DETAILED MINERALOGICAL AND GEOCHEMICALINVESTIGATION OF THE SURFACE AND INTERIOROF HAYABUSA PARTICLES
M. M. Grady1,2, M. C. Price3, D. Johnson1, N. A. Starkey1, I. A.
Franchi1, M. Anand1,2, R. Bradley4, J. D. Gilmour4, M. Lee5, I.
Lyon4, K. H. McDermott3, S. S. Russell2, Y. Sano6, P. Schofield2,and P. J. Withers4. 1Dept. Physical Sciences, The Open University, Milton Keynes, MK7 6AA, UK. E-mail: monica.grady@open.ac.uk. 2The Natural History Museum, London.
3
University of Kent. 4University of Manchester. 5University ofGlasgow. 6The University of Tokyo.
Introduction: The samples collected by Hayabusa from asteroid Itokawa provide a unique opportunity to investigate both
the geological history of the body and its surface history. Anhydrous mineral grains (tens of microns to sub-millimetre in size)
clearly survived the collection process, and most of the material
studied so far indicates that Itokawa is an LL chondrite of petrographic grade 5 [1, 2]. However, some of the grains appear to be
more unequilibrated, suggesting that Itokawa may exhibit a rangeof compositions that are sampled by the regolith [3]. Such grains
might be the more friable phases typically found in the most unequilibrated chondrites, including fine-grained matrix and carbonaceous material. They may only survive as much smaller, submicron-sized, grains preserved on the surfaces of the larger
grains. One of the important questions that we are seeking to answer is whether we can detect differences between the surface
and interior of the grains, to see if modification of the grains byirradiation and impact on Itokawa’s surface can be traced via
changes in structural, isotopic or elemental composition. We received two particles from the Hayabusa collection: sample RAQD02-0024 (mounted in resin and polished; slice removed byFIB prior to receipt) and sample RA-QD02-0162 (unmounted).
We have undertaken Raman and SEM analyses of the grains, toverify the different phases present, before submitting them for ion
microprobe measurement of oxygen isotopic composition (atOpen Univ.) and trace elements (at Univ. Tokyo).
RA-QD02-0024: As the grain was already mounted and polished, only one side could be mapped by both Raman and SEM.
Bot techniques showed that the dominant component of the grain
was olivine, accompanied by a smaller grain of diopside. RAQD02-0162: This grain was analysed by Raman spectroscopy
within the sample shipping container; only one side was mapped
as the grain adhered to the vessel wall. At least four anhydrous
sub-grains (5-20 m) were found: two olivines (Fo40-60) and two(distinct) pyroxenes. Weak features associated with disorderedorganic carbon were also apparent in some spectra, although it isunclear if the phase is internal to the grain or surficial. No otherphases were identifiable in the Raman spectra. Disordered carbon
has not previously been reported from Hayabusa samples. Further
investigation is planned in order to determine where the carbon issited and whether it is indigenous to the asteroidal particle or terrestrial contamination.
We thank JAXA and the Hayabusa consortium for generous
provision of material, and the opportunity to attend the symposium. Financial support is also acknowledged from STFC.
References: [1] Nakamura T. et al. 2011. Science
3333:1113–1115. [2] Yurimoto H. et al. 2011. Science3333:1116–1118. [3] A. Tsuchiyama et al. 2013. MAPS DOI:
10.1111/maps.12177.