Generation and evolution of impact-induced vapor clouds: Spectroscopic observations and hydrodynamic calculations

Details Generation and evolution of impact-induced vapor clouds: Spectroscopic observations and hydrodynamic calculations Generation and evolution of impact-induced vapor clouds: Spectroscopic observations and hydrodynamic calculations

Nov 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999phdt.........9s&link_type=abstract

Thesis (PhD). BROWN UNIVERSITY, Source DAI-B 60/05, p. 2041, Nov 1999, 268 pages.

Mathematics

Logic

Hypervelocity Collisions, Hydrocode Calculations

Scientific paper

Generation of vapor is a natural consequence of hypervelocity collisions between major planets and small bodies in the Solar System. Resulting impact vapor clouds may induce a variety of processes on the surface of a planet. One of the key factors in impact-induced vaporization is energy partitioning. Conventional wisdom teaches that the energy partitioned during an impact is predicted completely by the Rankine-Hugoniot equations and equations of states. Consequently, extensive efforts have been made both to develop mathematical/numerical methods to solve these equations accurately and to determine material-dependent constants using 1- dimensional impact experiments (i.e., flyer-plate experiments). Recent laboratory experiments, however, revealed that 3- dimensional hypervelocity impacts show intriguing processes that highly sophisticated hydrocodes do not readily account for, such as enhanced vaporization at low impact angles (measured from the horizontal) and impactor survival. Radar mapping of Venus by the Magellan spacecraft also revealed that craters on Venus have features consistent with processes observed in laboratory experiments. In particular, morphological observations indicate that run-out flows around Venus craters may be contributed largely by condensates from the downrange component of impact vapor clouds observed in laboratory experiments. Based on these new findings, the work presented in this thesis attempts to understand energy partitioning mechanisms during both generation and subsequent evolution of impact vapor clouds. To achieve this goal, I took two approaches. First, I looked at run-out flows around impact craters on Venus to extract information on impact-induced vapor clouds at planetary scales. In order to decipher this geologic record, I carried out numerical calculations of the interactions between an atmosphere and vapor clouds induced by oblique impacts. The second approach is to go back to a laboratory to understand the basic physics behind the vaporization phenomena during hypervelocity impacts. I developed a new spectroscopic technique to observe thermodynamical quantities of highly transient impact vapor clouds. Finally, I returned to the problem of the interaction between impact-induced vapor clouds and an atmosphere with the newly developed spectroscopic technique. Extensive comparison was made between the experimental results and theoretical calculations in order to find processes overlooked in previous theoretical considerations.

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