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K M Rockow - One of the best experts on this subject based on the ideXlab platform.
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Lunar meteorite queen alexandra range 93069 and the iron concentration of the Lunar Highlands surface
Meteoritics & Planetary Science, 1996Co-Authors: K M RockowAbstract:RANDY L. KOROTEV*, BRADLEY L. JOLLIFF AND KAYLYNN M. ROCKOW _..y'_ %,: ,-_//Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences,Washington University, St. Louis, Missouri 63130, USA*Correspondence author's e-mail address: r[k@levee.wustl.edu(Received 1995 December 19, accepted in revised form 1996 August 3)(Submitted as part of a series of papers on Queen Alexandra Range 93069 and other Lunar meteorites)Abstract--Lunar meteorite Queen Alexandra Range 93069 is a clast-rich, glassy-matrix regolith breccia offerroan, highly aluminous bulk composition. It is similar in composition to other feldspathic Lunar meteoritesbut differs in having higher concentrations of siderophile elements and incompatible trace elements. Basedon electron microprobe analyses of the fusion crust, glassy matrix, and clasts, and instrumental neutron acti-vation analysis of breccia fragments, QUE 93069 is dominated by nonmare components of ferroan, noritic-anorthosite bulk composition. Thin section QUE 93069,31 also contains a large, impact-melted, partiallydevitrified clast of magnesian, anorthositic-norite composition. The enrichment in Fe, Sc, and Cr and lowerMg/Fe ratio of Lunar meteorites Yamato 791197 and Yamato 82192/3 compared to other feldspathic Lunarmeteorites can be attributed to a small proportion (5-10%) of Iow-Ti mare basalt. It is likely that the non-mare components of Yamato 82192/3 are similar to and occur in similar abundance to those of Yamato86032, with which it is paired. There is a significant difference between the average FeO concentration ofthe Lunar Highlands surface as inferred from the feldspathic Lunar meteorites (mean: -5.0%; range: 4.3-6.1%) and a recent estimate based on data from the Clementine mission (3.6%).INTRODUCTIONLunar meteorite QUE 93069, a 21 g stone, was collected in An-tarctica -45 km from the collection site of the paired Lunar mete-orites MAC 88104 and MAC 88105 (hereafter: MAC 88104/5). Wereport here results of chemical analysis and petrographic examina-tion of QUE 93069 and compare those results with previous resultsfor MAC 88104/5 and other meteorites from the Lunar Highlands.We also report new data for Lunar meteorite Yamato 86032, some ofwhich were presented previously in a figure in Jolliff et al. (1991).Of the Lunar meteorites recovered so far, about half have highlyfeldspathic compositions (>25% A1203) and are thought to repre-sent several random locations in the Lunar Highlands (e.g., Palme etal., 1991; Warren, 1994). Most contain regolith components andthus appear to represent surface and near surface materials. The lowconcentrations of incompatible trace elements (ITE) in the feldspathicLunar meteorites compared to highland samples collected by theApollo missions have been taken to mean that the feldspathic mete-orites derive from locations on the Moon distant from the Apollolanding sites (e.g., Pieters et al., 1983; Korotev et al., 1983; Warrenand Kallemeyn, 1986; Jolliffetal., 1991; Palme etal., 1991). Thus,their compositions and components have special significance as theytell us about the nature of the Lunar Highlands far removed from anduncontaminated by mafic, ITE-rich, impact-melt qiecta from the largenearside basins. Compositional differences among the meteoritesand between the meteorites and the Apollo samples provide valuableinformation about regional variations in the lithologies and compo-sition of the Lunar surface. This type of information is particularlyimportant now that global, remotely sensed compositional data fromthe Clementine mission are available, because the feldspathic Lunarmeteorites provide a degree of "ground truth" lbr the vast otherwiseunsampled regions of the Highlands.In this paper, we examine the causes of some of the compositionaldifferences among the feldspathic Lunar meteorites, specifically, theeffects of different proportions of ferroan (low Mg/Fe) and magne-sian (high Mg/Fe) nonmarc components and different proportions ofmare-derived components. We also consider the implications of l:econcentrations in the feldspathic Lunar meteorites for estimates (Luceyet al., 1995) of the average surface Fe concentration determinedfrom Clementine data.SAMPLES STUDIED AND ANALYTICAL PROCEDURESFor QUE 93069, our study is based on bulk chemical analysis of five50-70-rag fragments (primary splits 9, 10, 11, 20, and 21; Fig. I) andpetrographic study of a thin section (93069,31). We broke each of the fivefragments with an agate mortar and pestle and divided all material fromeach fragment into two or three subsplits designated A, B, and C. In total,1I subsplits were prepared, which ranged in mass from 20 to 32 mg; ten ofthese were dominated by one large chip. Results of electron microprobeanalysis (EMPA) of glass and minerals in the thin section and instrumentalneutron activation analysis (INAA) of the subsplits are presented in TablesI-7.For Yamato 86032, we received 0.5 g of material as nine fragmcnlscollectively designated Yamato 86032, I 15. We broke four of the fragmentsinto smaller chips with an agate mortar and pestle. For INAA, we analyzed20 subsplits: 14 dark chips that appeared relatively devoid of large clasts(3-1 I mg each), 5 chips that were dominated by whitish clastic material (2-7 mg each), and a sample of residual fines (11 mg) [br a total of 114 mg InTable 8, column I contains the mass-weighted mean concentrations of theclast-poor chips and the residual fines subsplit; the sample standard devia-tion and minimum and maximum concentrations observed for these 15 sub-splits are listed in columns 5, 6, and 7. Column 2 contains mass-weightedmean concentrations for the five whitish, clast-rich chips, which were allsimilar in composition. We prepared fused beads for major element analysisby I';MPA of seven of the dark, matrix-rich chips analyzed by INAA andthin sections from three of the remaining large unirradiated fragments (A -107 mg, B = 22 mg, and C = 17 rag). The average major-element composi-lion of the fused beads is given in Table 9 along with the compositions of athick glass vein and the glassy breccia matrix taken from thin section A.All analytical procedures were the same as those described in Jolliff etaL (1991), except that for QUE 93069 the samples received a 24 h irradia-lion.RESULTSPetrography of QUE 93069Our petrographic description is based primarily on examinationof thin section QUE 93069,31 and to a lesser extent on examinationby binocular microscope of the chips analyzed by INAA. The rock909
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Lunar meteorite queen alexandra range 93069 and the iron concentration of the Lunar Highlands surface
Meteoritics & Planetary Science, 1996Co-Authors: K M RockowAbstract:Lunar meteorite Queen Alexandra Range 93069 is a clast-rich, glassy-matrix regolith breccia of ferroan, highly aluminous bulk composition. It is similar in composition to other feldspathic Lunar meteorites but differs in having higher concentrations of siderophile elements and incompatible trace elements. Based on electron microprobe analyses of the fusion crust, glassy matrix, and clasts, and instrumental neutron activation analysis of breccia fragments, QUE 93069 is dominated by nonmare components of ferroan, noritic- anorthosite bulk composition. Thin section QUE 93069,31 also contains a large, impact-melted, partially devitrified clast of magnesian, anorthositic-norite composition. The enrichment in Fe, Sc, and Cr and lower Mg/Fe ratio of Lunar meteorites Yamato 791197 and Yamato 82192/3 compared to other feldspathic Lunar meteorites can be attributed to a small proportion (5-10%) of low-Ti mare basalt. It is likely that the non- mare components of Yamato 82192/3 are similar to and occur in similar abundance to those of Yamato 86032, with which it is paired. There is a significant difference between the average FeO concentration of the Lunar Highlands surface as inferred from the feldspathic Lunar meteorites (mean: approx. 5.0%; range: 4.3-6.1 %) and a recent estimate based on data from the Clementine mission (3.6%).
J.w. Head - One of the best experts on this subject based on the ideXlab platform.
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the steepest slopes on the moon from Lunar orbiter laser altimeter lola data spatial distribution and correlation with geologic features
Icarus, 2016Co-Authors: M A Kreslavsky, J.w. HeadAbstract:Abstract We calculated topographic gradients over the surface of the Moon at a 25 m baseline using data obtained by the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. The relative spatial distribution of steep slopes can be reliably obtained, although some technical characteristics of the LOLA dataset preclude statistical studies of slope orientation. The derived slope-frequency distribution revealed a steep rollover for slopes close to the angle of repose. Slopes significantly steeper than the angle of repose are almost absent on the Moon due to (1) the general absence of cohesion/strength of the fractured and fragmented megaregolith of the Lunar Highlands, and (2) the absence of geological processes producing steep-slopes in the recent geological past. The majority of slopes steeper than 32°–35° are associated with relatively young large impact craters. We demonstrate that these impact craters progressively lose their steepest slopes. We also found that features of Early Imbrian and older ages have almost no slopes steeper than 35°. We interpret this to be due to removal of all steep slopes by the latest basin-forming impact (Orientale), probably by global seismic shaking. The global spatial distribution of the steepest slopes correlates moderately well with the predicted spatial distribution of impact rate; however, a significant paucity of steep slopes in the southern farside remains unexplained.
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detecting volcanic resurfacing of heavily cratered terrain flooding simulations on the moon using Lunar orbiter laser altimeter lola data
Planetary and Space Science, 2013Co-Authors: J L Whitten, J.w. HeadAbstract:Abstract Early extrusive volcanism from mantle melting marks the transition from primary to secondary crust formation. Detection of secondary crust is often obscured by the high impact flux early in solar system history. To recognize the relationship between heavily cratered terrain and volcanic resurfacing, this study documents how volcanic resurfacing alters the impact cratering record and models the thickness, area, and volume of volcanic flood deposits. Lunar Orbiter Laser Altimeter (LOLA) data are used to analyze three different regions of the Lunar Highlands: the Hertzsprung basin; a farside heavily cratered region; and the central Highlands. Lunar mare emplacement style is assumed to be similar to that of terrestrial flood basalts, involving large volumes of material extruded from dike-fed fissures over relatively short periods of time. Thus, each region was flooded at 0.5 km elevation intervals to simulate such volcanic flooding and to assess areal patterns, thickness, volumes, and emplacement history. These simulations show three primary stages of volcanic flooding: (1) Initial flooding is largely confined to individual craters and deposits are thick and localized; (2) basalt flows breach crater rim crests and are emplaced laterally between larger craters as thin widespread deposits; and (3) lateral spreading decreases in response to regional topographic variations and the deposits thicken and bury intermediate-sized and larger craters. Application of these techniques to the South Pole-Aitken basin shows that emplacement of ∼1−2 km of cryptomaria can potentially explain the paucity of craters 20–64 km in diameter on the floor of the basin relative to the distribution in the surrounding Highlands.
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Lunar floor fractured craters classification distribution origin and implications for magmatism and shallow crustal structure
Journal of Geophysical Research, 2012Co-Authors: L M Jozwiak, J.w. Head, Maria T Zuber, David E Smith, Gregory A NeumannAbstract:[1] Floor-Fractured Craters (FFCs) are a class of Lunar craters characterized by anomalously shallow floors cut by radial, concentric, and/or polygonal fractures; additional interior features are moats, ridges, and patches of mare material. Two formation mechanisms have been hypothesized—floor uplift in response to shallow magmatic intrusion and sill formation, and floor shallowing in response to thermally driven viscous relaxation. This study combines new Lunar Orbiter Laser Altimeter (LOLA) and Lunar Reconnaissance Orbiter Camera (LROC) data to characterize and categorize the population of FFCs and map their distribution on the Moon, and uses variations in floor-fractured crater morphology and regional distribution to investigate the proposed formation mechanisms. The population of FFCs was categorized according to the classes outlined by Schultz (1976). The distribution of these FFC categories shows an evolution of crater morphology from areas adjacent to Lunar impact basins to areas in the Lunar Highlands. We propose that this trend is supportive of formation by shallow magmatic intrusion and sill formation—crustal thickness determines the magnitude of magmatic driving pressure, and thus either piston-like floor uplift for high magnitude, or a convex floor profile for low magnitude. Predictions from previous studies modeling viscous relaxation are inconsistent with the observed altimetric profiles of FFCs. Hence our analysis favors FFC formation by shallow magmatic intrusion, with the variety of FFC morphologies being intimately linked with location and crustal thickness, and the driving pressure of the intrusion. Data from the GRAIL (Gravity Recovery and Interior Laboratory) mission will help to test these conclusions.
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global surface slopes and roughness of the moon from the Lunar orbiter laser altimeter
Journal of Geophysical Research, 2011Co-Authors: M A Rosenburg, Erwan Mazarico, J.w. Head, David E Smith, Gregory A Neumann, O Aharonson, M A KreslavskyAbstract:[1] The acquisition of new global elevation data from the Lunar Orbiter Laser Altimeter, carried on the Lunar Reconnaissance Orbiter, permits quantification of the surface roughness properties of the Moon at unprecedented scales and resolution. We map Lunar surface roughness using a range of parameters: median absolute slope, both directional (along‐track) and bidirectional (in two dimensions); median differential slope; and Hurst exponent, over baselines ranging from ∼17 m to ∼2.7 km. We find that the Lunar Highlands and the mare plains show vastly different roughness properties, with subtler variations within mare and Highlands. Most of the surface exhibits fractal‐like behavior, with a single or two different Hurst exponents over the given baseline range; when a transition exists, it typically occurs near the 1 km baseline, indicating a significant characteristic spatial scale for competing surface processes. The Hurst exponent is high within the Lunar Highlands, with a median value of 0.95, and lower in the maria (with a median value of 0.76). The median differential slope is a powerful tool for discriminating between roughness units and is useful in characterizing, among other things, the ejecta surrounding large basins, particularly Orientale, as well as the ray systems surrounding young, Copernican‐age craters. In addition, it allows a quantitative exploration on mare surfaces of the evolution of surface roughness with age.
Juliane Gross - One of the best experts on this subject based on the ideXlab platform.
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a rock fragment related to the magnesian suite in Lunar meteorite allan hills alha 81005
American Mineralogist, 2015Co-Authors: Allan H Treiman, Juliane GrossAbstract:Among the Lunar samples that were returned by the Apollo missions are many cumulate plutonic rocks with high Mg# [molar Mg/(Mg+Fe) in %] and abundances of KREEP elements (potassium, rare earth elements, phosphorus, U, Th, etc.) that imply KREEP-rich parental magmas. These rocks, collectively called the magnesian suite, are nearly absent from sampling sites distant from Imbrium basin ejecta, including those of Lunar Highlands meteorites. This absence has significant implications for the early differentiation of the Moon and its distribution of heat-producing elements (K, Th, U). Here, we analyze a unique fragment of basalt with the mineralogy and mineral chemistry of a magnesian suite rock, in the Lunar Highlands meteorite Allan Hills (ALH) A81005. In thin section, the fragment is 700 × 300 μm, and has a sub-ophitic texture with olivine phenocrysts, euhedral plagioclase grains (An97-70),and interstitial pyroxenes. Its minerals are chemically equilibrated. Olivine has Fe/Mn ~ 70 (consistent with a Lunar origin), and Mg# ~80, which is consistent with rocks of the magnesian suite and far higher than in mare basalts. It has a rich suite of minor minerals: fluorapatite, ilmenite, Zr-armalcolite, chromite, troilite, silica, and Fe metal (Ni = 3.8%, Co = 0.17%). The metal is comparable to that in chondrite meteorites, which suggests that the fragment is from an impact melt. The fragment itself is not a piece of magnesian suite rock (which are plutonic), but its mineralogy and mineral chemistry suggest that its protolith (which was melted by impact) was related to the magnesian suite. However, the fragment’s mineral chemistry and minor minerals are not identical to those of known magnesian suite rocks, suggesting that the suite may be more varied than apparent in the Apollo samples. Although ALHA81005 is from the Lunar Highlands (and likely from the farside), Clast U need not have formed in the Highlands. It could have formed in an impact melt pool on the nearside and been transported by meteoroid impact. Lunar Highlands meteorites should be searched for rock fragments related to the magnesian-suite rocks, but the fragments are rare and may have mineral compositions similar to some meteoritic (impactor) materials.
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Lunar feldspathic meteorites constraints on the geology of the Lunar Highlands and the origin of the Lunar crust
Earth and Planetary Science Letters, 2014Co-Authors: Juliane Gross, Allan H Treiman, Celestine N MercerAbstract:Abstract The composition of the Lunar crust provides clues about the processes that formed it and hence contains information on the origin and evolution of the Moon. Current understanding of Lunar evolution is built on the Lunar Magma Ocean hypothesis that early in its history, the Moon was wholly or mostly molten. This hypothesis is based on analyses of Apollo samples of ferroan anorthosites ( > 90 % plagioclase; molar Mg / ( Mg + Fe ) = Mg # 75 ) and the assumption that they are globally distributed. However, new results from Lunar meteorites, which are random samples of the Moonʼs surface, and remote sensing data, show that ferroan anorthosites are not globally distributed and that the Apollo highland samples, used as a basis for the model, are influenced by ejecta from the Imbrium basin. In this study we evaluate anorthosites from all currently available adequately described Lunar highland meteorites, representing a more widespread sampling of the Lunar Highlands than Apollo samples alone, and find that ∼ 80 % of them are significantly more magnesian than Apollo ferroan anorthosites. Interestingly, Luna mission anorthosites, collected outside the continuous Imbrium ejecta, are also highly magnesian. If the Lunar highland crust consists dominantly of magnesian anorthosites, as suggested by their abundance in samples sourced outside Imbrium ejecta, a reevaluation of the Lunar Magma Ocean model is a sensible step forward in the endeavor to understand Lunar evolution. Our results demonstrate that Lunar anorthosites are more similar in their chemical trends and mineral abundance to terrestrial massif anorthosites than to anorthosites predicted in a Lunar Magma Ocean. This analysis does not invalidate the idea of a Lunar Magma Ocean, which seems a necessity under the giant impact hypothesis for the origin of the moon. However, it does indicate that most rocks now seen at the Moonʼs surface are not primary products of a magma ocean alone, but are products of more complex crustal processes.
David E Smith - One of the best experts on this subject based on the ideXlab platform.
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Lunar floor fractured craters classification distribution origin and implications for magmatism and shallow crustal structure
Journal of Geophysical Research, 2012Co-Authors: L M Jozwiak, J.w. Head, Maria T Zuber, David E Smith, Gregory A NeumannAbstract:[1] Floor-Fractured Craters (FFCs) are a class of Lunar craters characterized by anomalously shallow floors cut by radial, concentric, and/or polygonal fractures; additional interior features are moats, ridges, and patches of mare material. Two formation mechanisms have been hypothesized—floor uplift in response to shallow magmatic intrusion and sill formation, and floor shallowing in response to thermally driven viscous relaxation. This study combines new Lunar Orbiter Laser Altimeter (LOLA) and Lunar Reconnaissance Orbiter Camera (LROC) data to characterize and categorize the population of FFCs and map their distribution on the Moon, and uses variations in floor-fractured crater morphology and regional distribution to investigate the proposed formation mechanisms. The population of FFCs was categorized according to the classes outlined by Schultz (1976). The distribution of these FFC categories shows an evolution of crater morphology from areas adjacent to Lunar impact basins to areas in the Lunar Highlands. We propose that this trend is supportive of formation by shallow magmatic intrusion and sill formation—crustal thickness determines the magnitude of magmatic driving pressure, and thus either piston-like floor uplift for high magnitude, or a convex floor profile for low magnitude. Predictions from previous studies modeling viscous relaxation are inconsistent with the observed altimetric profiles of FFCs. Hence our analysis favors FFC formation by shallow magmatic intrusion, with the variety of FFC morphologies being intimately linked with location and crustal thickness, and the driving pressure of the intrusion. Data from the GRAIL (Gravity Recovery and Interior Laboratory) mission will help to test these conclusions.
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global surface slopes and roughness of the moon from the Lunar orbiter laser altimeter
Journal of Geophysical Research, 2011Co-Authors: M A Rosenburg, Erwan Mazarico, J.w. Head, David E Smith, Gregory A Neumann, O Aharonson, M A KreslavskyAbstract:[1] The acquisition of new global elevation data from the Lunar Orbiter Laser Altimeter, carried on the Lunar Reconnaissance Orbiter, permits quantification of the surface roughness properties of the Moon at unprecedented scales and resolution. We map Lunar surface roughness using a range of parameters: median absolute slope, both directional (along‐track) and bidirectional (in two dimensions); median differential slope; and Hurst exponent, over baselines ranging from ∼17 m to ∼2.7 km. We find that the Lunar Highlands and the mare plains show vastly different roughness properties, with subtler variations within mare and Highlands. Most of the surface exhibits fractal‐like behavior, with a single or two different Hurst exponents over the given baseline range; when a transition exists, it typically occurs near the 1 km baseline, indicating a significant characteristic spatial scale for competing surface processes. The Hurst exponent is high within the Lunar Highlands, with a median value of 0.95, and lower in the maria (with a median value of 0.76). The median differential slope is a powerful tool for discriminating between roughness units and is useful in characterizing, among other things, the ejecta surrounding large basins, particularly Orientale, as well as the ray systems surrounding young, Copernican‐age craters. In addition, it allows a quantitative exploration on mare surfaces of the evolution of surface roughness with age.
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the shape and internal structure of the moon from the clementine mission
Science, 1994Co-Authors: Maria T Zuber, David E Smith, F G Lemoine, Gregory A NeumannAbstract:Global topographic and gravitational field models derived from data collected by the Clementine spacecraft reveal a new picture of the shape and internal structure of the moon. The moon exhibits a 16-kilometer range of elevation, with the greatest topographic excursions occurring on the far side. Lunar Highlands are in a state of near-isostatic compensation, whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age. A global crustal thickness map reveals crustal thinning under all resolvable Lunar basins. The results indicate that the structure and thermal history of the moon are more complex than was previously believed.
M A Kreslavsky - One of the best experts on this subject based on the ideXlab platform.
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the steepest slopes on the moon from Lunar orbiter laser altimeter lola data spatial distribution and correlation with geologic features
Icarus, 2016Co-Authors: M A Kreslavsky, J.w. HeadAbstract:Abstract We calculated topographic gradients over the surface of the Moon at a 25 m baseline using data obtained by the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. The relative spatial distribution of steep slopes can be reliably obtained, although some technical characteristics of the LOLA dataset preclude statistical studies of slope orientation. The derived slope-frequency distribution revealed a steep rollover for slopes close to the angle of repose. Slopes significantly steeper than the angle of repose are almost absent on the Moon due to (1) the general absence of cohesion/strength of the fractured and fragmented megaregolith of the Lunar Highlands, and (2) the absence of geological processes producing steep-slopes in the recent geological past. The majority of slopes steeper than 32°–35° are associated with relatively young large impact craters. We demonstrate that these impact craters progressively lose their steepest slopes. We also found that features of Early Imbrian and older ages have almost no slopes steeper than 35°. We interpret this to be due to removal of all steep slopes by the latest basin-forming impact (Orientale), probably by global seismic shaking. The global spatial distribution of the steepest slopes correlates moderately well with the predicted spatial distribution of impact rate; however, a significant paucity of steep slopes in the southern farside remains unexplained.
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global surface slopes and roughness of the moon from the Lunar orbiter laser altimeter
Journal of Geophysical Research, 2011Co-Authors: M A Rosenburg, Erwan Mazarico, J.w. Head, David E Smith, Gregory A Neumann, O Aharonson, M A KreslavskyAbstract:[1] The acquisition of new global elevation data from the Lunar Orbiter Laser Altimeter, carried on the Lunar Reconnaissance Orbiter, permits quantification of the surface roughness properties of the Moon at unprecedented scales and resolution. We map Lunar surface roughness using a range of parameters: median absolute slope, both directional (along‐track) and bidirectional (in two dimensions); median differential slope; and Hurst exponent, over baselines ranging from ∼17 m to ∼2.7 km. We find that the Lunar Highlands and the mare plains show vastly different roughness properties, with subtler variations within mare and Highlands. Most of the surface exhibits fractal‐like behavior, with a single or two different Hurst exponents over the given baseline range; when a transition exists, it typically occurs near the 1 km baseline, indicating a significant characteristic spatial scale for competing surface processes. The Hurst exponent is high within the Lunar Highlands, with a median value of 0.95, and lower in the maria (with a median value of 0.76). The median differential slope is a powerful tool for discriminating between roughness units and is useful in characterizing, among other things, the ejecta surrounding large basins, particularly Orientale, as well as the ray systems surrounding young, Copernican‐age craters. In addition, it allows a quantitative exploration on mare surfaces of the evolution of surface roughness with age.
