The Hamburg meteorite fell on January 16, 2018, near Hamburg, Michigan, after a fireball event widely observed in the U.S. Midwest and in Ontario, Canada. Several fragments fell onto frozen surfaces of lakes and, thanks to weather radar data, were recovered days after the fall. The studied rock fragments show no or little signs of terrestrial weathering. Here, we present the initial results from an international consortium study to describe the fall, characterize the meteorite, and probe the collision history of Hamburg. About 1 kg of recovered meteorites was initially reported. Petrology, mineral chemistry, trace element and organic chemistry, and O and Cr isotopic compositions are characteristic of H4 chondrites. Cosmic ray exposure ages based on cosmogenic ³He, ²¹Ne, and ³⁸Ar are ~12 Ma, and roughly agree with each other. Noble gas data as well as the cosmogenic ¹⁰Be concentration point to a small 40–60 cm diameter meteoroid. An ⁴⁰Ar‐³⁹Ar age of 4532 ± 24 Ma indicates no major impact event occurring later in its evolutionary history, consistent with data of other H4 chondrites. Microanalyses of phosphates with LA‐ICPMS give an average Pb‐Pb age of 4549 ± 36 Ma. This is in good agreement with the average SIMS Pb‐Pb phosphate age of 4535.3 ± 9.5 Ma and U‐Pb Concordia age of 4535 ± 10 Ma. The weighted average age of 4541.6 ± 9.5 Ma reflects the metamorphic phosphate crystallization age after parent body formation in the early solar system.

中文翻译：

---

密歇根州汉堡H4球粒陨石的坠落，恢复，分类和初始表征

在美国中西部和加拿大安大略省发生广泛的火球事件后，汉堡陨石于2018年1月16日坠落在密歇根州汉堡附近。几片碎片掉落在冰冻的湖面上，并且由于天气雷达的数据，在坠落后数天被回收。所研究的岩石碎片没有或几乎没有陆地风化的迹象。在这里，我们提供了国际财团研究的初步结果，以描述秋天，表征陨石和探究汉堡的碰撞历史。最初报告大约回收了1千克陨石。岩石学，矿物化学，微量元素和有机化学以及O和Cr同位素组成是H4球粒陨石的特征。宇宙射线的暴露年龄基于宇宙产生的³ He，²¹ Ne和³⁸ Ar约为12 Ma，彼此大致一致。稀有气体数据以及具有宇宙成因的¹⁰ Be浓度都指向直径为40-60 cm的小型流星体。与其他H4球粒陨石的数据一致，年龄为4532±24 Ma的⁴⁰ Ar‐ ³⁹ Ar年龄表明其演化历史的后期没有发生重大撞击事件。用LA‐ICPMS对磷酸盐进行的微量分析得出的平均Pb‐Pb年龄为4549±36 Ma。这与SIMS Pb-Pb磷酸盐的平均年龄为4535.3±9.5 Ma和U-Pb Concordia年龄为4535±10 Ma完全吻合。4541.6±9.5 Ma的加权平均年龄反映了太阳系早期母体形成后的变质磷酸盐结晶年龄。