Astromaterials Science Research Group|ISAS

【Research Highlights】 Classification of Ryugu samples based on its surface characteristics

 As part of the curation activities in ASRG (curation), this is the first effort to classify Ryugu returned samples into distinct categories.

 205 Ryugu samples larger than 1 mm (about 25% of the total weight) were classified into four groups based on morphological characteristics observed from optical microscopic imaging. We performed scanning electron microscopy and X-ray diffraction analysis on the representative samples from each group to observe the detailed structure and identify the compositions of minerals. The results suggest that the characteristics of each group may reflect the differences in the degree of space weathering and mineral assemblages.

 The degree of space weathering of a sample may be an indicator of how long the sample remained at the top surface of the Ryugu parent body. The process of space weathering to C-type asteroids remains largely unknown, and this process has currently been studied using Ryugu samples. Differences in mineral compositions provide clues to reconstructing what kind of the environment Ryugu parent body may have been. We hope that the results of this study will be used for researchers to select samples for International Announcement Opportunity, and will contribute to promoting future Ryugu sample research.

Classification of Ryugu samples based on its surface characteristics
Microscopic images of four representative grains. A: A0042, dark group. This feature is dominant in Ryugu returned samples. B: C0094, glossy group. C: A0017, bright group. D: C0041, white group. One-third of this grain exhibits white inclusions.

You can find the various samples at Ryugu sample catalog:

<From the primary author – Dr. Nakato>
This research is a unique study that examined a large number of samples, which is an advantage of curation. I was involved in picking up each Ryugu grain. Even early on, we have noticed the diversity of Ryugu samples in appearance, and discussed the appearances during the clean room activities, such as "Hey, this one looks kind of white-ish," or "There is a bright, shiny particle" and so on. I am glad that this study was able to clarify some of the causes of such differences in appearance.

Dr. Nakato
Dr. Nakato

Original article:

Journal:  Earth, Planets and Space
Title:  Variations of the surface characteristics of Ryugu returned samples
Author:  Nakato, A. et al.
DOI:  10.1186/s40623-022-01754-8
Published:  March 28, 2023

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