COMBINED CHEMICAL/ELEMENTAL ANALYSIS AND
CHARGING PROPERTIES MEASUREMENTS OF ITOKAWAGRAINS RETURNED BY THE HAYABUSA MISSION
F. Cipriani1, M. Ferrari2,3, V. Della Corte2, M. Accolla2,3, N. Drozdovski1, V. Mennella4, A. Rotundi2,3, D. Koschny1, P. Vernazza5, L. Colangeli1, O. Witasse1 1 ESA/ESTEC, Keplerlaan 1, 2200AG,
Noordwijk, The Netherlands E-mail : fabrice.cipriani@esa.int 2 INAFIstituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere
100, 00133 Roma, Italy 3 Dip. Scienze e Tecnologie, Universita degliStudi di Napoli “Parthenope”, Centro Direzionale I C4, 80143 Napoli,Italy 4 - INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy 5 Laboratoire d’Astrophysique de Marseille, CNRSIntroduction: The Hayabusa spacecraft collected submillimeterparticles from the Muses Sea region on asteroid (25143) Itokawa on
19th and 25th of November 2005 [1,2]. We proposed to use MicroInfrared spectroscopy, Micro-Raman spectroscopy, Energy Dispersive
X-Ray spectroscopy, and FE-SEM imaging to measure not only elemental abundances and chemical characteristics of grains RB-QD040083, RB-QD04-0072, RA-QD02-0136-14, and RA-QD02-0126-12,
but also their charging properties.
Sample holder and samples preparation: specific sample holders
have been designed to meet the constrains of this unique series ofmeasurement, carried out so far at the European Space Research andTechnology Center (ESTEC) in Noordwijk, INAF/Istituto di Astrofisica e Planetologia Spaziali in Rome, and INAF/ Osservatorio Astronomico di Capodimonte (OAC) in Naples. Grains are glued with conductive epoxy at the tip of Tungsten needles fed through a StainlessSteel mounting block accommodated on modified SEM-stubs hosting
Si calibration gratings in their centers. In preparation of any measurements to be performed with actual Itokawa grains, validation of thegrains attachment procedure, holder mounting and measurements chain
have been carried out with 10 to 30 microns Fosterite grains.
Micro-Raman and Micro-IR measurements: Micro-Raman
measurements are performed at ESTEC with grains kept in the original
JAXA containers using a confocal Micro-Raman spectroscopic systemusing an Ar ion laser beam at 514.5nm for excitation, and a long working distance objective. Micro-IR analysis is performed later on at OAC
in transmission mode with an IR microscope attached to a FTIR interferometer (Bruker Equinox 55) in range 7000-600 cm-1 (spectral resolution 4cm-1) but first on analog grains prepared on supporting tungsten needles, in order to calibrate the measurements and estimate thecontamination resulting from the epoxy glue.
FE-SEM imaging and Charging properties measurements : weuse a Quanta FEG 650 at low voltage beam to 1) observe the grains
morphology and 2) map the steady state electrostatic potential at thegrain surface subject to charging by the incident electron beam. The
beam energy is varied between 500eV and 2keV at this stage, while thecombination of FE-SEM images of the grain and underlying substrate
and an electrostatic model of the charging occurring in the FE-SEM
chamber allows to retrieve the grain surface potential distribution
where the surface is not covered by the conductive glue.
FESEM/EDX analysis: in addition, low voltage morphologicalobservations are performed at OAC a with a Zeiss Supra 25 equippedwith an Oxford Inca Energy 350 with a Si(Li) INCA X-Sight detector
followed by elemental analysis by EDX performed at 15keV.
References: [1] Fujiwara, A. et al, Hayabusa Mission to Asteroid Itokawa: In-Situ Observation and Sample Return, Dust in Planetary Systems, Proceedings, September 26-28, 2005 in Kaua'i, Hawaii. LPI Contribution No. 1280., p.50, [2] Yano, H. et al, 2006, Science, 312, 1350