¹Daisuke Nakashima,¹Yuri Fujioka,¹Kanchi Katayama,¹Tomoyo Morita,¹Mizuha Kikuiri,¹Kana Amano,¹Eiichi Kagawa,¹Tomoki Nakamura
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14036]
¹Department of Earth Science, Tohoku University, Sendai, Japan
Published by arrangement with John Wiley & Sons

Preparation procedures of polished sections of the Ryugu samples returned by theHayabusa2 spacecraft were established through tests using CI and CM chondrites as analogmaterials of the Ryugu samples and processing of the Ryugu samples. The proceduresconsisted of four steps: epoxy-coating, embedding in epoxy cylinders, cutting with a wiresaw, and dry polish by hand. There are three key points for successful preparation of thepolished sections: (1) ethanol-mixed epoxy with low viscosity for reinforcing the fragilesamples, (2) handling under dry conditions to avoid breakup of the samples on contact withliquids due to their highly porous nature, and (3) X-ray computed tomography data forexposing maximum surface areas of target mineral phases and clasts. These key points mayalso be important for processing of samples returned from asteroid Bennu and the MartianMoon Phobos, as those samples are likely to be hydrous carbonaceous chondrite-likematerials. The established procedures induce two side effects: zoning of the polished surfaceof the Ryugu samples in scanning electron microscope images reflecting differences incarbon contents due to permeation of low viscosity epoxy resin into the sample surface andfractures in anhydrous minerals possibly due to shear stress during dry polishing.