Far‐Ultraviolet Photometric Response of Apollo Soil 10084

Abstract

We report new measurements of the far‐ultraviolet (FUV) bidirectional reflectance of Apollo soil 10084 from the Southwest Research Institute ultraviolet reflectance chamber. The bidirectional reflectance distribution function of this mare soil, enriched in Ti and Fe content, is rather featureless in the FUV wavelength region of 115–180 nm, except for a small blue slope, which is attributed to the effects of space weathering. This soil preferentially backscatters FUV photons as indicated by the angular distribution of the bidirectional reflectance. The phase curves are fitted with a simplified Hapke photometric model to derive the average volume single scattering albedo and scattering phase function of the mare lunar grains. The albedo values and the backscattering nature reported here are consistent with Lunar Reconnaissance Orbiter's Lyman‐Alpha Mapping Project ultraviolet imaging spectrograph observations, despite expected morphological differences.

Far‐Ultraviolet Photometric Characteristics of JSC‐1A and LMS‐1 Lunar Regolith Simulants: Comparative Investigations With Apollo 10084

“…In each instance, the enhancement of reflectance in the FUV compared to visible (∼400 nm) wavelengths was attributed to the presence of npFe 0 resultant of solar wind and micrometeoroid bombardment of iron‐bearing minerals in the examined soils. Previous work on Apollo 10084 (Raut et al., 2018) has confirmed the blue slope in the FUV (115–200 nm) reflectance of this mature lunar mare soil, and also observed anisotropic backscattering at these FUV wavelengths, which may be attributable to space weathering features. Furthermore, observations of the lunar surface using the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project (LAMP) data show FUV spectral bluing in both mare and highland regions (Liu et al., 2018) and show that the Lyman‐α albedo is greater for more mature regions of the lunar surface as opposed to less mature regions (Byron et al., 2019).…”

The Far Ultraviolet Wavelength Dependence of the Lunar Phase Curve as Seen by LRO LAMP

“…Although much less significant, multiple scattering cannot be entirely ignored in FUV, as some photons may still be able to penetrate more porous part of lunar regolith and are scattered multiple times, which may cause weak phase reddening phenomenon in FUV. However, other effects such as the surface roughness cannot be excluded, as pointed by Schröder et al (), which needs future laboratory studies and simulations at FUV wavelengths using the new developed Southwest Ultraviolet Reflectance Chamber facility (Raut et al, ).…”

LRO‐LAMP Survey of Lunar South Pole Cold Traps: Implication for the Presence of Condensed H2O

“…We simulate albedo spectra assuming high and low regolith porosity within cold traps such that P = 0.75 ( K = 1.36) for high porosity (low compaction) and P = 0.30 ( K = 3.21) for low porosity (high compaction) (Raut et al., 2018). Further, μ 0 is the cosine of the incidence angle (or reflectance angle due to reciprocity).…”