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Time, tides and tectonics on icy satellites.

机译:冰冷卫星上的时间,潮汐和构造。

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摘要

In the outer solar system, we cannot use the radiometric dating techniques applied in terrestrial geology. We also lack the detailed understanding of the correspondence between crater size-frequency distributions and absolute ages that lunar samples has given us in the inner solar system. Additionally, many geologically interesting icy satellites are insufficiently cratered to yield precise relative ages. Thus we must find other ways to construct geological chronologies In this work I develop two techniques.;The first compares the linear tectonic features covering Jupiter's moon Europa to modeled tensile fractures resulting from tidal stresses due to the nonsynchronous rotation (NSR) of the satellite's decoupled, icy, lithospheric shell. The amount of shell rotation required to align a feature with the stress field resulting from NSR is used as a proxy for time. This translation is potentially convolved with a phase lag between the tidal potential and the stresses it induces, resulting from the shell's partially viscous response to the NSR forcing. The geography of individual lineaments is found to be no more consistent with NSR stresses than chance would predict, however, the ensemble of global lineaments displays a non-uniform apparent rate of lineament formation throughout the time period recorded by the surface. This non-uniformity may be explained either by steady state fracture formation, activity, quiescence and erasure, or by a transient episode of tectonics.;The second technique encodes the myriad superposition relationships evident between Europa's tectonic features as a directed graph enabling algorithmic analysis. The observed superposition relationships are generally insufficient to construct complete stratigraphic stacks, but we can calculate the degree to which they corroborate or contradict another hypothesized order of formation. We find that they tend to corroborate the hypothesis that the lineaments are tensile fractures due to prograde NSR stresses.;Together these results offer cautious support for the idea that Europa's shell rotates independently of its silicate interior, and demonstrate techniques useful in comparing tectonic features on other icy satellites to hypothesized mechanisms of formation.
机译:在外部太阳系中,我们无法使用在地球地质学中应用的辐射测年技术。我们还缺少对月牙样本给我们的太阳系内陨石坑的频率-频率分布与绝对年龄之间的对应关系的详细理解。另外,许多地质有趣的冰冷卫星没有足够的陨石坑来产生精确的相对年龄。因此,我们必须找到其他构造地质年代的方法。在这项工作中,我开发了两种技术:第一种方法将覆盖木星的卫星欧洲大陆的线性构造特征与由于卫星解耦的非同步旋转(NSR)引起的潮汐应力导致的模拟拉伸裂缝进行了比较。 ,冰冷的岩石圈壳。将特征与NSR产生的应力场对齐所需的壳体旋转量将用作时间的替代。这种转换可能与潮汐势与其所引起的应力之间的相位滞后卷积,这是由于壳对NSR强迫产生的部分粘性响应所致。发现单个线状体的地理位置与NSR应力的一致性并不比偶然预测的一致,但是,整体线状体的整体显示在整个表面记录的时间段内,线状体形成的表观速率不均匀。这种不均匀性可以通过稳态裂缝的形成,活动,静止和擦除或构造的短暂发作来解释。第二种技术将欧罗巴构造特征之间明显的无数叠加关系编码为有向图,从而可以进行算法分析。观察到的叠加关系通常不足以构成完整的地层,但是我们可以计算出它们证实或与另一个假设的形成顺序相矛盾的程度。我们发现它们趋于证实直线运动是NSR应力导致的拉伸断裂的假说。这些结果共同为Europa的壳层独立于其硅酸盐内部旋转的观点提供了谨慎的支持,并证明了在比较构造特征上有用的技术其他冰冷的卫星推测的编队机制。

著录项

  • 作者

    Selvans, Z. A.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Geophysics.;Planetology.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 157 p.
  • 总页数 157
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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