从地形数据看土卫二的真正极地漫游
True Polar Wander of Enceladus From Topographic Data
摘要：
太阳系中的许多天体都被怀疑经历过自转轴的重新定向。由于它们的自转速度很慢，形状接近球形，因此无论是内生还是外生过程，质量异常的形成都可以改变物体的转动惯量。因此，对象会重新定向，以使其最大转动惯量与其自旋轴对齐。这种现象被称为真正的极地漫游（TPW）。在这里，我们报告了在土星卫星土卫二上发现的一系列全球地形低点，我们解释说，这颗同步锁定的卫星已经经历了围绕潮汐轴约55°的TPW。我们使用改进的地形数据，从球谐膨胀的卡西尼肢体和立体测量，以表征区域地形表面的土卫二。我们确定了一组近对跖盆地正交的地形盆地链跟踪非赤道环地球带在土卫二的表面。我们认为，带和对跖地区的化石残留的早期赤道和两极，分别。我们认为，这些低点产生均衡补偿，其模式反映了空间变化的内部动态的冰壳。我们的假设与卡西尼图像中可见的各种地质特征一致。
英文摘要：
Many obsects in the solar system are suspected to have experience reorientation of their spin axes. As their rotation rates are slow and their shapes are nearly spherical, the formation of mass anomalies, by either endogenic of exogenic processes, can change objects' moments of inertia. Therefore, the objects reorient to align their largest moment of inertia with their spin axis. Such phenomenon is called True Polar Wander (TPW). Here we report the discovery of a global series of topographic lows on Saturn's satellite Enceladus that we interpret to show that this synchronously locked moon has undergone TPW by ~55° about the tidal axis. We use improved topographic data from the spherical harmonic expansion of Cassini limb and stereogrammetric measurements to characterize regional topography over the surface of Enceladus. We identify a group of nearly antipodal basins orthogonal to a topographic basin chain tracing a non-equatorial circumglobal belt across Enceladus' surface. We argue that the belt and the antipodal regions are fossil remnants of an earlier equator and poles, respectively. We argue that these lows arise from isostasic compensation and that their pattern reflects spatial variations in internal dynamics of the ice shell. Our hypothesis is consistent with a variety of geological features visible in Cassini images.
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