Three-Dimensional Structure of Hayabusa Samples: Origin and Evolution of Itokawa Regolith

Laboratory analysis of samples returned from an asteroid establishes a direct link between asteroids and meteorites and provides clues to the complex history of the asteroid and its surface. Regolith particles on the asteroid Itokawa were recovered by the Hayabusa mission. Their three-dimensional (3D) structure and other properties, revealed by x-ray microtomography, provide information on regolith formation. Modal abundances of minerals, bulk density (3.4 grams per cubic centimeter), and the 3D textures indicate that the particles represent a mixture of equilibrated and less-equilibrated LL chondrite materials. Evidence for melting was not seen on any of the particles. Some particles have rounded edges. Overall, the particles’ size and shape are different from those seen in particles from the lunar regolith. These features suggest that meteoroid impacts on the asteroid surface primarily form much of the regolith particle, and that seismic-induced grain motion in the smooth terrain abrades them over time.

[1]  Junichiro Kawaguchi,et al.  Irradiation History of Itokawa Regolith Material Deduced from Noble Gases in the Hayabusa Samples , 2011, Science.

[2]  Junichiro Kawaguchi,et al.  Itokawa Dust Particles: A Direct Link Between S-Type Asteroids and Ordinary Chondrites , 2011, Science.

[3]  N Shirai,et al.  Neutron Activation Analysis of a Particle Returned from Asteroid Itokawa , 2011, Science.

[4]  Junichiro Kawaguchi,et al.  Oxygen Isotopic Compositions of Asteroidal Materials Returned from Itokawa by the Hayabusa Mission , 2011, Science.

[5]  T. Hashimoto,et al.  Incipient Space Weathering Observed on the Surface of Itokawa Dust Particles , 2011, Science.

[6]  A. Nakamura,et al.  The shape distribution of boulders on Asteroid 25143 Itokawa: Comparison with fragments from impact experiments , 2010 .

[7]  Shinsuke Fujioka,et al.  Impact experiments with a new technique for acceleration of projectiles to velocities higher than Earth's escape velocity of 11.2 km/s , 2010 .

[8]  T. Matsushima,et al.  Statistics on 3D Particle Shapes of Lunar Soil (No. 60501) Obtained by Micro X-Ray CT and Its Image-Based DEM Simulation , 2010 .

[9]  D. Scheeres,et al.  Scaling forces to asteroid surfaces: The role of cohesion , 2010, 1002.2478.

[10]  T. Mccoy,et al.  Analysis of ordinary chondrites using powder X‐ray diffraction: 1. Modal mineral abundances , 2010 .

[11]  A. Takeuchi,et al.  Zernike phase-contrast x-ray microscope with pseudo-Kohler illumination generated by sectored (polygon) condenser plate , 2009 .

[12]  David P. O'Brien,et al.  Itokawa's cratering record as observed by Hayabusa: Implications for its age and collisional history , 2009 .

[13]  Guy J. Consolmagno,et al.  The significance of meteorite density and porosity , 2008 .

[14]  A. Nakamura,et al.  Size-frequency statistics of boulders on global surface of asteroid 25143 Itokawa , 2008 .

[15]  Hajime Yano,et al.  Regolith Migration and Sorting on Asteroid Itokawa , 2007, Science.

[16]  Kentaro Uesugi,et al.  Development of micro-tomography system with Fresnel zone plate optics at SPring-8 , 2006, SPIE Optics + Photonics.

[17]  J. Kawaguchi,et al.  The Rubble-Pile Asteroid Itokawa as Observed by Hayabusa , 2006, Science.

[18]  Kazuya Yoshida,et al.  Touchdown of the Hayabusa Spacecraft at the Muses Sea on Itokawa , 2006, Science.

[19]  Akira Fujiwara,et al.  Near-Infrared Spectral Results of Asteroid Itokawa from the Hayabusa Spacecraft , 2006, Science.

[20]  R. Jones.  Meteorites: A Petrologic, Chemical and Isotopic Synthesis , 2005 .

[21]  M. Robinson,et al.  The nature of ponded deposits on Eros , 2001, Nature.

[22]  Richard P. Binzel,et al.  MUSES‐C target asteroid (25143) 1998 SF36: A reddened ordinary chondrite , 2001 .

[23]  Y. Nakashima,et al.  Three-dimensional study on the interconnection and shape of crystals in a graphic granite by X-ray CT and image analysis , 2000, Mineralogical Magazine.

[24]  F. Bloss.  Crystallography and Crystal Chemistry: An Introduction , 1989 .

[25]  D. F. Marks,et al.  An introduction , 1988, Experientia.

[26]  P. N. Smith,et al.  Shapes of asteroids compared with fragments from hypervelocity impact experiments , 1984, Nature.

[27]  R. Hutchison.  Meteorites: A Petrologic, Chemical and Isotopic Synthesis , 1981 .

[28]  A. Fujiwara,et al.  Expected shape distribution of asteroids obtained from laboratory impact experiments , 1978, Nature.

[29]  Kentaro Uesugi,et al.  Quantitative evaluation of attenuation contrast of X-ray computed tomography images using monochromatized beams , 2005 .

[30]  Y. Nakashima,et al.  Observation and analysis of internal structure of rock using X-ray CT. , 2000 .