Now showing items 1-10 of 10

    • Effect of Shock on the Magnetic Properties of Pyrrhotite, the Martian Crust, and Meteorites 

      Louzada, Karin L.; Stewart, Sarah; Weiss, Benjamin P. (American Geophysical Union, 2007)
      We performed planar shock recovery experiments on natural pyrrhotite at pressures up to 6.9 GPa. We find that high-field isothermal remanent magnetization in pyrrhotite is demagnetized up to 90% by shock due to preferential ...
    • Effects of Planet Curvature and Crust on the Shock Pressure Field Around Impact Basins 

      Louzada, Karin; Stewart, Sarah (American Geophysical Union, 2009)
      We investigate the effects of planetary curvature and the crust-mantle boundary on the shock pressure field around impact basins on Mars using acoustic ray path calculations and hydrocode simulations. Planet curvature and, ...
    • Excess Ejecta Craters Record Episodic Ice-Rich Layers at Middle Latitudes on Mars 

      Black, Benjamin A.; Stewart, Sarah (American Geophysical Union, 2008)
      We infer Amazonian climate change events from the presence of fresh craters with excess volumes of ejecta. Using the Mars Orbiter Laser Altimeter data, the geometrical properties of 572 fresh impact craters with rim diameters ...
    • High-Pressure X-ray Diffraction and Raman Spectroscopy of Ice VIII 

      Yoshimura, Yukihiro; Stewart, Sarah; Somayazulu, Maddury; Mao, Ho-kwang; Hemley, Russell J. (American Institute of Physics, 2005)
      In situ high-pressure/low-temperature synchrotron x-ray diffraction and optical Raman spectroscopy were used to examine the structural properties, equation of state, and vibrational dynamics of ice VIII. The x-ray measurements ...
    • Impact Crater Formation in Icy Layered Terrains on Mars 

      Senft, Laurel E.; Stewart, Sarah (Meteoritical Society, 2008)
      We present numerical simulations of crater formation under Martian conditions with a single near-surface icy layer to investigate changes in crater morphology between glacial and interglacial periods. The ice fraction, ...
    • In Situ Raman Spectroscopy of Low-Temperature/High-Pressure Transformations of H2O 

      Stewart-Mukhopadhyay, Sarah; Hemley, Russell J.; Mao, Ho-kwang; Yoshimura, Yukihiro (American Institute of Physics, 2007)
      In situ Raman spectra of transformations of H[sub]2[sub]O as functions of pressure and temperature have been measured starting from high-density amorphous ice (HDA). Changes above T[sub]x[sub], the crystallization temperature ...
    • Martian Subsurface Properties and Crater Formation Processes Inferred From Fresh Impact Crater Geometries 

      Stewart, Sarah; Valiant, Gregory J. (Meteoritical Society, 2006)
      The geometry of simple impact craters reflects the properties of the target materials, and the diverse range of fluidized morphologies observed in Martian ejecta blankets are controlled by the near-surface composition and ...
    • Modeling Impact Cratering in Layered Surfaces 

      Senft, Laurel E.; Stewart, Sarah (American Geophysical Union, 2007)
      Impact craters are potentially powerful tools for probing large-scale structure beneath planetary surfaces. However, the details of how target structure affects the impact cratering process and final crater forms remain ...
    • On the Thermodynamics of Planetary Impact Events 

      Kraus, Richard Gordon (2013-09-30)
      The history of planet formation and evolution is strongly tied to understanding the outcomes of a wide range of impact events, from slow accretionary events to hypervelocity events that melt and vaporize large fractions ...
    • Shock Properties of H2O Ice 

      Stewart, Sarah; Ahrens, Thomas J. (American Geophysical Union, 2005)
      To understand the mechanics and thermodynamics of impacts on, and collisions between, icy planetary bodies, we measured the dynamic strength and shock states in H2O ice. Here, we expand upon previous analyses and present ...