(n.) Any one of numerous species of marine bivalve shells of the genus Venus or family Veneridae.(n.) The metal copper - probably so designated from the ancient use of the metal in making mirrors, a mirror being still the astronomical symbol of the planet Venus.As the morning star, it was called by the ancients Lucifer as the evening star, Hesperus. Its diameter is 7,700 miles, and its sidereal period 224.7 days. (n.) One of the planets, the second in order from the sun, its orbit lying between that of Mercury and that of the Earth, at a mean distance from the sun of about 67,000,000 miles.(n.) The goddess of beauty and love, that is, beauty or love deified.(6) By scanning electron microscopy it was observed that outer and inner surfaces of tesserae differ in appearance.(5) Calcospherites and hydroxyapatite crystals similar to those commonly seen on the surface of bone are present on the outer surface of the tessera adjacent to the perichondrium.(4) Individual tesserae develop peripherally at the boundary between cartilage and perichondrium.(3) The outer zone of tesserae, the cap, is composed of calcified tissue which appears to be produced by perichondrial fibroblasts more directly, i.e., without first differentiating as chondroblasts.(2) If so, the cap could be considered a thin veneer of bone atop the calcified cartilage of the body of a tessera.(1) Transmission electron microscopy shows calcification in close association with coarse collagen fibrils on the outer side of a tessera, but such fibrils are absent from the cartilaginous matrix along the under side of tesserae.(n.) A small piece of marble, glass, earthenware, or the like, having a square, or nearly square, face, used by the ancients for mosaic, as for making pavements, for ornamenting walls, and like purposes also, a similar piece of ivory, bone, wood, etc., used as a ticket of admission to theaters, or as a certificate for successful gladiators, and as a token for various other purposes.Understanding of the basic structural characteristics of trough and ridge terrain is more tentative, and models involving a spreading process or convergence and relaxation merit further study. We find that horizontal convergence and late stage gravitational relaxation are the most consistent with basic observations for subparallel ridged terrain and disrupted terrain. Modificational models, in which deformation occurs as a response to the presence of elevated regions, consist of (1) gravity sliding and (2) gravitational relaxation. Formational models, in which high topography is created along with surface deformation, include (1) horizontal convergence, (2) mantle upwelling, (3) crustal underplating, and (4) a seafloor spreading analogy. Observed characteristics of tessera terrain are compared to predictions of models in order to begin to address the question of its origin and evolution. Three types of tessera terrain can be defined on the basis of structural patterns: subparallel ridged terrain (T sr), trough and ridge terrain (T tr) and disrupted terrain (T ds). Available Pioneer Venus line of sight gravity data suggest that tessera terrain is compensated at shallow depths relative to many topographic highs on Venus and may be supported by crustal thickness variations. Tesserae are characterized by regionally high topography, a high degree of small scale surface roughness, and sets of intersecting tectonic features. Tessera terrain is the dominant tectonic landform in the northern high latitudes of Venus mapped by the Venera 15 and 16 orbiters and is concentrated in the region between the mountain ranges of western Ishtar Terra and Aphrodite Terra.
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