ASTEROID ITOKAWA STUDIED BY RAMAN AND
INFRARED SPECTROSCOPY, X-RAY TOMOGRAPHY
AND HIGH-SENSITIVITY NOBLE GAS ANALYSIS.
H. Busemann1, C. Alwmark2, S. Bajt3, U. Böttger4, J.D. Gilmour1, U. Heitmann5, H.-W. Hübers4, M.M.M. Meier2, S.G. Pavlov4, U. Schade6, N.H. Spring1, I. Weber5. 1SEAES, Univ. ofManchester, UK (henner.busemann@manchester.ac.uk), 2Dept.
of Geology, Lund Univ., Sweden, 3Photon Sciences, DESY,Hamburg, Germany, 4Institute of Planetary Research, DLR Berlin, Germany, 5IfP, WWU Münster, Germany, 6HelmholtzZentrum Berlin (HZB), Germany.
Introduction: S-type asteroid 25143 Itokawa has been successfully sampled by JAXA’s Hayabusa mission, representing,hence, the third planetary body probed by sample return. It consists mostly of type LL5-6 material and experienced severe space
weathering and intense surface losses [1-6]. We received material
to study the noble gases combined with Raman (RS) and Infrared(IR) spectroscopy, and synchrotron radiation X-ray tomographic
microscopy (SRXTM). Here, we summarize our consortium’sresults, which provide characterizations of grain volumes andmass, mineralogy, structure and noble gas abundances.
Samples & Methods: The allocated samples, including threecontinuously stored in N2 to prevent air contamination, are listed
in [7]. Methods are detailed there [7-9], too, as well as in companion abstracts presented at this symposium [10-11].
Results: All samples have been examined by RS and revealed the expected mixture of, occasionally relatively finegrained, minerals; mainly olivine, with some samples containing
also plagioclase and pyroxene, and micron-sized, non-siliceous
metal-bearing inclusions, mostly troilite, possibly taenite orchromite [1]. Goethite, likely due to terrestrial surface alterationof troilite, was found in a few areas in one of the polished “pottedbutts”. Carbon (including diamond) was also found only on thosesamples, stemming from the coating for preceding SIMS analysis
and polishing [2]. The olivine composition, as determined by IR
and RS [9], is Fo60 ±15%, broadly consistent with previous analyses [1,12], and expectations for LL5-6 chondritic material. Alack of anisotropy found by IR suggests olivine to consist ofsmall crystals. SRXTM of six grains revealed their 3D shape,mineral distributions, precise total and mineral phase volumes,and hence, mass, and the location of the denser, non-siliceous
inclusions. Due to instrumental difficulties with both highsensitivity mass spectrometers (He-Ne in Zurich [8,10] and Xe inManchester), only one particle (RQ-QD02-0035) has been analyzed for noble gases so far. It shows the expected presence ofabundant solar wind He and Ne. A cosmic-ray exposure age of~1-3 Ma [10], smaller, but consistent with the upper limit of 8
Ma given earlier [6] could be determined. This range, if can besubstantiated with further grains, implies either a young, continuously sputtered regolith in the Muses-C region [6], or may haveresulted from a recent event that produced and exposed material
that was previously shielded from cosmic rays, which, perhaps,
could have contributed to the present shape of asteroid Itokawa.
References: [1] Nakamura T. et al. [2] Yurimoto H. et al. [3]Ebihara M. et al. [4] Noguchi T. et al. [5] Tsuchiyama et al. [6]Nagao K. et al. all: 2011. Science 333: 1113-1131. [7] BusemannH. et al. [8] Meier M.M.M. et al. [9] Böttger U. et al. all: 2013.
LPSC 44: abstracts #2243, #1937, #2092. [10] Meier M.M.M. etal. [11] Böttger U. et al. both 2013. this volume. [12] Noguchi T.
et al. 2012. Bunseki Kagaku 61:299-310.