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1.
The titanium contents of lunar mare basalts   总被引：1，自引：0，他引：1  
Abstract— Lunar mare basalt sample data suggest that there is a bimodal distribution of TiO2 concentrations. Using a refined technique for remote determination of TiO2, we find that the maria actually vary continuously from low to high values. The reason for the discrepancy is that the nine lunar sample return missions were not situated near intermediate basalt regions. Moreover, maria with 2–4 wt% TiO2 are most abundant, and abundance decreases with increasing TiO2. Maria surfaces with TiO2 >5 wt% constitute only 20% of the maria. Although impact mixing of basalts with differing Ti concentrations may smear out the distribution and decrease the abundance of high‐Ti basalts, the distribution of basalt Ti contents probably reflects both the relative abundances of ilmenite‐free and ilmenite‐bearing mantle sources. This distribution is consistent with models of the formation of mare source regions as cumulates from the lunar magma ocean.  相似文献   

2.
Abstract— Three major periods of basaltic activity characterize the infill of the basins. Each of these periods was itself punctuated by discrete phases of widespread magma eruptions: three during both the Late Imbrian Epoch and the early Eratosthenian Period and then two in the late Eratosthenian Period. We found the youngest lavas off the eastern border of the Fra Mauro peninsula and, mantling a much larger area, over most of the central western Nubium basin. Our results place the Nubium/Cognitum basalts in the low‐Ti category (1–5 wt% TiO2). The data indicate that the majority (?90%) of the mare terrain has iron content between 18 and 22 wt%. In particular, FeO contents tend to concentrate toward two compositional poles, each of ?20 wt%, and a much smaller one of ?15 wt%. These values are typical of nearside lunar maria. To complement our compositional data, we present a census of craters larger than 500 m using Orbiter IV images. The result was a crater count average with frequency 5.6 × 10?2 km?2, translating into an inferred mean age of 3300 Ma for the exposed lava flows. By combining lava chemistry with age, we find a possible correlation between the ages of the most prominent flow units and their estimated titanium content, with younger basalts becoming progressively Ti‐richer with time (from 2–3 to 4–5 wt% TiO2).  相似文献   

3.
Thomas W. Thompson 《Icarus》1978,36(2):174-188
A high-resolution map of lunar radar reflectivity has been obtained using delay-Doppler interferometry techniques and the 7.5 m (40 Mhz) radar at the Arecibo Observatory in Arecibo, Puerto Rico. This new mapping, an extension of an earlier experiment, demonstrated an improvement of surface resolution to 25–40 km. The new map shows scattering behavior similar to other radar maps at 3.8 and 70 cm wavelengths. The maria backscatter less power than the terrae by factors of one-half to one-fourth, although a few terrae areas have the same low back-scatterer as the mare. The large young rayed craters like Tycho have backscatterer enhancement (over the environs) by about 1.5:1, a smaller difference than that observed at centimeter wavelengths. In addition, the mean scattering behavior of the Moon was measured for a range of angles from 10° to 67° and the new measurements differ little from previous measurements at 6 m wavelength. The radar map and mean backscatter data indicate that: (1) the average radar backscatter at 7.5 m wavelength for the large angles of incidence differs little from scatter at centimeter wavelengths; (2) the maria and terrae have a qualitatively similar scattering behavior although maria backscatter less power by factors of one-half to one quater; and (3) the large rayed craters show relatively small enhancements compared with enhancements at meter and centimeter wavelengths. Several different physical properties of the lunar surface could account for these results.  相似文献   

4.
This paper presents an updated stratigraphical and compositional study of the exposed maria within the Imbrium basin on the Moon. Clementine multispectral data were employed to derive TiO2 and FeO wt% abundance estimates of potentially distinct basaltic flows. Additionally, NASA Lunar Orbiter images were used to estimate flow ages using crater count statistics. Mare Imbrium shows evidence of a complex suite of low to high-Ti basaltic lava units infilling the basin over an 800 million year timescale. More than a third (37%) of identified mare basalts were found to contain 1-3 wt% TiO2. Two other major mare lithological units (representing about 25% of the surface each) show TiO2 values between 3-5 and 7-9 wt%. The dominant fraction (55%) of the sampled maria contain FeO between 16 and 18 wt%, followed by 27% of maria having 18-20 wt% and the remaining 18%, 14-16 wt% FeO. A crater frequency count (for diameters >500 m) shows that in three quarters of the sampled mare crater counts range between 3.5 and 5.5×10−2 per km2, which translates, according to a lunar cratering model chronology, into estimated emplacement ages between ∼3.3 and 2.5 Ga. A compositional convergence trend between the variations of iron and titanium oxides was identified, in particular for materials with TiO2 and FeO content broadly above 5 and 17 wt%, respectively, suggesting a related petrogenesis and evolution. According to these findings, three major periods of mare infill are exposed in the Imbrium basin; despite each period showing a range of basaltic compositions (classified according to their TiO2 content), it is apparent that, at least within these local geological settings, the igneous petrogenesis generally evolved through time towards more TiO2- and FeO-rich melts.  相似文献   

5.
The intensity distribution of lunar radar echoes has been mapped for two-thirds of the earth-visible lunar surface at a wavelength of 70 cm. The depolarizing effects of the lunar surface were observed by simultaneously receiving the radar echoes in opposite polarizations. These echoes were mapped with areal resolutions of 25–100 km2. Mappings with this resolution confirmed that the young craters have enhanced returns. A few craters were found to have enhanced echoes only from their rims. Backscattering differences were also observed between various areas within a mare, between different highland areas, and between maria and adjacent highlands. These scattering differences were interpreted with a simple model, which assumed that the surface backscattered with varying amounts of quasi-specular and diffuse power. Only an increase in the diffuse power was needed to give the numerical values of the enhancements.  相似文献   

6.
High-resolution lunar radar map at 70-cm wavelength   总被引：4，自引：0，他引：4  
New radar observations of the Moon in 1981–1984 were made using the 430 MHz (70 cm wavelength) radar at the Arecibo observatory, Puerto Rico. The new observations have produced a high resolution lunar radar map with radar cell-sizes near 2–5 km. This new resolution is a three-fold improvement over the previous mapping done in the late 1960's. Since the Arecibo radar antenna beam is only ten arc-minutes (about one-third of the width of the lunar disk), this new map is a mosaic of some eighteen observations. A radarmetric control between the various pieces of the mosaic was obtained via a beam-swing, limb-to-limb calibration.When the limb-to-limb calibration was combined with the mosaic, there were significant radar scattering differences across the maria. Eastern Mare Tranquillitatis and western Oceanus Procellarum have weaker echoes than other maria, while the central portion of Mare Serenitatis and northern Mare Imbrium have stronger echoes. There is a radar scattering difference across the southern terra as areas nearer Mare Orientale have stronger echoes than areas further from Mare Orientale.  相似文献   

7.
The circular maria - Orientale, Imbrium, Serenitatis, Crisium, Smythii, and Tsiolkovsky -lie nearly on a lunar great circle. This pattern can be considered the result of a very close, non-capture encounter between Moon and Earth early in solar-system history. Of critical importance in analyzing the effects of such an encounter is the position of the weightlessness limit of the Earth-Moon System which is located at about 1.63R e, measured from the center of Earth to center of Moon. Within this weightlessness limit, material can be pulled from the lunar surface and interior by Earth's gravity and either escape from the Moon or be redistributed onto the lunar surface. In the case of an encounter with a non-spinning Moon, backfalling materials would be distributed along a lunar great circle. However, if the Moon is rotating during the encounter, the backfall pattern will deviate from the great circle, the amount depending on the rate and direction of spin. Such a close encounter model may be related to the pattern of circular maria if materials departing from the source region are visualized as spheroids of molten lunar upper mantle basalt. These spheroids, then, would impact onto the lunar surface to form a pattern of lava lakes. Radiometric dates from mare rocks are consistent with this model of mare formation if the older mare rock dates are considered to date the encounter and younger dates are considered to date subsequent volcanic eruptions on a structurally weakened Moon.  相似文献   

8.
The mineralogy of mare basalts reflects the chemical composition of the magma source, as well as the physical and chemical environment of the rocks' formation. This is significant for understanding the thermal evolution of the Moon. In this study, the spatial distribution of mineralogy on the lunar northern nearside basalts was mapped using the Moon Mineralogy Mapper(M^3) data. The study area, which is an elongated mare, Mare Frigoris and northern Mare Imbrium, was mapped and characterized into 27 units based on multi-source data, including spectrum, terrain and element abundance. We extracted 177 M^3 spectra from fresh craters. Spectral parameters such as absorption center and band area ratio(BAR)were obtained through data processing. The variation of mafic minerals in this region was acquired by analyzing these parameters. The basaltic units in eastern Mare Frigoris, which are older, have been found to be dominated by clinopyroxene with lower CaO compared to the returned lunar samples; this is similar to older basaltic units in Mare Imbrium. The basaltic units of western Mare Frigoris and Sinus Roris which are younger have been found to be rich in olivine. The late-stage basalts in Oceanus Procellarum and Mare Imbrium show the same feature. These widespread olivine-rich basalts suggest uniqueness in the evolution of the Moon. Geographically speaking, Mare Frigoris is an individual mare, but the magma source region has connections with surrounding maria in consideration of mineral differences between western and eastern Frigoris, as well as mineral similarities with maria at the same location.  相似文献   

9.
Oceanus Procellarum, the largest lunar mare, is distributed with a large area of the late-stage (Eratosthenian) basalts. Research on the thickness, volume, and eruption flux of the late-stage basalts is essential for understanding the late thermal evolution of Oceanus Procellarum, even the Moon. The Eratosthenian basalts are rich in olivine and ilmenite, while the underlying Imbrian basalts are rich in pyroxene. Their significant spectral differences are easy to be distinguished using the hyperspectral data. We determine whether a crater has penetrated the overlying basalt layer by the data of Moon Mineralogy Mapper (M3), and estimate the thickness of Eratosthenian basalts in the Oceanus Procellarum region by using a crater excavation technique. A high-resolution thickness distribution map of the last-stage basalts within the Oceanus Procellarum has been acquired. The results show that the averaged thickness of Eratosthenian basalts in the Oceanus Procellarum region varies from (24 ± 2) m to (88 ± 2) m. Among them, the thickness of Eratosthenian basalts in the western Aristarchus is the greatest (>60 m), whereas the southernmost area of the study has a minimum thickness of about 28–31 m. The basalt thickness at the Chang’e-5 potential landing site Mons Rümker is about 31–38 m. The thickness of Eratosthenian basalts in the east of Marius is about 35–45 m, which is much smaller than the value of 100 ～ 300 m estimated by Weider et al. The total volume of Eratosthenian basalts is estimated to be ～1.39 × 104 km3, which is only about 1.6% of total basalts in Oceanus Procellarum. This indicates that the magmatism in the Eratosthenian period has been greatly weakened compared to the Imbrian period.  相似文献   

10.
The origin of lunar crater rays   总被引：5，自引：0，他引：5  
Lunar rays are filamentous, high-albedo deposits occurring radial or subradial to impact craters. The nature and origin of lunar rays have long been the subjects of major controversies. We have determined the origin of selected lunar ray segments utilizing Earth-based spectral and radar data as well as FeO, TiO2, and optical maturity maps produced from Clementine UVVIS images. These include rays associated with Tycho, Olbers A, Lichtenberg, and the Messier crater complex. It was found that lunar rays are bright because of compositional contrast with the surrounding terrain, the presence of immature material, or some combination of the two. Mature “compositional” rays such as those exhibited by Lichtenberg crater, are due entirely to the contrast in albedo between ray material containing highlands-rich primary ejecta and the adjacent dark mare surfaces. “Immaturity” rays are bright due to the presence of fresh, high-albedo material. This fresh debris was produced by one or more of the following: (1) the emplacement of immature primary ejecta, (2) the deposition of immature local material from secondary craters, (3) the action of debris surges downrange of secondary clusters, and (4) the presence of immature interior walls of secondary impact craters. Both composition and state-of-maturity play a role in producing a third (“combination”) class of lunar rays. The working distinction between the Eratosthenian and Copernican Systems is that Copernican craters still have visible rays whereas Eratosthenian-aged craters do not. Compositional rays can persist far longer than 1.1 Ga, the currently accepted age of the Copernican-Eratosthenian boundary. Hence, the mere presence of rays is not a reliable indication of crater age. The optical maturity parameter should be used to define the Copernican-Eratosthenian boundary. The time required for an immature surface to reach the optical maturity index saturation point could be defined as the Copernican Period.  相似文献   

11.
G.J. Black  D.B. Campbell 《Icarus》2010,209(1):224-229
We present radar imaging of Mercury using the Arecibo Observatory’s 70-cm wavelength radar system during the inferior conjunction of July 1999. At that time the sub-Earth latitude was ∼11°N and the highly reflective region at Mercury’s north pole that was first identified in radar images at the shorter wavelengths of 3.6 cm [Slade, M.A., Butler, B.J., Muhleman, D.O., 1992. Science 258, 635-640] and 13 cm [Harmon, J.K., Slade, M.A., 1992. Science 258, 640-643] was again clearly detected. The reflectivity averaged over a 75,000 km2 region including the pole is similar to that measured at the other wavelengths over a comparable area, and the 70 cm circular polarization ratio of μC∼0.87 is possibly slightly lower. If this strong backscattering results from volume scattering in low absorption layers, the persistence of this effect over more than an order of magnitude change in wavelength scale has implications for the depth and thickness of the deposits responsible. The resolution of the radar maps at this wavelength is not sufficient to resolve individual craters, nor to discern features at other latitudes, but the planet’s total reflectivity is consistent with previous work and the scattering function suggests a surface roughness at this wavelength similar to the lunar highlands.  相似文献   

12.
Mare basalts provide insights into the composition and thermal history of the lunar mantle. The ages of mare basalts suggest a first peak of magma activity at 3.2–3.8 Ga and a second peak at ~2 Ga. In this study, we reassess the correlation between the titanium contents and the eruption ages of mare basalt units using the compositional and chronological data updated by SELENE (Kaguya). Using morphological and geological criteria, we calculated the titanium content of 261 mare units across a representative area of each mare unit. In the Procellarum KREEP Terrane, where the latest eruptions are located, an increase in the mean titanium content is observed during the Eratosthenian period, as reported by previous studies. We found that the increase in the mean titanium content occurred within a relatively short period near approximately 2.3 Ga, suggesting that the magma source of the mare basalts changed at this particular age. Moreover, the high‐titanium basaltic eruptions are correlated with a second peak in volcanic activity near ~2 Ga. The high‐titanium basaltic eruptions occurring during the last volcanic activity period can be explained by the three possible scenarios (1) the ilmenite‐bearing cumulate rich layer in the core‐mantle boundary formed after the mantle overturn, (2) the basaltic material layers beneath the lunar crust formed through upwelling magmas, and (3) ilmenite‐bearing cumulate blocks remained in the upper mantle after the mantle overturn.  相似文献   

13.
Abstract— Clementine UV/VIS multi‐spectral data were used to map mare deposits in the eastern lunar nearside region (Mare Tranquillitatis, Mare Fecunditatis, Mare Serenitatis, Mare Crisium, Mare Nectaris) to understand the volcanic history of this region. An array of Clementine and Clementine‐derived data were used to classify mare basalts; these include: 750 nm albedo, UV/VIS ratio, 1 μm absorption signatures, and Clementine derived FeO and TiO2 contents. We have successfully identified several new geological units and have determined their spectral characteristics. For example, the relatively younger low‐Ti basalts were recognized in the eastern part of Mare Tranquillitatis. The central low‐Ti basalts in Mare Serenitatis, which had been classed as mISP, were divided into 2 groups. In Mare Nectaris, 2 types of mare basalts were identified, while only 1 group was recognized in the previous study. The stratigraphy constructed from the spectral analysis indicates that the mare deposits tend to become younger in the northern maria, including Serenitatis and Crisium, and older in the southern maria, including Tranquillitatis, Fecunditatis, and Nectaris. According to the relationship between the titanium contents of the mare units and their stratigraphy, the titanium content decreases with time in the early stage but increases toward the end of volcanism in the Serenitatis and Crisium region, while it increases with time but finally decreases in the Tranquillitatis and Fecunditatis region. In connection with the distribution of mare basalts, a large amount of high‐Ti mare basalts are found in Mare Tranquillitatis, especially in the western part, while other maria are covered by low‐Ti basalts. The iron contents show a similar distribution to that of titanium.  相似文献   

14.
The distribution of minerals on the lunar surface is information which could contribute to studying lunar origin and evolution. In this paper, the distribution of clinopyroxene, orthopyroxene, olivine, ilmenite, and plagioclase on the lunar surface has been mapped based on Hapke radiative transfer model and linear unmixing of spectra with Clementine UVVIS/NIR data. The results have been validated on the basis of minerals modal abundance data of the Apollo samples, and problems in the minerals abundance mapping have been analyzed. The validation based on analysis data of Apollo samples indicates that plagioclase mapped in this paper represents the total abundance of plagioclase and agglutinitic glass. The minerals mapping results show that the lunar surface is mainly composed of pyroxene, plagioclase, agglutinitic glass, and ilmenite. Basalt in the lunar mare is mainly composed of clinopyroxene and ilmenite, and lunar highland is mainly composed of plagioclase and agglutinitic glass. Orthopyroxene is mainly distributed on the north of Mare Imbrium, on the south of Maria and Aitken Basin. According to our results, there is probably no large area of olivine distribution on the lunar surface which is different from earlier published results. Therefore, emphasis should be put on the olivine distribution in the minerals mapping using hyperspectral data such as M3 of Chandrayaan-1 and IIM of ChangE-1.  相似文献   

15.
Radar, infrared, and photogeologic properties of lunar craters have been studied to determine whether there is a systematic difference in blocky craters between the maria and terrae and whether this difference may be due to a deep megaregolith of pulverized material forming the terra surface, as opposed to a layer of semi-coherent basalt flows forming the mare surface. Some 1310 craters from about 4 to 100 km diameter have been catalogued as radar and/or infrared anomalies. In addition, a study of Apollo Orbital Photography confirmed that the radar and infrared anomalies are correlated with blocky rubble around the crater.Analysis of the radar and infrared data indicated systematic terra—mare differences. Fresh terra craters smaller than 12 km were less likely to be infrared and radar anomalies than comparable mare craters: but terra and mare craters larger than 12 km had similar infrared and radar signatures. Also, there are many terra craters which are radar bright but not infrared anomalies.Our interpretation of these data is that while the maria are rock layers (basaltic flow units) where craters eject boulder fields, the terrae are covered by relatively pulverized megaregolith at least 2 km deep, where craters eject less rocky rubble. Blocky rubble, either in the form of actual rocks or partly consolidated blocks, contributes to the radar and infrared signatures of the crater. However, aging by impacts rapidly destroys these effects, possibly through burial by secondary debris or by disintegration of the blocks themselves, especially in terra regions.PSI Contribution No. 110.  相似文献   

16.
George E. McGill 《Icarus》1974,21(4):437-447
This paper is a test of published theoretical and experimental studies of crater erosion by micrometeorite bombardment which predict systematic variations in the morphology of lunar craters as a function of crater diameter and crater age. Numerical, ranking-type degradation classifications indicate that the craters on Mare Imbrium and Mare Tranquillitatus confirm these predictions by showing a systematic increase in degradation with decreasing diameter for craters smaller than a few kilometers in diameter but larger than the equilibrium diameter, and by showing fixed proportions of fresh, moderately degraded and very degraded craters under equilibrium conditions. Furthermore, the relative ages of the two mare surfaces may be determined using a diameter/mean-degradation-number curve. These determinations of relative age and process of crater erosion are both essentially independent of the traditionally studied crater diameter/frequency relationships. Morphologies of terra craters near Mare Humorum suggest a young, non-equilibrium crater population superposed on a perimordial population with about equilibrium proportions of fresh, moderately degraded and very degraded craters. The primordial population has been modified by pre-Imbrian or early Imbrian deposition of blanketing deposits. A comparative study of several crater degradation classifications indicates that all are essentially interchangeable.  相似文献   

17.
Magma genesis in the Moon could have been significantly altered by large impacts if they melted solidified residual liquids and late cumulates from the ‘magma ocean’. Calculations of the heat required to melt these materials, under different assumed conditions, are compared to estimates of the total kinetic energy of the Imbrium impact. For a significant amount of these materials to have been melted, they must have been near their solidus temperatures, the impacts must have been very large, and the lunar lithosphere must have been locally heated at depths of 70 to 140 km. Unless the Imbrium impact released at least the maximum estimated kinetic energy, only larger impacts, e.g., the proposed ‘Gargantuan’ impact, could have augmented the intrinsic lunar heat budget enough to locally alter the abundance, timing of eruption, and chemical compositions of lunar magmas. The mechanical and thermal energy generated by such an impact could have been critical in creating (1) the higher concentrations of radioactive elements in the Imbrium/Procellarum area by migration of residual liquids driven by differential lithospheric thickness; and (2) hybrid mare basalts (representing varying proportions of late cumulates and/or residual liquids incorporated into primitive magmas rising from the partially molten lunar interior). Complete compositional spectra of lunar basalts are to be expected, from primitive mare basalts to pure KREEP and to Ti-rich varieties. Comparison of the Gargantuan/Imbrium area with ancient basins in the eastern nearside area suggests that the interplay between the Moon's internal heat engine and the timing of large impacts was a crucial factor in determining the time of tunar volcanism and the chemical composition of the lavas.  相似文献   

18.
A study of the variation of the spectral relative ratios of reflectivity of selected mare lunar grounds between wavelengths 4000 and 8000 Å is given in comparison with lunar craters. The intensities at different wavelengths of each lunar region are corrected for the angles of illumination and viewing, and they are scaled to unity at =5538Å. Distinct variety in the spectral reflectivity values of mare grounds at short wavelengths are confirmed. The Mare Tranquillitatis type grounds (similar to Apollo-11 site), have relative ratio of reflectivity at short wavelength at =4035 Å; larger than or equal to 1.03 in addition to a bigger difference in reflectivity between the short and the long wavelength. The Mare Serenitatis type grounds (similar to Apollo-12) are characterized to give relative ratio of reflectivity less than 1.03 at =4035 Å, and smaller difference in reflectivity between short and long wavelengths. This is due to the variation in the colour of the Mare Tranquillitatis and Mare Serenitatis type ground due to compositional differences. The mare type grounds are generally different in shape than that of lunar craters grounds.Presented at the IAU-COSPAR Julian Schmidt Symposium on 100 Years of Lunar Mapping held at Lagonissi, Greece, 25–27 May, 1978.  相似文献   

19.
In the context of sample evidence alone, the high-alumina (HA) basalts appear to be an unique, and rare variety of mare basalt. In addition to their distinct chemistry, radiometric dating reveals these basalts to be among the oldest sampled mare basalts. Yet, HA basalts were sampled by four missions spanning a lateral range of ∼2400 km, with ages demonstrating that aluminous volcanism lasted at least 1 billion years. This evidence suggests that HA basalts may be a widespread phenomenon on the Moon. Knowing the distribution of HA mare basalts on the lunar surface has significance for models of the origin and the evolution of the Lunar Magma Ocean. Surface exposures of HA basalts can be detected with compositional remote sensing data from Lunar Prospector Gamma Ray Spectrometer and Clementine. We searched the lunar surface for regions of interest (ROIs) that correspond to the intersection of three compositional constraints taken from values of sampled HA basalts: 12-18 wt% FeO, 1.5-5 wt% TiO2, and 0-4 ppm Th. We then determined the “true” (unobscured by regolith) composition of basalt units by analyzing the rims and proximal ejecta of small impacts (0.4-4 km in diameter) into the mare surface of these ROIs. This paper focuses on two ROIs that are the best candidates for sources of sampled HA basalts: Mare Fecunditatis, the landing site of Luna 16; and northern Mare Imbrium, hypothesized origin of the Apollo 14 HA basalts. We demonstrate our technique's ability for delineating discrete basalt units and determining which is the best compositional match to the HA basalts sampled by each mission. We identified two units in Mare Fecunditatis that spectrally resemble HA basalts, although only one unit (Iltm) is consistent with the compositional and relative age of the Luna 16 HA samples. Northern Mare Imbrium also reveals two units that are within the compositional constraints of HA basalts, with one (Iltm) best matching the composition of the basalts sampled by Apollo 14.  相似文献   

20.
G. Leonard Tyler 《Icarus》1979,37(1):29-45
Quasi-specular radar data used to determine apparent surface roughness σχ of geologic surfaces displays a variable wavelength λ dependence ranging between σχ ～ λ0and σχ ～ λ?13 for 0.01 ? λ ? 1 m. The strongest changes in σχ with wavelength are observed in lunar mare, while scatter from lunar highlands is nearly wavelength independent. Commonly used, gently undulating surface models for electromagnetic scatter predict no wavelength dependence. Wavelength dependence occurs whenever a significant fraction of the surface has local radii of curvature comparable to the observing wavelength. This condition can be determined by comparison of the value of the integrated surface curvature spectrum with the radar wavenumber, multiplied by a constant that depends on the geometry. Variations in curvature statistics calculated from photogrammetric reduction of lunar images are consistent with the observed variations in quasi-specular scatter between λ = 13 and 116 cm at the same locations. Variations in the strength of the wavelength dependence are correlated with the sizes of lunar craters that lie near the upper size limit for the local steady-state distribution. This correlation is also consistent with variations in the curvature spectrum calculated from crater size-frequency distributions.  相似文献   

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