This project studies how hydrogen and redox state gradients are preserved in volcanic glasses on the lunar surface, comparing the specially curated pristine Apollo samples to previously studied lunar glasses that have been exposed to air for decades. It will provide the most accurate estimates to date of the oxidation state of lunar volcanic glasses and their source regions. This project will also constrain the intrinsic oxygen fugacity (fO2) of the lunar interior because these pyroclastic glass beads provide the most primitive samples available for the Moon’s mantle. Recent preparatory work on lunar samples stored without special containment suggests that some lunar volcanic glass beads possess surprisingly high ferric iron contents, which may reflect oxidation due to eruptive or post-eruptive degassing of H or OH from the cooling beads. Other beads from different locations are zoned to lower ferric iron rims, possibly representing a subsequent reduction of iron in the lunar vacuum. This project will also relate the oxidation state measurements to reflectance data that quantify the hydrogen contents of the lunar glass beads at the same scale as the redox measurements. Because hydrogen and ferric iron contents may be related, these complementary data sets will further our understanding of the mechanisms by which pre-and posteruptive hydrogen and ferric iron are related, and inform oxidative and reductive conditions in lunar igneous materials and the lunar interior. To truly understand the fO2 and FH2 evolution of the lunar interior, it is critical to compare pristine lunar samples to previously-studied ones that have had lengthy exposures to Earth’s oxygen-rich atmosphere.
This team includes members from the Planetary Science Institute, Mount Holyoke College, the University of Tennessee (Knoxville), the University of Chicago, Argonne National Laboratory, and the University of Massachusetts (Amherst).
Contact Information: M. Darby Dyar, [email protected]