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

这项研究的主要目的是获取格陵兰岛GISP2冰芯中铂、铱和锇的浓度和锇同位素比率的记录，以研究在12900年前新仙女木期突变气候事件开始时发生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代用物的高分辨率测量相结合。锇同位素不仅有可能最终证实或驳斥地外撞击的存在，而且如果有撞击得到证实，还可以提供有关撞击物大小和类型的信息。大气环流的高分辨率分析钠、钙和铁代表了冰芯分析分辨率的飞跃，从每三年一个样本到每年100多个样本。拟议的研究活动将有助于了解新仙女木期发生了什么，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。根据最近关于GISP2冰芯中铂浓度异常的报道，达特茅斯学院和缅因大学的四名研究人员提出了一系列关于新仙女木时期GISP2冰芯样本的合作分析：(1)评估新仙女木期开始时铂峰值的潜在污染以及火山和陆地来源的贡献；(2)测量锇浓度和同位素组成，以评估新仙女木期开始时是否发生了影响，并评估任何影响因素的性质；(3)通过测量铁来评估这一关键气候转变期间的环境变化。在风暴尺度分辨率的钠和钙使用新的激光烧蚀质谱系统。拟议的研究将为学生提供参与式学习的机会，以增加他们对地球化学调查如何为影响北极的气候变化提供见解的兴趣和知识。特别是，本研究将构成博士论文和本科毕业论文的主要部分。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.