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1. Fast boulder fracturing by thermal fatigue detected on stony asteroids

Author

A. Lucchetti, S. Cambioni, R. Nakano, O. S. Barnouin, M. Pajola, L. Penasa, F. Tusberti, K. T. Ramesh, E. Dotto, C. M. Ernst, R. T. Daly, E. Mazzotta Epifani, M. Hirabayashi, L. Parro, G. Poggiali, A. Campo Bagatin, R.-L. Ballouz, N. L. Chabot, P. Michel, N. Murdoch, J. B. Vincent, Ö. Karatekin, A. S. Rivkin, J. M. Sunshine, T. Kohout, J.D.P. Deshapriya, P.H.A. Hasselmann, S. Ieva, J. Beccarelli, S. L. Ivanovski, A. Rossi, F. Ferrari, C. Rossi, S. D. Raducan, J. Steckloff, S. Schwartz, J. R. Brucato, M. Dall’Ora, A. Zinzi, A. F. Cheng, M. Amoroso, I. Bertini, A. Capannolo, S. Caporali, M. Ceresoli, G. Cremonese, V. Della Corte, I. Gai, L. Gomez Casajus, E. Gramigna, G. Impresario, R. Lasagni Manghi, M. Lavagna, M. Lombardo, D. Modenini, P. Palumbo, D. Perna, S. Pirrotta, P. Tortora, M. Zannoni, and G. Zanotti

Subjects
Science
Abstract

Abstract Spacecraft observations revealed that rocks on carbonaceous asteroids, which constitute the most numerous class by composition, can develop millimeter-to-meter-scale fractures due to thermal stresses. However, signatures of this process on the second-most populous group of asteroids, the S-complex, have been poorly constrained. Here, we report observations of boulders’ fractures on Dimorphos, which is the moonlet of the S-complex asteroid (65803) Didymos, the target of NASA’s Double Asteroid Redirection Test (DART) planetary defense mission. We show that the size-frequency distribution and orientation of the mapped fractures are consistent with formation through thermal fatigue. The fractures’ preferential orientation supports that these have originated in situ on Dimorphos boulders and not on Didymos boulders later transferred to Dimorphos. Based on our model of the fracture propagation, we propose that thermal fatigue on rocks exposed on the surface of S-type asteroids can form shallow, horizontally propagating fractures in much shorter timescales (100 kyr) than in the direction normal to the boulder surface (order of Myrs). The presence of boulder fields affected by thermal fracturing on near-Earth asteroid surfaces may contribute to an enhancement in the ejected mass and momentum from kinetic impactors when deflecting asteroids.

Published
2024
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2. Evidence for multi-fragmentation and mass shedding of boulders on rubble-pile binary asteroid system (65803) Didymos

Author

M. Pajola, F. Tusberti, A. Lucchetti, O. Barnouin, S. Cambioni, C. M. Ernst, E. Dotto, R. T. Daly, G. Poggiali, M. Hirabayashi, R. Nakano, E. Mazzotta Epifani, N. L. Chabot, V. Della Corte, A. Rivkin, H. Agrusa, Y. Zhang, L. Penasa, R.-L. Ballouz, S. Ivanovski, N. Murdoch, A. Rossi, C. Robin, S. Ieva, J. B. Vincent, F. Ferrari, S. D. Raducan, A. Campo-Bagatin, L. Parro, P. Benavidez, G. Tancredi, Ö. Karatekin, J. M. Trigo-Rodriguez, J. Sunshine, T. Farnham, E. Asphaug, J. D. P. Deshapriya, P. H. A. Hasselmann, J. Beccarelli, S. R. Schwartz, P. Abell, P. Michel, A. Cheng, J. R. Brucato, A. Zinzi, M. Amoroso, S. Pirrotta, G. Impresario, I. Bertini, A. Capannolo, S. Caporali, M. Ceresoli, G. Cremonese, M. Dall’Ora, I. Gai, L. Gomez Casajus, E. Gramigna, R. Lasagni Manghi, M. Lavagna, M. Lombardo, D. Modenini, P. Palumbo, D. Perna, P. Tortora, M. Zannoni, and G. Zanotti

Subjects
Science
Abstract

Abstract Asteroids smaller than 10 km are thought to be rubble piles formed from the reaccumulation of fragments produced in the catastrophic disruption of parent bodies. Ground-based observations reveal that some of these asteroids are today binary systems, in which a smaller secondary orbits a larger primary asteroid. However, how these asteroids became binary systems remains unclear. Here, we report the analysis of boulders on the surface of the stony asteroid (65803) Didymos and its moonlet, Dimorphos, from data collected by the NASA DART mission. The size-frequency distribution of boulders larger than 5 m on Dimorphos and larger than 22.8 m on Didymos confirms that both asteroids are piles of fragments produced in the catastrophic disruption of their progenitors. Dimorphos boulders smaller than 5 m have size best-fit by a Weibull distribution, which we attribute to a multi-phase fragmentation process either occurring during coalescence or during surface evolution. The density per km2 of Dimorphos boulders ≥1 m is 2.3x with respect to the one obtained for (101955) Bennu, while it is 3.0x with respect to (162173) Ryugu. Such values increase once Dimorphos boulders ≥5 m are compared with Bennu (3.5x), Ryugu (3.9x) and (25143) Itokawa (5.1x). This is of interest in the context of asteroid studies because it means that contrarily to the single bodies visited so far, binary systems might be affected by subsequential fragmentation processes that largely increase their block density per km2. Direct comparison between the surface distribution and shapes of the boulders on Didymos and Dimorphos suggest that the latter inherited its material from the former. This finding supports the hypothesis that some asteroid binary systems form through the spin up and mass shedding of a fraction of the primary asteroid.

Published
2024
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3. The bearing capacity of asteroid (65803) Didymos estimated from boulder tracks

Author

J. Bigot, P. Lombardo, N. Murdoch, D. J. Scheeres, D. Vivet, Y. Zhang, J. Sunshine, J. B. Vincent, O. S. Barnouin, C. M. Ernst, R. T. Daly, C. Sunday, P. Michel, A. Campo-Bagatin, A. Lucchetti, M. Pajola, A. S. Rivkin, and N. L. Chabot

Subjects
Science
Abstract

Abstract The bearing capacity - the ability of a surface to support applied loads - is an important parameter for understanding and predicting the response of a surface. Previous work has inferred the bearing capacity and trafficability of specific regions of the Moon using orbital imagery and measurements of the boulder tracks visible on its surface. Here, we estimate the bearing capacity of the surface of an asteroid for the first time using DART/DRACO images of suspected boulder tracks on the surface of asteroid (65803) Didymos. Given the extremely low surface gravity environment, special attention is paid to the underlying assumptions of the geotechnical approach. The detailed analysis of the boulder tracks indicates that the boulders move from high to low gravitational potential, and provides constraints on whether the boulders may have ended their surface motion by entering a ballistic phase. From the 9 tracks identified with sufficient resolution to estimate their dimensions, we find an average boulder track width and length of 8.9 $$\pm$$ ± 1.5 m and 51.6 $$\pm$$ ± 13.3 m, respectively. From the track widths, the mean bearing capacity of Didymos is estimated to be 70 N/m2, implying that every 1 m2 of Didymos’ surface at the track location can support only ~70 N of force before experiencing general shear failure. This value is at least 3 orders of magnitude less than the bearing capacity of dry sand on Earth, or lunar regolith.

Published
2024
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4. VADER: Probing the Dark Side of Dimorphos with LICIACube LUKE

Author

Angelo Zinzi, P. H. A. Hasselmann, V. Della Corte, J. D. P. Deshapriya, I. Gai, A. Lucchetti, M. Pajola, A. Rossi, E. Dotto, E. Mazzotta Epifani, R. T. Daly, M. Hirabayashi, T. Farnham, C. M. Ernst, S. L. Ivanovski, J.-Y. Li, L. M. Parro, M. Amoroso, J. Beccarelli, I. Bertini, J. R. Brucato, A. Capannolo, S. Caporali, M. Ceresoli, G. Cremonese, M. Dall’Ora, L. Gomez Casajus, E. Gramigna, S. Ieva, G. Impresario, R. Lasagni Manghi, M. Lavagna, M. Lombardo, D. Modenini, B. Negri, P. Palumbo, D. Perna, S. Pirrotta, G. Poggiali, P. Tortora, F. Tusberti, M. Zannoni, and G. Zanotti

Subjects
Asteroids, Near-Earth objects, Astronomy, QB1-991
Abstract

The ASI cubesat LICIACube has been part of the first planetary defense mission DART, having among its scopes to complement the DRACO images to better constrain the Dimorphos shape. LICIACube had two different cameras, LEIA and LUKE, and to accomplish its goal, it exploited the unique possibility of acquiring images of the Dimorphos hemisphere not seen by DART from a vantage point of view, in both time and space. This work is indeed aimed at constraining the tridimensional shape of Dimorphos, starting from both LUKE images of the nonimpacted hemisphere of Dimorphos and the results obtained by DART looking at the impacted hemisphere. To this aim, we developed a semiautomatic Computer Vision algorithm, named VADER, able to identify objects of interest on the basis of physical characteristics, subsequently used as input to retrieve the shape of the ellipse projected in the LUKE images analyzed. Thanks to this shape, we then extracted information about the Dimorphos ellipsoid by applying a series of quantitative geometric considerations. Although the solution space coming from this analysis includes the triaxial ellipsoid found by using DART images, we cannot discard the possibility that Dimorphos has a more elongated shape, more similar to what is expected from previous theories and observations. The result of our work seems therefore to emphasize the unique value of the LICIACube mission and its images, making even clearer the need of having different points of view to accurately define the shape of an asteroid.

Published
2024
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5. The Unusual Brightness Phase Curve of (65803) Didymos

Author

P. H. Hasselmann, V. Della Corte, P. Pravec, S. Ieva, I. Gai, D. Perna, J. D. P. Deshapriya, E. Mazzotta-Epifani, E. Dotto, A. Zinzi, G. Poggiali, I. Bertini, A. Lucchetti, M. Pajola, J. Beccarelli, M. Dall’Ora, J.-Y. Li, S. L. Ivanovski, A. Rossi, J. R. Brucato, C. A. Thomas, O. Barnouin, J. M. Sunshine, A. S. Rivkin, M. Amoroso, A. Capannolo, S. Caporali, M. Ceresoli, G. Cremonese, R. T. Daly, G. Impresario, R. Lasagni-Manghi, M. Lavagna, D. Modenini, E. E. Palmer, P. Palumbo, S. Pirrotta, P. Tortora, M. Zannoni, and G. Zanotti

Subjects
Asteroids, Asteroid surfaces, Phase angle, Near-Earth objects, Photometry, RGB photometry, Astronomy, QB1-991
Abstract

On 2022 September 26, NASA's Double Asteroid Redirection Test (DART) successfully hit Dimorphos, the smaller companion of the binary system formed with the asteroid (65803) Didymos. Both the binary system and the impact event were imaged by the Light Italian Cubesat for Imaging of Asteroids, detached from DART 15 days before the impact. Images from the onboard LUKE red, green, and blue camera together with ground-based observations enabled the reconstruction of Didymos's brightness phase curve, with phase angles ranging from 2.35° to 107.7°. The opposition effect regime was studied using the exponential-linear equation, the “Shevchenko” function and the linear-by-parts model while the IAU-official HG1G2 magnitude system was applied to the full phase curve. The opposition effect indicates an unusual asteroid surface for an S type, with characteristics similar to M-type asteroids. While the HG1G2 parameters from the full phase curve place Didymos well among asteroids of the taxonomic C complex. Didymos’s phase curve parameters when compared to near-Earth asteroids are very close to the Q type (1862) Apollo, indicating possible depletion of fine submicrometric grains through resurfacing. Didymos's geometric albedo (0.15 ± 0.01) is reported to be 30%–45% smaller than the average geometric albedo for near-Earth S types (0.26 ± 0.04). We propose that Didymos might be an LL ordinary chondrite analog containing albedo-suppressing, shock-darkened/impact melt minerals that have undergone resurfacing processes in the past. A comparison with meteorites indicates that, less likely, Didymos could also contain materials analog to carbon-bearing brecciated L3 ordinary chondrites.

Published
2024
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6. Pre-impact Albedo Map and Photometric Properties of the (65803) Didymos Asteroid Binary System from DART and Ground-based Data

Author

B. J. Buratti, J. Pittichová, I. Mishra, J. K. Hillier, J. A. Mosher, S. R. Chesley, J. M. Sunshine, O. Barnouin, C. M. Ernst, R. T. Daly, J-Y Li, A. F. Cheng, A. S. Rivkin, and J. Rizos

Subjects
Asteroid surfaces, Near-Earth objects, Astronomy, QB1-991
Abstract

This study provides a pre-impact map of the albedo of the Double Asteroid Redirection Test (DART) target Dimorphos corrected for all the effects of viewing geometry, as well as an estimate of photometric roughness for the hemisphere imaged by DART. Other photometric properties are derived for the (65803) Didymos binary system based on DART and ground-based measurements obtained at JPL’s Table Mountain Observatory. The roughness, geometric albedo, phase curve and phase integral, and single particle phase function are typical of the S-family of asteroids. The major remaining uncertainty lies in the behavior of the phase curve below 7°. These results provide a baseline for comparison with Hera measurements, leading to an understanding of the quantitative effects of the kinetic impactor mitigation strategy.

Published
2024
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7. Characterization of the DART Impact Ejecta Plume on Dimorphos from LICIACube Observations

Author

J. D. P. Deshapriya, P. H. Hasselmann, I. Gai, M. Hirabayashi, E. Dotto, A. Rossi, A. Zinzi, V. Della Corte, I. Bertini, S. Ieva, E. Mazzotta Epifani, M. Dall’Ora, S. Ivanovski, D. Perna, T. L. Farnham, M. Amoroso, J. R. Brucato, A. Capannolo, S. Caporali, M. Ceresoli, Nancy L. Chabot, A. Cheng, G. Cremonese, R. T. Daly, E. G. Fahnestock, L. Gomez Casajus, E. Gramigna, G. Impresario, R. Lasagni Manghi, M. Lavagna, J.-Y. Li, M. Lombardo, A. Lucchetti, D. Modenini, M. Pajola, E. Palmer, P. Palumbo, S. Pirrotta, G. Poggiali, A. S. Rivkin, P. Sanchez, G. Tancredi, P. Tortora, F. Tusberti, M. Zannoni, and G. Zanotti

Subjects
Asteroids, Astronomy, QB1-991
Abstract

We modeled the geometry and the three-dimensional orientation of the ejecta cone triggered by the impact of the DART spacecraft on the asteroid Dimorphos. We used eight LUKE images of the impact acquired by the CubeSat LICIACube that flew by the Didymos system shortly after the impact. These images, which show the ejecta cone in both face-on and side-on profiles, enabled us to reconstruct the ejecta cone in inertial space. We started our model as a simple cone with a circular base and developed it to a rotated cone with an elliptical base that best fit the data. The cone axis points to R.A., decl. (in J2000): ${147}_{-10^\circ }^{+1^\circ }$ , + ${16}_{-6^\circ }^{+4^\circ }$ . The cone is characterized by two perpendicular half-angles of $\eta ={69}_{-3^\circ }^{+1^\circ },\gamma ={51}_{-11^\circ }^{+1^\circ }$ and a rotation of ω = 12° around its axis. The apex of the cone is located near the center of Dimorphos within 15 m. The intersection of the cone and the surface of Dimorphos (surface enclosed by the cone) would correspond to a crater with a maximum radius of about 65 m. The characterization of the cone axis is directly related to the computation of the momentum enhancement factor ( β ) of the impact, and it hence proves the crucial need of studying impacts in the context of planetary defence scenarios. The results of this work could potentially be used to constrain whether the impact took place in a strength-dominated or a gravity-dominated regime. This work shows the important scientific return of the LICIACube CubeSat in the context of planetary defence.

Published
2023
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8. Stereophotoclinometry on the OSIRIS-REx Mission: Mathematics and Methods

Author

R. W. Gaskell, O. S. Barnouin, M. G. Daly, E. E. Palmer, J. R. Weirich, C. M. Ernst, R. T. Daly, and D. S. Lauretta

Subjects
Photogrammetry, Asteroids, Astronomy, QB1-991
Abstract

Stereophotoclinometry (SPC) makes it possible to extract the shapes of surfaces by combining information from images, namely stereo parallax data and surface shading from slopes, with knowledge of the location of a spacecraft. This technique has been used extensively in the past few decades to describe the shapes of planets and small bodies, such as asteroids and comets. It has also been used to carefully navigate spacecraft around very small bodies, as in the case of the OSIRIS-REx mission to the ∼500 m diameter asteroid (101955) Bennu. This paper describes the mathematical foundation of SPC, with examples from the OSIRIS-REx mission.

Published
2023
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9. Global geologic map of asteroid (101955) Bennu indicates heterogeneous resurfacing in the past 500,000 years

Author

E R Jawin, T J McCoy, K J Walsh, H C Connolly, R-L Ballouz, A J Ryan, H H Kaplan, M Pajola, V E Hamilton, O S Barnouin, J P Emery, B Rozitis, D N DellaGiustina, M G Daly, C A Bennett, D R Golish, M E Perry, R T Daly, E B Bierhaus, M C Nolan, H L Enos, and D S Lauretta

Subjects
Lunar And Planetary Science And Exploration, Astronomy
Abstract

Global geologic maps are useful tools for efficient interpretation of a planetary body, and they provide global context for the diversity and evolution of the surface. We used data acquired by the OSIRIS-REx spacecraft to create the first global geologic map of the near-Earth asteroid (101955) Bennu. As this is the first geologic map of a small, non-spherical, rubble-pile asteroid, we discuss the distinctive mapping challenges and best practices that may be useful for future exploration of similar asteroids, such as those to be visited with the Hera and Janus missions. By mapping on two centimeter-scale global image mosaics (2D projected space) and a centimeter-scale global shape model (3D space), we generated three input maps respectively describing Bennu’s shape features, geologic features, and surface texture. Based on these input maps, we defined two geologic units: the Smooth Unit and the Rugged Unit. The units are differentiated primarily on the basis of surface texture, concentrations of boulders, and the distributions of lineaments, mass movement features, and craters. They are bounded by several scarps. The Rugged Unit contains abundant boulders and signs of recent mass movement. It also has fewer small(<20 m), putatively fresh craters than the Smooth Unit, suggesting that such craters have been erased in the former. Based on these geologic indicators, we infer that the Rugged Unit has the younger surface of the two. Differential crater size-frequency distributions and the distribution of the freshest craters suggest that both unit surfaces formed ~10–65 million years ago, when Bennu was located in the Main Asteroid Belt, and the Smooth Unit has not been significantly resurfaced in the past 2 million years. Meanwhile, the Rugged Unit has experienced resurfacing within the past ~500,000years during Bennu’s lifetime as a near-Earth asteroid. The geologic units are consistent with global diversity in slope, surface roughness, normal albedo, and thermal emission spectral characteristics. The site on Bennu where the OSIRIS-REx mission collected a regolith sample is located in the Smooth Unit, in a small crater nested within a larger one. So although the Smooth Unit is an older surface than the Rugged Unit, the impact-crater settingindicates that the material sampled was recently exposed. Several similarities are apparent between Bennu and asteroid (162173) Ryugu from a global geologic perspective, including two geologic units distinguishable by variations in the number density of boulders, as well as in other datasets such as brightness.

Published
2022
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10. Crater Population on Asteroid (101955) Bennu Indicates Impact Armouring and a Young Surface

Author

E B Bierhaus, D Trang, R T Daly, C A Bennett, O S Barnouin, K J Walsh, R -L Ballouz, W F Bottke, K N Burke, M E Perry, E R Jawin, T J McCoy, H C Connolly, Jr, M G Daly, J P Dworkin, D N DellaGiustina, P L Gay, J I Brodbeck, J Nolau, J. Padilla, S Stewart, S Schwartz, P Michel, M Pajola, and D S Lauretta

Subjects
Lunar and Planetary Science and Exploration
Abstract

The impactor-to-crater size scaling relationships that enable estimates of planetary surface ages rely on an accurate formulation of impactor–target physics. An armouring regime, specific to rubble-pile surfaces, has been proposed to occur when an impactor is comparable in diameter to a target surface particle (for example, a boulder). Armouring is proposed to reduce crater diameter, or prevent crater formation in the asteroid surface, at small crater diameters. Here, using measurements of 1,560 craters on the rubble-pile asteroid (101955) Bennu, we show that the boulder population controls a transition from crater formation to armouring at crater diameters ~2–3 m, below which crater formation in the bulk surface is increasingly rare. By combining estimates of impactor flux with the armouring scaling relationship, we find that Bennu’s crater retention age (surface age derived from crater abundance) spans from 1.6–2.2 Myr for craters less than a few meters to ~10–65 Myr for craters >100 m in diameter, reducing the maximum surface age by a factor of >15 relative to previous estimates. The range of crater retention ages, together with latitudinal variations in large-crater spatial density, indicate that ongoing resurfacing processes render the surface many times younger than the bulk asteroid.

Published
2022
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11. The Morphometry of Impact Craters on Bennu

Author

R. T. Daly, E. B. Bierhaus, O. S. Barnouin, M. G. Daly, J. A. Seabrook, J. H. Roberts, C. M. Ernst, M. E. Perry, H. Nair, R. C. Espiritu, E. E. Palmer, R. W. Gaskell, J. R. Weirich, H. C. M. Susorney, C. L. Johnson, K. J. Walsh, M. C. Nolan, E. R. Jawin, P. Michel, D. Trang, and D. S. Lauretta

Published
2020
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12. Hemispherical differences in the shape and topography of asteroid (101955) Bennu

Author

M. G. Daly, O. S. Barnouin, J. A. Seabrook, J. Roberts, C. Dickinson, K. J. Walsh, E. R. Jawin, E. E. Palmer, R. Gaskell, J. Weirich, T. Haltigin, D. Gaudreau, C. Brunet, G. Cunningham, P. Michel, Y. Zhang, R.-L. Ballouz, G. Neumann, M. E. Perry, L. Philpott, M. M. Al Asad, C. L. Johnson, C. D. Adam, J. M. Leonard, J. L. Geeraert, K. Getzandanner, M. C. Nolan, R. T. Daly, E. B. Bierhaus, E. Mazarico, B. Rozitis, A. J. Ryan, D. N. DellaGiustina, B. Rizk, H. C. M. Susorney, H. L. Enos, and D. S. Lauretta

Subjects
Space Sciences (General)
Abstract

We investigate the shape of near-Earth asteroid (101955) Bennu by constructing a high-resolution (20 cm) global digital terrain model from laser altimeter data. By modeling the northern and southern hemispheres separately, we find that longitudinal ridges previously identified in the north extend into the south but are obscured there by surface material. In the south, more numerous large boulders effectively retain surface materials and imply a higher average strength at depth to support them. The north has fewer large boulders and more evidence of boulder dynamics (toppling and downslope movement) and surface flow. These factors result in Bennu's southern hemisphere being rounder and smoother, whereas its northern hemisphere has higher slopes and a less regular shape. We infer an originally asymmetric distribution of large boulders followed by a partial disruption, leading to wedge formation in Bennu's history.

Published
2020
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13. Exogenic Basalt on Asteroid (101955) Bennu

Author

D N DellaGiustina, H H Kaplan, A A Simon, W F Bottke, C Avdellidou, M Delbo, R-L Ballouz, D R Golish, K J Walsh, M Popescu, H Campins, M A Barucci, G Poggiali, R T Daly, L Le Corre, V E Hamilton, N Porter, E R Jawin, T J McCoy, H C Connolly Jr, J L Rizos Garcia, E Tatsumi, J de Leon, J Licandro, S Fornasier, M G Daly, M M Al Asad, L Philpott, J Seabrook, O S Barnouin, B E Clark, M C Nolan, E S Howell, R P Binzel, B Rizk, D C Reuter, and D S Lauretta

Subjects
Lunar And Planetary Science And Exploration
Abstract

When rubble-pile asteroid 2008 TC3 impacted Earth on October 7, 2008, the recovered rock fragments indicated that such asteroids can contain exogenic material. However, spacecraft missions to date have only observed exogenous contamination on large, monolithic asteroids that are impervious to collisional disruption. Here we report the presence of meter-scale exogenic boulders on the surface of near-Earth asteroid (101955) Bennu - the 0.5-km, rubble-pile target of the OSIRIS-REx mission which has been spectroscopically linked to the CM carbonaceous chondrite meteorites. Hyperspectral data indicate that the exogenic boulders have the same distinctive pyroxene composition as the howardite-eucrite-diogenite (HED) meteorites that come from (4) Vesta, a 525-km diameter asteroid that has undergone differentiation and extensive igneous processing. Delivery scenarios include the infall of Vesta fragments directly onto Bennu or indirectly onto Bennu’s parent body, where the latter’s disruption created Bennu from a mixture of endogenous and exogenic debris. Our findings demonstrate that rubble-pile asteroids can preserve evidence of inter-asteroid mixing that took place at macroscopic scales well after planetesimal formation ended. Accordingly, the presence of HED-like material on the surface of Bennu provides previously unrecognized constraints on the collisional and dynamical evolution of the inner main belt.

Published
2020
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14. Global Patterns of Recent Mass Movement on Asteroid (101955) Bennu

Author

E. R. Jawin, K. J. Walsh, O. S. Barnouin, T. J. McCoy, R.‐L. Ballouz, D. N. DellaGiustina, H. C. Connolly, J. Marshall, C. Beddingfield, M. C. Nolan, J. L. Molaro, C. A. Bennett, D. J. Scheeres, M. G. Daly, M. Al Asad, R. T. Daly, E. B. Bierhaus, H. C. M. Susorney, H. H. Kaplan, H. L. Enos, and D. S. Lauretta

Published
2020
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15. Low surface strength of the asteroid Bennu inferred from impact ejecta deposit

Author

M. E. Perry, O. S. Barnouin, R. T. Daly, E. B. Bierhaus, R.-L. Ballouz, K. J. Walsh, M. G. Daly, D. N. DellaGiustina, M. C. Nolan, J. P. Emery, M. M. Al Asad, C. L. Johnson, C. M. Ernst, E. R. Jawin, P. Michel, D. R. Golish, W. F. Bottke, J. A. Seabrook, and D. S. Lauretta

Subjects
General Earth and Planetary Sciences
Published
2022

16. The unexpected surface of asteroid (101955) Bennu

Author

D. S. Lauretta, D. N. DellaGiustina, C. A. Bennett, D. R. Golish, K. J. Becker, S. S. Balram-Knutson, O. S. Barnouin, T. L. Becker, W. F. Bottke, W. V. Boynton, H. Campins, H. C. Connolly Jr, C. Y. Drouet d’Aubigny, J. P. Dworkin, J. P. Emery, H. L. Enos, V. E. Hamilton, C. W. Hergenrother, E. S. Howell, M. R. M. Izawa, H. H. Kaplan, M. C. Nolan, B. Rizk, H. L. Roper, D. J. Scheeres, P. H. Smith, K. J. Walsh, C. W. V. Wolner, D. E. Highsmith, J. Small, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C. M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, L. McGraw, R. Ghent, R. P. Binzel, M. M. Al Asad, C. L. Johnson, L. Philpott, H. C. M. Susorney, E. A. Cloutis, R. D. Hanna, F. Ciceri, A. R. Hildebrand, E.-M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, B. E. Clark, S. Ferrone, C. A. Thomas, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto, J. R. Brucato, G. Poggiali, M. Pajola, E. Dotto, E. Mazzotta Epifani, M. K. Crombie, C. Lantz, J. de Leon, J. Licandro, J. L. Rizos Garcia, S. Clemett, K. Thomas-Keprta, S. Van wal, M. Yoshikawa, J. Bellerose, S. Bhaskaran, C. Boyles, S. R. Chesley, C. M. Elder, D. Farnocchia, A. Harbison, B. Kennedy, A. Knight, N. Martinez-Vlasoff, N. Mastrodemos, T. McElrath, W. Owen, R. Park, B. Rush, L. Swanson, Y. Takahashi, D. Velez, K. Yetter, C. Thayer, C. Adam, P. Antreasian, J. Bauman, C. Bryan, B. Carcich, M. Corvin, J. Geeraert, J. Hoffman, J. M. Leonard, E. Lessac-Chenen, A. Levine, J. McAdams, L. McCarthy, D. Nelson, B. Page, J. Pelgrift, E. Sahr, K. Stakkestad, D. Stanbridge, D. Wibben, B. Williams, K. Williams, P. Wolff, P. Hayne, D. Kubitschek, M. A. Barucci, J. D. P. Deshapriya, S. Fornasier, M. Fulchignoni, P. Hasselmann, F. Merlin, A. Praet, E. B. Bierhaus, O. Billett, A. Boggs, B. Buck, S. Carlson-Kelly, J.Cerna, K. Chaffin, E. Church, M. Coltrin, J. Daly, A. Deguzman, R. Dubisher, D. Eckart, D. Ellis, P. Falkenstern, A. Fisher, M. E. Fisher, P. Fleming, K. Fortney, S. Francis, S. Freund, S. Gonzales, P. Haas, A. Hasten, D. Hauf, A. Hilbert, D. Howell, F. Jaen, N. Jayakody, M. Jenkins, K. Johnson, M. Lefevre, H. Ma, C. Mario, K. Martin, C. May, M. McGee, B. Miller, C. Miller, G. Miller, A. Mirfakhrai, E. Muhle, C. Norman, R. Olds, C. Parish, M. Ryle, M. Schmitzer, P. Sherman, M. Skeen, M. Susak, B. Sutter, Q. Tran, C. Welch, R. Witherspoon, J. Wood, J. Zareski, M. Arvizu-Jakubicki, E. Asphaug, E. Audi, R.-L. Ballouz, R. Bandrowski, S. Bendall, H. Bloomenthal, D. Blum, J. Brodbeck, K. N. Burke, M. Chojnacki, A. Colpo, J. Contreras, J. Cutts, D. Dean, B. Diallo, D. Drinnon, K. Drozd, R. Enos, C. Fellows, T. Ferro, M. R. Fisher, G. Fitzgibbon, M. Fitzgibbon, J. Forelli, T. Forrester, I. Galinsky, R. Garcia, A. Gardner, N. Habib, D. Hamara, D. Hammond, K. Hanley, K. Harshman, K. Herzog, D. Hill, C. Hoekenga, S. Hooven, E. Huettner, A. Janakus, J. Jones, T. R. Kareta, J. Kidd, K. Kingsbury, L. Koelbel, J. Kreiner, D. Lambert, C. Lewin, B. Lovelace, M. Loveridge, M. Lujan, C. K. Maleszewski, R. Malhotra, K. Marchese, E. McDonough, N. Mogk, V. Morrison, E. Morton, R. Munoz, J. Nelson, J. Padilla, R. Pennington, A. Polit, N. Ramos, V. Reddy, M. Riehl, S. Salazar, S. R. Schwartz, S. Selznick, N. Shultz, S. Stewart, S. Sutton, T. Swindle, Y. H. Tang, M. Westermann, D. Worden, T. Zega, Z. Zeszut, A. Bjurstrom, L. Bloomquist, C. Dickinson, E. Keates, J. Liang, V. Nifo, A. Taylor, F. Teti, M. Caplinger, H. Bowles, S. Carter, S. Dickenshied, D. Doerres, T. Fisher, W. Hagee, J. Hill, M. Miner, D. Noss, N. Piacentine, M. Smith, A. Toland, P. Wren, M. Bernacki, D. Pino Munoz, S.-i. Watanabe, S. A. Sandford, A. Aqueche, B. Ashman, M. Barker, A. Bartels, K. Berry, B. Bos, R. Burns, A. Calloway, R. Carpenter, N. Castro, R. Cosentino, J. Donaldson, J. Elsila Cook, C. Emr, D. Everett, D. Fennell, K. Fleshman, D. Folta, D. Gallagher, J. Garvin, K. Getzandanner, D. Glavin, S. Hull, K. Hyde, H. Ido, A. Ingegneri, N. Jones, P. Kaotira, L. F. Lim, A. Liounis, C. Lorentson, D. Lorenz, J. Lyzhoft, E. M. Mazarico, R. Mink, W. Moore, M. Moreau, S. Mullen, J. Nagy, G. Neumann, J. Nuth, D. Poland, D. C. Reuter, L. Rhoads, S. Rieger, D. Rowlands, D. Sallitt, A. Scroggins, G. Shaw, A. A. Simon, J. Swenson, P. Vasudeva, M. Wasser, R. Zellar, J. Grossman, G. Johnston, M. Morris, J. Wendel, A. Burton, L. P. Keller, L. Mcnamara, S. Messenger, K. Messenger, A. Nguyen, K. Righter, E. Queen, K. Bellamy, K. Dill, S. Gardner, M. Giuntini, B. Key, J. Kissell, D. Patterson, D. Vaughan, B. Wright, R. W. Gaskell, L. Le Corre, J.-Y. Li, J. L. Molaro, E. E. Palmer, M. A. Siegler, P. Tricarico, J. R. Weirich, X.-D. Zou, T. Ireland, K. Tait, P. Bland, S. Anwar, N. Bojorquez-Murphy, P. R. Christensen, C. W. Haberle, G. Mehall, K. Rios, I. Franchi, B. Rozitis, C. B. Beddingfield, J. Marshall, D. N. Brack, A. S. French, J. W. McMahon, E. R. Jawin, T. J. McCoy, S. Russell, M. Killgore, J. L. Bandfield, B. C. Clark, M. Chodas, M. Lambert, R. A. Masterson, M. G. Daly, J. Freemantle, J. A. Seabrook, K. Craft, R. T. Daly, C. Ernst, R. C. Espiritu, M. Holdridge, M. Jones, A. H. Nair, L. Nguyen, J. Peachey, M. E. Perry, J. Plescia, J. H. Roberts, R. Steele, R. Turner, J. Backer, K. Edmundson, J. Mapel, M. Milazzo, S. Sides, C. Manzoni, B. May, M. Delbo, G. Libourel, P. Michel, A. Ryan, F. Thuillet, and B. Marty

Subjects
Astronomy, Exobiology
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 scale5,6,7,8,9,10,11. 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.

Published
2019
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17. Anticipated Geological Assessment of the (65803) Didymos–Dimorphos System, Target of the DART–LICIACube Mission

Author

M. Pajola, O. S. Barnouin, A. Lucchetti, M. Hirabayashi, R.-L. Ballouz, E. Asphaug, C. M. Ernst, V. Della Corte, T. Farnham, G. Poggiali, J. M. Sunshine, E. Mazzotta Epifani, N. Murdoch, S. Ieva, S. R. Schwartz, S. Ivanovski, J. M. Trigo-Rodriguez, A. Rossi, N. L. Chabot, A. Zinzi, A. Rivkin, J. R. Brucato, P. Michel, G. Cremonese, E. Dotto, M. Amoroso, I. Bertini, A. Capannolo, A. Cheng, B. Cotugno, M. Dall’Ora, R. T. Daly, V. Di Tana, J. D. P. Deshapriya, I. Gai, P. H. A. Hasselmann, G. Impresario, M. Lavagna, A. Meneghin, F. Miglioretti, D. Modenini, P. Palumbo, D. Perna, S. Pirrotta, E. Simioni, S. Simonetti, P. Tortora, M. Zannoni, G. Zanotti, Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE), Pajola, M., Barnouin, O. S., Lucchetti, A., Hirabayashi, M., Ballouz, R.-L., Asphaug, E., Ernst, C. M., Della Corte, V., Farnham, T., Poggiali, G., Sunshine, J. M., Epifani, E. Mazzotta, Murdoch, N., Ieva, S., Schwartz, S. R., Ivanovski, S., Trigo-Rodriguez, J. M., Rossi, A., Chabot, N. L., Zinzi, A., Rivkin, A., Brucato, J. R., Michel, P., Cremonese, G., Dotto, E., Amoroso, M., Bertini, I., Capannolo, A., Cheng, A., Cotugno, B., Dall’Ora, M., Daly, R. T., Di Tana, V., Deshapriya, J. D. P., Gai, I., Hasselmann, P. H. A., Impresario, G., Lavagna, M., Meneghin, A., Miglioretti, F., Modenini, D., Palumbo, P., Perna, D., Pirrotta, S., Simioni, E., Simonetti, S., Tortora, P., Zannoni, M., Zanotti, G., Agenzia Spaziale Italiana, Istituto Nazionale di Astrofisica, University of Arizona, National Aeronautics and Space Administration (US), Ministerio de Ciencia, Innovación y Universidades (España), European Commission, Agencia Estatal de Investigación (España), European Space Agency, and Centre National de la Recherche Scientifique (France)

Subjects
Asteroid surface, Geophysics, Autre, Space and Planetary Science, Asteroid satellites, Asteroid, Earth and Planetary Sciences (miscellaneous), In-situ characterization, Astronomy and Astrophysics, Planetary defense, Mission
Abstract

M. Pajola et al., On 2022 September 26, the DART spacecraft will impact the surface of Dimorphos, the ∼160 m size satellite of the binary near-Earth asteroid (NEA) (65803) Didymos. What will be observed on the surfaces of both asteroids and at the DART impact site is largely unknown, beyond the details of Didymos revealed by previous Arecibo and Goldstone radar observations. We present here the expected DART and LICIACube observations of the Didymos system and discuss the planned mapping strategies. By searching similar geological features and processes identified on other NEAs, we constrain the impact conditions that DART might encounter at Dimorphos, assessing both the asteroid's surface and interior structure., This work was supported by the Italian Space Agency (ASI) within the LICIACube project (ASI-INAF agreement AC n. 2019-31-HH.0). This work was supported by the DART mission, NASA Contract No. 80MSFC20D0004. E.A. is funded by the University of Arizona. S.S. acknowledges support from NASA as part of the Double Asteroid Redirection Test (DART) Participating Scientist Program. J.M.T.-R. is funded by the research project (PGC2018-097374-B-I00), funded by FEDER/Ministerio de Ciencia e Innovación—Agencia Estatal de Investigación. P.M. acknowledges ESA as well as funding from the French space agency CNES, from the European Union's Horizon 2020 research and innovation program under grant agreement No. 870377 (project NEO-MAPP) and from the CNRS through the MITI interdisciplinary programs.

Published
2022

18. The Formation of Terraces on Asteroid (101955) Bennu

Author

O. S. Barnouin, M. G. Daly, J. A. Seabrook, Y. Zhang, F. Thuillet, P. Michel, J. H. Roberts, R. T. Daly, M. E. Perry, H. C. M. Susorney, E. R. Jawin, R.‐L. Ballouz, K. J. Walsh, M. M. Sevalia, M. M. Al Asad, C. L. Johnson, E. B. Bierhaus, R. W. Gaskell, E. E. Palmer, J. Weirich, B. Rizk, C. Y. Drouet D’Aubigny, M. C. Nolan, D. N. DellaGiustina, D. J. Scheeres, J. W. McMahon, H. C. Connolly, D. C. Richardson, C. W. V. Wolner, and D. S. Lauretta

Subjects
Geophysics, Space and Planetary Science, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous)
Published
2022

19. Impact-crater ejecta on Bennu indicate a surface with very low strength

Author

Edward B. Bierhaus, J. A. Seabrook, Patrick Michel, Carolyn M. Ernst, Michael Daly, Olivier S. Barnouin, Dante S. Lauretta, Daniella DellaGiustina, Michael C. Nolan, Josh Emory, William F. Bottke, Catherine Johnson, Dathon Golish, Ronald-Louis Ballouz, Erica Jawin, R. T. Daly, Manar Al Asad, Kevin J. Walsh, and Mark E. Perry

Subjects
Surface (mathematics), Impact crater, Ejecta, Geology, Astrobiology
Abstract

A planetary surface’s resistance to change is generally described as its “strength” (units of stress). The surface strength of small, rubble-pile asteroids, which consist of fragments of larger bodies that were collisionally disrupted, is poorly constrained due to their wide departure from terrestrial analogs. Here, we report the observation of an ejecta deposit surrounding an impact crater that limits the maximum surface strength of the near-Earth rubble-pile asteroid (101955) Bennu. The presence of this deposit implies that ejecta were mobilized with velocities less than the escape velocity of Bennu, 20 cm/s. Because ejecta velocities increase with surface strength, the ejecta deposit can only be explained if the effective strength of the surface material near the crater is exceedingly low, ≤100 Pa. This is three orders of magnitude below values commonly used for asteroid surfaces, but is supported by previous observations of an artificial impact crater on a similar asteroid, Ryugu. Our findings indicate a mobile surface that has likely been renewed multiple times since Bennu’s initial assembly and have far-reaching implications for interpreting observations of Bennu and other rubble piles.

Published
2021

20. The Future of Planetary Defense in the Era of Advanced Surveys

Author

R. T. Daly, Timothy D. Swindle, Sean E. Marshall, Marco Delbo, A. Wong, T. Grav, Judy Pipher, Sarah Greenstreet, Alan Stern, Amy Mainzer, D. C. Hickson, Kynan H.G. Hughson, Joseph Lazio, Daniel T. Britt, B. Betts, Rosaly M. C. Lopes, Michele T. Bannister, Edgard G. Rivera-Valentín, Mario Juric, Peter Eisenhardt, Sean Carey, Walter M. Harris, James F. Bell, Joseph Masiero, Robert S. McMillan, Maria Gritsevich, Daniel J. Scheeres, Devanshu Jha, M. Bruckner, Alan W. Harris, D. Takir, C. A. Schambeau, F. Marchis, Michael C. Nolan, Flaviane Venditti, Betul Kacar, T. Okada, Yan Fernandez, P. Michel, Patrick A. Taylor, C. McMurtry, Ronald A. Fevig, William F. Bottke, P. Abell, Jennifer E.C. Scully, J. Barnes, Cristina A. Thomas, Maitrayee Bose, D. Cotto-Figueroa, J. Chesley, Anne Virkki, P. W. Chodas, Timothy Spahr, D. Mathias, Brent W. Barbee, Lance A. M. Benner, Michael W. Busch, Shantanu P. Naidu, Carol A. Raymond, Heidi B. Hammel, M. Brozovic, Željko Ivezić, Lynne Jones, E. Christensen, M. Telus, Julie Castillo-Rogez, Dante S. Lauretta, S. Sonnett, Andrew S. Rivkin, Edward L. Wright, J. Dotson, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU]Sciences of the Universe [physics], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

21. Apophis 2029 Planetary Defense Mission Options

Author

J. M. Sunshine, Derek C. Richardson, Andrew F. Cheng, Richard P. Binzel, R. T. Daly, Brett W. Denevi, Nicholas Schmerr, J. V. DeMartini, Olivier S. Barnouin, Carolyn M. Ernst, Joshua T.S. Cahill, and J. B. Plescia

Published
2021

22. Spectral analysis of craters on (101955) Bennu

Author

M. A. Barucci, D. C. Reuter, M. Fulchignoni, Beth E. Clark, Dante S. Lauretta, Edward A. Cloutis, Victoria E. Hamilton, Daniella DellaGiustina, Pedro Hasselmann, X. D. Zou, Amy Simon, Frederic Merlin, A. Praet, David Trang, R. T. Daly, E. B. Bierhaus, Cateline Lantz, John Robert Brucato, Jian-Yang Li, Sonia Fornasier, J. D. P. Deshapriya, S. Ferrone, Giovanni Poggiali, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Lockheed Martin Space, Department of Physics, Missouri University of Science and Technology (Missouri S&T), University of Missouri System-University of Missouri System, NASA Goddard Space Flight Center (GSFC), University of Winnipeg, Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Hawaii Institute of Geophysics and Planetology (HIGP), University of Hawai‘i [Mānoa] (UHM), Lunar and Planetary Laboratory [Tucson] (LPL), and University of Arizona

Subjects
010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Context (language use), Astrophysics, 01 natural sciences, Regolith, Spectral line, Impact crater, 13. Climate action, Space and Planetary Science, Asteroid, Absorption band, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Spectral slope, Spectroscopy, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

Using data acquired by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission, we investigate spectral properties of craters on the near-Earth asteroid (101955) Bennu. We compare Bennu's craters with its global average by means of four spectral parameters: (a) minimum position of the band at 2.7 μm, (b) depth of the hydrated phyllosilicate absorption band at 2.7 μm, (c) normalized spectral slope from 0.55 to 2.0 μm, and (d) reflectance factor at 0.55 μm. We examine 45 craters using spectral data obtained under various observing conditions. For 20 craters, we find a shortward shift of the 2.7-μm band minimum relative to the global 2.7-μm band minimum, which we attribute to the presence of relatively fresh (less space-weathered) material excavated from the sub-surface by crater-forming impacts. For three craters, we find an anti-correlation between spectral slopes and reflectance factor for a series of spectra acquired during a specific scan, where we observe that spectra become redder and darker towards the center of the crater. We attribute this to the presence of fine-particulate regolith. Localized spectral heterogeneities are apparent inside a prominent equatorial crater on Bennu, which is one of the asteroid's oldest geological features. We propose that such local spectral heterogeneities could be used as a tracer of mass movement on Bennu. We show that younger craters are redder, brighter, and have deeper 2.7-μm bands. Comparing global average spectral values of Bennu and crater frequency distributions as a function of the chosen spectral parameters, we find that craters evolve to assume the global average spectral properties of Bennu. A positive correlation identified between the reflectance factor and 2.7-μm band depth suggests that brighter craters tend to be more hydrated. Finally, we put into context, the results from the Small Carry-on Impactor experiment by the Hayabusa2 spacecraft, which created an artificial crater on the near-Earth asteroid (162173) Ryugu.

Published
2021

23. Rotational states and shapes of Ryugu and Bennu: Implications for interior structure and strength

Author

Kevin J. Walsh, Daniel J. Scheeres, Gregory A. Neumann, S. Sugita, Naoyuki Hirata, Patrick Michel, James H. Roberts, Jay W. McMahon, J. R. Weirich, R. T. Daly, Naru Hirata, Robert Gaskell, S. Watanabe, Yun Zhang, Eric Palmer, Michael C. Nolan, Dante S. Lauretta, Mark E. Perry, J. A. Seabrook, Olivier S. Barnouin, M. G. Daly, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, 010504 meteorology & atmospheric sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Spherical harmonics, Astronomy and Astrophysics, Geometry, Shape model, Rotation, 01 natural sciences, Asteroids, law.invention, Rotational dynamics, Space and Planetary Science, Asteroid, law, Orientation (geometry), 0103 physical sciences, Bennu, Cohesion (geology), Reflection (physics), Surface roughness, Ryugu, Hydrostatic equilibrium, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

International audience; Images of asteroids (162173) Ryugu and (101955) Bennu acquired by the Hayabusa2 and OSIRIS-REx missions, respectively, reveal rocky worlds covered in rubble. These two asteroids do not have hydrostatic shapes, indicating that they possess some internal friction and/or cohesion even if they lack tensile strength. Understanding the deviation of the surfaces of these bodies from those of idealized shapes helps constrain the mechanical properties of their interiors. Here, we focus on the feedback between YORP-induced spin-up (in which asymmetric reflection and re-emission of solar radiation from the surface systematically change the rotation rate), long-wavelength topography (which provides a structure to control the orientation), and surface roughness on Ryugu and Bennu. By performing spherical harmonic analyses of the shapes of these two asteroids, we find that although they are superficially similar, they exhibit different long-wavelength topography that implies different internal structures and rotational histories. Bennu's shape and rotation rate require a modest amount of internal strength through some combination of at least 17° of internal friction or a few Pa of cohesion, whereas Ryugu could be nearly strengthless. Bennu's longitudinal ridges make it susceptible to YORP spin-up, consistent with the observed increase in rotation rate that is not seen on Ryugu. These longitudinal ridges also suggest a heterogeneous density structure for Bennu, consistent with gravity data.

Published
2021

24. The Morphometry of Impact Craters on Bennu

Author

J. A. Seabrook, R. C. Espiritu, P. Michel, H. Nair, Olivier S. Barnouin, Carolyn M. Ernst, Robert Gaskell, Dante S. Lauretta, Mark E. Perry, J. R. Weirich, Michael C. Nolan, James H. Roberts, Hannah C.M. Susorney, David Trang, R. T. Daly, Eric Palmer, E. B. Bierhaus, Kevin J. Walsh, Catherine L. Johnson, Erica Jawin, Michael Daly, Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Lockheed Martin Space, Department of Earth and Space Science and Engineering [York University - Toronto] (ESSE), York University [Toronto], Planetary Science Institute [Tucson] (PSI), University of Bristol [Bristol], University of British Columbia (UBC), Southwest Research Institute [Boulder] (SwRI), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Smithsonian Institution National Museum of Natural History (NMNH), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Hawai'i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, and University of Hawai'i [Honolulu] (UH)

Subjects
Geophysics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010504 meteorology & atmospheric sciences, Impact crater, [SDU]Sciences of the Universe [physics], 0103 physical sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], General Earth and Planetary Sciences, 010303 astronomy & astrophysics, 01 natural sciences, Geomorphology, Geology, 0105 earth and related environmental sciences
Abstract

International audience; Bennu is an~500-m-diameter rubble-pile asteroid that is the target of detailed study by the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Here we use data from the OSIRIS-REx Laser Altimeter to assess depth-to-diameter ratios (d/D) of 108 impact craters larger than 10 m in diameter. The d/D of craters on Bennu ranges from 0.02 to 0.19. The mean is 0.10 ± 0.03. The smallest craters show the broadest range in d/D, consistent with d/D measurements on other asteroids. A few craters have central mounds, which is interpreted as evidence that a more competent substrate lies a few meters beneath them. The range of d/D narrows as crater size increases, with craters larger than 80 m tending toward smaller d/D. At large scales, increases in target strength with depth, combined with target curvature, may affect crater morphometry.

Published
2020

25. Geologic Context of the OSIRIS-REx Sample Site from High-resolution Topography and Imaging

Author

O. S. Barnouin, E. R. Jawin, R. T. Daly, R.-L. Ballouz, M. G. Daly, J. A. Seabrook, P. Michel, Y. Zhang, C. L. Johnson, K. J. Walsh, M. M. Al Asad, R. Gaskell, J. Weirich, E. Palmer, E. B. Bierhaus, M. C. Nolan, C. W. V. Wolner, and D. S. Lauretta

Subjects
Geophysics, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Astronomy and Astrophysics
Abstract

The OSIRIS-REx spacecraft collected a surface sample from Hokioi crater (55.8° N, 42.3° E; diameter ∼20 m) on the asteroid Bennu in 2020 October. We explore the geology of the sample collection site, known as Nightingale, by using digital terrain models, relative albedo maps, and images collected by the OSIRIS-REx spacecraft. Hokioi crater sits at the northwest edge of an older, larger (120 m diameter) crater between two north–south ridges respectively located at roughly 0° and 90° longitude, between which unconsolidated material generally migrates from the geopotential high at the north (+Z) pole to the geopotential low at the equator. The impact that formed Hokioi crater exposed relatively unweathered, fine-grained dark material that we observe within and ejected beyond the crater. The regional slope and steep crater walls to the north of the Nightingale site have enabled a mix of the dark debris and brighter material (which may include carbonates and/or exogenic basalts) surrounding Hokioi crater to migrate onto the crater floor, where the sample was collected; some of this material may be old ejecta excavated from up to 10 m depth when the 120 m diameter crater formed. We therefore expect the OSIRIS-REx sample to include materials of varying brightnesses, compositions, and exposure ages, derived primarily from the 0°–90° longitude quadrant and from as deep as 10 m. The sample may also include material derived from the impactor that formed Hokioi crater. We expect it to have low cohesion (≪0.6 Pa) and a friction angle between 32° and 39°.

Published
2022

26. Author Correction: Shape of (101955) Bennu indicative of a rubble pile with internal stiffness

Author

M. Lefevre, Aaron S. Burton, Carina Bennett, J. A. Mapel, Renu Malhotra, Peter Fleming, J. McAdams, N. Mogk, R. L. Ballouz, P. H. Smith, V. Nifo, C. K. Maleszewski, Timothy D. Swindle, E. Dotto, Stephen R. Schwartz, C. May, J. Bayron, D. Patterson, D. Guevel, Ellen S. Howell, Humberto Campins, J. Kissell, E. Brown, J. Wood, E. Muhle, John Robert Brucato, J. Small, B. Miller, Oleksiy Golubov, R. Pennington, K. Harshman, J. Nelson, Catherine Elder, M. McGee, R. Burns, J. Contreras, S. Hull, D. Kubitschek, D. Noss, Andrew J. Liounis, J. Backer, B. May, G. Fitzgibbon, J. Donaldson, D. Worden, Bashar Rizk, R. Witherspoon, Catherine L. Johnson, Erica Jawin, G. Shaw, A. Aqueche, Dolores H. Hill, D. Folta, S. Ferrone, M. Lujan, Giovanni Poggiali, B. G. Williams, S. Selznick, Melissa A. Morris, K. Rios, Sara S. Russell, D. Lambert, J. Hong, Jeffrey B. Plescia, H. Bloomenthal, D. Drinnon, Olivier S. Barnouin, Derek S. Nelson, Amanda E. Toland, Michael C. Moreau, J. A. Seabrook, K. Dill, A. Mirfakhrai, K. Hyde, J. D. P. Deshapriya, Hannah Kaplan, Timothy P. McElrath, Juliette I. Brodbeck, N. Ramos, S. Stewart, James B. Garvin, Sei-ichiro Watanabe, M. Arvizu-Jakubicki, Jason P. Dworkin, Matthew A. Siegler, Collin Lewin, Masatoshi Hirabayashi, L. Bloomquist, S. Gardner, Keiko Nakamura-Messenger, A. H. Nair, M. Schmitzer, P. Haas, Julie Bellerose, Dolan E. Highsmith, L. Koelbel, C. C. Lorentson, J. Zareski, E. Queen, S. R. Chesley, Philip A. Bland, A. Cheuvront, V. E. Hamilton, Ronald G. Mink, N. Mastrodemos, H. C. Connolly, K. Bellamy, M. Killgore, A. Gardner, Y. Takahashi, M. Lambert, R. C. Espiritu, Z. Zeszut, E. T. Morton, Kevin J. Walsh, Timothy D. Glotch, M. Skeen, Brian Kennedy, Matthew R.M. Izawa, G. Neumann, F. Teti, D. Doerres, A. Hasten, F. Ciceri, D. Howell, A. Deguzman, J. Nagy, D. Vaughan, H. Ma, C. Lantz, D. N. Brack, David K. Hammond, Erwan Mazarico, Leilah K. McCarthy, L. Rhoads, Kathleen L. Craft, C. Welch, Jay W. McMahon, C. L. Parish, D. C. Reuter, M. Giuntini, N. Castro, Clive Dickinson, J. Kreiner, K. Kingsbury, S. Dickenshied, Joseph A. Nuth, Alan R. Hildebrand, Erik Asphaug, H. Ido, Eric M. Sahr, A. Harbison, Arlin E. Bartels, T. Forrester, D. Eckart, R. Bandrowski, Michael K. Barker, Robert Gaskell, J. Wendel, S. Freund, Marc Bernacki, Ryan S. Park, A. Taylor, E. B. Bierhaus, S. Millington-Veloza, J. Stromberg, L. B. Breitenfeld, K. Stakkestad, D. Ellis, Timothy J. McCoy, M. Susak, Richard G. Cosentino, C. Manzoni, Hisayoshi Yurimoto, C. Drouet d'Aubigny, A. Bjurstrom, Masako Yoshikawa, S. Francis, J. Peachey, J. Geeraert, K. Marchese, O. Billett, M. Rascon, F. Jaen, B. Diallo, Martin Miner, Kris J. Becker, E. Mazzotta Epifani, Florian Thuillet, A. Knight, James H. Roberts, Pasquale Tricarico, Edward A. Cloutis, T. Fisher, Dale Stanbridge, A. Colpo, Osiris-Rex Team, S. Gonzales, Q. Tran, M. K. Crombie, John Marshall, N. Bojorquez-Murphy, David Vokrouhlický, Allen W. Lunsford, H. Bowles, K. L. Edmundson, R. A. Masterson, Peter G. Antreasian, N. Gorius, Benjamin Rozitis, D. Pino Muñoz, S. Carlson-Kelly, C. Thayer, J. Elsila Cook, B. C. Clark, N. Piacentine, José C. Aponte, M. Al Asad, M. A. Barucci, D. Blum, P. Falkenstern, Neil Bowles, Matthew Chojnacki, J. M. Leonard, J. Daly, K. Yetter, M. R. Fisher, Jeffrey N. Grossman, A. Boggs, N. Jayakody, Cristina A. Thomas, C.M. Ernst, Namrah Habib, J. N. Kidd, R. J. Steele, Andrew B. Calloway, Andrew Ryan, Kimberly T. Tait, Paul O. Hayne, J. Y. Li, K. L. Berry, William V. Boynton, Yanga R. Fernandez, D. A. Lorenz, M. Wasser, Daniel J. Scheeres, K. Fortney, A. Scroggins, B. Allen, B. Sutter, T. Ferro, Jonathan Joseph, Derek C. Richardson, D. Hoak, Brian Carcich, W. Chang, P. Wren, C. Boyles, Kaj E. Williams, B. Marty, J. Liang, J. Hoffman, A. Harch, Daniel R. Wibben, Jamie Molaro, S. Rieger, R. Enos, C. W. Hergenrother, Stephen R. Sutton, J. Grindlay, E. J. Lessac-Chenen, E. Huettner, C. Norman, P. Sherman, L. Swanson, M. Coltrin, S. Van wal, B. Buck, A. Fisher, Kevin Righter, Brian Rush, David D. Rowlands, Lauren McGraw, A. Levine, K. Drozd, D. Gaudreau, A. Nguyen, S. Sides, M. Chodas, R. Dubisher, B. Ashman, Michael Caplinger, Amy Simon, W. Moore, S. S. Balram-Knutson, R. Carpenter, S. Fornasier, Shogo Tachibana, Russell Turner, Ian A. Franchi, Trevor Ireland, Chloe B. Beddingfield, D. F. Everett, M. Corvin, Lindsay P. Keller, Tammy L. Becker, S. Carter, J. L. Rizos Garcia, Mark E. Perry, E. Keates, Michael C. Nolan, P. Vasudeva, C. Fellows, K. Herzog, Mark A. Jenkins, J. R. Weirich, J. Swenson, D. R. Golish, Davide Farnocchia, Lydia C. Philpott, Rebecca R. Ghent, Hannah C.M. Susorney, S. W. Squyres, Pedro Hasselmann, J. Hill, Thomas J. Zega, B. Key, Marco Delbo, A. S. French, P. Sánchez, A. Hilbert, J. Y. Pelgrift, R. P. Binzel, L. McNamara, Vishnu Reddy, Michael Daly, Scott Messenger, Daniella DellaGiustina, Maurizio Pajola, Charles Brunet, Joshua L. Bandfield, J. Padilla, A. Janakus, M. Moreau, R. Garcia, R. A. Chicoine, P. Michel, P. Kaotira, K. S. Johnson, J. Forelli, G. Miller, K. Martin, I. Galinsky, S. Desjardins, Naru Hirata, Christine Hartzell, M. L. Jones, S. Hooven, D. Velez, R. Munoz, Carolyn M. Ernst, C. Emr, N. Martinez-Vlasoff, S. Bendall, R. Zellar, E. Church, Theodore Kareta, T. Warren, P. Wolff, V. Morrison, C. Bryan, S. Bhaskaran, N. Jones, D. Hauf, Jeremy Bauman, R. T. Daly, R. Olds, M. M. Westermann, D. K. Hamara, E. Audi, G. Johnston, Eric Palmer, Courtney Mario, Daniel P. Glavin, T. Haltigin, J. Cutts, Javier Licandro, Xiao-Duan Zou, H. L. Roper, Gregory A. Neumann, William M. Owen, S. Sugita, Y. H. Tang, Kevin Burke, H. L. Enos, D. Gallagher, William F. Bottke, K. Getzandanner, Philip R. Christensen, C. W. V. Wolner, K. Fleshman, D. Poland, J. P. Emery, M.M. Riehl, D. Fennell, D. Sallitt, A. D. Rogers, M. Fitzgibbon, John H. Jones, S. Mullen, S. Salazar, S. Oliver, A. T. Polit, J. Cerna, A. Praet, Mark E. Holdridge, E. M. Ibrahim, Coralie D. Adam, J. de León, Christopher J. Miller, M. Ryle, J. Lyzhoft, M. Loveridge, C. Hoekenga, Brent J. Bos, S. Anwar, K. Chaffin, Devin L. Schrader, B. Lovelace, Romy D. Hanna, C. D. Adam, G. L. Mehall, K. L. Donaldson Hanna, F. Merlin, B. Wright, Guy Libourel, L. F. Lim, N. Shultz, Dante S. Lauretta, K. Hanley, Beth E. Clark, L. Le Corre, K. Thomas-Keprta, Moses Milazzo, W. Hagee, B. Page, M. Fisher, E. McDonough, D. Trang, S. Clemett, A. Rubi, A. Ingegneri, Scott A. Sandford, D. Dean, J. Freemantle, Michael D. Smith, Christopher W. Haberle, L. Nguyen, M. Fulchignoni, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL), Centre de Mise en Forme des Matériaux (CEMEF), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], 010504 meteorology & atmospheric sciences, Rubble, Stiffness, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, [SDU]Sciences of the Universe [physics], engineering, medicine, General Earth and Planetary Sciences, Geotechnical engineering, medicine.symptom, Pile, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

International audience

Published
2020

27. Bennu’s near-Earth lifetime of 1.75 million years inferred from craters on its boulders

Author

M. Al Asad, Olivier S. Barnouin, P. Michel, Jamie Molaro, C. Avdellidou, Carina Bennett, E. B. Bierhaus, Dante S. Lauretta, Michael C. Nolan, Kevin J. Walsh, Harold C. Connolly, Stephen R. Schwartz, Daniella DellaGiustina, C. W. V. Wolner, Bashar Rizk, Marco Delbo, Maurizio Pajola, R. L. Ballouz, Dathon Golish, Erica Jawin, M. G. Daly, David Trang, R. T. Daly, William F. Bottke, Erik Asphaug, Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Southwest Research Institute [Boulder] (SwRI), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France., Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
education.field_of_study, Multidisciplinary, 010504 meteorology & atmospheric sciences, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Population, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 01 natural sciences, Astrobiology, Impact crater, Asteroid, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Size frequency, Asteroid belt, education, 010303 astronomy & astrophysics, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

An asteroid’s history is determined in large part by its strength against collisions with other objects1,2 (impact strength). Laboratory experiments on centimetre-scale meteorites3 have been extrapolated and buttressed with numerical simulations to derive the impact strength at the asteroid scale4,5. In situ evidence of impacts on boulders on airless planetary bodies has come from Apollo lunar samples6 and images of the asteroid (25143) Itokawa7. It has not yet been possible, however, to assess directly the impact strength, and thus the absolute surface age, of the boulders that constitute the building blocks of a rubble-pile asteroid. Here we report an analysis of the size and depth of craters observed on boulders on the asteroid (101955) Bennu. We show that the impact strength of metre-sized boulders is 0.44 to 1.7 megapascals, which is low compared to that of solid terrestrial materials. We infer that Bennu’s metre-sized boulders record its history of impact by millimetre- to centimetre-scale objects in near-Earth space. We conclude that this population of near-Earth impactors has a size frequency distribution similar to that of metre-scale bolides and originates from the asteroidal population. Our results indicate that Bennu has been dynamically decoupled from the main asteroid belt for 1.75 ± 0.75 million years. Analysis of the size and depth of craters on boulders on the asteroid (101955) Bennu indicates that Bennu has been in near-Earth space for 1.75 ± 0.75 million years.

Published
2020

28. Exogenic basalt on asteroid (101955) Bennu

Author

Javier Licandro, Erica Jawin, M. Al Asad, J. A. Seabrook, Michael C. Nolan, M. A. Barucci, Kevin J. Walsh, Lydia C. Philpott, G. Poggiali, Timothy J. McCoy, R. P. Binzel, Marco Delbo, C. Avdellidou, Dante S. Lauretta, Marcel Popescu, J. L. Rizos Garcia, D. C. Reuter, Ellen S. Howell, Daniella DellaGiustina, Humberto Campins, Bashar Rizk, William F. Bottke, Hannah Kaplan, Amy Simon, Harold C. Connolly, Eri Tatsumi, V. E. Hamilton, M. G. Daly, Olivier S. Barnouin, Beth E. Clark, L. Le Corre, N. A. Porter, J. de León, Ronald-Louis Ballouz, R. T. Daly, Dathon Golish, Sonia Fornasier, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and ANR-18-CE31-0014,ORIGINS,A la recherche des planétésimaux de notre système solaire(2018)

Subjects
Basalt, Planetesimal, 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, 01 natural sciences, Parent body, Astrobiology, Igneous rock, Planetary science, Meteorite, 13. Climate action, Asteroid, [SDU]Sciences of the Universe [physics], Carbonaceous chondrite, 0103 physical sciences, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

When rubble-pile asteroid 2008 TC3 impacted Earth on 7 October 2008, the recovered rock fragments indicated that such asteroids can contain exogenic material1,2. However, spacecraft missions to date have only observed exogenous contamination on large, monolithic asteroids that are impervious to collisional disruption3,4. Here, we report the presence of metre-scale exogenic boulders on the surface of near-Earth asteroid (101955) Bennu—the 0.5-km-diameter, rubble-pile target of the OSIRIS-REx mission5 that has been spectroscopically linked to the CM carbonaceous chondrite meteorites6. Hyperspectral data indicate that the exogenic boulders have the same distinctive pyroxene composition as the howardite–eucrite–diogenite (HED) meteorites that come from (4) Vesta, a 525-km-diameter asteroid that has undergone differentiation and extensive igneous processing7–9. Delivery scenarios include the infall of Vesta fragments directly onto Bennu or indirectly onto Bennu’s parent body, where the latter’s disruption created Bennu from a mixture of endogenous and exogenic debris. Our findings demonstrate that rubble-pile asteroids can preserve evidence of inter-asteroid mixing that took place at macroscopic scales well after planetesimal formation ended. Accordingly, the presence of HED-like material on the surface of Bennu provides previously unrecognized constraints on the collisional and dynamical evolution of the inner main belt. Six bright boulders of exotic material on near-Earth asteroid (101955) Bennu stand out from the average asteroidal surface. This unexpected record of impactors offers clues to the formation history of Bennu.

Published
2020

29. Global Patterns of Recent Mass Movement on Asteroid (101955) Bennu

Author

M. Al Asad, Daniella DellaGiustina, John Marshall, Daniel J. Scheeres, Kevin J. Walsh, E. B. Bierhaus, M. G. Daly, Olivier S. Barnouin, Jamie Molaro, Ronald-Louis Ballouz, R. T. Daly, Dante S. Lauretta, Harold C. Connolly, Carina Bennett, Erica Jawin, Timothy J. McCoy, Chloe B. Beddingfield, Michael C. Nolan, Hannah C.M. Susorney, H. L. Enos, and Hannah Kaplan

Subjects
Geophysics, Mass movement, Space and Planetary Science, Geochemistry and Petrology, Asteroid, Earth and Planetary Sciences (miscellaneous), Geology, Astrobiology
Published
2020

30. Hemispherical differences in the shape and topography of asteroid (101955) Bennu

Author

James H. Roberts, Benjamin Rozitis, Yun Zhang, E. B. Bierhaus, J. A. Seabrook, K. Getzandanner, Michael Daly, D. N. DellaGuistina, Clive Dickinson, P. Michel, Mark E. Perry, J. R. Weirich, Lydia C. Philpott, R. T. Daly, Robert Gaskell, Hannah C.M. Susorney, J. Geeraert, Andrew Ryan, Eric Palmer, G. Cunningham, Charles Brunet, M. Al Asad, Jason M. Leonard, M. C. Nolan, R. L. Ballouz, H. L. Enos, Olivier S. Barnouin, Dante S. Lauretta, D. Gaudreau, Coralie D. Adam, T. Haltigin, Bashar Rizk, Erwan Mazarico, Gregory A. Neumann, Catherine L. Johnson, Erica Jawin, Kevin J. Walsh, Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Southwest Research Institute [Boulder] (SwRI), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), and University of Arizona

Subjects
business.product_category, 010504 meteorology & atmospheric sciences, Longitudinal ridges, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 01 natural sciences, 0103 physical sciences, Asymmetric distribution, Altimeter, Digital elevation model, 010303 astronomy & astrophysics, Geomorphology, Southern Hemisphere, Research Articles, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Multidisciplinary, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Northern Hemisphere, SciAdv r-articles, Wedge (mechanical device), Asteroid, [SDU]Sciences of the Universe [physics], business, Space Sciences, Geology, Research Article
Abstract

A lidar model of asteroid (101955) Bennu has a north-south asymmetry in shape and evidence of an early partial disruption., We investigate the shape of near-Earth asteroid (101955) Bennu by constructing a high-resolution (20 cm) global digital terrain model from laser altimeter data. By modeling the northern and southern hemispheres separately, we find that longitudinal ridges previously identified in the north extend into the south but are obscured there by surface material. In the south, more numerous large boulders effectively retain surface materials and imply a higher average strength at depth to support them. The north has fewer large boulders and more evidence of boulder dynamics (toppling and downslope movement) and surface flow. These factors result in Bennu’s southern hemisphere being rounder and smoother, whereas its northern hemisphere has higher slopes and a less regular shape. We infer an originally asymmetric distribution of large boulders followed by a partial disruption, leading to wedge formation in Bennu’s history.

Published
2020
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31. Projectile preservation during oblique hypervelocity impacts

Author

R. T. Daly and Peter H. Schultz

Subjects
Geophysics, Materials science, 010504 meteorology & atmospheric sciences, Space and Planetary Science, business.industry, Projectile, Hypervelocity, Oblique case, Aerospace engineering, 010502 geochemistry & geophysics, business, 01 natural sciences, 0105 earth and related environmental sciences
Published
2018

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