1
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Walsh KJ, Ballouz RL, Bottke WF, Avdellidou C, Connolly HC, Delbo M, DellaGiustina DN, Jawin ER, McCoy T, Michel P, Morota T, Nolan MC, Schwartz SR, Sugita S, Lauretta DS. Numerical simulations suggest asteroids (101955) Bennu and (162173) Ryugu are likely second or later generation rubble piles. Nat Commun 2024; 15:5653. [PMID: 38969628 PMCID: PMC11226714 DOI: 10.1038/s41467-024-49310-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Accepted: 05/29/2024] [Indexed: 07/07/2024] Open
Abstract
Rubble pile asteroids are widely understood to be composed of reaccumulated debris following a catastrophic collision between asteroids in the main asteroid belt, where each disruption can make a family of new asteroids. Near-Earth asteroids Ryugu and Bennu have been linked to collisional families in the main asteroid belt, but surface age analyses of each asteroid suggest these bodies are substantially younger than their putative families. Here we show, through a coupled collisional and dynamical evolution of members of these families, that neither asteroid was likely to have been created at the same time as the original family breakups, but rather are likely remnants of later disruptions of original family members, making them second, or later, generation remnants. Our model finds about 80% and 60% of asteroids currently being delivered to near-Earth orbits from the respective families of New Polana and Eulalia are second or later generation. These asteroids delivered today in the 0.5-1 km size range have median ages since their last disruption that are substantially younger than the family age, reconciling their measured crater retention ages with membership in these families.
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Affiliation(s)
- K J Walsh
- Southwest Research Institute, Boulder, CO, USA.
| | - R-L Ballouz
- Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, USA
| | - W F Bottke
- Southwest Research Institute, Boulder, CO, USA
| | - C Avdellidou
- Laboratoire Lagrange, Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
- School of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
| | - H C Connolly
- Dept. of Geology, Rowan University, Glassboro, NJ, USA
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
- American Museum of Natural History, New York, NY, USA
| | - M Delbo
- Laboratoire Lagrange, Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - D N DellaGiustina
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E R Jawin
- Smithsonian Institution National Air and Space Museum, Washington, DC, USA
| | - T McCoy
- Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - P Michel
- Laboratoire Lagrange, Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
- University of Tokyo, Tokyo, Japan
| | - T Morota
- University of Tokyo, Tokyo, Japan
| | - M C Nolan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - S Sugita
- University of Tokyo, Tokyo, Japan
| | - D S Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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2
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Adams FC, Napier KJ. Transfer of Rocks Between Planetary Systems: Panspermia Revisited. ASTROBIOLOGY 2022; 22:1429-1442. [PMID: 36475961 DOI: 10.1089/ast.2021.0187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Motivated by the recent discovery of interstellar objects passing through the solar system, and by recent developments in dynamical simulations, this article reconsiders the likelihood for life-bearing rocks to be transferred from one planetary system to another. The astronomical aspects of this lithopanspermia process can now be estimated, including the cross sections for rock capture, the velocity distributions of rocky ejecta, the survival times for captured objects, and the dynamics of the solar system in both its birth cluster and in the field. The remaining uncertainties are primarily biological, that is, the probability of life developing on a planet, the time required for such an event, and the efficiency with which life becomes seeded in a new environment. Using current estimates for the input quantities, we find that the transfer rates are enhanced in the birth cluster, but the resulting odds for success are too low for panspermia to be a likely occurrence. In contrast, the expected inventory of alien rocks in the solar system is predicted to be substantial (where the vast majority of such bodies are not biologically active and do not interact with the Earth).
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Affiliation(s)
- Fred C Adams
- Department of Physics and University of Michigan, Ann Arbor, Michigan, USA
- Department of Astronomy, University of Michigan, Ann Arbor, Michigan, USA
| | - Kevin J Napier
- Department of Physics and University of Michigan, Ann Arbor, Michigan, USA
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3
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Zhang Y, Michel P, Barnouin OS, Roberts JH, Daly MG, Ballouz RL, Walsh KJ, Richardson DC, Hartzell CM, Lauretta DS. Inferring interiors and structural history of top-shaped asteroids from external properties of asteroid (101955) Bennu. Nat Commun 2022; 13:4589. [PMID: 35933392 PMCID: PMC9357032 DOI: 10.1038/s41467-022-32288-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 07/20/2022] [Indexed: 11/30/2022] Open
Abstract
Asteroid interiors play a key role in our understanding of asteroid formation and evolution. As no direct interior probing has been done yet, characterisation of asteroids’ interiors relies on interpretations of external properties. Here we show, by numerical simulations, that the top-shaped rubble-pile asteroid (101955) Bennu’s geophysical response to spinup is highly sensitive to its material strength. This allows us to infer Bennu’s interior properties and provide general implications for top-shaped rubble piles’ structural evolution. We find that low-cohesion (≲0.78 Pa at surface and ≲1.3 Pa inside) and low-friction (friction angle ≲ 35∘) structures with several high-cohesion internal zones can consistently account for all the known geophysical characteristics of Bennu and explain the absence of moons. Furthermore, we reveal the underlying mechanisms that lead to different failure behaviours and identify the reconfiguration pathways of top-shaped asteroids as functions of their structural properties that either facilitate or prevent the formation of moons. Asteroid interiors are key to understand their formation and evolution. Here, the authors show that numerically simulated low-cohesion and low-friction structures with several high-cohesion internal zones can explain asteroid Bennu’s geophysical characteristics and the absence of the moons.
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Affiliation(s)
- Yun Zhang
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France. .,Department of Aerospace Engineering, University of Maryland, College Park, MD, USA.
| | - Patrick Michel
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - Olivier S Barnouin
- The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA
| | - James H Roberts
- The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA
| | - Michael G Daly
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
| | - Ronald-L Ballouz
- The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA.,Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | | | - Christine M Hartzell
- Department of Aerospace Engineering, University of Maryland, College Park, MD, USA
| | - Dante S Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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4
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Walsh KJ, Ballouz RL, Jawin ER, Avdellidou C, Barnouin OS, Bennett CA, Bierhaus EB, Bos BJ, Cambioni S, Connolly HC, Delbo M, DellaGiustina DN, DeMartini J, Emery JP, Golish DR, Haas PC, Hergenrother CW, Ma H, Michel P, Nolan MC, Olds R, Rozitis B, Richardson DC, Rizk B, Ryan AJ, Sánchez P, Scheeres DJ, Schwartz SR, Selznick SH, Zhang Y, Lauretta DS. Near-zero cohesion and loose packing of Bennu's near subsurface revealed by spacecraft contact. SCIENCE ADVANCES 2022; 8:eabm6229. [PMID: 35857450 PMCID: PMC9262326 DOI: 10.1126/sciadv.abm6229] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
When the OSIRIS-REx spacecraft pressed its sample collection mechanism into the surface of Bennu, it provided a direct test of the poorly understood near-subsurface physical properties of rubble-pile asteroids, which consist of rock fragments at rest in microgravity. Here, we find that the forces measured by the spacecraft are best modeled as a granular bed with near-zero cohesion that is half as dense as the bulk asteroid. The low gravity of a small rubble-pile asteroid such as Bennu effectively weakens its near subsurface by not compressing the upper layers, thereby minimizing the influence of interparticle cohesion on surface geology. The underdensity and weak near subsurface should be global properties of Bennu and not localized to the contact point.
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Affiliation(s)
- Kevin J. Walsh
- Southwest Research Institute, Boulder, CO, USA
- Corresponding author.
| | - Ronald-Louis Ballouz
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - Erica R. Jawin
- National Air and Space Museum, Smithsonian Institution, Washington, DC, USA
| | - Chrysa Avdellidou
- Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
| | | | - Carina A. Bennett
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - Brent J. Bos
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - Saverio Cambioni
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Harold C. Connolly
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
- Department of Geology, Rowan University, Glassboro, NJ, USA
| | - Marco Delbo
- Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
| | | | - Joseph DeMartini
- Department of Astronomy, University of Maryland, College Park, MD, USA
| | - Joshua P. Emery
- Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ, USA
| | - Dathon R. Golish
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | | | - Huikang Ma
- Lockheed Martin Space, Littleton, CO, USA
| | - Patrick Michel
- Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - Michael C. Nolan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - Ryan Olds
- Lockheed Martin Space, Littleton, CO, USA
| | - Benjamin Rozitis
- School of Physical Sciences, The Open University, Milton Keynes, UK
| | | | - Bashar Rizk
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - Andrew J. Ryan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - Paul Sánchez
- Colorado Center for Astrodynamics Research, University of Colorado Boulder, Boulder, CO, USA
| | - Daniel J. Scheeres
- Colorado Center for Astrodynamics Research, University of Colorado Boulder, Boulder, CO, USA
- Smead Aerospace Engineering Sciences Department, University of Colorado Boulder, Boulder, CO, USA
| | - Stephen R. Schwartz
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
- Planetary Science Institute, Tucson, AZ, USA
| | | | - Yun Zhang
- Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - Dante S. Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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5
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Lauretta DS, Adam CD, Allen AJ, Ballouz RL, Barnouin OS, Becker KJ, Becker T, Bennett CA, Bierhaus EB, Bos BJ, Burns RD, Campins H, Cho Y, Christensen PR, Church ECA, Clark BE, Connolly HC, Daly MG, DellaGiustina DN, Drouet d’Aubigny CY, Emery JP, Enos HL, Freund Kasper S, Garvin JB, Getzandanner K, Golish DR, Hamilton VE, Hergenrother CW, Kaplan HH, Keller LP, Lessac-Chenen EJ, Liounis AJ, Ma H, McCarthy LK, Miller BD, Moreau MC, Morota T, Nelson DS, Nolau JO, Olds R, Pajola M, Pelgrift JY, Polit AT, Ravine MA, Reuter DC, Rizk B, Rozitis B, Ryan AJ, Sahr EM, Sakatani N, Seabrook JA, Selznick SH, Skeen MA, Simon AA, Sugita S, Walsh KJ, Westermann MM, Wolner CWV, Yumoto K. Spacecraft sample collection and subsurface excavation of asteroid (101955) Bennu. Science 2022; 377:285-291. [DOI: 10.1126/science.abm1018] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Carbonaceous asteroids, such as (101955) Bennu, preserve material from the early Solar System, including volatile compounds and organic molecules. We report spacecraft imaging and spectral data collected during and after retrieval of a sample from Bennu’s surface. The sampling event mobilized rocks and dust into a debris plume, excavating a 9-m-long elliptical crater. This exposed material that is darker, spectrally redder, and more abundant in fine particulates than the original surface. The bulk density of the displaced subsurface material was 500–700 kg per cubic meter, about half that of the whole asteroid. Particulates that landed on instrument optics spectrally resemble aqueously altered carbonaceous meteorites. The spacecraft stored 250 ± 101 g of material, which will be delivered to Earth in 2023.
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Affiliation(s)
- D. S. Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - A. J. Allen
- Physics Department, University of Central Florida, Orlando, FL, USA
| | - R.-L. Ballouz
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - O. S. Barnouin
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - K. J. Becker
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - T. Becker
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - C. A. Bennett
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - B. J. Bos
- Goddard Space Flight Center, Greenbelt, MD, USA
| | - R. D. Burns
- Goddard Space Flight Center, Greenbelt, MD, USA
| | - H. Campins
- Physics Department, University of Central Florida, Orlando, FL, USA
| | - Y. Cho
- Department of Earth and Planetary Environmental Science, University of Tokyo, Tokyo, Japan
| | - P. R. Christensen
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | | | - B. E. Clark
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
| | - H. C. Connolly
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
- Department of Geology, Rowan University, Glassboro, NJ, USA
| | - M. G. Daly
- Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada
| | | | | | - J. P. Emery
- Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ, USA
| | - H. L. Enos
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | | | | | - D. R. Golish
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | | | | | | | | | | | - H. Ma
- Lockheed Martin Space, Littleton, CO, USA
| | | | | | | | - T. Morota
- Department of Earth and Planetary Environmental Science, University of Tokyo, Tokyo, Japan
| | | | - J. O. Nolau
- Physics Department, University of Central Florida, Orlando, FL, USA
| | - R. Olds
- Lockheed Martin Space, Littleton, CO, USA
| | - M. Pajola
- INAF (Italian National Institute for Astrophysics) – Astronomical Observatory of Padova, Padova, Italy
| | | | - A. T. Polit
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | | | - B. Rizk
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - B. Rozitis
- School of Physical Sciences, Open University, Milton Keynes, UK
| | - A. J. Ryan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - N. Sakatani
- Department of Physics, Rikkyo University, Tokyo, Japan
| | - J. A. Seabrook
- Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada
| | - S. H. Selznick
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - A. A. Simon
- Goddard Space Flight Center, Greenbelt, MD, USA
| | - S. Sugita
- Department of Earth and Planetary Environmental Science, University of Tokyo, Tokyo, Japan
| | - K. J. Walsh
- Southwest Research Institute, Boulder, CO, USA
| | - M. M. Westermann
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - C. W. V. Wolner
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - K. Yumoto
- Department of Earth and Planetary Environmental Science, University of Tokyo, Tokyo, Japan
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6
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Banik D, Gaurav K, Sharma I. Regolith flow on top-shaped asteroids. Proc Math Phys Eng Sci 2022. [DOI: 10.1098/rspa.2021.0972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We develop a continuum framework of regolith flow on asteroids. We focus on top-shaped asteroids that may be taken as consisting of regolith lying on a solid core. Depth-averaging is employed to model the regolith flow, and effects due to the asteroid’s rotation and its complex gravity field are retained. Angular momentum conservation is invoked to couple regolith flow to the asteroid’s changing shape and spin. This framework is first used to explore the equilibrium of regolith as a function of its friction, and the asteroid’s shape and spin rate. Next, we study regolith flow on top-shaped spinning asteroids and find conditions for the regolith’s shedding or deposition. We also discuss how the regolith’s flow and the asteroid’s spin influence each other. Finally, as an application, we propose and investigate the following evolution history of Bennu: a fast spinning Bennu was slowed down by multiple, impact-induced global landslides to its present spin state. Regolith was shed if the spin was higher than a critical rate. Once the spin rate fell below this critical value, regolith flow from higher latitudes began depositing regolith at its equator, giving Bennu its distinctive shape.
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Affiliation(s)
- Deepayan Banik
- Department of Aerospace Engineering, Indian Institute of Technology, Kanpur, India
- Applied Mechanics Laboratory, Department of Mechanical Engineering, Indian Institute of Technology, Kanpur, India
| | - Kumar Gaurav
- Applied Mechanics Laboratory, Department of Mechanical Engineering, Indian Institute of Technology, Kanpur, India
| | - Ishan Sharma
- Applied Mechanics Laboratory, Department of Mechanical Engineering, Indian Institute of Technology, Kanpur, India
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7
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Golish DR, Simon AA, Reuter DC, Ferrone S, Clark BE, Li JY, DellaGiustina DN, Drouet d’Aubigny C, Rizk B, Lauretta DS. Cross-Instrument Comparison of MapCam and OVIRS on OSIRIS-REx. SPACE SCIENCE REVIEWS 2022; 218:5. [PMID: 35250103 PMCID: PMC8885487 DOI: 10.1007/s11214-022-00873-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 02/08/2022] [Indexed: 06/14/2023]
Abstract
Two of the instruments onboard the OSIRIS-REx spacecraft, the MapCam color imager and the OVIRS visible and infrared spectrometer, observed the surface of asteroid (101955) Bennu in partially overlapping wavelengths. Significant scientific advances have been enabled by using data from these two instruments in tandem, but a robust statistical understanding of their relationship is needed for future analyses to cross-compare their data as accurately and sensitively as possible. Here we present a cross-instrument comparison of data acquired by MapCam and OVIRS, including methods and results for all global and site-specific observation campaigns in which both instruments were active. In our analysis, we consider both the absolute radiometric offset and the relative (normalized) variation between the two instruments; we find that both depend strongly on the photometric and instrumental conditions during the observation. The two instruments have a large absolute offset (>15%) due to their independent radiometric calibrations. However, they are very consistent (relative offset as low as 1%) when each instrument's response is normalized at a single wavelength, particularly at low phase angles where shadows on Bennu's rough surface are minimized. We recommend using the global datasets acquired at 12:30 pm local solar time for cross-comparisons; data acquired at higher phase angles have larger uncertainties.
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Affiliation(s)
- D. R. Golish
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ USA
| | - A. A. Simon
- NASA Goddard Space Flight Center, Greenbelt, MD USA
| | - D. C. Reuter
- NASA Goddard Space Flight Center, Greenbelt, MD USA
| | - S. Ferrone
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY USA
| | - B. E. Clark
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY USA
| | - J.-Y. Li
- Planetary Science Institute, Tucson, AZ USA
| | | | | | - B. Rizk
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ USA
| | - D. S. Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ USA
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8
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Mid-infrared emissivity of partially dehydrated asteroid (162173) Ryugu shows strong signs of aqueous alteration. Nat Commun 2022; 13:364. [PMID: 35042881 PMCID: PMC8766556 DOI: 10.1038/s41467-022-28051-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 01/06/2022] [Indexed: 11/09/2022] Open
Abstract
The near-Earth asteroid (162173) Ryugu, the target of Hayabusa2 space mission, was observed via both orbiter and the lander instruments. The infrared radiometer on the MASCOT lander (MARA) is the only instrument providing spectrally resolved mid-infrared (MIR) data, which is crucial for establishing a link between the asteroid material and meteorites found on Earth. Earlier studies revealed that the single boulder investigated by the lander belongs to the most common type found on Ryugu. Here we show the spectral variation of Ryugu's emissivity using the complete set of in-situ MIR data and compare it to those of various carbonaceous chondritic meteorites, revealing similarities to the most aqueously altered ones, as well as to asteroid (101955) Bennu. The results show that Ryugu experienced strong aqueous alteration prior to any dehydration.
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9
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Cambioni S, Delbo M, Poggiali G, Avdellidou C, Ryan AJ, Deshapriya JDP, Asphaug E, Ballouz RL, Barucci MA, Bennett CA, Bottke WF, Brucato JR, Burke KN, Cloutis E, DellaGiustina DN, Emery JP, Rozitis B, Walsh KJ, Lauretta DS. Fine-regolith production on asteroids controlled by rock porosity. Nature 2021; 598:49-52. [PMID: 34616055 DOI: 10.1038/s41586-021-03816-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 07/08/2021] [Indexed: 11/09/2022]
Abstract
Spacecraft missions have observed regolith blankets of unconsolidated subcentimetre particles on stony asteroids1-3. Telescopic data have suggested the presence of regolith blankets also on carbonaceous asteroids, including (101955) Bennu4 and (162173) Ryugu5. However, despite observations of processes that are capable of comminuting boulders into unconsolidated materials, such as meteoroid bombardment6,7 and thermal cracking8, Bennu and Ryugu lack extensive areas covered in subcentimetre particles7,9. Here we report an inverse correlation between the local abundance of subcentimetre particles and the porosity of rocks on Bennu. We interpret this finding to mean that accumulation of unconsolidated subcentimetre particles is frustrated where the rocks are highly porous, which appears to be most of the surface10. The highly porous rocks are compressed rather than fragmented by meteoroid impacts, consistent with laboratory experiments11,12, and thermal cracking proceeds more slowly than in denser rocks. We infer that regolith blankets are uncommon on carbonaceous asteroids, which are the most numerous type of asteroid13. By contrast, these terrains should be common on stony asteroids, which have less porous rocks and are the second-most populous group by composition13. The higher porosity of carbonaceous asteroid materials may have aided in their compaction and cementation to form breccias, which dominate the carbonaceous chondrite meteorites14.
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Affiliation(s)
- S Cambioni
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA. .,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
| | - M Delbo
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - G Poggiali
- INAF - Osservatorio Astrofisico di Arcetri, Florence, Italy
| | - C Avdellidou
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - A J Ryan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - J D P Deshapriya
- LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, Meudon, France
| | - E Asphaug
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - R-L Ballouz
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - M A Barucci
- LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, Meudon, France
| | - C A Bennett
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - W F Bottke
- Southwest Research Institute, Boulder, CO, USA
| | - J R Brucato
- INAF - Osservatorio Astrofisico di Arcetri, Florence, Italy
| | - K N Burke
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E Cloutis
- Department of Geography, University of Winnipeg, Winnipeg, Manitoba, Canada
| | - D N DellaGiustina
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - J P Emery
- Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ, USA
| | - B Rozitis
- School of Physical Sciences, The Open University, Milton Keynes, UK
| | - K J Walsh
- Southwest Research Institute, Boulder, CO, USA
| | - D S Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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Particle Size-Frequency Distributions of the OSIRIS-REx Candidate Sample Sites on Asteroid (101955) Bennu. REMOTE SENSING 2021. [DOI: 10.3390/rs13071315] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We manually mapped particles ranging in longest axis from 0.3 cm to 95 m on (101955) Bennu for the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission. This enabled the mission to identify candidate sample collection sites and shed light on the processes that have shaped the surface of this rubble-pile asteroid. Building on a global survey of particles, we used higher-resolution data from regional observations to calculate particle size-frequency distributions (PSFDs) and assess the viability of four candidate sites for sample collection (presence of unobstructed particles ≤ 2 cm). The four candidate sites have common characteristics: each is situated within a crater with a relative abundance of sampleable material. Their PSFDs, however, indicate that each site has experienced different geologic processing. The PSFD power-law slopes range from −3.0 ± 0.2 to −2.3 ± 0.1 across the four sites, based on images with a 0.01-m pixel scale. These values are consistent with, or shallower than, the global survey measurements. At one site, Osprey, the particle packing density appears to reach geometric saturation. We evaluate the uncertainty in these measurements and discuss their implications for other remotely sensed and mapped particles, and their importance to OSIRIS-REx sampling operations.
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