The role of volatiles and lithology in the impact cratering process, Rev

• Main Authors: Susan Werner Kieffer, Charles H. Simonds
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1980
• Subjects: Ice; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.210.6774; http://www.geology.illinois.edu/people/skieffer/Sites/papers/VolatilesLithology_RGSP1980.pdf

A survey of published descriptions of 32 of the largest, least eroded terrestrial impact structures reveals that the amount of melt at craters in crystalline rocks is approximately 2 orders of magnitude greater than at craters in sedimentary rocks. In this paper we present a model for the impact process and examine whether this difference in melt abundance is due to differences in the amount of melt generated in various target materials or due to differences in the fate of the melt during late stages of the impact. The model consists of a theoretical part for the early stages of impact, based on a Birch-Murnaghan equation of state, a penetration scheme after Shoemaker (1963), and an attenuation model modified from Gault and Heitowit (1963), and a descriptive part for the later stages of impact, based on field observations at the large terrestrial craters. The impacts of iron, stone, permafrost, and ice meteorites I km in diameter into crystalline, carbonate, dry sandstone, ice-saturated sand, and ice targets are modeled for velocities of 6.25, 17, and 24.6 km/s. Tables of calculated crater volume, depth of penetration of the meteorite, equivalent scaled depth of burst, radii to various peak pressure isobars, volume of silicate melt, and volume of water vapor (or, in the case of carbonate, carbon dioxide vapor) are presented. Simple algebraic expressions for pressure attenuation are derived: for the near field, dX/dR = 3Xn/R(I- n), where X is the pressure normalized to an averaged bulk modulus for the target rocks, R is the radius normalized to the