Collaborative Research: Investigating Geochemical Signatures in Greenland ice of a Possible Extraterrestrial Impact During the Younger Dryas Climate Event

这项拟议研究的主要目标是获得GISP2格陵兰冰芯中的铂、铱、Os浓度和Os同位素比率的记录，以调查在12,900年前年轻的仙女座突然气候事件开始时有陨石或彗星撞击的假设。这些分析将与在相同样本上获得的气候指标的高分辨率测量相结合。Os同位素不仅有可能最终证实或驳斥地外撞击的存在，而且如果得到证实，还可以提供关于撞击器的大小和类型的信息。对大气环流指标钠、钙和铁的高分辨率分析代表着冰芯分析分辨率的飞跃，从每三年一个样本增加到每年100多个样本。拟议的研究活动将有助于了解年轻的仙女座所发生的事情，这将引起地质学家、地球化学家、气候学家、考古学家、天文学家和公众的广泛兴趣。继最近有关GISP2冰芯中铂浓度异常的报道后，四名研究人员提议对年轻仙女木年龄的GISP2冰芯样本进行一系列协作分析：(1)评估年轻仙女木爆发时的铂峰是否有潜在污染以及来自火山和陆地来源的贡献；(2)测量Os浓度和同位素组成，以评估年轻仙女木爆发时是否发生了撞击并评估任何影响因素的性质；以及(3)通过使用新的激光烧蚀质谱仪测量风暴尺度下的铁、钠和钙元素，评估整个关键气候过渡期间的环境变化。拟议的研究将为学生提供参与学习的机会，以增加他们对地球化学调查如何深入了解影响北极的气候变化的兴趣和知识。特别是，这项研究将构成博士论文和本科高级论文的主要部分。它将使研究生和本科生接触到尖端的地球化学和质谱学技术。

The primary objective of the proposed research is to obtain records of platinum, iridium, and osmium concentrations and osmium isotope ratios in the GISP2 Greenland ice core in order to investigate the hypothesis that there was a meteorite or comet impact at the onset of the Younger Dryas abrupt climate event 12,900 years ago. These analyses will be combined with high-resolution measurements of climate proxies obtained on the same samples. Osmium isotopes have the potential not only to conclusively confirm or refute the presence of an extraterrestrial impact, but also to provide information about the size and type of the impactor, should one be confirmed. High-resolution analyses of the atmospheric circulation proxies sodium, calcium, and iron represent a leap in ice core analysis resolution from one sample per three years to over 100 samples per year. The proposed research activities would contribute towards an understanding of what happened at the Younger Dryas, which will be of broad interest to geologists, geochemists, climatologists, archeologists, astronomers, and the general public. Following recent reports of a large anomaly in platinum concentration in the GISP2 ice core, four investigators propose a series of collaborative analyses at Dartmouth College and the University of Maine on GISP2 ice core samples of Younger Dryas age to: (1) evaluate the platinum spike at the Younger Dryas onset for potential contamination and contributions from volcanic and terrestrial sources, (2) measure osmium concentration and isotope composition to evaluate whether an impact occurred at the Younger Dryas onset and assess the nature of any impactor, and (3) assess the environmental change across this critical climate transition by measuring iron, sodium and calcium at storm-scale resolution using a new laser ablation mass-spectrometry system. The proposed research will provide students with opportunities for engaged learning in order to increase their interest and knowledge of how geochemical investigations provide insights to climate change affecting the Arctic. In particular, this study will constitute a major portion of a Ph.D. thesis and an undergraduate Senior Thesis. It will expose graduate and undergraduate students to cutting-edge geochemical and mass spectrometric techniques.