A new chronology of the early solar system

同位素地球化学的最新分析进展已经开始导致我们对早期太阳系年代学的理解发生根本性的改变。经典模型认为球粒陨石是最古老、最原始的太阳系物质，构成行星和星子。许多星子随后分化并发展出金属地核和硅酸盐地幔。结合Hf-W， U-Pb和Al-Mg年代学现在表明，铁陨石是更古老的星子的残余物，而构成球粒陨石的一些物质是来自这些早期形成的星子的再加工物质。在两个相关的项目中，我们将通过(1)使用不同的时计（即Hf-W）对早期太阳系物质进行定年，以及(2)通过测量180Ta和180W来评估早期太阳系的均质化过程，来评估新提出的时间顺序方案。这两种同位素都非常罕见，对核合成条件极其敏感。因此，在过去，足够精确的测量几乎是不可能的。解决这些关键问题的先决条件是使用最先进的质谱仪（新一代多收集器ICPMS）进行相关分析。在德国的大学或研究机构中，目前还没有这样的仪器用于宇宙化学的研究。

Recent analytical advances in isotope geochemistry have started to lead to a fundamental revision of our understanding of early solar system chronology. Classical models regarded chondritic meteorites as the oldest and most primitive solar system matter, building planets and planetesimals. Many planetesimals subsequently differentiated and developed metal cores and silicate mantles. Combined Hf-W, U-Pb and Al-Mg chronology now suggests that iron meteorites are remnants of even older planetesimals and that some of the material that makes up chondritic meteorites is reprocessed material from these early formed planetesimals. In two related projects we will evaluate the newly proposed chronological scheme by (1) dating of early solar system materials with different chronometers (i.e., Hf-W) and (2) by assessing homogenisation processes in the early solar system through 180Ta and 180W measurements. Both isotopes are very rare and extremely sensitive to nucleosynthetic conditions. Hence, sufficiently precise measurements were nearly impossible in the past. A prerequisite for resolving these key issues is the availability of a state of the art mass spectrometer (new generation Multicollector ICPMS) for the relevant analyses. No such instrument is currently used for research in cosmochemistry at a German university or research institution.