Abstract
Lunar soils gradually become mature when they are exposed to a space environment, and nanophase metallic iron (npFe0) generates within them. npFe0 significantly changes the optical properties of lunar soils and affects the interpretation of the remotely sensed data of the lunar surface. In this study, a correlation analysis was conducted between npFe0 abundance and reflectance spectra at short wavelengths for lunar soil samples in four size groups based on their spectral and compositional data, collected by the Lunar Soil Characterization Consortium (LSCC). Results show that 540 nm single scattering albedo (SSA) of lunar soils correlates well with their corresponding npFe0 abundance for each size group of lunar soil samples. However, it is poorly correlated with npFe0 abundance when all size groups were considered because of the strong interference from grain size variation of lunar soils. To minimize the effect of grain size, the correlation of npFe0 abundance with the spectral ratio of 540 nm/810 nm SSA of all size groups for LSCC samples was calculated and results show that a higher correlation existed between them (R2 = 0.91). This ratio can serve as a simple empirical model for estimating npFe0 abundance in lunar soils. However, bias could be introduced to the estimation result when lunar soils possess a high content of agglutinitic glass and ilmenite. Our future work will focus on improving the model’s performance for these lunar soils.
Highlights
Space weathering represents any natural processes pursuing an airless planetary body that largely modify its surface material’s physical and compositional characteristics [1,2]
Our result suggests that this simple single scattering albedo (SSA) ratio is suited for npFe0 estimation of lunar soils showing a wide range of maturity
The 540 nm/810 nm SSA ratio is highly correlated to npFe0 abundance in lunar soils. This spectral ratio highlights the spectral importance of npFe0, reduces the grain size effect of lunar soils on the short wavelengths reflectance spectra and, can be considered as a useful spectral index for the
Summary
Space weathering represents any natural processes pursuing an airless planetary body that largely modify its surface material’s physical and compositional characteristics [1,2] It is mainly induced by solar wind ion implantation and micrometeoroid bombardment and has been generally applied to planetary observations, such as on the Moon or Mercury as well as asteroids [3,4,5,6]. We developed a simple empirical model to estimate npFe0 abundance in lunar soils from measured reflectance data This model correlates the npFe0 abundance with the ratio of single scattering albedo (SSA) of two wavelengths outside the absorption bands of lunar soils and requires no longer-wavelength spectral data. Grain size effects of lunar soils on npFe0 abundance estimation are partially removed according to this model
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