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Crater morphology in sandstone targets: The MEMIN impact parameter study

 
: Dufresne, A.; Poelchau, M.H.; Kenkmann, T.; Deutsch, A.; Hoerth, T.; Schäfer, F.; Thoma, K.

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Meteoritics & planetary science 48 (2013), Nr.1, S.50-70
ISSN: 1086-9379
ISSN: 0026-1114
Deutsche Forschungsgemeinschaft DFG
KE 732/16-1
Englisch
Zeitschriftenaufsatz
Fraunhofer EMI ()

Abstract
Hypervelocity (2.57.8 km s-1) impact experiments into sandstone were carried out to investigate the influence of projectile velocity and mass, target pore space saturation, target-projectile density contrast, and target layer orientation on crater size and shape. Crater size increases with increasing projectile velocity and mass as well as with increasing target pore space saturation. Craters in water-saturated porous targets are generally shallower and larger in volume and in diameter than craters from equivalent impacts into dry porous sandstone. Morphometric analyses of the resultant craters, 540 cm in diameter, reveal features that are characteristic of all of our experimental craters regardless of impact conditions (I) a large central depression within a fragile, light-colored central part, and (II) an outer spallation zone with areas of incipient spallation. Two different mechanical processes, grain fragmentation and intergranular tensile fracturing, are recorded within these crater morphologies. Zone (I) approximates the shape of the transient crater formed by material compression, displacement, comminution, and excavation flow, whereas (II) is the result of intergranular tensile fracturing and spallation. The transient crater dimensions are reconstructed by fitting quadric parabolas to crater profiles from digital elevation models. The dimensions of this transient and of the final crater show the same trends: both increase in volume with increasing impact energy, and with increasing water saturation of the target pore space. The relative size of the transient crater (in percent of the final crater volume) decreases with increasing projectile mass and velocity, signifying a greater contribution of spallation on the final crater size when projectile mass and velocity are increased.

: http://publica.fraunhofer.de/dokumente/N-234412.html