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diaplectic glass - This refers to glass that originated by hypervelocity shock. A synonym is thetomorphic glass.
maskelynite - This is a glass that formed by shock-deformation
of plagioclase feldspar. Maskelynite retains crystal outlines and
approximately the composition of feldspar, but it appears amorphous under
cross-polarized transmitted light. It was named after the crater
Maskelyne near the Apollo 11 landing site.
undulose/undulatory extinction - This refers to the appearance of a slightly strained birefringent crystal in cross-polarized transmitted light. A crystal showing undulose extinction has somewhat non-uniform extinction caused by slight-to-moderate misorientation of the crystal lattice as a result of plastic deformation.
Quartz (grey) showing undulose extinction.
This particular quartz was derived from a plutonic
Olivine (center) showing weak undulose extinction and some
planar fractures (grain adjacent and to the right of the central
grain) in the Framville H6(S3) chondrite. The width of the image is
650 microns. Cross-polarized transmitted light image.
mosaicism/mosaic extinction - This refers to the appearance of an intensely strained birefringent grain in cross-polarized transmitted light. A crystal showing mosaic extinction has patchy extinction caused by moderate-to-large misorientation of the crystal lattice as a result of plastic deformation.
Olivine showing mosaic extinction in the Paranaiba L6(S6)
chondrite. The width of the image is 350 microns. Cross-polarized
transmitted light image.
(shock-induced) recrystallization - This is the formation of new, relatively strain-free grains in a heavily-shocked rock. Recrystallization requires relatively high post-shock temperatures and occurs in heavily-shocked rocks.
regolith breccia - This is a breccia which appears to have originated in a regolith, as evidenced by such features as the presence of solar-wind impanted gases, solar flare and cosmic ray track damage in minerals, or the presence of intergranular, shock-produced glass. In lunar regolith (but for reasons that are unclear, not in asteroidal regolith samples), the intergranular glass can form agglutinates, which are glass-bonded soil aggregates.
fragmental breccia - This term is sometimes used to denote a type of breccia that is neither extensively shock-melted nor contains any features indicative of having originated in a regolith. Often a rock that contains supposed impact-melt generated clasts is termed a fragmental breccia.
martensite - This is a metal alloy (designated alpha-2) that forms by inversion of taenite upon relatively quick cooling. Shocked meteorites often contain martensite instead of kamacite.
escape velocity - This is the velocity needed for an object to overcome the gravitational pull of another larger object such as a planet, moon, planetesimal, etc. It is given by:
Vesc = squareroot (2GM/r)
where Vesc = escape velocity, M = mass of the larger object, r = distance from the center of the larger object, and G = gravitational constant. As planetary mass increases, so does escape velocity. It equals 11.2 km/s for Earth, 2.4 km/s for the Moon, and only 650 m/s for Ceres, the largest asteroid.
collisional (impact) velocity - This is the relative velocity between two colliding objects. It is found from:
(Vcoll)^2 = (Vesc)^2 + (Vapp)^2
where Vcoll = collisional velocity, Vesc = escape velocity of the more massive object, and Vapp = approach velocity, the relative velocity of the two objects when they are far from one another. This formula indicates that collisional velocity always will be higher when more massive objects are involved, as a result of higher Vesc (and increased gravitational acceleration) by the larger object.
Note that Table 3.6.2 extends onto two pages (177 and
178, neither of which is labeled).