A CONSORTIUM STUDY FOR THE LARGEST PARTICLE OF THE HAYABUSA-RETURNED SAMPLES.
M. Uesugi1, T. Yada1, Y. Karouji1, Y. Ishibashi1, T. Okada1, M.
Abe1 and A. Tsuchiyama2. 1JAXA/ISAS. 2Kyoto University.
E-mail: uesugi@planeta.sci.isas.jaxa.jp.
Introduction: Hayabusa-returned samples retrieved by theHayabusa spacecraft were already distributed and investigated in
the preliminary examinations and international A/Os. Throughthe investigations, several insights have been obtained on theformation process of 25143 Itokawa and surface processes occurred on the asteroid, as well as the confirmation that the particles were certainly regolith particles from there [1-6].
There are several particles, however, which have not been
distributed for those examinations because of their rare featuresappeared in the initial description done by extraterrestrial sample
curation team (ESCuTe) of JAXA. Though those particles will
provide us further information for Itokawa and evolution of theasteroid, the samples should be investigated as carefully as possible to reduce consumption and damage of the samples. Referring the method and results of the previous studies, we decided tostart the investigations of those rare particles by constructing theconsortium of each particle. We will accept proposals for theconsortium studies in order to maximize scientific gain from theHayabusa-returned samples [7,8]. In this paper, we show anoverview and a tentative research plan for the one of the consortium particles.
RA-QD02-0136-01: RA-QD02-0136-01 is currently thelargest sample of Hayabusa-returned samples recovered from thesample catcher. The major axis of the particle ra is around 310µm, and weight of the particles is estimated around 150 µg, assuming the volume V = 4/3πrarbrc ~ 4/3π/(2√2)ra3 and density ofthe particle as 3.4 g/cm3 [5]. The RA-QD02-0136-01 is mainlycomposed of Ca-rich pyroxene, and also contains minor amountof low-Ca pyroxene, olivine, plagioclase and troilite. The surfaceof the particle is in irregular shape, and showing variable structure such as large crystal base and aggregation of small particles.
Research plan: The textural and mineralogical information
will be obtained at first, using Synchrotron radiation (SR) CT anddiffraction. These observations will be operated without exposing
the sample to the atmosphere, and also without any adhesive material using a special sample holder for the SR experiments. We
can obtain the textures inside the particle, and rough chemicalcomposition of the minerals combining the linear absorption coefficient in the CT image and EDS observation of the surface ofthe particle.
Further studies using the particle will become possible using
the results of the SR experiments, such as detection of the solar
wind, cosmogenic and the radiogenic nuclides, as well as studies
based on the specific minerals or structures. We are also planningto cut the sample by laser, and distribute the pieces to the several
lines of the investigations.
The research plan is tentative and anyone can propose theiranalysis to the consortium study.
References: [1] Nakamura et al. 2011. Science 333:11131116. [2] Yurimoto et al. 2011. Science 333:1116-1119. [3]Ebihara et al. 2011. Science 333:1119-1121. [4] Noguchi et al.
(2011) Science 333:1121-1125. [5] Tsuchiyama et al. 2011. Science 333:1125-1128. [6] Nagao et al. 2011. Science 333:11281131. [7] Abe et al. 2013. Meteoritics & Planetary Science
48:A5147. [7] Uesugi et al. 2013. Meteoritics & Planetary
Science 48:A5146.