The Influence of Mantle Rheology on the Early Differentiation of Icy Satellites

地幔流变学对冰卫星早期分化的影响

• 批准号: 248760695
• 负责人: Dr. Tiziana Boffa Ballaran
• 金额: --
• 依托单位: Bayerisches Forschungsinstitut für Experimentelle Geochemie und Geophysik (BGI)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/248760695?language=en
• 关键词: Influence; Mantle; Rheology; Early; Differentiation

Icy materials dominated by H2O but also containing ammonia and methane form the bulk of Neptune and Uranus in addition to the 22 major satellites orbiting the outer planets. These satellites, which are believed to have mainly accreted before the dispersal of the solar nebula, are of particular interest to planetary science as they show a range of diverse geological features including the only extraterrestrial evidence for liquid oceans, active plate tectonics and volcanism. The diverse surface expressions of these satellites reflect differing internal processes active since accretion, which have led, for example, to varying degrees of differentiation of the interiors. A key parameter controlling early differentiation was heat loss from the interior through convection. Only bodies that rapidly established convective regimes would have been able to maintain temperatures low enough to prevent melting and complete differentiation, as appears to be the case on Callisto, for example. In order to explore early dynamic processes, detailed constraints on the viscosity of icy materials must be obtained from laboratory measurements of rheological properties. Currently such data are not available for the range of conditions and compositions likely encompassed by the icy satellites. In this project the mechanical properties of ice and icy compounds at pressures and temperatures compatible with the entire range of conditions within icy satellites will be studied. In addition, structural and elastic data will be extracted for many icy materials including clathrates for which data at high pressures are absent. Stress and strain relations will be used to derive flow laws from experiments performed in the diamond anvil cell. These experiments will employ a novel approach of using single crystal x-ray diffraction to determine lattice strains. By examining single and multiple crystal assemblages, fundamental new insights will be made into local stress perturbations within polycrystalline assemblages. Ices are perfect model materials through which to develop such models, which are vital for interpreting high pressure rheological x-ray measurements on silicate materials. Structural, static and dynamic properties of ices will be integrated into models for the internal composition and viscosity of the large icy satellites of Jupiter and Saturn. These models will be used to examine factors during and subsequent to accretion which lead to some satellites differentiating into silicate cores surrounded by ices, while others remained mainly undifferentiated.

冰冷的材料以H2O为主，但还含有氨和甲烷，除了22个主要的卫星外，还形成了大部分海王星和天王星。这些卫星被认为主要在太阳星云扩散之前积聚，这对行星科学特别感兴趣，因为它们显示了一系列不同的地质特征，包括液态海洋，活性板块构造和火山主义的唯一外星证据。这些卫星的各种表面表达式反映了自吸收以来活跃的不同内部过程，例如，内部分化的程度不同。控制早期分化的关键参数是通过对流从内部造成的热量损失。例如，只有快速建立对流制度的身体才能保持足够低的温度以防止融化和完全分化，例如，在Callisto上似乎是这种情况。为了探索早期的动态过程，必须从冰冷材料的粘度上详细限制。当前，这些数据不适合冰冷卫星所包含的各种条件和组成。在该项目中，将研究与压力和温度兼容的与冰冷卫星中整个条件兼容的机械性能。此外，将针对许多冰冷的材料提取结构和弹性数据，包括缺乏高压数据的杂质。应力和应变关系将用于从钻石砧细胞中执行的实验中得出流量定律。这些实验将采用一种使用单晶X射线衍射来确定晶格菌株的新方法。通过检查单个和多个晶体组合，将在多晶组合中对局部应力扰动进行基本的新见解。 ICE是开发此类模型的理想模型材料，这对于解释硅酸盐材料上的高压流变学X射线测量至关重要。 ICE的结构，静态和动态特性将集成到木星和土星的大型冰卫星的内部组成和粘度的模型中。这些模型将在积聚期间和之后检查因素，从而导致一些卫星区分为硅酸盐岩心，而硅酸盐岩心被冰包围，而其他卫星则主要是未分化的。