Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session C5: Geophysics and Planetary Science I: Impacts, Asteroids, and Meteorites |
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Room: Regency Ballroom B |
Monday, July 10, 2017 11:15AM - 11:30AM |
C5.00001: Meteorites: impact and damage. An inside view of asteroidal microstructure David Eastwood, Serafina Garcea, Sam McDonald, Kate Dobson, Rhian Jones, Jenny Woods, Neil Bourne, Christoph Rau, George T. Gray III \textunderscore \textunderscore Meteorites provide an important window into the formation and evolution of the solar system and planets. Chondrite meteorites preserve a record of the epoch when the solar system consisted of a cloud of dusty gas surrounding the newly formed Sun, as well as recording 4.6 billion years of geological history on asteroids. From meteorite studies we know that many asteroids contained water when they first accreted. In many cases this water later melted and flowed through the rock, leaving evidence of its tracks in the remaining minerals. Water and other fluids dissolved some of the original material, leaving void spaces. We have used tomography to assess the extent to which the original components of chondrites were affected by dissolution, by observing the nature and distribution of the resulting void space. Tomography allows us to assess the relative abundances of each to the overall porosity, and to visualize connectivity through pore space. Based on such information we can hypothesise about the agglomeration processes and the effect of impact processes on asteroid formation and microstructure. [Preview Abstract] |
Monday, July 10, 2017 11:30AM - 11:45AM |
C5.00002: Continuum modeling of porous compaction in asteroid materials Kirsten Howley, Laura Chen, Damian Swift Models of the response of porous materials to dynamic loading are important for simulations of asteroid impact and deflection scenarios. In hydrocode calculations, porosity is commonly treated by modifying the scalar equation of state (EOS), such as by describing the pressure during compression from the initial, porous state to solid density with an empirically-derived compaction curve. This approach is simple but not rigorous or predictive in general, for different initial porosities, because the compaction process is dominated by shear strain as pores are closed. Detailed compaction processes can be investigated using resolved-microstructure simulations, but the response can be represented at the continuum level by modifying the strength model to include the variation of shear modulus and flow stress with porosity as well as the compression and temperature of the solid. [Preview Abstract] |
Monday, July 10, 2017 11:45AM - 12:00PM |
C5.00003: Abstract Withdrawn
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Monday, July 10, 2017 12:00PM - 12:15PM |
C5.00004: Development of methodology for component testing under impact loading for space applications Phillip Church, Nicholas Taylor, Marie-Claire Perkinson, Alex Wishart, Sanjay Vijendran, Chris Braithwaite A number of recent studies have highlighted the scientific benefits of penetrator technology in conducting exploration on other planetary bodies and moons within the solar system. Such a ``hard landing" approach is cheaper and easier than the traditional ``soft landing" method. However it is necessary for the science package of such a mission to withstand the rapid decelerations that will occur upon impact. This paper outlines an approach that has been developed to simulate the loading appropriate to Europa and also to monitor component performance before, during and after the impact. [Preview Abstract] |
Monday, July 10, 2017 12:15PM - 12:30PM |
C5.00005: Self-Assembly of Prebiotic Organic Materials from Impact Events of Amino Acid Solutions Nir Goldman Proteinogenic amino acids can be produced on or delivered to a planet via abiotic sources and were consequently likely present before the emergence of life on early Earth. However, the role that these materials played in the in the emergence of life remains an open question, in part because little is known about the survivability and reactivity of astrophysical prebiotic compounds upon impact with a planetary surface. To this end, we have used a force matched semi-empirical quantum simulation method in development in our group to study oblique impacts of aqueous glycine solutions at conditions of up to 40 GPa and 3000 K. We find that these elevated conditions induce the formation of glycine-oligomeric structures with a number of different chemical moieties such as hydroxyl and amine groups diffusing on and off the C-N backbones. The C-N backbones of these structures generally remain stable during cooling and expansion, yielding relatively large three-dimensional molecules that contain a number of different functional groups and embedded bonded regions akin to oligo-peptides. Our results help determine the role of comets and other celestial bodies in both the delivery and synthesis of polypeptides and homochirality to early Earth. [Preview Abstract] |
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