Mössbauer Investigation of Apollo 11 Lunar Samples

Abstract

Mössbauer spectroscopy has been used to study samples of lunar dust and rocks returned on the Apollo 11 mission. In addition to iron metal, the Fe²⁺ minerals ilmenite, pyroxene, troilite, and iron-containing glass were identified. There was no evidence for Fe³⁺ or for unusual iron charge-state ions. Heavy liquids were used to separate the dust into fractions of differing specific-gravity ranges. The light part, which contained most of the glass, also contained most of the iron metal. The antiferromagnetic transition in the ilmenite of the dust and rocks was investigated by the constant-velocity counting rate method. All samples studied had transition temperatures of 57° ± 2°K, corresponding to stoichiometric FeTiO₃. A magnetically separated sample of rock 10057 was used to clarify the nature of the magnetically ordered phases in the rocks, principally troilite with minor amounts of iron metal. As illustrated by the ilmenite iron to silicate iron ratio, the compositions of the dust and breccia were similar, but differed significantly from the typical rock compositions.

Work supported in part by NASA Contract NAS 9-1028. A major part of this paper reviews results presend by A. H. Muir, Jr., R. M. Housley, R. W. Grant, M. Abdel-Gawad, and M. Blander at the Apollo 11 Lunar Sciene Conference, reference [5], with emphasis on the Mössbauer spectrosopy aspects of that work.