Space weathering and compositional stratigraphy of Apollo 17 double drive tube 73001/2

Abstract

The double drive tube 73001/2 is a regolith core and was collected on the Light Mantle at Station 3 during the Apollo 17 mission. This core preserves an in situ record of space weathering and compositional stratigraphy, providing insights to the thickness of the Light Mantle and the local regolith reworking time scale. We measured the dissection passes 2–3 of core 73002 and passes 1–3 of core 73001 using a high-spatial resolution multispectral imaging system, and analyzed the space weathering products on individual soil grains from pass 2 of 73002 using transmission electron microscopy analysis. Our results indicate that the double drive tube 73001/2 contains a zone of submature to mature soil overlying a zone of immature soil. The top more mature zone is about 6–7 cm thick, corresponding to the local regolith reworking depth. On the basis of this depth, the estimated regolith reworking time scale for core 73001/2 is approximately 9–13 million years. Due to mixing with basaltic materials from the central valley, the top mature zone exhibits an FeO content 1–3 wt% higher than the underlying immature soils. Spectral images indicate that the double drive tube failed to penetrate the bottom of the Light Mantle but may have reached the edge of the landslide-valley material mixing zone. The local landslide deposit is thicker than the maximum sampling depth of the double drive tube, which is about 70 cm.