Central peaks in lunar craters

Allen, Carlton C.

doi:10.1007/bf00577935

Cited by 16 publications

(10 citation statements)

References 19 publications

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“…The actual variation of the percentage of ejecta which is redeposited within a crater as a function of crater size is unknown. Similarly, although morphological evidence indicates that the height and area of central peaks within lunar craters increase with increasing crater size [Wood, 1973;Allen, 1975], the volume of substrate material which is actually translated above the floor and walls of an impact excavation cavity by the rebound process is unknown. We are presently analyzing these two crater modification processes in order to estimate quantitatively the extent to which they have altered the structure of initial cavities formed by large impact events.…”

Section: Discussionmentioning

confidence: 99%

The role of rim slumping in the modification of lunar impact craters

Settle¹,

Head²

1979

J. Geophys. Res.

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Wall failure has significantly altered the structure of virtually all large, fresh‐appearing lunar craters. Terrace blocks exposed upon a crater's interior walls are interpreted to be sections of the transient cavity rim that slumped into the cavity during the terminal stages of crater formation. Impact excavation cavities have been reconstructed by restoring the innermost terrace block exposed within a crater to its inferred original position at the cavity rim and accounting for the volume of material that slumped into the cavity. Critical model assumptions include (1) the radial variation of topography near the initial cavity rim crest, (2) the structure of the failure surface along which terrace blocks slumped into the cavity, and (3) the geometric shape of the initial cavity. This terrace restoration model has been applied to 12 fresh lunar craters with observed rim crest diameters D0 ranging from 19 to 137 km. Up to an initial cavity diameter Di of 30 km, reconstructed cavity depths are comparable to or greater than cavity depths extrapolated from nonterraced craters of less than 15 km in diameter. For a wide range of model parameters the reconstructed depths of impact cavities 15–30 km in diameter are significantly greater than depths predicted by small‐crater morphometry, implying that cavity depths inferred from depth/diameter ratios observed for small craters may substantially underestimate the depth of excavation of impact cratering events in this size class. Reconstructed cavity depths for Di > 70 km, however, are consistently less than cavity depths extrapolated from smaller craters. This indicates that the morphometric transition from small, relatively unmodified, bowl‐shaped craters (D0 < 15 km) to large, terraced, saucer‐shaped craters (D0 > 80–90 km) cannot be solely attributed to rim‐slumping modification. Ejecta fallback and basement rebound also play a role in modifying impact crater cavities; however, the manner in which the volume of fallback ejecta and basement rebound material varies with increasing crater size is unknown. The discrepancy between cavity depths extrapolated from small craters and those obtained from the terrace restoration model suggests that impact excavation cavities become relatively shallower at larger diameters. However, this cannot be conclusively demonstrated until the effects of rebound and ejecta fallback are quantitatively accounted for.

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Section: Discussionmentioning

confidence: 99%

The role of rim slumping in the modification of lunar impact craters

Settle¹,

Head²

1979

J. Geophys. Res.

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“…) and Pluto (Moore et al. ), but a few central pit craters also have been reported for volatile‐poor bodies such as the Moon (Allen ; Schultz ; Xiao et al. ) and Mercury (Schultz ; Xiao and Komatsu ).…”

Section: Introductionmentioning

confidence: 99%

“…Complex impact craters often contain a central peak but can occasionally contain an inner depression called a central pit. Central pit craters primarily have been reported on bodies with volatile-rich crusts, including Mars (see summary in Barlow 2010), Ganymede (Passey and Shoemaker 1982;Schenk 1993;Alzate and Barlow 2011;Bray et al 2012), Callisto (Passey and Shoemaker 1982;Schenk 1993), a few of the intermediate-sized icy moons in the Saturnian and Uranian systems (Schenk 1993;Moore et al 2004), and most recently on Ceres (Nathues et al 2015) and Pluto (Moore et al 2016), but a few central pit craters also have been reported for volatile-poor bodies such as the Moon (Allen 1975;Schultz 1976;Xiao et al 2014) and Mercury (Schultz 1988;Xiao and Komatsu 2013). The higher frequency of central pit craters on bodies with volatile-rich crusts has led to the development of a number of formation models involving near-surface ice (Wood et al 1978;Greeley et al 1982;Passey and Shoemaker 1982;Senft and Stewart 2011;Bray et al 2012;Elder et al 2012;Williams et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Comparison of central pit craters on Mars, Mercury, Ganymede, and the Saturnian satellites

Barlow

Ferguson

Horstman

et al. 2017

Meteorit & Planetary Scien

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We report on the first results of a large‐scale comparison study of central pit craters throughout the solar system, focused on Mars, Mercury, Ganymede, Rhea, Dione, and Tethys. We have identified 10 more central pit craters on Rhea, Dione, and Tethys than have previously been reported. We see a general trend that the median ratio of the pit to crater diameter (Dp/Dc) decreases with increasing gravity and decreasing volatile content of the crust. Floor pits are more common on volatile‐rich bodies while summit pits become more common as crustal volatile content decreases. Uplifted bedrock from below the crater floor occurs in the central peak upon which summit pits are found and in rims around floor pits, which may or may not break the surface. Peaks on which summit pits are found on Mars and Mercury share similar characteristics to those of nonpitted central peaks, indicating that some normal central peaks undergo an additional process to create summit pits. Martian floor pits do not appear to be the result of a central peak collapse as the median ratio of the peak to crater diameter (Dpk/Dc) is about twice as high for central peaks/summit pits than Dp/Dc values for floor pits. Median Dpk/Dc is twice as high for Mars as for Mercury, reflecting differing crustal strength between the two bodies. Results indicate that a complicated interplay of crustal volatiles, target strength, surface gravity, and impactor energy along with both uplift and collapse are involved in central pit formation. Multiple formation models may be required to explain the range of central pits seen throughout the solar system.

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“…In this regard, most of the manual analyses on lunar craters have been carried out for simple craters (Pike, 1976;Ravine and Grieve, 1986) and complex craters (Allen, 1975) on small number. But, the craters with small diameter form the largest population on the lunar surface.…”

Section: Introductionmentioning

confidence: 99%