Crater degradation on the lunar maria: Topographic diffusion and the rate of erosion on the Moon

Fassett, C. I.; Thomson, B. J.

doi:10.1002/2014je004698

Cited by 192 publications

(351 citation statements)

References 57 publications

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“…In other words, the roughness signature of craters blends with the background with time. Smoothing of the rough ejecta blankets on the Moon occurs due to regolith formation and its gardening, which effectively mutes topography at scales of several hundreds of meters and shorter (Basilevskii, ; Craddock & Howard, ; Fassett & Thomson, ; Kreslavsky et al, ). On Vesta and Ceres, impact gardening cannot roughen their smooth ejecta blankets.…”

Section: Discussionmentioning

confidence: 99%

Surface Roughness and Gravitational Slope Distributions of Vesta and Ceres

et al. 2019

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Heavily cratered terrains dominate the surfaces of asteroid 4 Vesta and dwarf planet 1 Ceres. The data from the Dawn spacecraft allowed reconstruction of high‐resolution shape models of these bodies. We used the stereophotoclinometric shape models to compute gravitational slopes and topographic roughness of Vesta and Ceres. We compute the slope distributions of Vesta and Ceres and compare them to those of the other bodies with heavily cratered terrains. The distribution of slopes of Vesta and Ceres has a kink at ≈34°. The slope distribution is steeper for slopes higher than ≈34°. The Moon and Mars have a similar kink but at a lower (shallower) slope (≈29°–30°). We hypothesize that this kink corresponds to the angle of repose, which is higher on the two minor bodies compared to that of Mars and the Moon. We have also analyzed the topographic roughness of Vesta and Ceres. Vesta's topography is characterized by lower roughness in the southern hemisphere that was resurfaced by giant impacts. The roughness of Ceres is mostly controlled by regional‐scale geology with no significant large‐scale variations. Large, fresh craters have smooth ejecta blankets on both Vesta and Ceres unlike previously observed rough ejecta on the Moon, Mars, and Mercury. On Ceres, the smooth ejecta craters also have smooth floors explained by impact slurry. Lineaments of elevated roughness are abundant on Ceres, whereas are nearly absent on Vesta. The roughness maps we produced provide a synoptic view of the surface texture and could be used to aid geologic mapping.

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Section: Discussionmentioning

confidence: 99%

Surface Roughness and Gravitational Slope Distributions of Vesta and Ceres

et al. 2019

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“…The model ages were suggested to be consistent with those derived from crater densities, which were based on the lunar crater chronology model of Neukum et al []. The crater degradation models predicted that the maximum lifetime of a D = 200–300 m lunar crater was less than 3 Byrs, 800 Myrs for D = 150 m crater, and 70 Myrs for D = 20 m crater [ Fassett and Thomson , ]. If the 109 ± 4 and 800 ± 15 Myrs sample ages were true for Tycho and Copernicus, respectively, the melt pools on the crater rims should have D eq at least being 20 m and 150 m, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…However, the observed D eq on these surfaces are much smaller (Table 1). Therefore, either the real ages of Tycho and Copernicus are substantially less than the prevalent sample ages and the crater chronology model of Neukum et al [] may have indicated larger than real ages for a given crater population, or that the crater degradation models may have overestimated the surface erosion rate on the Moon due to the possibly nonlinear topographic degradation rates for craters larger and less than 800 m diameter [ Fassett and Thomson , ]. The former, however, is disproved by recent work by Werner and Medvedev [] and Werner et al [].…”

Section: Discussionmentioning

confidence: 99%

Size‐frequency distribution of crater populations in equilibrium on the Moon

2015

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Overprinting of craters by subsequent impacts and topographic degradation complicates crater statistics, especially for old surfaces and small‐diameter crater populations. A crater population is regarded as in equilibrium at a particular crater size when smaller craters are being produced at the same rate at which they are being destroyed. Evaluating the equilibrium state of crater populations is challenging, and empirical equilibrium densities are frequently inferred. By performing careful crater counts and cross comparisons on several lunar surfaces, we study the size‐frequency distributions (SFD) for the crater populations, which have portions in equilibrium. The results are one of the few observational constraints on the SFD of crater populations in equilibrium, showing that referring to empirical equilibrium densities is not safe for evaluating the equilibrium states of crater populations. Equilibrium densities are not positively correlated with the ages of crater populations, and some populations in equilibrium have crater densities less than those previously believed to represent equilibrium conditions. Besides the SFD of the production population, different crater removal rates at different diameters also affect the SFD of crater populations in equilibrium. The equilibrium onset diameter (Deq) of a crater population can be translated to model ages because older populations have larger Deq, and those for same‐aged surfaces are comparable. We show that the crater populations studied here are in equilibrium at much smaller diameters than those predicted for same‐aged surfaces by crater degradation models, thus indicating lower crater degradation rates on the Moon, and/or younger ages of the counting areas.

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“…Based on the straight relationship formulated by Basilevsky (1976), TMa =2.5*D, (TMA is time in Ma and D is crater diameter in meters) the small secondary craters excavated by the surge should all but eroded long ago (~50 Ma lifetime for the 20 m fraction, or ~70 Ma, Fassett and Thomson, 2014). Given that the event is estimated at ~110 Ma (Arvidson et al 1976), the crater count should have approached the background level by now.…”

Section: Discussionmentioning

confidence: 99%

Small Craters and Their Diagnostic Potential

Bugiolacchi

2017

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:I analysed and compared the size-frequency distributions of craters in the Apollo 17 landing region, comprising of six mare terrains with varying morphologies and cratering characteristics, along with three other regions allegedly affected by the same secondary event (Tycho secondary surge). I propose that for the smaller crater sizes (in this work 9-30 m), a] an exponential curve of power -0.18D can approximate Nkm -2 crater densities in a regime of equilibrium, while b] a power function D -3 closely describes the factorised representation of craters by size (1 m). The saturation level within the Central Area suggests that c] either the modelled rates of crater erosion on the Moon should be revised, or that the Tycho event occurred much earlier in time than the current estimate. We propose that d] the size-frequency distribution of small secondary craters may bear the signature (in terms of sizefrequency distribution of debris/surge) of the source impact and that this observation should be tested further.

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Crater degradation on the lunar maria: Topographic diffusion and the rate of erosion on the Moon

Cited by 192 publications

References 57 publications

Surface Roughness and Gravitational Slope Distributions of Vesta and Ceres

Surface Roughness and Gravitational Slope Distributions of Vesta and Ceres

Size‐frequency distribution of crater populations in equilibrium on the Moon

Small Craters and Their Diagnostic Potential

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