17:15 〜 19:15
[PPS03-P06] Surface Geology of Asteroid Ryugu: A Comprehensive Geologic Map
キーワード：Ryugu, Hayabusa 2, Boulder, Crater Stratigraphy
Asteroid 162173 Ryugu, a Cb-type carbonaceous rubble-pile asteroid, was extensively explored by JAXA’s Hayabusa2 mission, revealing a low bulk density, high porosity, and a boulder-rich surface, indicative of a complex geological history shaped by impact events, rotational evolution, and mass-wasting processes. However, prior geological maps lacked the resolution needed to fully characterize the asteroid’s surface complexity and compilation of
This study presents a detailed geological map of Ryugu, integrating Optical Navigation Camera imagery (Sugita et al., 2019), thermal images (Okada et al., 2020), and Digital Elevation Models processed using an ArcGIS-based workflow (Sugita et al., 2022). Following USGS planetary mapping guidelines, we classified key geological units and structural features, including the equatorial ridge, impact craters, non-crater depressions, large boulders, low-boulder-density zones, and mass-wasting features. Additionally, lineaments and trough-like features were mapped to assess Ryugu’s tectonic history, providing insights into the internal cohesion of its rubble-pile structure and its response to impacts and rotational stresses.
Crater classification distinguishes: (1) high-confidence craters with well-defined rims, (2) moderately degraded craters with partial rim preservation, and (3) large, highly eroded circular structures, possibly ancient impact craters. The Western Bulge exhibits distinct geologic characteristics, suggesting past surface modification. These findings refine our understanding of rubble-pile asteroid evolution, with implications for impact mechanics, regolith stability, and planetary surface processes.
Furthermore, over 50,000 boulders were identified, showing notably lower densities in large craters, likely due to Ryugu’s weak gravity and regolith migration. Boulder orientations reveal a NE-SW alignment in the northern hemisphere and NW-SE in the southern hemisphere, possibly influenced by Ryugu’s spin direction (Watanabe et al., 2019). Comparisons with asteroid Bennu (Lauretta et al., 2019) suggest that boulder distribution and orientations may be linked to spin-induced resurfacing, further informing our understanding of rubble-pile asteroid dynamics and their long-term evolution in space.
References:
[1] Sugita S. et al. (2019) Science, 364(6437), eaaw0422. [2] Sugita S. et al. (2022) NASA PDS Hayabusa2 ONC Bundle V1.0. [3] Okada T. et al. (2020), Nature, 579, 518-522. [6] Watanabe S. et al. (2019) Science, 364(6437), 268–272. [7] Lauretta et al., 2019 (2020) Nature, 568(7750), 55-60.
This study presents a detailed geological map of Ryugu, integrating Optical Navigation Camera imagery (Sugita et al., 2019), thermal images (Okada et al., 2020), and Digital Elevation Models processed using an ArcGIS-based workflow (Sugita et al., 2022). Following USGS planetary mapping guidelines, we classified key geological units and structural features, including the equatorial ridge, impact craters, non-crater depressions, large boulders, low-boulder-density zones, and mass-wasting features. Additionally, lineaments and trough-like features were mapped to assess Ryugu’s tectonic history, providing insights into the internal cohesion of its rubble-pile structure and its response to impacts and rotational stresses.
Crater classification distinguishes: (1) high-confidence craters with well-defined rims, (2) moderately degraded craters with partial rim preservation, and (3) large, highly eroded circular structures, possibly ancient impact craters. The Western Bulge exhibits distinct geologic characteristics, suggesting past surface modification. These findings refine our understanding of rubble-pile asteroid evolution, with implications for impact mechanics, regolith stability, and planetary surface processes.
Furthermore, over 50,000 boulders were identified, showing notably lower densities in large craters, likely due to Ryugu’s weak gravity and regolith migration. Boulder orientations reveal a NE-SW alignment in the northern hemisphere and NW-SE in the southern hemisphere, possibly influenced by Ryugu’s spin direction (Watanabe et al., 2019). Comparisons with asteroid Bennu (Lauretta et al., 2019) suggest that boulder distribution and orientations may be linked to spin-induced resurfacing, further informing our understanding of rubble-pile asteroid dynamics and their long-term evolution in space.
References:
[1] Sugita S. et al. (2019) Science, 364(6437), eaaw0422. [2] Sugita S. et al. (2022) NASA PDS Hayabusa2 ONC Bundle V1.0. [3] Okada T. et al. (2020), Nature, 579, 518-522. [6] Watanabe S. et al. (2019) Science, 364(6437), 268–272. [7] Lauretta et al., 2019 (2020) Nature, 568(7750), 55-60.