Construction of a method of a sequential petrologic andcrystallographic analysis at JAXA for the study of thedifference of two sampling points of Hayabusa.
M. Uesugi1, T. Yada1, Y. Karouji1, Y. Ishibashi1, T. Okada1 and
M. Abe1. 1JAXA/ISAS.
E-mail: uesugi@planeta.sci.isas.jaxa.jp.
Introduction: Hayabusa spacecraft retrieved regolithparticles from two points on the surface of the asteroid, Itokawa.
The regolith particles from the first touch down point were stored
to Room B of the sample catcher, and those of second touchdown point were stored to Room A. If there are differences
between the Itokawa particles of Room A and B, it suggests theheterogeneity of the materials on the surface of Itokawa. The
heterogeneity would be a key of the evolution of Itokawa, and we
can quantitatively investigate the evolution through the analysesof Itokawa particles. Though the study should require the data ofa large number of samples, it is one of the important issues forthe study of the Hayabusa-returned samples.
Yada et al. (2012) showed a possible difference of themineral composition of the Room A and Room B. The particles
in Room B is slightly higher plagioclase contents compared to
Room A particles in several size bins. Difference of theabundance of the shock melted minerals might be a possible
origin of the difference, if it is the actual tendency of the two
sampling points,. Melt textures observed in chondrites
characterized by several features. Plagioclases (or maskelynites)with tiny blebs are one of the important minerals whichcharacterize the shock melt. We can investigate the difference of
two sampling points quantitatively by observing the petrologic
and crystallographic features of minerals, such as chemicalcompositions, shocked textures and dislocation density of theminerals. In this paper, we describe a sequence of theinvestigation of the crystallographic analysis of the regolithparticles of the Itokawa, that is now constructed at theextraterrestrial sample curation center (ESCuC).
Method: The analyzed Itokawa particles will be also possible
samples for further detailed investigations of the international
announcement of opportunity (A/O). So we should avoid orreduce contaminations through the investigations, especially fromthe terrestrial atmosphere which contains abundant water vapor,oxygen and noble gas species. In this new procedure of theinvestigations, we can avoid the atmospheric exposure bydeveloping new sample holders.
The samples were fixed in a SiN membrane holder. With thisholder, we can perform XRD installed at ESCuC without
exposing the terrestrial atmosphere and any adhesive materials.
Through the investigation by XRD and micro-Raman
spectroscopy, we can determine the mineral phases and roughcrystal directions. It is important that we can also perform
Synchrotron Radiation experiments with the holder. Because
SEM observations were already done by the Extraterrestrial
sample curation team (ESCuTe), chemical composition can beobtained. After those non-destructive observations, further
investigations are also possible for some samples. We can extract
ultra-thin sections by FIB for the high resolution investigations
by TEM/STEM. Currently all procedures except for TEM/STEM
observation can be operated at ESCuC without atmosphericexposure. We will include ultramicrotomy in the procedure in
future works.
References: [1] Yada et al. 2012. Meteoritics & Planetary
Science 47:A5245.