来解释。观测到的下层基底因冰荷载产生的最大约100米的挠曲意味着，现今平衡弹性岩石圈的厚度大于300千米。或者，对荷载的响应可能处于由地幔粘度控制的过渡状态。这两种情况可能都要求火星的产热元素丰度低于球粒陨石。
