46th Lunar and Planetary Science Conference (2015)
M. Yesiltas1, J. Sedlmair2, C. Hirschmugl3, and R. E. Peale1. 1University of Central Florida (1Dept. of Physics, University of Central Florida, 4000 Central Florida Blvd. PS 430, Orlando, FL, 32816, Email: [email protected]), 2Forest Products Laboratory (US Department of Agriculture Forest Service, Madison, WI
53726), 3University of Wisconsin-Milwaukee (Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI 53211).
Introduction: Carbonaceous chondrites are primitive meteorites whose chemical composition is highly
heterogeneous. Their composition can be affected by
various extraterrestrial processes in different enviroments, such as aqueous and thermal alteration in their
parent bodies. Study of organic matter, its distribution,
and spatial relationships is key to understanding processes and mechanisms for the formation of organic
matter in the early solar system [1]. Our knowledge on
formation and processing of organic matter is very poor
[2], however study of composition and petrology of
carbonaceous chondrites in situ can reveal these complex parent body processes and origin of constituents
of meteorites.
We have previously shown that organic matter and
mineral species can be mapped in situ in meteorites
using two-dimensional infrared images with high resolution [3,4], which reveals relationships between organic matter and minerals micron length scales. In this
work we study spatial distributions of organics and
minerals in Murchison by utilizing a highly novel technique: synchrotron-based three dimensional infrared
microspectroscopy. This technique is potentially the
most efficient method for investigation of how and
where different molecular functional groups are spatially distributed in situ in extraterrestrial samples.
Experimental: Three-dimensional infrared microtomography has recently been made possible for the
first time, which reveals internal chemical composition
and spatial distributions. A full mid-infrared range
spectrum is obtained for every voxel, providing a fourth
spectral dimension [5]. We have conducted our FTIR
spectro-microtomography experiments at IRENI beamline at the Synchrotron Radiation Center, University of
Wisconsin in Madison. A large number of transmission
images were collected as the meteorite sample was rotated in time. These images constitute our tomographic
dataset for three-dimensional representation of the meteorite sample [e.g., 6]. Additionally, full mid-infrared
spectrum was collected for each orientation as a fourth
dimension. Reconstruction of tomographic data is
done in software.
Results: Infrared spectrum of the Murchison sample studied here shows signatures of several molecular
functional groups. Si-O stretching, C-H bending, C=O
stretching, C-H stretching, and O-H stretching vibrational modes are among those we observed. Threedimensional reconstructions show that silicate-rich and
silicate-poor regions are distinctly visible in the reconstruction. Structural water obtained from H-O-H bending vibrational modes is distributed roughly uniformly
throughout the grain, and appears as small grains. Distinct from the others is the distribution of carbonyls,
which is distributed mostly in the lower half of the
Figure 1. Three dimensional reconstruction of Si-O
stretch in silicates (left) and C-H bend in aliphatics
In addition to individual reconstructions, we also
generated reconstructions of combinations of chemical
functional groups in order to reveal relative spatial relations among organics and minerals, and allow pair-wise
comparisons in three dimensions. For instance, sulfates
and structural water appear to overlap well, which may
have implications regarding the formation of sulfates
from aqueous alteration. Finally, we generated reconstructions of all of the components observed in this
study, which makes up the whole Murchison grain
(Figure 2).
46th Lunar and Planetary Science Conference (2015)
Figure 2. Three dimensional reconstruction of all
of the chemical components observed in this study via
infrared micro-spectroscopy.
The fourth dimension in our dataset is the infrared
spectra. In addition to visual investigation in threedimensional space, different regions of the grain can be
studied spectrally since reconstruction of the whole
Murchison grain investigated here consists of more
than two million voxels, each with associated full midinfrared spectrum. Infrared spectra extracted from different regions of the studied Murchison grain presents
correlations of organics with minerals. For instance,
silicates and sulfates appear to be positively correlated
with carbonates, all of which are products of aqueous
Summary: Three-dimensional infrared spectromicrotomography is a highly novel non-destructive
technique which has the advantage of locating specific
organics and minerals within samples of interest in
three dimensional space and reveiling their interrelationships. Infrared spectra obtained from voxels offer
spectral characterization of meteoritic constituents
within their local mineralogy. This technique has significant potential for the investigation and characterization of extraterrestrial samples including samples returned from missions such as Osiris-REx and Hayabusa-2.
References: [1] Pearson et al. (2002) Meteoritics &
Planet. Sci., 37, 1829-1833. [2] Herd et al. (2011) Science 332:1304-1307. [3] Yesiltas et al. (2013) Meteoritics & Planet. Sci., 48:S5. [4] Yesiltas et al. (2014)
Meteoritics & Planet. Sci., 49, 2027-2037. [5] Martin
et al. (2013) Nat Meth, 10(9), 861-864. [6] Mattson et
al. (2014) Infrared and Raman Spec. Imaging: Second,
Completely Rev. and Up. Ed. (eds R. Salzer and H. W.