Using the potassium-argon laser experiment (KArLE) to date ancient, low-K chondritic meteorites

1,2,3Fanny CATTANI,2Barbara A. COHEN,4Cameron M. MERCER,5Agnes J. DAHL
Meteoritics & Planetary Science 58, 591-611 Open Access Link to Article [doi: 10.1111/maps.13960]
1The Catholic University of America, Washington, DC, USA
2Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
3Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, Maryland, USA
4U.S. Geological Survey, Geology, Geophysics, Geochemistry Science Center, Denver, Colorado, USA
5Department of Earth Sciences, University of Gothenburg, Goteborg, Sweden
Published by arrangement with John Wiley & Sons

Several laboratories have been investigating the feasibility of in situ K-Ar dating foruse in future landing planetary missions. One drawback of these laboratory demonstrations isthe insufficient analogy of the analyzed analog samples with expected future targets. Wepresent the results obtained using the K-Ar laser experiment (KArLE) on two old and K-poorchondritic samples, Pułtusk and Hvittis, as better lunar analogs. The KArLE instrument useslaser ablation to vaporize rock samples and quantifies K content by laser-induced breakdownspectroscopy (LIBS), Ar by quadrupole mass spectrometry (QMS), and ablated mass by laserprofilometry. We performed 64 laser ablations on the chondrites to measure spots with a rangeof K2O and Ar content and used the data to construct isochrons to determine the chondriteformation age. The KArLE isochron ages on Pułtusk and Hvittis are 5059892 Ma and4721793 Ma, respectively, which is within the uncertainty of published reference ages, andinterpreted as the age of their formation. The uncertainty (2σ) on the KArLE ages obtained inthis study is better than 20% (18% for Pułtusk and 17% for Hvittis). The precision, whichcompares our obtained ages to the reference ages, is also better than 20% (11% for Pułtuskand 4% for Hvittis). These results are encouraging for understanding the limits of thistechnique to measure ancient planetary samples and for guiding future improvements to theinstrument.


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