A CONSORTIUM STUDY OF A HALITE-BEARING
ITOKAWA PARTICLE.
T. Yada1, M. E. Zolensky2, M. Uesugi1, Y. Karouji1, Y.
Ishibashi1, T. Okada1,3 and M. Abe1,3. 1Instit. Space Astronaut.
Sci. and 3Lunar Planet. Explor. Program Group, Japan Aerosp.
Explor. Agency, JAPAN. E-mail: yada@planeta.sci.isas.jaxa.jp.
2
Johnson Space Center, NASA, U.S.A.
Introduction: Hayabusa spacecraft returned its reentry
capsule which enclosed asteroid Itokawa particles inside in 2010[1]. The returned Hayabusa samples described to date number tomore than 400, and 80% of them are from Itokawa [2]. So far,more than 100 of these have been distributed via an international
announcement of opportunity (AO). Some of those having rarefeatures, such as large size or rare mineral species have not been
provided for the international AO because of their rarety. Basedon the Memorandum of Understanding between JAXA andNASA, 15% of the returned samples are assigned to JAXA.
Utilizing this fraction, JAXA is now starting consortium studiesof rare Itokawa particles. Here, we introduce one of theconsortium studies, for a particle containing NaCl (halite).
A halite-bearing Itokawa particle: Particle RA-QD02-0129
is mainly composed of silica-rich glass or plagioclase andcontains three euhedral halites on its surface. The particle
measures 40 µm and the halite size is from 2 to 5 µm. This is the
only Itokawa grain mainly composed of silicate with halites sofar. Because of its rarity and scientific importance, it wasassigned to a consortium study.
Halites in extraterrestrial samples: In extraterrestrial
samples, halites have been reported in regolith breccia H
chondrites Monahans (1998) and Zag [3, 4], the carbonaceouschondrite Murchison [5], ureilites [6], a Martian meteorite [7],and lunar soil [8, 9]. Dating by three techniques, including 129I,
revealed that the halite formed in the early solar system, 1.7Ma
later than Murchison (CM) formation [4]. Methane-bearing
compounds were discovered within Monahans halite, and it has
been suggested that halite parent body should be a large
carbonaceous object having cryovolcanism, like Saturnian
satellite Enceladus, orbiting in the main belt and that one of thepossible candidate is Ceres [10, 11].
A plan for analysis for this particle: What is essential to theconsortium study of the halite-bearing particle is to verify theextraterrestrial origin of halite. We are now accepting proposals
for analyses for the particle until this Oct. Then we will discusswith researchers about a research scheme for the particle in orderto maximize its scientific gain. So far, we initially plan to observe
the particle with optical microscopy to confirm the color ofhalites, because those found in Monahans and Zag show
purple/blue color due to the cosmic ray irradiation [3]. Then weplan to perform non-destructive analysis including synchrotron
computed tomography before moving to destructive analysis, liketransmitted electron microscopy and secondary ion mass
spectrometry.
References: [1] Abe M. et al. (2011) LPS XLII: #1638. [2]Yada T. et al. (2013)a in this symposium. [3] Zolensky M. E. et al.
(1999) Science 285: 1377. [4] Whitby J. et al. (2000) Science
288: 1819. [5] Barber D. J. (1981) GCA 45: 945. [6] Berkley J. L.
et al. (1978) GRL 5: 1075. [7] Bridges J. et al. (2001) Space Sci.
Rev. 96: 1365. [8] Clanton U. S. et al. (1978) Proc. Lunar Planet.
Sci. Conf. 9th 1945. [9] Ashikhmina N. A. et al. (1979) LPSC X:
53. [10] Fries M. D. et al. (2012) 75th MetSoc.: #5381. [11]Zolensky M. E. et al. (2013) 76th MetSoc.: #5200.