Showing papers by "Olivier S. Barnouin published in 2019"

Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—A spinning top–shaped rubble pile

Abstract: The Hayabusa2 spacecraft arrived at the near-Earth carbonaceous asteroid 162173 Ryugu in 2018. We present Hayabusa2 observations of Ryugu’s shape, mass, and geomorphology. Ryugu has an oblate “spinning top” shape, with a prominent circular equatorial ridge. Its bulk density, 1.19 ± 0.02 grams per cubic centimeter, indicates a high-porosity (>50%) interior. Large surface boulders suggest a rubble-pile structure. Surface slope analysis shows Ryugu’s shape may have been produced from having once spun at twice the current rate. Coupled with the observed global material homogeneity, this suggests that Ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation. From these remote-sensing investigations, we identified a suitable sample collection site on the equatorial ridge.

The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes

Abstract: Additional co-authors: N Namiki, S Tanaka, Y Iijima, K Yoshioka, M Hayakawa, Y Cho, M Matsuoka, N Hirata, N Hirata, H Miyamoto, D Domingue, M Hirabayashi, T Nakamura, T Hiroi, T Michikami, P Michel, R-L Ballouz, O S Barnouin, C M Ernst, S E Schroder, H Kikuchi, R Hemmi, G Komatsu, T Fukuhara, M Taguchi, T Arai, H Senshu, H Demura, Y Ogawa, Y Shimaki, T Sekiguchi, T G Muller, T Mizuno, H Noda, K Matsumoto, R Yamada, Y Ishihara, H Ikeda, H Araki, K Yamamoto, S Abe, F Yoshida, A Higuchi, S Sasaki, S Oshigami, S Tsuruta, K Asari, S Tazawa, M Shizugami, J Kimura, T Otsubo, H Yabuta, S Hasegawa, M Ishiguro, S Tachibana, E Palmer, R Gaskell, L Le Corre, R Jaumann, K Otto, N Schmitz, P A Abell, M A Barucci, M E Zolensky, F Vilas, F Thuillet, C Sugimoto, N Takaki, Y Suzuki, H Kamiyoshihara, M Okada, K Nagata, M Fujimoto, M Yoshikawa, Y Yamamoto, K Shirai, R Noguchi, N Ogawa, F Terui, S Kikuchi, T Yamaguchi, Y Oki, Y Takao, H Takeuchi, G Ono, Y Mimasu, K Yoshikawa, T Takahashi, Y Takei, A Fujii, C Hirose, S Nakazawa, S Hosoda, O Mori, T Shimada, S Soldini, T Iwata, M Abe, H Yano, R Tsukizaki, M Ozaki, K Nishiyama, T Saiki, S Watanabe, Y Tsuda

The unexpected surface of asteroid (101955) Bennu

Abstract: NASA'S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine-that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu's global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5-11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid's properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu's thermal inertia12 and radar polarization ratios13-which indicated a generally smooth surface covered by centimetre-scale particles-resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.

Properties of Rubble-Pile Asteroid (101955) Bennu from OSIRIS-REx Imaging and Thermal Analysis

Abstract: Establishing the abundance and physical properties of regolith and boulders on asteroids is crucial for understanding the formation and degradation mechanisms at work on their surfaces. Using images and thermal data from NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft, we show that asteroid (101955) Bennu’s surface is globally rough, dense with boulders, and low in albedo. The number of boulders is surprising given Bennu’s moderate thermal inertia, suggesting that simple models linking thermal inertia to particle size do not adequately capture the complexity relating these properties. At the same time, we find evidence for a wide range of particle sizes with distinct albedo characteristics. Our findings imply that ages of Bennu’s surface particles span from the disruption of the asteroid’s parent body (boulders) to recent in situ production (micrometre-scale particles).

Craters, boulders and regolith of (101955) Bennu indicative of an old and dynamic surface

Abstract: Small, kilometre-sized near-Earth asteroids are expected to have young and frequently refreshed surfaces for two reasons: collisional disruptions are frequent in the main asteroid belt where they originate, and thermal or tidal processes act on them once they become near-Earth asteroids. Here we present early measurements of numerous large candidate impact craters on near-Earth asteroid (101955) Bennu by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission, which indicate a surface that is between 100 million and 1 billion years old, predating Bennu’s expected duration as a near-Earth asteroid. We also observe many fractured boulders, the morphology of which suggests an influence of impact or thermal processes over a considerable amount of time since the boulders were exposed at the surface. However, the surface also shows signs of more recent mass movement: clusters of boulders at topographic lows, a deficiency of small craters and infill of large craters. The oldest features likely record events from Bennu’s time in the main asteroid belt.

Shape of (101955) Bennu indicative of a rubble pile with internal stiffness.

Abstract: The shapes of asteroids reflect interplay between their interior properties and the processes responsible for their formation and evolution as they journey through the Solar System. Prior to the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission, Earth-based radar imaging gave an overview of (101955) Bennu’s shape. Here we construct a high-resolution shape model from OSIRIS-REx images. We find that Bennu’s top-like shape, considerable macroporosity and prominent surface boulders suggest that it is a rubble pile. High-standing, north–south ridges that extend from pole to pole, many long grooves and surface mass wasting indicate some low levels of internal friction and/or cohesion. Our shape model indicates that, similar to other top-shaped asteroids, Bennu formed by reaccumulation and underwent past periods of fast spin, which led to its current shape. Today, Bennu might follow a different evolutionary pathway, with an interior stiffness that permits surface cracking and mass wasting. Near-Earth asteroid Bennu has a top-like shape with longitudinal ridges, macroporosity, prominent boulders and surface mass wasting, suggesting that it is a stiff rubble pile, according to early observations by the OSIRIS-REx mission.

The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements

Abstract: The top-shaped morphology characteristic of asteroid (101955) Bennu, often found among fast-spinning asteroids and binary asteroid primaries, may have contributed substantially to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, we find a notable transition in Bennu’s surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu’s surface has been most recently migrating towards its equator (given Bennu’s increasing spin rate), we infer that Bennu’s surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior is a mixture of voids and boulders. The presence of such heterogeneity and Bennu’s top shape are consistent with spin-induced failure at some point in its past, although the manner of its failure cannot yet be determined. Future measurements by the OSIRIS-REx spacecraft will provide insight into and may resolve questions regarding the formation and evolution of Bennu’s top-shape morphology and its link to the formation of binary asteroids.

Shape of (101955) Bennu indicative of a rubble pile with internal stiffness

Abstract: The shapes of asteroids reflect interplay between their interior properties and the processes responsible for their formation and evolution as they journey through the Solar System. Prior to the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission, Earth-based radar imaging gave an overview of (101955) Bennu’s shape. Here we construct a high-resolution shape model from OSIRIS-REx images. We find that Bennu’s top-like shape, considerable macroporosity and prominent surface boulders suggest that it is a rubble pile. High-standing, north–south ridges that extend from pole to pole, many long grooves and surface mass wasting indicate some low levels of internal friction and/or cohesion. Our shape model indicates that, similar to other top-shaped asteroids, Bennu formed by reaccumulation and underwent past periods of fast spin, which led to its current shape. Today, Bennu might follow a different evolutionary pathway, with an interior stiffness that permits surface cracking and mass wasting.Near-Earth asteroid Bennu has a top-like shape with longitudinal ridges, macroporosity, prominent boulders and surface mass wasting, suggesting that it is a stiff rubble pile, according to early observations by the OSIRIS-REx mission.

The Western Bulge of 162173 Ryugu Formed as a Result of a Rotationally Driven Deformation Process

Abstract: 162173 Ryugu, the target of Hayabusa2, has a round shape with an equatorial ridge, which is known as a spinning top shape. A strong centrifugal force is a likely contributor to Ryugu's top-shaped features. Observations by the Optical Navigation Camera on board Hayabusa2 show a unique longitudinal variation in geomorphology; the western side of this asteroid, later called the western bulge, has a smooth surface and a sharp equatorial ridge, compared to the other side. Here, we propose a structural deformation process that generated the western bulge. Applying the mission-derived shape model, we employ a finite element model technique to analyze the locations that experience structural failure within the present shape. Assuming that materials are uniformly distributed, our model shows the longitudinal variation in structurally failed regions when the spin period is shorter than ~3.75 hr. Ryugu is structurally intact in the subsurface region of the western bulge while other regions are sensitive to structural failure. We infer that this variation is indicative of the deformation process that occurred in the past, and the western bulge is more relaxed structurally than the other region. Our analysis also shows that this deformation process might occur at a spin period between ~3.5 and ~3.0 hr, providing the cohesive strength ranging between ~4 and ~10 Pa.

The Western Bulge of 162173 Ryugu Formed as a Result of a Rotationally Driven Deformation Process

Abstract: 162173 Ryugu, the target of Hayabusa2, has a round shape with an equatorial ridge, which is known as a spinning top-shape. A strong centrifugal force is a likely contributor to Ryugu's top-shaped features. Observations by Optical Navigation Camera onboard Hayabusa2 show a unique longitudinal variation in geomorphology; the western side of this asteroid, later called the western bulge, has a smooth surface and a sharp equatorial ridge, compared to the other side. Here, we propose a structural deformation process that generated the western bulge. Applying the mission-derived shape model, we employ a finite element model technique to analyze the locations that experience structural failure within the present shape. Assuming that materials are uniformly distributed, our model shows the longitudinal variation in structurally failed regions when the spin period is shorter than ~3.75 h. Ryugu is structurally intact in the subsurface region of the western bulge while other regions are sensitive to structural failure. We infer that this variation is indicative of the deformation process that occurred in the past, and the western bulge is more relaxed structurally than the other region. Our analysis also shows that this deformation process might occur at a spin period between ~3.5 h and ~3.0 h, providing the cohesive strength ranging between ~4 Pa and ~10 Pa.

Asteroid (101955) Bennu's Crater Population: Morphologies, Size-Frequency Distribution, and Consequences for Surface Age(s)

Abstract: DISTRIBUTION, AND CONSEQUENCES FOR SURFACE AGE(S). E. B. Bierhaus, O. Barnouin, T. J. McCoy, H. C. Connolly Jr., E. Jawin, K. J. Walsh, B.C. Clark, A. Hildebrand, M. Daly, H. Susorney, P. Michel, M. Pajola, D. Trang, B. Rizk, B. E. Clark, D. DellaGiustina, D. S. Lauretta, and the OSIRIS-REx team. Lockheed Martin, Applied Physics Laboratory, Smithsonian Institution, Rowan University, Southwest Research Institute, Space Science Institute, University of Calgary, York University, University of British Columbia, Côte d’Azur Observatory, Astronomical Observatory of Padova, University of Hawaii, University of Arizona, Ithaca College.

Disruption and Reaccumulation as the Possible Origin of Ryugu and Bennu Top Shapes

Abstract: Introduction: Images sent by the two sample-return space missions Hayabusa2 (JAXA) and OSIRIS-REx (NASA) show that asteroids Ryugu and Bennu are top shapes: oblate spheroids with a more or less pronounced equatorial bulge, also referred to as diamonds or bi-cones. Radar models of other asteroids , including binary primaries, as well as images by the ESA mission Rosetta of the asteroid Steins, suggest that such shapes are common, which implies a systematic mechanism that favors their formation. The thermal effect called YORP [1] and its consequent spin-up has been invoked as the origin of top shapes [e.g., 2], but other processes may also lead to such a shape, or at least contribute to it. Here, we investigate the disruption and reaccumulation process and its role in the formation of top shapes. Disruption and reaccumulation: Asteroids as small as Ryugu and Bennu are likely fragments formed from a larger body that was disrupted. Numerical simulations of asteroid disruptions-including both the fragmentation phase during which the asteroid is broken up into small pieces and the gravitation-al phase during which fragments may reaccumulate due to their mutual attractions and form rubble piles-were first conducted in the early 2000s and successfully reproduced asteroid families [3]. These simulations showed that most asteroids with diameters greater than 200 m and formed by the disruption of a larger body are rubble piles produced by the reaccu-mulation of smaller fragments during the disruption. Early simulations concentrated on the size distribution and ejection speeds of the final bodies, to be compared to those of asteroid families, and not on the actual shapes of reaccumulated bodies. Improvements in the modeling [4] allowed assessing shapes, and the first resulting simulations reproduced successfully the shape of the asteroid Itokawa, as well as the presence of boulders on its surface [5]. Approach: To assess the role of the disrup-tion/reaccumulation process in the formation of top

Publisher Correction: Craters, boulders and regolith of (101955) Bennu indicative of an old and dynamic surface

Abstract: In the version of this Article originally published, in the sentence “There are three identified boulders with long axes exceeding 40 m and more than 200 boulders larger than 10 m”, the term “10 m” should have been “10 m (ref)” This has now been corrected

OSIRIS-REx Gravity Field Estimates for Bennu Using Spacecraft and Natural Particle Tracking Data

Abstract: The current best estimates of Bennu’s gravity field will be presented, based on the independent solutions from four different teams involved on the OSIRIS-REx mission. The discovery of ejected particles about Bennu that may remain in orbit for several days or more provide a unique opportunity to probe the gravity field to higher degree and order than possible by using conventional spacecraft tracking. However, the non-gravitational forces acting on these particles must also be characterized, and their impact on solution accuracy must be assessed. This talk will present the latest results from the mission, incorporating spacecraft tracking from the lowest orbit in which the satellite will be during the mission.

OSIRIS-REx Arrives at Asteroid (101955) Bennu: Exploration of a Hydrated Primitive Near-Earth Asteroid

Abstract: PRIMITIVE NEAR-EARTH ASTEROID. D. S. Lauretta1, M. M. Al Asad2, R.-L. Ballouz1, O. S. Barnouin3, E. B. Bierhaus4, W. V. Boynton1, L. B. Breitenfeld5, M. J. Calaway6, M. Chojnacki1, P. R. Christensen7, B. E. Clark8, H. C. Connolly Jr.9,1, C. Drouet d’Aubigny1, M. G. Daly10, R. T. Daly3, M. Delbó11, D. N. DellaGiustina1, J. P. Dworkin12, J. P. Emery13, H. L. Enos1, D. Farnocchia14, D. R. Golish1, C. W. Haberle7, V. E. Hamilton15, C. W. Hergenrother1, E. R. Jawin16, H. H. Kaplan15, L. Le Corre17, T. J. McCoy16, J. W. McMahon18, P. Michel11, J. L. Molaro17, M. C. Nolan1, M. Pajola19, E. Palmer17, M. E. Perry3, D. C. Reuter12, B. Rizk1, J. H. Roberts3, A. Ryan11, D. J. Scheeres18, S. R. Schwartz1,11, A. A. Simon12, H. C. M. Susorney2, K. J. Walsh15, X.-D. Zou8, and the OSIRIS-REx Team. 1Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA (lauretta@lpl.arizona.edu), 2Dept. of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada, 3The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA, 4Lockheed Martin Space Systems, USA, 5Dept. of Geosciences, Stony Brook University, Stony Brook, NY, USA. 6NASA Johnson Space Center, Houston, TX, USA, 7School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA, 8Dept. of Physics and Astronomy, Ithaca College, Ithaca, NY, USA, 9Dept. of Geology, Rowan University, Glassboro, NJ, USA,10Dept. of Earth and Space Science and Engineering, York University, Toronto, ON, Canada, 11UCA–CNRS–Observatoire de la Côte d’Azur, Nice, France, 12NASA Goddard Space Flight Center, Greenbelt, MD, USA, 13Dept. of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA, 14Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA, USA, 15Southwest Research Institute, Boulder, CO, USA, 16Smithsonian National Museum of Natural History, Washington, DC, USA, 17Planetary Science Institute, Tucson, AZ, USA, 18Smead Dept. of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA, 19INAF–Astronomical Observatory of Padova, Padova, Italy.

Comparing the Radar Shape Model of (101955) Bennu with Ground Truth from OSIRIS-REx

Abstract: OSIRIS-REX. M. C. Nolan1, M. M. Al Asad2, O. S. Barnouin3, L. A. M. Benner4, M. G. Daly5, C. Y. Drouet d’Aubigny1, J. P. Emery6, B. Rozitis7, R. W. Gaskell8, J. D. Giorgini4, C. W. Hergenrother1, E. S. Howell1, C. Magri9, J. L. Margot10, E. E. Palmer8, M. Pajola11, M. E. Perry3, B. Rizk1, H. Susorney2, J. R. Weirich8, D. S. Lauretta1, 1Lunar and Planetary Laboratory, University of Arizona (Tucson, AZ, USA, nolan@lpl.arizona.edu), 2University of British Columbia (Vancouver, Canada), 3The Johns Hopkins University Applied Physics Laboratory (Laurel, MD, USA), 4Jet Propulsion Laboratory, California Institute of Technology (Pasadena, CA, USA), 5York University (Toronto, Ont., Canada,), 6Northern Arizona University (Flagstaff, AZ, USA), 7Open University (Milton Keynes, UK), 8Planetary Science Institute (Tucson, AZ, USA), 9University of Maine at Farmington (Farmington, ME, USA), 10University of California, Los Angeles (Los Angeles, CA, USA), 11INAF-Astronomical Observatory of Padova (Padova, Italy).

Timescale of Reddening Process of the Ryugu Surface Based on the Crater Size-Frequency Distribution

Abstract: FREQUENCY DISTRIBUTION. T. Morota, Y. Cho, M. Kanamaru, R. Honda, S. Kameda, E. Tatsumi, Y. Yokota, T. Kouyama, H. Suzuki, M. Yamada, N. Sakatani, C. Honda, M. Hayakawa, K. Yoshioka, M. Matsuoka, T. Michikami, H. Miyamoto, H. Kikuchi, R. Hemmi, M. Hirabayashi, C. M. Ernst, O. Barnouin, N. Hirata, N. Hirata, H. Sawada, and S. Sugita, Nagoya Univ., Nagoya 464-8601, Japan (morota@eps.nagoyau.ac.jp), Univ. of Tokyo, Tokyo, Japan, Osaka Univ., Osaka, Japan, Kochi Univ., Kochi, Japan, Rikkyo Univ., Tokyo, Japan, JAXA, Sagamihara, Japan, AIST, Tsukuba, Japan, Meiji Univ., Kawasaki, Japan, Chiba Institute of Technology, Narashino, Japan, Univ. of Aizu, Aizu-Wakamatsu, Japan, Kindai Univ., Higashi-Hiroshima, Japan, Auburn Univ., Auburn, USA, APL/JHU, Laurel, USA, Kobe Univ., Kobe, Japan.

High Porosity Nature of the Top-Shape C-Type Asteroid 162173 Ryugu as Observed by Hayabusa2

Abstract: BY HAYABUSA2. S. Watanabe, M. Hirabayashi, N. Hirata, N. Hirata, R. Noguchi, Y. Shimaki, H. Ikeda, E. Tatsumi, M. Yoshikawa, S. Kikuchi, H. Yabuta, T. Nakamura, S. Tachibana, Y. Ishihara, T. Morota, K. Kitazato, N. Sakatani, K. Matsumoto, K. Wada, H. Senshu, C. Honda, T. Michikami, H. Takeuchi, T. Kouyama, R. Honda, S. Kameda, T. Fuse, H. Miyamoto, G. Komatsu, S. Sugita, T. Okada, N. Namiki, M. Arakawa, M. Ishiguro, M. Abe, R. Gaskell, E. Palmer, O. S. Barnouin, P. Michel, A. S. French, J. W. McMahon, D. J. Scheeres, P. A. Abell, Y. Yamamoto, S. Tanaka, K. Shirai, M. Matsuoka, M. Yamada, Y. Yokota, H. Suzuki, K. Yoshioka, Y. Cho, S. Tanaka, N. Nishikawa, T. Sugiyama, H. Kikuchi, R. Hemmi, T. Yamaguchi, N. Ogawa, G. Ono, Y. Mimasu, K. Yoshikawa, T. Takahashi, Y. Takei, A. Fujii, C. Hirose, T. Iwata, M. Hayakawa, S. Hosoda, O. Mori, H. Sawada, T. Shimada, S. Soldini, H. Yano, R. Tsukizaki, M. Ozaki, Y. Iijima, K. Ogawa, M. Fujimoto, T.-M. Ho, A. Moussi, R. Jaumann, J.-P. Bibring, C. Krause, F. Terui, T. Saiki, S. Nakazawa, Y. Tsuda, Nagoya University, Nagoya 464-8601, Japan, (seicoro@eps.nagoya-u.ac.jp), Institute of Space and Astronautical Science, JAXA, Japan, Auburn University, Auburn, AL 36849, USA, University of Aizu, Aizu-Wakamatsu 965-8580, Japan, Kobe University, Kobe 657-8501, Japan, Research and Development Directorate, JAXA, Sagamihara 252-5210, Japan, University of Tokyo, Tokyo 113-0033, Japan, Hiroshima University, Higashi-Hiroshima 739-8526, Japan, Tohoku University, Sendai 980-8578, Japan, National Astronomical Observatory of Japan, Mitaka 181-8588, Japan, SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193, Japan, Chiba Institute of Technology, Narashino 275-0016, Japan, Kindai University, Higashi-Hiroshima 739-2116, Japan, National Institute of Advanced Industrial Science and Technology, Tokyo 135-0064 Japan, Kochi University, Kochi 780-8520, Japan, Rikkyo University, Tokyo 171-8501, Japan, National Institute of Information and Communications Technology, Kashima 314-8501, Japan, Università d’Annunzio, 65127 Pescara, Italy, Seoul National University, Seoul 08826, Korea, Planetary Science Institute, Tucson, AZ 85710, USA, Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, 06304 Nice, France, University of Colorado, Boulder, CO 80309, USA, NASA Johnson Space Center, Houston, TX 77058, USA, Meiji University, Kawasaki 214-8571, Japan, DLR (German Aerospace Center), Institute of Space Systems, 28359 Bremen, Germany. CNES (Centre National d'Etudes Spatiales), 31401 Toulouse, France, DLR, Institute of Planetary Research, 12489 Berlin-Adlershof, Germany, Institute d’Astrophysique Spatiale, 91405 Orsay, France, DLR, Microgravity User Support Center, 51147 Cologne, Germany. Current affiliation: National Institute for Environmental Studies, Tsukuba 305-8506, Japan, Current affiliation: Mitsubishi Electric Corporation, Kamakura 247-8520, Japan, Deceased.

Spatial Distribution and Morphology of Craters on Ryugu: Implications for Surface Processes on the C-Type Asteroid

Abstract: SURFACE PROCESSES ON THE C-TYPE ASTEROID. Y. Cho1, T. Morota2, M. Kanamaru3, C. M. Ernst4, O. S. Barnouin4, E. Tatsumi1, M. Hirabayashi5, K. A. Otto6, N. Schmitz6, R. J. Wagner6, R. Jaumann6, H. Miyamoto1, H. Kikuchi1, R. Hemmi1, R. Honda7, S. Kameda8, Y. Yokota9, T. Kouyama10, H. Suzuki11, M. Yamada12, N. Sakatani9, C. Honda13, M. Hayakawa9, K. Yoshioka1, M. Matsuoka9, T. Michikami14, N. Hirata15, H. Sawada9 and S. Sugita1. 1The University of Tokyo (7-3-1 Hongo, Bunkyo, Tokyo, Japan, cho@eps.s.u-tokyo.ac.jp), 2Nagoya Univ., 3Osaka Univ., 4JHU/APL, 5Auburn Univ., 6DLR Berlin, 7Kochi Univ., 8Rikkyo Univ., 9ISAS/JAXA, 10AIST, 11Meiji Univ., 12Chiba Inst. Tech., 13Univ. Aizu, 14Kindai Univ., 15Kobe Univ.