We are developing an in situ, rock‐dating spectrometer for spaceflight called the Chemistry, Organics, and Dating EXperiment (CODEX). CODEX will measure Rb‐Sr compositions and determine ages of samples on the Moon or Mars, and can be augmented to obtain Pb‐Pb ages. Coupling Rb‐Sr and Pb‐Pb measurements broadens the suite of samples that can be dated, and could provide tests of concordance. Here we assess whether geochronologically meaningful Pb‐Pb data could be measured in situ by tuning the prototype CODEX to acquire Pb‐Pb data from a suite of well‐characterized specimens from the Earth, Moon, and Mars. For Keuhl Lake zircon 91500 our ²⁰⁷Pb/²⁰⁶Pb age of 1090 ± 40 Ma is indistinguishable from the accepted age. In each of the Martian meteorites we studied, we could not resolve more than a single component of Pb, and could not uniquely determine ages; nevertheless, our isotopic measurements were consistent with most previous analyses. On the other hand, we uniquely determined ages for three lunar meteorites. Our age for MIL 05035 is 3550 ± 170 Ma, within 2σ of published ages for this specimen, in spite of it having <1 ppm Pb. LAP 02205 was contaminated by terrestrial Pb, but by filtering our data to exclude the most contaminated spots, we obtained an age of 3010 ± 70 Ma, coincident with published values. Finally, our age for NWA 032 is nearly 1000 Ma older than its age determined from other isotopic systems, and is supported by additional Pb measurements made after chemical leaching.

中文翻译：

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使用共振电离质谱法对地球和外星样品进行 Pb-Pb 定年


我们正在开发一种用于航天的原位岩石测年光谱仪，称为化学、有机物和测年实验（CODEX）。 CODEX 将测量 Rb-Sr 成分并确定月球或火星上样本的年龄，并可对其进行增强以获得 Pb-Pb 年龄。 Rb-Sr 和 Pb-Pb 测量的耦合扩大了可测年的样品范围，并可以提供一致性测试。在这里，我们评估是否可以通过调整原型 CODEX 从地球、月球和火星的一组特征良好的样本中获取 Pb-Pb 数据来现场测量具有地质年代学意义的 Pb-Pb 数据。对于 Keuhl Lake 锆石 91500，我们的²⁰⁷ Pb/ ²⁰⁶ Pb 年龄为 1090 ± 40 Ma，与公认的年龄无法区分。在我们研究的每块火星陨石中，我们无法解析出超过单一的铅成分，也无法唯一地确定年龄；尽管如此，我们的同位素测量结果与大多数以前的分析是一致的。另一方面，我们独特地确定了三块月球陨石的年龄。我们对 MIL 05035 的年龄为 3550 ± 170 Ma，与该样本公布的年龄相差 2σ 以内，尽管它的 Pb 含量<1 ppm。 LAP 02205 受到陆地铅污染，但通过过滤我们的数据以排除污染最严重的点，我们获得了 3010 ± 70 Ma 的年龄，与公布的值一致。最后，我们对 NWA 032 的年龄比其他同位素系统确定的年龄要早近 1000 Ma，并且得到化学浸出后进行的额外 Pb 测量的支持。