Geology topics
Publications and source records attributed to E.M. Shoemaker.
Io and Earth are the only planetary bodies known to be volcanically active; the energetics of the eruptive plumes on Io have important structural implications and are closely linked with the presence of sulphur and SO 2 .
Ballistic and aerodynamic models are proposed to explain the volcanic plumes on Io, with particular reference to Plumes 1 and 3 which seem to have the same origin.
The cameras aboard Voyager 1 have provided a closeup view of the Jupiter system, revealing heretofore unknown characteristics and phenomena associated with the planet's atmosphere and the surfaces of its five major satellites. On Jupiter itself, atmospheric motions—the interaction of cloud systems—display complex vorticity. On its dark side, lightning and auroras are observed. A ring was discovered surrounding Jupiter. The satellite surfaces display dramatic differences including extensive active volcanism on Io, complex tectonism on Ganymede and possibly Europa, and flattened remnants of enormous impact features on Callisto.
Voyager 2, during its encounter with the Jupiter system, provided images that both complement and supplement in important ways the Voyager 1 images. While many changes have been observed in Jupiter's visual appearance, few, yet significant, changes have been detected in the principal atmospheric currents. Jupiter's ring system is strongly forward scattering at visual wavelengths and consists of a narrow annulus of highest particle density, within which is a broader region in which the density is lower. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but does reveal a complex and, as yet, little-understood system of overlapping bright and dark linear features. Ganymede is found to have at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered.
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The regolith at Tranquillity Base is a layer of fragmental debris that ranges in thickness from about 3 to 6 meters. The thickness of the regolith and the exposure histories of its constituent fragments can be related, by means of a relatively simple model, to the observed crater distribution.
This report provides a preliminary description of the geologic setting of the lunar samples returned fromt he Apollo 12 mission. A more complete interpretation of the geology of the site will be prepared after thorough analysis of the data.
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The Apollo 11 LM landed approximately 20 km south-southwest of the crater Sabine D in the southwestern part of Mare Tranquillitatis ( fig. 3-1 ). The landing site is 41.5 km north-northeast of the western promontory of the Kant Plateau (ref. 3-1 ), which is the nearest highland region. The Surveyor 5 spacecraft is approximately 25 km north-northwest of the Apollo 11 landing site, and the impact crater formed by Ranger 8 is 68 km northeast of the landing site.
Material of basaltic composition at the Surveyor V landing site implies that differentiation has occurred in the moon, probably due to internal sources of heat. The results are consistent with the hypothesis that extensive volcanic flows have been responsible for flooding and filling the mare basins. The processes and products of lunar magmatic activity are apparently similar to those of the earth.
Surveyor V landed in a small crater, 8.5 meters wide and 12.5 meters long, which was probably formed by drainage of surficial fragmental debris into a subsurface fissure. The lunar surface debris layer is exposed in the walls of this crater. At depths below about 10 centimeters, the debris appears to be composed mainly of shock-compressed aggregates, ranging from a few millimeters up to 3 centimeters in diameter, set in a matrix of less-coherent finer particles. Rocky chips and fragments larger than a millimeter are dispersed as a subordinate constituent of the debris.