An acid-etch study of the Kapoeta achondrite: Implications for the argon-36/argon-38 ratio in the solar wind

Abstract— Noble gases were measured in the Kapoeta achondrite by means of step-wise closed-system acid-etching with H₂SO₃. Isotopic ratios indicate that He, Ne and Ar are primarily solar in origin, although elemental abundance ratios indicate that the He and Ne have been significantly depleted relative to the Ar. Xenon is dominated by a typical trapped meteoritic component, and the same is probably true for Kr. The initial 11% of the Ar released from the sample by acid etching has a cumulative ³⁶Ar/³⁸Ar ratio of 5.58 ± 0.03, which indicates that the solar wind at some time in the past had a ³⁶Ar/³⁸Ar ratio significantly above previous values suggested for this ratio.