Engineering topics

Mckinnon, William B.

Publications and source records attributed to Mckinnon, William B..

23 records · Page 2

NASA NTRS1987

Ring geometry on Ganymede and Callisto

Geometrical considerations are brought to bear on a discussion of the impact and internal origin scenarios for the major furrow system of Ganymede, which was remapped in order to take advantage of improvements in coordinate control. Furrow occurrence and geometry are judged to be consistent with an impact origin; the perceived current nonalignment of the presumably once-concentric furrows may be adduced as evidence for large-scale lateral motion of dark terrain blocks in Ganymede's crust, in association with bright terrain formation.

Schenk, Paul M.↗

NASA NTRS1987

Studies of outer planet satellites, Mercury and Uranus

Arguments were made, based on geometry, for both an impact and an internal origin for the ancient, partially preserved furrow system of Ganymede. It was concluded that furrows were not concentric, but could be impact related if multiringed structures on icy satellites are initially noncircular. The geometry of the Valhalla ring structure on Callisto was examined in order to assess the circularity of an unmodified ring system. The Ganymede furrow system was remapped to make use of improvements in coordinate control. The least-squares center of curvature for all furrows in the Marius and Galileao Regio is -20.7, and 179.2 degrees. Furrows in Marius and Galileo Regio are reasonably concentric, and are much more circular than previously estimated. The perceived present nonalignment of the assumed originally concentric furrows were used to argue for large-scale lateral motion of dark terrain blocks in Ganymede's crust, presumably in association with bright terrain formation., The overall alignment of furrows as well as the inherent scatter in centers of curvature from subregions of Galileo and Marius do not support this hypothesis.

Mckinnon, William B.↗

NASA NTRS1987

Jovian and Saturnian satellites

Theoretical and empirical models of the Jovian and Saturnian satellites are discussed, reviewing results published during the period 1983-1986. The emphasis is on analyses of Voyager and Pioneer data. Io, Europa, Ganymede and Callisto, and Titan are characterized in detail, and consideration is also given to the intermediate-sized Saturnian satellites, some of the smaller satellites, and the rings of Saturn.

Mckinnon, William B.↗

NASA NTRS1986

Cratering of planetary satellites

Recent findings concerning craters and cratering populations on the satellites of Jupiter and Saturn are discussed. Current understanding of cratering mechanics is reviewed with emphasis placed on scaling and ejecta and the differences between cratering in rock and ice. Evidence from crater statistics regarding cratering histories on various planetary satellites is discussed and connections are made with what is known about the cratering record on the terrestrial bodies. Consideration is given to the source populations and an attempt is made to summarize and critique the various scenarios that have been proposed for linking the cratering records on the various planets and satellites. It is noted that early Voyager Uranus results seem compatible with the present summary.

Chapman, Clark R.↗

NASA NTRS1986

Ganymede and Callisto

The differences existing between Ganymede and Callisto are studied as well as their volcanic, tectonic, impact and surface processes. An attempt is made to explain the relatively vigorous history of geologic activity on Ganymede and the apparent lack of internal activity on Callisto. Observations reveal that the optical surfaces and regoliths of both bodies are ice rich, and thus unlikely to be remnants of a crust created by homogeneous accretion. Ganymede's relatively clean mantle was the source region for the water, slush, or ice that resurfaced more than half the satellite; this resurfacing material is structurally confined in broad rifts or troughs and is often captured to form grooved terrain. An explanation for resurfacing and tectonism on Ganymede and its near total absence on Callisto is that Ganymede is at least partially differentiated while Callisto is undifferentiated.

Mckinnon, William B.↗