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

Liu, Y.; Retherford, Kurt D.; Greathouse, Thomas; Raut, U.; Mandt, K.; Hendrix, Amanda; Cahill, Joshua; Gladstone, G. R.; Grava, C.; Egan, A. F.; Kaufmann, D. E.; Pryor, W. R.

doi:10.1029/2018je005580

Cited by 11 publications

(20 citation statements)

References 56 publications

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“…In that study, wavelength‐dependent asymmetry parameters (g) were derived for highlands and mare terrains using data in the 27–73° phase angle range using a single‐lobed Henyey‐Greenstein phase function. Based on those results, we use g = −0.48 in this analysis, which is well within the error bars of Liu et al () for both highlands and mare regions at all wavelengths considered here. Hendrix et al () showed that the lunar spectral slopes measured in the 164–173 nm region are controlled by level of hydration and are found to be diurnally variable; an adjacent spectral region (175–190 nm) is not affected by hydration and shows no trend with local time, supporting the case that the slopes in the 164–173 nm region—and their variation throughout the lunar day—are indeed due to hydration.…”

Section: Discussionsupporting

confidence: 72%

Diurnally Migrating Lunar Water: Evidence From Ultraviolet Data

Hendrix

Crider

Farrell

et al. 2019

Geophysical Research Letters

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Data from the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project and Diviner are consistent with surface water on the Moon varying in abundance with both terrain type and local time/temperature. A thermal desorption model including latitudinally varying desorption activation energy reproduces the observations. We interpret the observed variability in spectral slopes as water molecules in the uppermost lunar regolith (<1% of a monolayer) thermally adsorbing and desorbing from grains depending upon the local temperature and availability of chemisorption sites. The Lyman Alpha Mapping Project data also demonstrate that in the Earth's magnetotail, where the solar wind source of protons is absent, a decrease in H2O on the surface is not observed. This rules out a steady state process involving a prompt solar wind source and favors a migration mechanism for the distribution of adsorbed water on the Moon.

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Section: Discussionsupporting

confidence: 72%

Diurnally Migrating Lunar Water: Evidence From Ultraviolet Data

Hendrix

Crider

Farrell

et al. 2019

Geophysical Research Letters

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“…This tool enables large spatial coverage and high signal‐to‐noise ratio at low spectral resolution. The second tool we use is the LAMP Spectral Mapper (Byron et al, ; Liu et al, ; Mandt et al, ), which produces 3‐D data cubes over a specified region of interest at up to ~250‐m/pixel spatial resolution. This tool enables higher spectral resolution (68 wavelength bins at 2‐nm resolution) over smaller areas of the lunar surface.…”

Section: Methodsmentioning

confidence: 99%

“…The mapper tools calculate the radiance factor I/F (where I is the radiance measured by LAMP and F is the flux incident upon the surface) by dividing the LAMP‐measured brightness by TIMED SEE solar spectrum data (Woods et al, ), and then correcting for observational geometry using the photometric correction described in Liu et al (). The corrected reflectance product reported in this work is a normalized radiance factor, defined as

normalI / F_{norm} = \frac{normalI / normalF}{{normalr}_{i, e, g}} r_{i_{s}, e_{s}, g_{s}}

where

r_{i_{s}, e_{s}, g_{s}}

is the simplified Hapke bidirectional reflectance at the standard angles i = g = 30° and e = 0° (Hapke, ).…”

Section: Methodsmentioning

confidence: 99%

Far‐UV Observations of Lunar Rayed Craters with LRO‐LAMP

et al. 2020

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Using data from the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP), we investigate the spectral properties of rayed craters in the far‐ultraviolet (FUV). Because LAMP is sensitive to the uppermost layer of the lunar surface and regolith grains, it is ideal for characterizing regolith maturity and space weathering products such as submicroscopic iron. We find that crater rays from a survey of the largest Copernican‐age craters have high Off‐band (155–190 nm)/On‐band (130–155 nm) albedo (Off/On) LAMP product ratios, consistent with immature regolith and low amounts of submicroscopic iron. The Off/On ratio of the highlands crater rays decreases linearly over time (0.095 per 100 My), and we use this trend to estimate the age of Jackson crater (~152 My). Some large young highlands craters (e.g., Tycho, Jackson, Giordano Bruno, and Necho) display lower ratio halos around the crater cavity, at regions where previous studies have suggested abundant impact melt exists. The lower Off/On ratio is likely due to the increased glass component of the regolith at these highlands regions, which would act to increase absorption at Off‐band wavelengths. We also find that ejecta blankets from large maria craters (e.g., Copernicus and Aristillus) have a similar Off/On ratio to the mature background highlands. This supports previous findings that determined that the rays from these craters are composed of highlands material excavated from beneath the maria and subsequently weathered to maturity.

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“…The blue slope persists in the single scattering albedo spectra, as w decreases with increasing wavelengths above 130 nm. We find reasonable agreement between the laboratory and LAMP w ( Figure 6, top panel) derived from observations of a sample mare region (Liu et al, 2016(Liu et al, , 2017, despite expected differences in soil porosity/morphology. Apollo soil in the laboratory likely lacks the fairy castle-like structure formed via tribocharging in the low lunar-gravity environment.…”

Section: Journal Of Geophysical Research: Planetsmentioning

confidence: 99%

Far‐Ultraviolet Photometric Response of Apollo Soil 10084

et al. 2018

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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.

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

Cited by 11 publications

References 56 publications

Diurnally Migrating Lunar Water: Evidence From Ultraviolet Data

Diurnally Migrating Lunar Water: Evidence From Ultraviolet Data

Far‐UV Observations of Lunar Rayed Craters with LRO‐LAMP

Far‐Ultraviolet Photometric Response of Apollo Soil 10084

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