View in EDS

An Analysis of the Exposure History of Apollo 17 Soils: Exploring Relationships Between Lunar Soil Maturity Indices.

Saved in:
Bibliographic Details
Title: An Analysis of the Exposure History of Apollo 17 Soils: Exploring Relationships Between Lunar Soil Maturity Indices.
Authors: McFadden, J. A.1 (AUTHOR) mcfadde8@purdue.edu, Thompson, M. S.1 (AUTHOR)
Source: Journal of Geophysical Research. Planets. Jan2026, Vol. 131 Issue 1, p1-15. 15p.
Subject Terms: *Radiation exposure, *Landslides, Lunar soil, Regolith, Electron microscopy, Space environment, Space flight to the moon
Company/Entity: Apollo program (U.S.)
Abstract: Analysis of space weathering features in lunar regolith using transmission electron microscopy (TEM) allows researchers to characterize the surface exposure timescale of individual grains from the Moon. TEM analysis of regolith grains from Apollo 17 scoop samples, collected from five different locations in the Taurus‐Littrow Valley (TLV), each with unique surface exposure histories, was conducted. Results show that the extent of space weathering in both mature and immature soil is significant and demonstrate that non‐agglutinitic grains in the samples have almost all experienced exposure to interplanetary space on the lunar surface. Solar energetic particle (SEP) track density derived exposure age distributions, when compared to observations from lunar core samples and regolith development models, suggest evidence of varying degrees of regolith mixing and overturn on the surface of the Moon. Exposure age distributions may be indicative of mixing of mature and immature regolith. Median exposure ages for mature soils saturate between 2.0 and 3.0 Ma while mean values will continue to increase with continued exposure on the lunar surface. The saturation of median exposure ages for individual grains may be attributed to high rates of reworking on the top millimeter of regolith. Recent analysis of LROC reflectance images found that the TLV light mantle could form from reoccurring landslide events. Maximum SEP exposure ages for particles in light mantle soils appear to indicate the relative landslide depositional order. Together, these observations can be used to interpret the mixing and depositional histories of geologic units in the TLV. Plain Language Summary: We examined characteristics associated with surface exposure on the lunar surface in scoop samples collected from the Apollo 17 field site. When examining irradiation damage in surface‐exposed grains, we found that exposure age distributions are either right skewed or normal, and that median exposure age values tend to saturate over the course of a few million years, while mean values will continue to increase with longer exposure. Right skewed distributions and deviations in median and mean trends can indicate that a soil has undergone regolith mixing. The saturation of median values may indicate regolith reworking timescales from high frequencies of small impactors which mix the top millimeter of regolith, after which a significant proportion of surface exposed grains may have migrated below the influence of solar irradiation. Remote sensing data showed that the Apollo 17 light mantle could be from two landslide depositional events. Results in this work suggest that grains with the highest amounts of irradiation damage may indicate the relative exposure and depositional histories of the Apollo 17 light mantle landslides. Key Points: Mature and immature soils contain 97%–100% non‐agglutinitic, surface exposed fragmentsSEP track derived exposure age distributions may indicate high reworking rates from small impactors over million‐year timescalesMean, median, and maximum exposure ages correlate with mixing models and the depositional history of landslides in the Taurus‐Littrow Valley [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Planets is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: GreenFILE
Description
Abstract:Analysis of space weathering features in lunar regolith using transmission electron microscopy (TEM) allows researchers to characterize the surface exposure timescale of individual grains from the Moon. TEM analysis of regolith grains from Apollo 17 scoop samples, collected from five different locations in the Taurus‐Littrow Valley (TLV), each with unique surface exposure histories, was conducted. Results show that the extent of space weathering in both mature and immature soil is significant and demonstrate that non‐agglutinitic grains in the samples have almost all experienced exposure to interplanetary space on the lunar surface. Solar energetic particle (SEP) track density derived exposure age distributions, when compared to observations from lunar core samples and regolith development models, suggest evidence of varying degrees of regolith mixing and overturn on the surface of the Moon. Exposure age distributions may be indicative of mixing of mature and immature regolith. Median exposure ages for mature soils saturate between 2.0 and 3.0 Ma while mean values will continue to increase with continued exposure on the lunar surface. The saturation of median exposure ages for individual grains may be attributed to high rates of reworking on the top millimeter of regolith. Recent analysis of LROC reflectance images found that the TLV light mantle could form from reoccurring landslide events. Maximum SEP exposure ages for particles in light mantle soils appear to indicate the relative landslide depositional order. Together, these observations can be used to interpret the mixing and depositional histories of geologic units in the TLV. Plain Language Summary: We examined characteristics associated with surface exposure on the lunar surface in scoop samples collected from the Apollo 17 field site. When examining irradiation damage in surface‐exposed grains, we found that exposure age distributions are either right skewed or normal, and that median exposure age values tend to saturate over the course of a few million years, while mean values will continue to increase with longer exposure. Right skewed distributions and deviations in median and mean trends can indicate that a soil has undergone regolith mixing. The saturation of median values may indicate regolith reworking timescales from high frequencies of small impactors which mix the top millimeter of regolith, after which a significant proportion of surface exposed grains may have migrated below the influence of solar irradiation. Remote sensing data showed that the Apollo 17 light mantle could be from two landslide depositional events. Results in this work suggest that grains with the highest amounts of irradiation damage may indicate the relative exposure and depositional histories of the Apollo 17 light mantle landslides. Key Points: Mature and immature soils contain 97%–100% non‐agglutinitic, surface exposed fragmentsSEP track derived exposure age distributions may indicate high reworking rates from small impactors over million‐year timescalesMean, median, and maximum exposure ages correlate with mixing models and the depositional history of landslides in the Taurus‐Littrow Valley [ABSTRACT FROM AUTHOR]
ISSN:21699097
DOI:10.1029/2025JE009185