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Pike, R. J.

Publications and source records attributed to Pike, R. J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Average Spacing for Rings of Individual Multi-ring Basins Is 2.0(0.5)D

The mathematically regular spacing of the concentric rings of planetary impact basins are examined. It is shown that a constant radial increment of x (sub 0.5) D, where x is about 2.0 and D is ring diameter, separates adjacent statistical groups of rings and arcs of multiring basins on Mars, Mercury, and the Moon. Statistics of spacing for adjacent rings of individual basins on the three planets are presented, and single basins from ring measurements of newly-recognized basins on Mercury and Mars are revised. Analysis of ring rank: ring diameter for adjacent rings of individual basins also yields an average spacing of about 2.0 (sup 0.5) D, specifically (2.01 + or - 0.26) (sup 0.5) D.

Pike, R. J.↗
NASA NTRS1985

Ring-diameter Ratios for Multi-ring Basins Average 2.0(0.5)D

The spacing of the concentric rings of planetary impact basins was studied. It is shown that a radial increment of x (sup 0.5) D, where x is about 2.0 and D = ring diameter, separates both (1) adjacent least-squares groups of rings and arcs of multi-ring basins on Mars, Mercury, and the Moon; and (2) adjacent rings of individual basins on the three planets. Statistics for ratios of ring diameters are presented, the first and most-applied parameter of ring spacing. It is found that ratios excluding rings flanking the main ring also have a mean spacing increment of about 2.0. Ratios including such rings, as for the least-squares groups, and (1) above, have a larger increment, averaging 2.1. The F-test indicates, that these spacings of basin ring locations, and mode of ring formation are controlled by the mechanics of the impact event itself, rather than by crustal properties.

Pike, R. J.↗
NASA NTRS1985

Some morphologic systematics of complex impact structures

Current measurements of the horizontal dimensions of complex meteorite structures are summarized. The measurements were used in a least squares analysis of correlations among the dimensions of the crater rings and central peaks of compact meteorites. Some geometric similarities between terrestrial complex impact structures and the large multiring basin of the planets are demonstrated, and the possible physical constraints on ring formation are discussed.

Pike, R. J.↗
NASA NTRS1984

Ring spacing of Mercurian multi-ring basins and basin ring formation

Recent systematic mapping of Mercury has revealed many ancient and previously unrecognized multiring basins. The population of these basins now stands at 20, possibly is as large as 25, and includes at least 76 measurable rings. From the new data base, we present some systematics of basin ring spacing on Mercury, compare them with similar data for the Moon, and draw some preliminary conclusions on conditions of ring formation for basins on the terrestrial planets.

Pike, R. J.↗
NASA NTRS1984

Ode to gravity: Depth/diameter for fresh craters on Mercury

Opinions conflict over the role of surface gravity in shaping impact craters on Mercury. One view holds that the effects of g are evident in measurable aspects of crater form; other investigators find little or no evidence for g's geomorphic importance. Ambiguity in the role of g and other variables in cratering on Mercury stems largely from uncertainty in identifying major geomorphic contrasts and the crater sizes at which they occur. One of these, depth/diameter (d/D), undergoes a major change at the transition from simple (bowl shaped) to complex (peaks and terraces) crater interiors. Four least-squares d/D fits for fresh craters on Mercury were attemped. The results are inconsistent. The d/D data that should resolve previous shortcomings is presented. The revised d/D distributions for simple and complex craters, which intersect at a diameter of about 5 km, support the initial thesis that g substantially influences the form of Mercury's craters.

Pike, R. J.↗
NASA NTRS1980

Formation of complex impact craters - Evidence from Mars and other planets

An analysis of the depth vs diameter data of Arthur (1980), is given along with geomorphic data for 73 Martian craters. The implications for the formation of complex impact craters on solid planets is discussed. The analysis integrates detailed morphological observations on planetary craters with geologic data from terrestrial meteorite and explosion craters. The simple to complex transition for impact craters on Mars appears at diameters in the range of 3 to 8 km. Five features appear sequentially with increasing crater size, flat floors, central peaks and shallower depths, scalloped rims, and terraced walls. This order suggests that a shallow depth of excavation and a rebound mechanism have produced the central peaks, not centripetal collapse and deep sliding. Simple craters are relatively uniform in shape from planet to planet, but complex craters vary considerably. Both the average onset diameter for complex impact craters on Mars and the average depth of complex craters vary inversely with gravitational acceleration on four planets.

Pike, R. J.↗
NASA NTRS1980

Control of crater morphology by gravity and target type - Mars, earth, moon

The process involved in the formation of impact craters on solid planets and satellites in the solar system is thought to be essentially the same everywhere. However, the resulting landforms are not all alike. The possible reasons for the differences in crater morphology are investigated. The obtained results suggest that both gravitational acceleration and target characteristics have affected the morphology of impact craters across the solar system. Neither of these important influences alone can explain all of the many observations on craters. The relative importance of gravity and target type differs from planet to planet. Intraplanetary contrasts in crater shape which reflect differences in target materials appear to be large on earth, significant but minor on Mars and the moon, and minimal on Mercury. Whole-planet differences in crater shape between earth and the moon, on the other hand, seem to be entirely dependent on g.

Pike, R. J.↗
NASA NTRS1978

Volcanoes on the inner planets - Some preliminary comparisons of gross topography

The paper extends previous numerical work on analogs of planetary landform (Pike, 1974, 1978) by concentrating on volcanic edifices rather than impact craters. Two kinds of extraterrestrial volcanic constructs - domes on the lunar maria and calderas on Mars - are compared with terrestrial volcanoes. According to available data, neither type of landform unequivocally resembles a specific class of terrestrial volcano. The quantitative models of volcanoes presented necessarily are statistical because the shapes of volcanic landforms vary over a wide range of values.

Pike, R. J.↗
NASA NTRS1977

Apparent depth/apparent diameter relation for lunar craters

Photogrammetric measurements from Apollo metric-quality pictures ensure high accuracy of apparent depth (R sub a) and apparent diameter (D sub a) data for fresh lunar craters. R sub a is a direct function of D sub a and the R sub a/D sub a distribution inflects sharply at an apparent diameter of about 15 km. Each of the two resulting subgroups of craters requires two separate least-squares fits. For simple lunar craters (less than 15 km across), the ratio of R sub a to D sub a is about 0.2; the ratio for complex (larger) craters ranges from 0.1 to 0.01. Apparent depth does not exceed 3400 m, regardless of crater size, possibly as a result of isostasy, substrate layering, or curvature of the moon. R sub a/D sub a differences for mare versus terra craters are either absent or are equivocal. The ratio of apparent diameter to rim-crest diameter (D sub a/D sub r) averages 0.83 for smaller craters and 0.86 for larger craters, indicating another simple-to-complex contrast in crater morphology on the moon, and confirms a prediction by R. B. Baldwin for simple craters. Close similarity of D sub a/D sub r for terrestrial experimental craters and simple lunar craters is especially consistent with impact origin for the moon's craters.

Pike, R. J.↗
NASA NTRS1977

Size-dependence in the shape of fresh impact craters on the moon

The transition from small simple craters to large complex or modified craters is characterized by eleven changes in the shape of fresh lunar craters which occur within a diameter range of 10 to 30 km. In the present paper, seven ratio-level variations - those of rim-crest diameter with depth, rim height, flank width, rimwall slope, floor diameter, circularity, and rim-crest evenness - are defined for fresh-appearing craters from the new Apollo data and are expressed mathematically where practicable. These relations constitute a shape model for interpreting fresh craters on the moon. The size dependent changes reflect the occurrence of central peaks, rimwall terraces, and a flat floor within craters measuring 10 to 20 km in diameter.

Pike, R. J.↗
NASA NTRS1977

Nested-crater model of lunar ringed basins

We propose a model for the origin of impact-basin rings whereby the main topographic rim of a basin approximates the limit of excavation and inner rings approximate the rims of craters formed inside the transient crater by some perturbation in the cratering process. The cause of this complexity in transient cavities may be the presence of discontinuities in the target material. The second inward ring may have formed at the seismic discontinuity about 20 km deep in the lunar crust, and the third, innermost ring of a few large basins at the crust-mantle interface about 60 km deep. Slumping increased the original diameters of many rings and split some initially coherent rings into subsidiary or partial rings. Deformation outside the transient crater produced external arcs. This model differs from prevalent hypotheses of ring formation whereby an inner ring approximates the transient crater rim and major faulting of the flank produced the outer ring structures.

Wilhelms, D. E.↗
NASA NTRS1976

Crater dimensions from Apollo data and supplemental sources

A catalog of crater dimensions that were compiled mostly from the Apollo-based Lunar Topographic Orthophotomaps is presented in its entirety. Values of crater diameter, depth, rim height, flank width, circularity, and floor diameter (where applicable) are tabulated for a sample of 484 craters on the moon and 22 craters on earth. Systematic techniques of mensuration are detailed. The lunar craters range in size from 400 m to 300 km across and include primary impact craters of the main sequence, secondary impact craters, craterlets atop domes and cones, and dark-halo craters. The terrestrial craters are between 10 m and 22.5 km in diameter and were formed by meteorite impact.

Pike, R. J.↗
NASA NTRS1976

Disharmony of the spheres - Recent trends in planetary surface nomenclature

Inadvisable departures from tradition in naming newly mapped features on Mars, Mercury, and the moon have been implemented and proposed since 1970. Functional need for place names also has become confused with cartographic convenience. Much of the resulting new nomenclature is neither unique, efficient, nor imaginative. The long-standing classical orientation in Solar System geography needs to be firmly reasserted. The Maedler scheme for designating smaller craters on the moon should be retained and extended to the farside. Names of surface features on other bodies might best reflect the traditional connotations of planet and satellite names: for example, most craters on Mars would be named for mythical heroes and military personalities in ancient history, craters on Mercury might commemorate explorers or commercial luminaries, and features on Venus would bear the names of famous women.

Pike, R. J.↗
NASA NTRS1975

Size-morphology relations of lunar craters - Discussion

Morphologic as well as morphometric changes occur in the character of fresh lunar craters at a diameter range of about 10-20 km. The continuous size/morphology sequence advocated by Smith and Sanchez (1973) is sustained by their data only for craters between 10-20 km and about 100 km in diameter. The cumulative-morphology index, and the frequency-of-occurrence of wall terraces, central peaks, flat floors, and 'swirl texture' (Smith and Sanchez, 1973) support the existence of a morphologic transition at a crater diameter of 10-20 km, rather than a continuous gradation in shape within craters between 4 and 150 km in diameter.

Pike, R. J.↗
NASA NTRS1974

Depth/diameter relations of fresh lunar craters - Revision from spacecraft data

The first systematic data from Apollo photogrammetry provide a high standard of accuracy for the depth/diameter relation of fresh lunar craters. Apollo depth-diameter results resemble results obtained by measuring shadows on Lunar Orbiter imagery. The depth-diameter distribution inflects at a crater diameter of 10 to 15 km. Lunar craters less than 15 km across are at least 50% deeper than older, telescopic data indicated, but larger craters are not much deeper. There is no marked depth-diameter difference between fresh upland and postmare craters. The new depth-diameter relation for small lunar craters resembles those of experimental and impact craters on earth.

Pike, R. J.↗
NASA NTRS1974

Ejecta from large craters on the moon - Comments on the geometric model of McGetchin et al

Amendments to a quantitative scheme developed by T. R. McGetchin et al. (1973) for predicting the distribution of ejecta from lunar basins yield substantially thicker estimates of ejecta, deposited at the basin rim-crest and at varying ranges beyond, than does the original model. Estimates of the total volume of material ejected from a basin, illustrated by Imbrium, also are much greater. Because many uncertainties affect any geometric model developed primarily from terrestrial analogs of lunar craters, predictions of ejecta thickness and volume on the moon may range within at least an order of magnitude. These problems are exemplified by the variability of T, thickness of ejecta at the rim-crest of terrestrial experimental craters. The proportion of T to crater rim-height depends critically upon scaled depth-of-burst and whether the explosive is nuclear or chemical.

Pike, R. J.↗