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Chromium isotopic composition of the implanted solar wind-bearing component in Apollo 16 lunar soils.

机译：阿波罗16号月球土壤中植入的太阳含风成分的铬同位素组成。

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摘要

Chromium isotopes are scientifically interesting for many reasons. For example, 53Mn decays to 53Cr which has allowed for the development of a fine-scale chronometer, 54Cr is a neutron-rich isotope believed to be generated in Type Ia supernovae which sheds light on local nucleosynthetic processes, and variations in 53Cr may be due to incorporation of differing amounts of live 53Mn. This 53Mn may be linearly, radially heterogeneous (Lugmair and Shukolyukov, 1998). Therefore, to investigate these issues, the isotopic composition of the implanted solar wind-bearing component was measured by thermal ionization mass spectrometry of acid etches of plagioclase grains from two Apollo 16 lunar soils. Small aliquots of the etches were spiked with Cr and Ca for isotope dilution. Spiking for Ca allows for the determination of etch depth and the Cr/Ca ratio which acts as a proxy for solar wind content. From these isotope dilution data, three important observations were made. First, the etch depth is in line with the solar wind implantation depths of noble gases (e.g. Eberhardt et al., 1970). Second, the Cr/Ca ratio falls off quickly with depth, peaks in the Etch 1 fraction of 62281 at 0.0006 and 0.0009 for 60601 and returns to the lunar Cr/Ca ratio of 0.00007 by weight by Etch 5. The coronal ratio is 0.224 (Anders and Grevesse, 1989). Third, the absolute abundance of Cr peaks in Etch 1 and falls off with progressive etches. Therefore, it is inferred that the solar wind-bearing component has been successfully isolated from the background lunar signature. The isotopic composition of this component is 3.9 ± 0.4 ϵ53Cr and 8.5 ± 0.6 ϵ54Cr for 62281 and 4.5 ± 0.1 and 15.0 ± 0.3, respectively, for 60601. These data are surprising. It will be shown that contributions from contamination, spallation and isobaric interferences are unlikely to be significant. The Cr data presented here are not linearly mass-dependent. Therefore, the linear, mass-dependent processes of volatilization, sputtering and vapor deposition are inadequate to explain these results. Alternative theories and resultant implications are discussed with emphasis on the hypothesis that these Cr results are attributable to spallation in the solar atmosphere.
机译：由于许多原因，铬同位素在科学上很有趣。例如， 53 Mn衰变为 53 Cr，这使得精细天文钟表得以发展， 54 Cr是富含中子的天文钟。认为是在Ia型超新星中产生的同位素，揭示了局部核合成过程， 53 Cr的变化可能是由于掺入了不同数量的活着的 53 Mn而引起的。该 53 Mn可能是线性的，径向异质的（Lugmair和Shukolyukov，1998）。因此，为了研究这些问题，通过热电离质谱法对两种阿波罗16号月球土壤中斜长石晶粒的酸蚀进行了热电离质谱分析，测量了植入的太阳含风组分的同位素组成。将少量等分试样的蚀刻液加入Cr和Ca进行同位素稀释。掺入Ca可以确定蚀刻深度和Cr / Ca之比，以替代太阳风含量。根据这些同位素稀释数据，得出了三个重要的观察结果。首先，蚀刻深度与稀有气体的太阳风注入深度一致（例如，Eberhardt等，1970）。其次，Cr / Ca比值随深度迅速降低，在60601的Etch 1分数62281中分别为0.0006和0.0009，并且按Etch 5的重量计返回月牙Cr / Ca比值为0.00007。冠状比为0.224（ Anders和Grevesse，1989年）。第三，Cr的绝对丰度在蚀刻1中达到峰值，并随着进行性蚀刻而下降。因此，可以推断出太阳风携带成分已经成功地与背景月球信号隔离了。该成分的同位素组成分别为3.9±0.4＆epsiv; 53 Cr和8.5±0.6＆epsiv; 54 Cr对于62281和4.5±0.1和15.0±0.3 60601.这些数据令人惊讶。结果表明，污染，散裂和等压干扰的影响不太明显。此处显示的Cr数据与质量不是线性相关的。因此，挥发，溅射和气相沉积的线性，质量相关的过程不足以解释这些结果。讨论了其他理论和由此产生的含义，重点是这些Cr结果归因于太阳大气层裂的假设。

著录项

  • 作者

    Kitts, Bunnie Kathleen.;

  • 作者单位

    Washington University.;

  • 授予单位 Washington University.;
  • 学科 Geochemistry.; Physics Astronomy and Astrophysics.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 129 p.
  • 总页数 129
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;天文学;
  • 关键词

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