Engineering topics

Hale, W.

Publications and source records attributed to Hale, W..

3 records

NASA NTRS1980

Orientations of central peaks in lunar craters - Implications for regional structural trends

Impact craters are dominant features on the lunar surface and all fresh craters with diameters greater than 35 km possess central peaks. Approximately half of these central peaks (54%) have either linear or arcuate geometry and display some preferential orientation. These orientations were measured for 200 lunar craters of Pre-Nectarian to Copernican age. A pervasive regional north-south trend is identified for central peak orientation, with secondary trends at + or - 20-30 deg from this axis. No evidence for regional east-west trends is found. These orientations are shown to persist in craters formed through the last 4 billion years of lunar history. A lack of coincidence between impact direction, as determined from ejecta asymmetries and peak orientation, argues for structural control by the target as a source of the linear peak morphology. This is supported by the regional and temporal persistence of preferred peak orientations. It is proposed that linear central peak orientations in lunar craters reflect a pervasive regional structural system which developed early in lunar history and has persisted through geologic time.

Hale, W.↗

NASA NTRS1980

Central peaks in Mercurian craters - Comparisons to the moon

A key question in cratering studies continues to be the mode of formation of central structures. Studies of central peaks, the smallest and simplest central features found in impact structures, could provide clues to the formational mechanisms of the entire morphologic sequence of central features. The present investigation is concerned with a systematic examination of central peaks in fresh Mercurian craters, and a comparison of Mercurian and lunar central peak morphometry and morphology. It is found that the central peak diameter/rim diameter relation on Mercury is indistinguishable from the lunar case. The gravitational field strength of the planet, therefore, does not appear to be the dominant force controlling central peak formation. Of the presently proposed processes for central peak formation, dynamic rebound best fits current observations.

Hale, W.↗

NASA NTRS1979

Central peaks in lunar craters - Morphology and morphometry

Fresh lunar craters with diameters from 17 to 175 km are found to display a linear relationship between the central peak morphology and morphometry and such critical crater parameters as rim crest diameter, floor diameter, and substrate. Some other previously established linear relationships have been cited as evidence that floor diameter, peak height, and peak ring diameter are related to the kinetic energy of impact. The two new relations derived in the present work would therefore indicate that the central peaks, too, are related to the kinetic energy of impact, and probably begin to form early in the cratering event as suggested by Milton and Roddy (1972) and Head (1978). There seems to be no obvious reason to expect such linear relationships between central peak diameter and rim crest and floor diameter if the peaks are formed by gravity induced failure of the transient cavity, as suggested by Dence et al. (1968).

Hale, W.↗