Extraterrestrial Components from Deep Sea Sediments of Indian Ocean
Extraterrestrial Components from Deep Sea Sediments of Indian Ocean
复制标题
印度洋深海沉积物中的外星成分
DOI：
10.16943/ptinsa/2016/48474
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
M. ShyamPrasad
中科院分区：
文献类型：
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作者：
N. G. Rudraswami;M. ShyamPrasad
在过去几年中，进行了两种不同类型的地外微粒物质收集-使用包裹在沿着海底拖曳的挖泥船中的磁铁，以及筛选大量深海沉积物，随后从中分离出宇宙球粒。对近1000个宇宙球粒切片的详细研究显示，在所有三种基本类型的宇宙球粒中都存在Pt族金块-所有这些球粒都有碳质陨石作为前体，因此在某种程度上统一了它们。此外，在所有类型的宇宙球粒中的铁镍珠进一步证实了这一发现。硅酸盐宇宙球粒中残余颗粒的氧同位素表明，碳质陨石球粒是主要贡献者。此外，在几个宇宙球粒中观察到的残留铬铁矿颗粒和尘埃橄榄石表明，至少3%的落在地球上的宇宙物质来自普通的铬铁矿。在印度洋发现的澳大拉西亚微玻璃陨石保留了独特的微撞击特征，这些特征是在喷出物中的粒子间碰撞造成的。这一独特的现象说明了撞击过程在估算从月球物质估算的宇宙尘埃通量过程中的重要性。
Two different types of extraterrestrial particulate matter collections were undertaken during the last few years – by using magnets encased in dredges that were dragged along the seafloor and by sieving massive quantities of deep sea sediments from which cosmic spherules were subsequently isolated. Detailed investigations on close to 1000 sectioned cosmic spherules revealed the presence of Pt-group nuggets in all the three basic types of cosmic spherules – all of whom had carbonaceous chondritic meteorites as precursors, thus in a way unifying them. Further, Fe-Ni beads in all types of the investigated cosmic spherules further confirmed this finding. Oxygen isotopes of relict-grains in silicate cosmic spherules suggested chondrules from carbonaceous chondrites to be major contributors. In addition, relict chromite grains and dusty olivines observed in several cosmic spherules suggested that at least 3% of the cosmic material that rains on the earth is sourced from ordinary chondrites. The Australasian microtektites found in the Indian Ocean retained unique microimpact features generated while they were in flight due to inter-particle collisions in the ejecta. This unique phenomenon outlined the importance of the impact process during estimation of cosmic dust fluxes estimated from lunar materials.