Microstructure modifications of silicates induced by the collection in aerogel: Experimental approach and comparison with Stardust results
Microstructure modifications of silicates induced by the collection in aerogel: Experimental approach and comparison with Stardust results
复制标题
气凝胶中的收集引起的硅酸盐微观结构的改变：实验方法以及与星尘结果的比较
DOI：
10.1111/j.1945-5100.2011.01305.x
复制
发表时间：
2012
影响因子：
2.2
通讯作者：
M. Burchell
中科院分区：
文献类型：
--
作者：
J. Stodolna;D. Jacob;H. Leroux;M. Burchell
摘要-81P/Wild 2彗星的粒子是在飞越星尘任务期间用二氧化硅气凝胶捕获的。在气凝胶的超高速撞击过程中，收藏品的很大一部分遭到破坏。在这项研究中，我们使用轻气枪在类似于收集Wild 2彗星粒子的条件下对橄榄石和辉石粉末气凝胶进行了撞击实验。用透射电子显微镜研究了喷丸样品的微观结构。由于与气凝胶的摩擦，橄榄石和辉石样品都显示出热蚀变的证据。收集后所有的颗粒都有圆形的边缘，而在最初的火药组中，它们的形状是棱角的。这可能与粒子的质量损失有关。颗粒的边缘明显融化，与气凝胶混合在一起。橄榄石颗粒的核心保存较好，但有些颗粒含有滑移组态的位错。我们将这些位错解释为由于颗粒核心和边缘之间的高温度梯度而产生的热应力所产生的。大部分辉石颗粒已经完全熔化。它们的高二氧化硅浓度反映了熔融的气凝胶的强烈浸渍。与橄榄石相比，辉石优先熔融是由于熔融温度相差300°所致。这种熔点差异可能会导致对Wild 2彗星中橄榄石/辉石比值的测量产生偏差。在收集到气凝胶中的样品中，Wild 2上的辉石比例可能高于预期。
Abstract– Particles from comet 81P/Wild 2 were captured with silica aerogel during the flyby Stardust mission. A significant part of the collection was damaged during the impact at hypervelocity in the aerogel. In this study, we conducted impact experiments into aerogel of olivine and pyroxene powder using a light‐gas gun in similar conditions as that of the comet Wild 2 particles collection. The shot samples were investigated using transmission electron microscopy to characterize their microstructure. Both olivine and pyroxene samples show evidence of thermal alteration due to friction with the aerogel. All the grains have rounded edges after collection, whereas their shape was angular in the initial shot powder set. This is probably associated with mass loss of particles. The rims of the grains are clearly melted and mixed with aerogel. The core of olivine grains is fairly well preserved, but some grains contain dislocations in glide configuration. We interpret these dislocations as generated by the thermal stresses that have emerged due to the high temperature gradients between the core and the rim of the grains. Most of the pyroxene grains have been fully melted. Their high silica concentration reflects a strong impregnation with melted aerogel. The preferential melting of pyroxene compared with olivine is due to a difference in melting temperatures of 300°. This melting point difference probably induces a bias in the measurements of the ratio olivine/pyroxene in the Wild 2 comet. The proportion of pyroxene was probably higher on Wild 2 than expected from the samples collected into aerogel.