¹Toshihiro Tada,^1,2,3Ryuji Tada,⁴Paul A. Carling,⁵Wickanet Songtham,⁵Praphas Chansom,¹Toshihiro Kogure,¹Yu Chang,¹Eiichi Tajika
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13908]
¹Institute for Geo-Cosmology, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba, 275-0016 Japan
²Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-0033 Japan
³Research Center for Earth System Science, Yunnan University, Chenggong District, Kunming, 650500 People’s Republic of China
⁴Geography and Environmental Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ UK
⁵Northeastern Research Institute of Petrified Wood & Mineral Resources, Nakhon Ratchasima Rajabhat University, Baan Kroke Duen Ha, Suranaree Sub-district, Muang Nakhon Ratchasima District, Nakhon Ratchasima, 30000 Thailand
Published by arrangement with John Wiley & Sons

The Australasian Tektite Event, approximately 0.8 Ma, is the youngest record of a large impact event on Earth. Although it is estimated that it occurred somewhere in Indochina based on the distribution of tektites, the crater has never been located. Here, we report the discovery and occurrence of shocked quartz with planar deformation features (PDFs) in the Quaternary depositional sequence at Huai Om in northeastern Thailand. Measurements of the orientation of lamellae using a universal stage microscope as well as observation using scanning electron microscopy and transmission electron microscopy were conducted to confirm the presence of PDFs. Together with the occurrence of in situ layered tektite fragments, we identify the depositional sequence as the ejecta deposit formed by the Australasian Tektite Event. We further describe the detailed lithostratigraphy of the ejecta deposit, which will allow the tracing of its distribution and lateral changes in its thickness, grain size, and grain composition. Further investigation of the lateral distribution of the ejecta deposit would provide information about the location, magnitude, and target rocks of the Australasian Tektite Event.

¹Allan H. Treiman,²Jacob M. LaManna,²Daniel S. Hussey,³Isabella deClue,⁴Lawrence M. Anovitz
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13904]
¹Lunar and Planetary Institute, Universities Space Research Association, 3600 Bay Area Boulevard, Houston, Texas, 77058 USA
²Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland, 20899 USA
³University of Chicago, Chicago, Illinois, 60637 USA
⁴Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37830 USA
Published by arrangement with John Wiley & Sons

The presence and distribution of hydrogen-bearing materials in meteorites are important constraints on processes in the early solar system, and the delivery of volatile constituents to growing planets. Here, we show that coordinated neutron and X-ray computed tomography, NXCT, can reveal the presence and distributions of hydrogen-bearing materials in meteorites, and thus help constrain the presence and actions of water in the early solar system. NXCT is nearly nondestructive of meteorite samples. Neutron fluence in NXCT is approximately seven orders of magnitude less than in typical instrumental neutron activation analysis, and so produces little residual radioactivity and currently undetectable changes in isotope ratios. Heating during NXCT is minimal, but NXCT will overprint the record of cosmic ray exposure held in natural thermoluminescence. Two meteorites were examined. EET 87503 is a howardite, a regolith breccia inferred to be from the asteroid 4 Vesta, and contains fragments of eucrite basalt, diogenite pyroxenite, and H-rich carbonaceous chondrites. With NXCT, the chondrite fragments within the meteorite piece can be clearly located and characterized, in preparation for possible extraction and detailed analyses. Graves Nunataks (GRA) 06100 is a CR2 chondrite meteorite that contains abundant iron metal and H-bearing silicates from aqueous alteration. In NXCT, H-bearing altered material is clearly distinguished from metal, and its distribution in three dimensions is revealed as a constraint on the processes of alteration.