Nanoscale infrared imaging analysis of carbonaceous chondrites to understand organic-mineral interactions during aqueous alteration

1Yoko Kebukawa,2Hanae Kobayashi,2Norio Urayama,2Naoki Baden,3Masashi Kondo,4Michael E. Zolensky,2Kensei Kobayashi
Proceedings of the National Academy of Sciences of the United States of America 116, 753-758 Link to Article []
1Faculty of Engineering, Yokohama National University, 240-8501 Yokohama, Japan;
2Nihon Thermal Consulting Co., Ltd., 160-0023 Tokyo, Japan
3Instrumental Analysis Center, Yokohama National University, 240-8501 Yokohama, Japan
4Astromaterials Research and Exploration Science, National Aeronautics and Space Administration Johnson Space Center, Houston, TX 77058

Organic matter in carbonaceous chondrites is distributed in fine-grained matrix. To understand pre- and postaccretion history of organic matter and its association with surrounding minerals, microscopic techniques are mandatory. Infrared (IR) spectroscopy is a useful technique, but the spatial resolution of IR is limited to a few micrometers, due to the diffraction limit. In this study, we applied the high spatial resolution IR imaging method to CM2 carbonaceous chondrites Murchison and Bells, which is based on an atomic force microscopy (AFM) with its tip detecting thermal expansion of a sample resulting from absorption of infrared radiation. We confirmed that this technique permits ∼30 nm spatial resolution organic analysis for the meteorite samples. The IR imaging results are consistent with the previously reported association of organic matter and phyllosilicates, but our results are at much higher spatial resolution. This observation of heterogeneous distributions of the functional groups of organic matter revealed its association with minerals at ∼30 nm spatial resolution in meteorite samples by IR spectroscopy.


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