Master's und Bachelor's theses

UV laser ablation is a valuable extraction technique for the measurement of in situ ablated noble gases. In this project, we developed and established the use of the UV laser at ETH Zurich for meteorites and compared it to other extraction techniques such as conventional melt extraction in an oven and melting with an IR laser. In order to contribute to the understanding of differentiation in planetary bodies, we studied the micro-distribution of He and Ne isotopes in iron-rich meteorites, so-called winonaites and pallasites. UV laser ablation allowed the noble gas isotopic composition of single ablated minerals to be distinguished and revealed a chemistry-dependent cosmogenic composition (Figure).

Cosmic ray exposure (CRE) in space produces cosmogenic noble gases including ³He, ²¹Ne and ³⁸Ar, which are depleted in unexposed material. These can be used to calculate a “CRE age”, i.e., for how long a meteorite travelled from its parent body to the earth. However, discrepancies are often observed between CRE ages derived for the above isotopes for the same meteorite. We examined the effect of chemical heterogeneity on cosmogenic noble gas concentrations in the “ordinary” chondrite Knyahinya (chemical class LL/L5). Both noble gas and major element compositions of multiple small aliquots of Knyahinya were measured. The concentrations of the major elements were determined and some vary significantly from sample to sample and correlate with ³⁸Ar_cosm. The results were presented at an international conference. This study demonstrates that it is essential to measure both element concentrations and ³⁸Ar_cosm in the same sample aliquot to understand ³⁸Ar CRE ages.