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The objectives are to explain Venus's evolution, with emphasis on argon, both primordial and radiogenic, to understand the apparently catastrophic nature of Venus's tectonics, and to help infer the terminal phases of planetesimal infall. The main components of the research are (1) models of the global evolution of Venus, emphasizing lithosphere: convection interaction relevant to the radiogenic argon evolution; (2) Three-diemsional computer experiments on convection with dry rheology; (3) laboratory experiments on argon diffusion, both grain boundary and intragranular, with emphasis on dryness; (4) Computer modellings of large bolide imacts into a massive atmosphere, with emphasis on bolide volatiles. The work is significant to understanding the long term evolution of the terrestrial planets; in particular, why Venus, closest to Earth in primary properties, is so different in secondary properties. This proposal builds on previous work under NAG5-3596 investigating the Venus A-40/K-40 problem [Kaula 1998: Icarus, subm.]; three-dimensional convective modellings [Tackley 1996 JGR v. 101, p. 3311]; modelings of the K/T boundary impact [Newman et al 1998 Icarus, subm.]; and long experience with argon in the laboratory [e.g., McDougall & Harrison 1988 book]. |
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