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Effects of Impact and Heating on the Properties of Clays on Mars

Effects of Impact and Heating on the Properties of Clays on Mars. Patricia Gavin V. Chevrier, K. Ninagawa, S. Hasegawa. Clays surrounded by lava flows and in crater ejecta Heat and shock effects Possible effects on clays Loss of water Structural change New phases formed Experiments

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Effects of Impact and Heating on the Properties of Clays on Mars

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  1. Effects of Impact and Heating on the Properties of Clays on Mars Patricia Gavin V. Chevrier, K. Ninagawa, S. Hasegawa

  2. Clays surrounded by lava flows and in crater ejecta Heat and shock effects Possible effects on clays Loss of water Structural change New phases formed Experiments Heat in oven Impact in light gas gun Introduction Poulet et al., 2005 Mangold et al., 2007

  3. Heating experiments • 2 relevant clays • Montmorillonite (Ca, Al clay) • Nontronite (Fe3+ clay) • Thermal treatment in tube oven • 350oC < T < 1150oC • 4 hr < t < 24 hr • Air and CO2 atmosphere • Analysis • XRD • ESEM • Reflectance spectra

  4. Color Changes UntreatedHeated Nontronite Montmorillonite

  5. Nontronite: Low temperature Counts/sec Untreated Air, T = 630oC CO2, T = 475oC • T < 750oC: Loss of interlayer peak • Collapse of structure • Loss of water • ~25% mass

  6. Nontronite: Low Temperature Untreated T = 475oC T = 630oC OH band Water band Metal - OH band

  7. 800 < T < 1000oC: complex mixture of secondary phases Large peaks = nanocrystalline phases Solid-solid transformation no melting Nontronite: Intermediate Temperature Counts/sec Offset by 100 units

  8. Nontronite: High temperature Counts/sec • T > 1100oC: melting and crystallization of high temperature phases • sillimanite • hematite • cristobalite • glass

  9. Nontronite: Intermediate and High Temperature Untreated T = 810oC T = 975oC T = 1130oC

  10. Montmorillonite: Low Temperature Counts/sec • T < 750oC: most peaks still intact • More resistant to thermal alteration • Quartz • Albite Untreated T = 630oC Offset by 400 units

  11. Montmorillonite: High Temperature • T > 1100oC: formation of high temperature phases • silimanite • cristobalite • mica • amorphous glass Counts/sec

  12. Montmorillonite heated in Air T = 880oC T = 630oC Untreated T = 1130oC

  13. Impact Experiments • Same clays • Montmorillonite (Ca, Al clay) • Nontronite (Fe3+ clay) • Impact with light gas gun • Velocity 2 - 3.3 km/s • SUS projectile • Analysis • XRD • Reflectance spectra • Autodyne software • Max pressure and temperature

  14. Impacted nontronite Counts/sec • No real change • All peaks still visible • Interlayer peak intact • Peak intensity decrease v = 2.47km/s v = 3.27km/s Offset by 400 units

  15. Impacted Nontronite Untreated v = 2.5 km/s v = 2.15 km/s v = 2.07 km/s v = 3.27 km/s

  16. Shock Wave Propagation Modeling 10ms time step v = 2.47km/s

  17. Shock Wave Propagation Modeling v = 2.47km/s

  18. Shock Wave Propagation Modeling v = 2.47km/s

  19. Shock Wave Propagation Modeling v = 2.47km/s

  20. Shock Wave Propagation Modeling v = 2.47km/s

  21. Shock Wave Propagation Modeling v = 2.47km/s

  22. Shock Wave Propagation Modeling v = 2.47km/s

  23. Shock Wave Propagation Modeling v = 2.47km/s

  24. Shock Wave Propagation Modeling v = 2.47km/s

  25. Shock Wave Propagation Modeling v = 2.47km/s

  26. Shock Wave Propagation Modeling v = 2.47km/s

  27. Shock Wave Propagation Modeling v = 2.47km/s

  28. Shock Wave Propagation Modeling v = 2.47km/s

  29. Shock Wave Propagation Modeling v = 2.47km/s

  30. Shock Wave Propagation Modeling v = 2.47km/s

  31. Shock Wave Propagation Modeling v = 2.47km/s

  32. Shock Wave Propagation Modeling v = 2.47km/s

  33. Shock Wave Propagation Modeling v = 2.47km/s

  34. Shock Wave Propagation Modeling v = 2.47km/s

  35. Shock Wave Propagation Modeling v = 2.47km/s

  36. Shock Wave Propagation Modeling v = 2.47km/s

  37. Impacted Montmorillonite Untreated v = 2.5 km/s

  38. Clays in Craters on Mars Mangold, et al., 2007

  39. Clays in Craters on Mars T = 475oC T = 630oC

  40. Magnetization (Am2/kg) Applied Field (T) Magnetic Properties • T < 600oC: paramagnetic Fe3+ • T > 1000oC: • Low saturation magnetization • High remanent magnetization • High coercitive field • Similar to hematite

  41. Magnetization (Am2/kg) Applied Field (T) Magnetization (Am2/kg) Applied Field (T) Magnetic Properties • 800oC < T < 1000oC: Wasp-waisted • Two or more components present • Multidomain and paramagnetic particles • Maghemite? 5.1 A

  42. Conclusions • No distinctive effect of CO2 on clay transformations • Heating: intense effect on clays • Loss of water at relatively low temperatures • Melting and recrystallization at high temperatures • Disappearance of bands in FTIR • Impact affects smectites • Decrease in band depth (impact glass?) • Magnetic properties • Possible new phase at intermediate temperatures • Non-stiochiometric phase

  43. Implications for Mars • Clays detected in small crater ejecta were pre-existing • Different spectral features from untreated samples • Large impacts may generate enough heat to induce transformations • Contact with lava flows should strongly affect clays • Heated nontronite may explain origin and magnetic properties of red dust • Hematite (superparamagnetic phase) • Maghemite

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