Single-crystal elasticity of martian mantle minerals and a flexible CO2 laser heating system

火星地幔矿物的单晶弹性和灵活的二氧化碳激光加热系统

• 批准号: 411764160
• 负责人: Dr. Alexander Kurnosov
• 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: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/411764160?language=en
• 关键词: Single; crystal; elasticity; martian; mantle

Observations of the seismic wave velocity structure of the Martian interior are becoming increasingly available from the SEIS seismometer on the NASA InSight lander. The interpretation of such data relies crucially on the ability to model the mineralogy and seismic velocities of the Martian interior in order to test plausible compositions and temperature gradients. To date, however, such models for the Martian mantle are constructed using thermodynamic parameters that are either estimated, not determined from the most recent phase equilibria and elasticity data or are not suitable for determining Martian compositions. Very few elasticity measurements exist at simultaneous high pressure and temperature conditions, requiring data for most minerals to be extrapolated to some extent, which introduces significant uncertainties.In the first period of this project a new system was developed to measure acoustic wave velocities at pressures and temperatures corresponding to the entire Martian mantle. The system, where Brillouin spectroscopy measurements are performed simultaneously with CO2-laser heating in a diamond anvil cell, has been successfully benchmarked by performing measurements on single crystals of pyrope. By combining these data with further measurements on Fe-rich ringwoodite and recent data from the literature, an updated mineral-physics model for the base of the Martian mantle has been obtained. Significant differences exist with previous models based on properties of terrestrial materials. Using the new model to interpret a proposed Martian mantle discontinuity at 1140 km, implies a temperature at this depth in the range 1870-1970 K. In the renewal phase, simultaneous single crystal X-ray diffraction measurements will be also implemented, to obtain a truly unique system capable of determining the full elastic tensor of any mineral throughout the conditions of any terrestrial planet. Using this system, the determination of the full elastic tensors of the main Martian minerals will be completed by examining Fe-rich single crystals of majoritic garnet, olivine and even the low symmetry mineral clinopyroxene, at pressures and temperatures of their stability in the Martian mantle. These data will be used to develop a an internally consistent thermodynamic model to predict the mineralogy and seismic wave velocities of the Martian mantle with vastly reduced uncertainties. This model will not only be used to interpret the emerging observations of Martian seismic structure and assess the uncertainties in these interpretations, but will also provide a first assessment of how seismic anisotropy has the potential to influence observations of the Martian interior. Moreover, by studying minerals comprised of different solid solution components, we will address a central issue in mineral physics as to whether the properties of intermediate compositions can be effectively described using linear combinations of end member properties.

在NASA Insight Lander上的Seis Seismometer中，火星内部的地震波速度结构的观察变得越来越多。对此类数据的解释至关重要地取决于模拟火星内部矿物学和地震速度的能力，以测试合理的组成和温度梯度。然而，迄今为止，使用热力学参数构建了这种火星地幔的模型，这些模型要么是估计的，因此不是根据最新的相位平衡和弹性数据确定，或者不适合确定火星组成。在同时高压和温度条件下，很少有弹性测量值，需要在一定程度上推断出大多数矿物的数据，这引入了重大的不确定性。在该项目的第一阶段，开发了一个新的系统来测量与整个火星壁炉相似的压力和温度下的声波速度。该系统通过在钻石砧室中同时进行二氧化碳 - 激光加热同时进行，通过对Pyrope的单晶体进行测量，已成功进行了基准测试。通过将这些数据与关于富含铁的林木和文献的最新数据相结合，已经获得了一个更新的火星披风底座的矿物质模型。基于陆地材料的性质，先前模型存在显着差异。使用新模型来解释在1140 km处的提议的火星地幔不连续性，这意味着在1870-1970 K范围内的温度处于该深度。在更新阶段，同时进行单晶X射线衍射测量值也将被实现，以获得真正独特的系统。使用该系统，将通过检查Martian Martiant的稳定性和温度下，确定了Martian矿物质的完整弹性张量，将完成主要石榴石，橄榄石甚至低对称性矿物斜叶烯的富含Fe的单晶。这些数据将用于开发一种内部一致的热力学模型，以预测火星地幔的矿物学和地震波速度，其不确定性大大降低。该模型将不仅用于解释火星地震结构的新兴观察结果并评估这些解释中的不确定性，而且还将首先评估地震各向异性如何影响火星内部的观察结果。此外，通过研究由不同的固体溶液组成的矿物质，我们将使用最终成员性质的线性组合有效地描述矿物质物理学中的核心问题。