Reanalysis of the Benešov bolide and recovery of polymict breccia meteorites – old mystery solved after 20 years
Reanalysis of the Benešov bolide and recovery of polymict breccia meteorites – old mystery solved after 20 years
复制标题
贝内绍夫火流星的重新分析和多角砾陨石的回收——20年后解开的老谜团
DOI：
10.1051/0004-6361/201424308
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发表时间：
2014
影响因子：
6.5
通讯作者：
P. Halodová
中科院分区：
文献类型：
--
作者：
P. Spurný;J. Haloda;J. Borovička;L. Shrbený;P. Halodová
这项工作的主要动机是解释和解决与1991年5月7日在捷克共和国中部上空对贝内绍夫超火流星进行详细仪器观测有关的古老谜团。对这颗陨石坠落的详细分析发表在几篇论文中，这是有史以来观测到的最好的火流星之一（至少是超级火流星类别）。然而，尽管有高质量的数据，有利的轨道，相对较大的终端质量，特别是巨大的努力和许多尝试，在坠落后的几周和几年内没有发现陨石。在这里，我们解决和解释这个古老的谜团。2011年春天，就在这一特殊事件发生20周年之前，我们重新测量了所有可用的全天记录，并重新分析了数据。我们使用了略微不同的方法和新的方法，并逐渐发展了这些方法来分析最近几个通过仪器观测到的陨石福尔斯（Moravka、Neuschwanstein、耶塞尼采、邦布拉Rockhole、Mason Gully和Košice）。我们收集了一个新的关于贝内绍夫事件的一致图片，这导致了对撞击位置的轻微修改，并提出了一个新的策略，可能会导致贝内绍夫陨石在20年后的恢复。现实完全证实了我们的所有假设，并超出了我们的预期。我们发现了四个小的高度风化的碎片，形状不规则，完全没有融合外壳，总质量为11.63 g（1.54 g（H5），7.72 g（无球粒碎屑），1.99 g，0.38 g（均为LL3.5））。它们是在相应质量的预测撞击区域准确地回收的，即在距离最高概率线40米以内。虽然所有碎片都非常小，风化等级很高（所有碎片的风化等级都是W3），但它们的内部保存完好，足以进行可靠的分析（最小的碎片除外）。该陨石被归类为一种复混合角砾岩，包含三种公认的岩性，具有不同的质地，化学和矿物成分。这一成果在许多方面都具有开创性。我们证明，在某些特殊情况下，仍然有可能在坠落后很长一段时间内预测和发现陨石。然而，最重要的结果是回收的陨石的异质性。这种情况清楚地表明，较大的流星体可能是成分非常复杂的天体。我们发现贝内绍夫流星体至少由三种不同类型的物质组成-- LL3.5、H5和原始无球粒陨石。这种情况也意味着，研究尽可能多的碎片是非常有用的，因为它们之间可能存在显着差异。
The main motivation for this work was to explain and solve the old mystery connected with the detailed instrumental observation of the Benešov superbolide on 7 May 1991 over the central part of the Czech Republic. Detailed analyses of this undoubted meteorite fall were published in several papers, and this is one of the best documented bolides (at least of the superbolide category) ever observed. However, despite high-quality data, favorable trajectory, relatively large terminal mass, and especially great efforts and many attempts, no meteorite was found in the weeks and years after the fall. Here we solve and explain this old mystery. In spring 2011, just before the twentieth anniversary of this extraordinary case, we remeasured all available all-sky records and reanalyzed the data. We used slightly different methods and new approaches, which we gradually developed to analyze several recent instrumentally observed meteorite falls (Morávka, Neuschwanstein, Jesenice, Bunburra Rockhole, Mason Gully, and Košice). We assembled a new consistent picture of the Benešov event, which resulted in a slightly revised impact location and suggested a new strategy that might lead to a recovery of Benešov meteorites after 20 years. The reality completely confirmed all our assumptions and surpassed our expectations. We found four small highly weathered fragments irregular in form and completely without fusion crust with a total mass of 11.63 g (1.54 g (H5), 7.72 g (with achondritic clast), 1.99 g, 0.38 g (all LL3.5)). They were recovered exactly in the predicted impact area for corresponding masses, namely within 40 m from the highest probability line. Although all fragments are very small and their weathering grade is high (W3 for all pieces), their interior was preserved enough for reliable analysis (except for the smallest one). The meteorite is classified as a polymict breccia containing three recognized lithologies with different texture, chemical, and mineralogical composition. This result is pioneering in many aspects. We proved that in some special cases it is still possible to predict and find meteorites a long time after the fall. The most important result, however, is the heterogeneity of the recovered meteorites. This case clearly shows that larger meteoroids can be compositionally very complicated bodies. We discovered that the Benešov meteoroid consisted of at least three different types of material – LL3.5, H5, and primitive achondrite. This case also implies that it is very useful to study as many fragments as possible from one fall because there can be significant differences among them.