1
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DellaGiustina DN, Burke KN, Walsh KJ, Smith PH, Golish DR, Bierhaus EB, Ballouz RL, Becker TL, Campins H, Tatsumi E, Yumoto K, Sugita S, Deshapriya JDP, Cloutis EA, Clark BE, Hendrix AR, Sen A, Al Asad MM, Daly MG, Applin DM, Avdellidou C, Barucci MA, Becker KJ, Bennett CA, Bottke WF, Brodbeck JI, Connolly HC, Delbo M, de Leon J, Drouet d'Aubigny CY, Edmundson KL, Fornasier S, Hamilton VE, Hasselmann PH, Hergenrother CW, Howell ES, Jawin ER, Kaplan HH, Le Corre L, Lim LF, Li JY, Michel P, Molaro JL, Nolan MC, Nolau J, Pajola M, Parkinson A, Popescu M, Porter NA, Rizk B, Rizos JL, Ryan AJ, Rozitis B, Shultz NK, Simon AA, Trang D, Van Auken RB, Wolner CWV, Lauretta DS. Variations in color and reflectance on the surface of asteroid (101955) Bennu. Science 2020; 370:science.abc3660. [PMID: 33033157 DOI: 10.1126/science.abc3660] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 09/24/2020] [Indexed: 11/02/2022]
Abstract
Visible-wavelength color and reflectance provide information about the geologic history of planetary surfaces. Here we present multispectral images (0.44 to 0.89 micrometers) of near-Earth asteroid (101955) Bennu. The surface has variable colors overlain on a moderately blue global terrain. Two primary boulder types are distinguishable by their reflectance and texture. Space weathering of Bennu surface materials does not simply progress from red to blue (or vice versa). Instead, freshly exposed, redder surfaces initially brighten in the near-ultraviolet region (i.e., become bluer at shorter wavelengths), then brighten in the visible to near-infrared region, leading to Bennu's moderately blue average color. Craters indicate that the time scale of these color changes is ~105 years. We attribute the reflectance and color variation to a combination of primordial heterogeneity and varying exposure ages.
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Affiliation(s)
- D N DellaGiustina
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA. .,Department of Geosciences, University of Arizona, Tucson, AZ, USA
| | - K N Burke
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - K J Walsh
- Southwest Research Institute, Boulder, CO, USA
| | - P H Smith
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - D R Golish
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - R-L Ballouz
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - T L Becker
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - H Campins
- Department of Physics, University of Central Florida, Orlando, FL, USA
| | - E Tatsumi
- Instituto de Astrofísica de Canarias and Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain.,Department of Earth and Planetary Science, University of Tokyo, Tokyo, 113-0033, Japan
| | - K Yumoto
- Department of Earth and Planetary Science, University of Tokyo, Tokyo, 113-0033, Japan
| | - S Sugita
- Department of Earth and Planetary Science, University of Tokyo, Tokyo, 113-0033, Japan
| | - J D Prasanna Deshapriya
- LESIA (Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique), Observatoire de Paris, Université PSL (Paris Sciences & Lettres), CNRS (Centre National de la Recherche Scientifique), Université de Paris, Sorbonne Université, 92195 Meudon, France
| | - E A Cloutis
- Department of Geography, University of Winnipeg, Winnipeg, MB R3B 2E9, Canada
| | - B E Clark
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
| | - A R Hendrix
- Planetary Science Institute, Tucson, AZ, USA
| | - A Sen
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
| | - M M Al Asad
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada
| | - M G Daly
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
| | - D M Applin
- Department of Geography, University of Winnipeg, Winnipeg, MB R3B 2E9, Canada
| | - C Avdellidou
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - M A Barucci
- LESIA (Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique), Observatoire de Paris, Université PSL (Paris Sciences & Lettres), CNRS (Centre National de la Recherche Scientifique), Université de Paris, Sorbonne Université, 92195 Meudon, France
| | - K J Becker
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - C A Bennett
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - W F Bottke
- Southwest Research Institute, Boulder, CO, USA
| | - J I Brodbeck
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - H C Connolly
- Department of Geology, Rowan University, Glassboro, NJ, USA
| | - M Delbo
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - J de Leon
- Instituto de Astrofísica de Canarias and Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
| | | | - K L Edmundson
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - S Fornasier
- LESIA (Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique), Observatoire de Paris, Université PSL (Paris Sciences & Lettres), CNRS (Centre National de la Recherche Scientifique), Université de Paris, Sorbonne Université, 92195 Meudon, France.,Institut Universitaire de France (IUF), 1 rue Descartes, 75231 Paris CEDEX 05, France
| | | | - P H Hasselmann
- LESIA (Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique), Observatoire de Paris, Université PSL (Paris Sciences & Lettres), CNRS (Centre National de la Recherche Scientifique), Université de Paris, Sorbonne Université, 92195 Meudon, France
| | - C W Hergenrother
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E S Howell
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E R Jawin
- Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - H H Kaplan
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - L Le Corre
- Planetary Science Institute, Tucson, AZ, USA
| | - L F Lim
- Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - J Y Li
- Planetary Science Institute, Tucson, AZ, USA
| | - P Michel
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - J L Molaro
- Planetary Science Institute, Tucson, AZ, USA
| | - M C Nolan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - J Nolau
- Lockheed Martin Space, Littleton, CO, USA
| | - M Pajola
- Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Padova, Padua, Italy
| | - A Parkinson
- Department of Geography, University of Winnipeg, Winnipeg, MB R3B 2E9, Canada
| | - M Popescu
- Astronomical Institute of the Romanian Academy, Bucharest, Romania.,Instituto de Astrofísica de Canarias and Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
| | - N A Porter
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - B Rizk
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - J L Rizos
- Instituto de Astrofísica de Canarias and Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
| | - A J Ryan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - B Rozitis
- The School of Physical Sciences, The Open University, Milton Keynes, UK
| | - N K Shultz
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - A A Simon
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - D Trang
- University of Hawai'i at Mānoa, Hawai'i Institute of Geophysics and Planetology, Honolulu, HI, USA
| | - R B Van Auken
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - C W V Wolner
- 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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2
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Rozitis B, Ryan AJ, Emery JP, Christensen PR, Hamilton VE, Simon AA, Reuter DC, Al Asad M, Ballouz RL, Bandfield JL, Barnouin OS, Bennett CA, Bernacki M, Burke KN, Cambioni S, Clark BE, Daly MG, Delbo M, DellaGiustina DN, Elder CM, Hanna RD, Haberle CW, Howell ES, Golish DR, Jawin ER, Kaplan HH, Lim LF, Molaro JL, Munoz DP, Nolan MC, Rizk B, Siegler MA, Susorney HCM, Walsh KJ, Lauretta DS. Asteroid (101955) Bennu's weak boulders and thermally anomalous equator. Sci Adv 2020; 6:eabc3699. [PMID: 33033037 PMCID: PMC7544501 DOI: 10.1126/sciadv.abc3699] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 09/09/2020] [Indexed: 05/18/2023]
Abstract
Thermal inertia and surface roughness are proxies for the physical characteristics of planetary surfaces. Global maps of these two properties distinguish the boulder population on near-Earth asteroid (NEA) (101955) Bennu into two types that differ in strength, and both have lower thermal inertia than expected for boulders and meteorites. Neither has strongly temperature-dependent thermal properties. The weaker boulder type probably would not survive atmospheric entry and thus may not be represented in the meteorite collection. The maps also show a high-thermal inertia band at Bennu's equator, which might be explained by processes such as compaction or strength sorting during mass movement, but these explanations are not wholly consistent with other data. Our findings imply that other C-complex NEAs likely have boulders similar to those on Bennu rather than finer-particulate regoliths. A tentative correlation between albedo and thermal inertia of C-complex NEAs may be due to relative abundances of boulder types.
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Affiliation(s)
- B Rozitis
- School of Physical Sciences, The Open University, Milton Keynes, UK.
| | - A J Ryan
- 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
| | - P R Christensen
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | | | - A A Simon
- NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD, USA
| | - D C Reuter
- NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD, USA
| | - M Al Asad
- Department of Earth, Atmospheric, and Ocean Science, University of British Columbia, Vancouver, BC, Canada
| | - 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
| | - C A Bennett
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - M Bernacki
- Mines ParisTech, PSL Research University, CEMEF-Centre de mise en forme des matériaux, Sophia Antipolis Cedex, France
| | - K N Burke
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - S Cambioni
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - B E Clark
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
| | - M G Daly
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
| | - M Delbo
- 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
| | - C M Elder
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - R D Hanna
- Jackson School of Geosciences, University of Texas, Austin, TX, USA
| | - C W Haberle
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | - E S Howell
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - D R Golish
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E R Jawin
- Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - H H Kaplan
- NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD, USA
| | - L F Lim
- NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD, USA
| | - J L Molaro
- Planetary Science Institute, Tucson, AZ, USA
| | - D Pino Munoz
- Mines ParisTech, PSL Research University, CEMEF-Centre de mise en forme des matériaux, Sophia Antipolis Cedex, France
| | - M C Nolan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - B Rizk
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - M A Siegler
- Planetary Science Institute, Tucson, AZ, USA
| | - H C M Susorney
- School of Earth Sciences, University of Bristol, Bristol, 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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3
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Scheeres DJ, French AS, Tricarico P, Chesley SR, Takahashi Y, Farnocchia D, McMahon JW, Brack DN, Davis AB, Ballouz RL, Jawin ER, Rozitis B, Emery JP, Ryan AJ, Park RS, Rush BP, Mastrodemos N, Kennedy BM, Bellerose J, Lubey DP, Velez D, Vaughan AT, Leonard JM, Geeraert J, Page B, Antreasian P, Mazarico E, Getzandanner K, Rowlands D, Moreau MC, Small J, Highsmith DE, Goossens S, Palmer EE, Weirich JR, Gaskell RW, Barnouin OS, Daly MG, Seabrook JA, Al Asad MM, Philpott LC, Johnson CL, Hartzell CM, Hamilton VE, Michel P, Walsh KJ, Nolan MC, Lauretta DS. Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu. Sci Adv 2020; 6:eabc3350. [PMID: 33033036 PMCID: PMC7544499 DOI: 10.1126/sciadv.abc3350] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 09/16/2020] [Indexed: 05/18/2023]
Abstract
The gravity field of a small body provides insight into its internal mass distribution. We used two approaches to measure the gravity field of the rubble-pile asteroid (101955) Bennu: (i) tracking and modeling the spacecraft in orbit about the asteroid and (ii) tracking and modeling pebble-sized particles naturally ejected from Bennu's surface into sustained orbits. These approaches yield statistically consistent results up to degree and order 3, with the particle-based field being statistically significant up to degree and order 9. Comparisons with a constant-density shape model show that Bennu has a heterogeneous mass distribution. These deviations can be modeled with lower densities at Bennu's equatorial bulge and center. The lower-density equator is consistent with recent migration and redistribution of material. The lower-density center is consistent with a past period of rapid rotation, either from a previous Yarkovsky-O'Keefe-Radzievskii-Paddack cycle or arising during Bennu's accretion following the disruption of its parent body.
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Affiliation(s)
- D J Scheeres
- Smead Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA.
| | - A S French
- Smead Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA
| | - P Tricarico
- Planetary Science Institute, Tucson, AZ, USA
| | - S R Chesley
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Y Takahashi
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - D Farnocchia
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - J W McMahon
- Smead Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA
| | - D N Brack
- Smead Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA
| | - A B Davis
- Smead Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA
| | - R-L Ballouz
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E R Jawin
- Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - B Rozitis
- Planetary and Space Sciences, School of Physical Sciences, The Open University, Milton Keynes, UK
| | - J P Emery
- Department of Astronomy and Planetary Sciences, Northern Arizona University, Flagstaff, AZ, USA
| | - A J Ryan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - R S Park
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - B P Rush
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - N Mastrodemos
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - B M Kennedy
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - J Bellerose
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - D P Lubey
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - D Velez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - A T Vaughan
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | | | - J Geeraert
- KinetX Aerospace Inc., Simi Valley, CA, USA
| | - B Page
- KinetX Aerospace Inc., Simi Valley, CA, USA
| | | | - E Mazarico
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | | | - D Rowlands
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - M C Moreau
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - J Small
- Aerospace Corporation, Chantilly, VA, USA
| | | | - S Goossens
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
- Center for Research and Exploration in Space Science and Technology, University of Maryland, Baltimore County, Baltimore, MD, USA
| | - E E Palmer
- Planetary Science Institute, Tucson, AZ, USA
| | - J R Weirich
- Planetary Science Institute, Tucson, AZ, USA
| | - R W Gaskell
- Planetary Science Institute, Tucson, AZ, USA
| | - O S Barnouin
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - M G Daly
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
| | - J A Seabrook
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
| | - M M Al Asad
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - L C Philpott
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - C L Johnson
- Planetary Science Institute, Tucson, AZ, USA
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - C M Hartzell
- Department of Aerospace Engineering, University of Maryland, College Park, MD, USA
| | - V E Hamilton
- Department of Space Studies, Southwest Research Institute, Boulder, CO, USA
| | - P Michel
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - K J Walsh
- Department of Space Studies, Southwest Research Institute, Boulder, CO, USA
| | - M C Nolan
- 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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4
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Daly MG, Barnouin OS, Seabrook JA, Roberts J, Dickinson C, Walsh KJ, Jawin ER, Palmer EE, Gaskell R, Weirich J, Haltigin T, Gaudreau D, Brunet C, Cunningham G, Michel P, Zhang Y, Ballouz RL, Neumann G, Perry ME, Philpott L, Al Asad MM, Johnson CL, Adam CD, Leonard JM, Geeraert JL, Getzandanner K, Nolan MC, Daly RT, Bierhaus EB, Mazarico E, Rozitis B, Ryan AJ, DellaGiustina DN, Rizk B, Susorney HCM, Enos HL, Lauretta DS. Hemispherical differences in the shape and topography of asteroid (101955) Bennu. Sci Adv 2020; 6:eabd3649. [PMID: 33033038 PMCID: PMC7544500 DOI: 10.1126/sciadv.abd3649] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 09/14/2020] [Indexed: 05/18/2023]
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.
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Affiliation(s)
- M G Daly
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada.
| | - O S Barnouin
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - J A Seabrook
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
| | - J Roberts
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | | | - K J Walsh
- Southwest Research Institute, Boulder, CO, USA
| | - E R Jawin
- Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - E E Palmer
- Planetary Science Institute, Tucson, AZ, USA
| | - R Gaskell
- Planetary Science Institute, Tucson, AZ, USA
| | - J Weirich
- Planetary Science Institute, Tucson, AZ, USA
| | - T Haltigin
- Canadian Space Agency, St. Hubert, QC, Canada
| | - D Gaudreau
- Canadian Space Agency, St. Hubert, QC, Canada
| | - C Brunet
- Canadian Space Agency, St. Hubert, QC, Canada
| | | | - P Michel
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - Y Zhang
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - R-L Ballouz
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - G Neumann
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - M E Perry
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - L Philpott
- University of British Columbia, Vancouver, BC, Canada
| | - M M Al Asad
- University of British Columbia, Vancouver, BC, Canada
| | - C L Johnson
- University of British Columbia, Vancouver, BC, Canada
- Planetary Science Institute, Tucson, AZ, USA
| | - C D Adam
- KinetX Inc., Simi Valley, CA, USA
| | | | | | | | | | - R T Daly
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | | | - E Mazarico
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - B Rozitis
- School of Physical Sciences, Open University, Milton Keynes, UK
| | - A J Ryan
- KinetX Inc., Simi Valley, CA, USA
| | - D N DellaGiustina
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - B Rizk
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - H L Enos
- 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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5
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Leonard JM, Adam CD, Pelgrift JY, Lessac‐Chenen EJ, Nelson DS, Antreasian PG, Liounis AJ, Moreau MC, Hergenrother CW, Chesley SR, Nolan MC, Lauretta DS. Initial Orbit Determination and Event Reconstruction From Estimation of Particle Trajectories About (101955) Bennu. Earth Space Sci 2020; 7:e2019EA000937. [PMID: 33043099 PMCID: PMC7540059 DOI: 10.1029/2019ea000937] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 02/10/2020] [Accepted: 02/25/2020] [Indexed: 06/11/2023]
Abstract
The OSIRIS-REx mission has observed multiple instances of particles being ejected from the surface of near-Earth asteroid (101955) Bennu. The ability to quickly identify the particle trajectories and origins is necessary following a particle ejection event. Using proven initial orbit determination techniques, we can rapidly estimate particle trajectories and ejection locations. We present current results pertaining to the identification of particle tracks, an evaluation of the estimated orbits and the excess velocity necessary to induce the particle ejection from the surface, and the uncertainty quantification of the ejection location. We estimate energies per particle ranging from 0.03 to 11.03 mJ for the largest analyzed events and velocities ranging from 5 to 90 cm/s, though we exclude the highest-velocity particles in this technique. We estimate ejection times for eight events and constrain six of the analyzed ejection events to have occurred between about 16:30 and 19:00 local solar time, with the largest events occurring between 16:30 and 18:05.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - S. R. Chesley
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - M. C. Nolan
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
| | - D. S. Lauretta
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
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6
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Bottke WF, Moorhead AV, Connolly HC, Hergenrother CW, Molaro JL, Michel P, Nolan MC, Schwartz SR, Vokrouhlický D, Walsh KJ, Lauretta DS. Meteoroid Impacts as a Source of Bennu's Particle Ejection Events. J Geophys Res Planets 2020; 125:e2019JE006282. [PMID: 32999798 PMCID: PMC7507787 DOI: 10.1029/2019je006282] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 02/07/2020] [Accepted: 04/23/2020] [Indexed: 06/11/2023]
Abstract
Asteroid (101955) Bennu, a near-Earth object with a primitive carbonaceous chondrite-like composition, was observed by the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft to undergo multiple particle ejection events near perihelion between December 2018 and February 2019. The three largest events observed during this period, which all occurred 3.5 to 6 hr after local noon, placed numerous particles <10 cm on temporary orbits around Bennu. Here we examine whether these events could have been produced by sporadic meteoroid impacts using the National Aeronautics and Space Administration's (NASA) Meteoroid Engineering Model 3.0. Most projectiles that impact Bennu come from nearly isotropic or Jupiter-family comets and have evolved toward the Sun by Poynting-Robertson drag. We find that 7,000-J impacts on Bennu occur with a biweekly cadence near perihelion, with a preference to strike in the late afternoon (~6 pm local time). This timing matches observations. Crater scaling laws also indicate that these impact energies can reproduce the sizes and masses of the largest observed particles, provided the surface has the cohesive properties of weak, porous materials. Bennu's ejection events could be caused by the same kinds of meteoroid impacts that created the Moon's asymmetric debris cloud observed by the Lunar Atmosphere and Dust Environment Explorer (LADEE). Our findings also suggest that fewer ejection events should take place as Bennu moves further away from the Sun, a result that can be tested with future observations.
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Affiliation(s)
| | - A. V. Moorhead
- NASA Meteoroid Environment Office, Marshall Space Flight Center EV44HuntsvilleALUSA
| | - H. C. Connolly
- Department of GeologyRowan UniversityGlassboroNJUSA
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
| | | | | | - P. Michel
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire LagrangeNiceFrance
| | - M. C. Nolan
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
| | - S. R. Schwartz
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
| | - D. Vokrouhlický
- Institute of AstronomyCharles UniversityPragueCzech Republic
| | | | - D. S. Lauretta
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
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7
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Scheeres DJ, McMahon JW, Brack DN, French AS, Chesley SR, Farnocchia D, Vokrouhlický D, Ballouz R, Emery JP, Rozitis B, Nolan MC, Hergenrother CW, Lauretta DS. Particle Ejection Contributions to the Rotational Acceleration and Orbit Evolution of Asteroid (101955) Bennu. J Geophys Res Planets 2020; 125:e2019JE006284. [PMID: 32714726 PMCID: PMC7375169 DOI: 10.1029/2019je006284] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 02/07/2020] [Accepted: 02/11/2020] [Indexed: 05/29/2023]
Abstract
This paper explores the implications of the observed Bennu particle ejection events for that asteroid's spin rate and orbit evolution, which could complicate interpretation of the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) and Yarkovsky effects on this body's spin rate and orbital evolution. Based on current estimates of particle ejection rates, we find that the overall contribution to Bennu's spin and orbital drift is small or negligible as compared to the Yarkovsky and YORP effects. However, if there is a large unseen component of smaller mass ejections or a strong directionality in the ejection events, it could constitute a significant contribution that could mask the overall YORP effect. This means that the YORP effect may be stronger than currently assumed. The analysis is generalized so that the particle ejection effect can be assessed for other bodies that may be subject to similar mass loss events. Further, our model can be modified to address different potential mechanisms of particle ejection, which are a topic of ongoing study.
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Affiliation(s)
- D. J. Scheeres
- Smead Department of Aerospace Engineering SciencesUniversity of Colorado BoulderBoulderCOUSA
| | - J. W. McMahon
- Smead Department of Aerospace Engineering SciencesUniversity of Colorado BoulderBoulderCOUSA
| | - D. N. Brack
- Smead Department of Aerospace Engineering SciencesUniversity of Colorado BoulderBoulderCOUSA
| | - A. S. French
- Smead Department of Aerospace Engineering SciencesUniversity of Colorado BoulderBoulderCOUSA
| | - S. R. Chesley
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - D. Farnocchia
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - D. Vokrouhlický
- Institute of AstronomyCharles UniversityPragueCzech Republic
| | - R.‐L. Ballouz
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
| | - J. P. Emery
- Department of Earth and Planetary SciencesUniversity of TennesseeKnoxvilleTNUSA
| | - B. Rozitis
- Planetary and Space Sciences, School of Physical SciencesThe Open UniversityMilton KeynesUK
| | - M. C. Nolan
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
| | | | - D. S. Lauretta
- Lunar and Planetary LaboratoryUniversity of ArizonaTucsonAZUSA
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8
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Lauretta DS, DellaGiustina DN, Bennett CA, Golish DR, Becker KJ, Balram-Knutson SS, Barnouin OS, Becker TL, Bottke WF, Boynton WV, Campins H, Clark BE, Connolly HC, Drouet d'Aubigny CY, Dworkin JP, Emery JP, Enos HL, Hamilton VE, Hergenrother CW, Howell ES, Izawa MRM, Kaplan HH, Nolan MC, Rizk B, Roper HL, Scheeres DJ, Smith PH, Walsh KJ, Wolner CWV. The unexpected surface of asteroid (101955) Bennu. Nature 2019; 568:55-60. [PMID: 30890786 PMCID: PMC6557581 DOI: 10.1038/s41586-019-1033-6] [Citation(s) in RCA: 268] [Impact Index Per Article: 53.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 02/15/2019] [Indexed: 11/09/2022]
Abstract
NASA'S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine-that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu's global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5-11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid's properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu's thermal inertia12 and radar polarization ratios13-which indicated a generally smooth surface covered by centimetre-scale particles-resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.
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Affiliation(s)
- D S Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA.
| | - D N DellaGiustina
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - C A Bennett
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - D R Golish
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - K J Becker
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - O S Barnouin
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - T L Becker
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - W F Bottke
- Southwest Research Institute, Boulder, CO, USA
| | - W V Boynton
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - H Campins
- Department of Physics, University of Central Florida, Orlando, FL, USA
| | - B E Clark
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
| | - H C Connolly
- Department of Geology, Rowan University, Glassboro, NJ, USA
| | | | - J P Dworkin
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - J P Emery
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA
| | - H L Enos
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - C W Hergenrother
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E S Howell
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - M R M Izawa
- Institute for Planetary Materials, Okayama University-Misasa, Misasa, Japan
| | - H H Kaplan
- Southwest Research Institute, Boulder, CO, USA
| | - M C Nolan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - B Rizk
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - H L Roper
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - D J Scheeres
- Smead Department of Aerospace Engineering, University of Colorado, Boulder, CO, USA
| | - P H Smith
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - K J Walsh
- Southwest Research Institute, Boulder, CO, USA
| | - C W V Wolner
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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9
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Scheeres DJ, McMahon JW, French AS, Brack DN, Chesley SR, Farnocchia D, Takahashi Y, Leonard JM, Geeraert J, Page B, Antreasian P, Getzandanner K, Rowlands D, Mazarico E, Small J, Highsmith DE, Moreau M, Emery JP, Rozitis B, Hirabayashi M, Sánchez P, Wal SV, Tricarico P, Ballouz RL, Johnson CL, Asad MMA, Susorney HCM, Barnouin OS, Daly MG, Seabrook J, Gaskell RW, Palmer EE, Weirich JR, Walsh KJ, Jawin ER, Bierhaus EB, Michel P, Bottke WF, Nolan MC, Connolly HC, Lauretta DS. The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements. Nat Astron 2019; 3:352-361. [PMID: 32601603 PMCID: PMC7323631 DOI: 10.1038/s41550-019-0721-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 02/11/2019] [Indexed: 05/18/2023]
Abstract
The top-shape morphology of asteroid (101955) Bennu is commonly found among fast-spinning asteroids and binary asteroid primaries, and might have contributed significantly to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of OSIRIS-REx, we find a significant transition in Bennu's surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu's surface has been most recently migrating towards its equator (given Bennu's increasing spin rate), we infer that Bennu's surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior has a distribution of voids and boulders. The presence of such heterogeneity and Bennu's top-shape is consistent with spin-induced failure at some point in its past, although the manner of its failure cannot be determined yet. Future measurements by the OSIRIS-REx spacecraft will give additional insights and may resolve questions regarding the formation and evolution of Bennu's top-shape morphology and its link to the formation of binary asteroids.
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Affiliation(s)
- D J Scheeres
- Smead Department of Aerospace Engineering, University of Colorado, Boulder, CO, USA
| | - J W McMahon
- Smead Department of Aerospace Engineering, University of Colorado, Boulder, CO, USA
| | - A S French
- Smead Department of Aerospace Engineering, University of Colorado, Boulder, CO, USA
| | - D N Brack
- Smead Department of Aerospace Engineering, University of Colorado, Boulder, CO, USA
| | - S R Chesley
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - D Farnocchia
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Y Takahashi
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - J M Leonard
- KinetX Aerospace, Inc., Simi Valley, CA, USA
| | - J Geeraert
- KinetX Aerospace, Inc., Simi Valley, CA, USA
| | - B Page
- KinetX Aerospace, Inc., Simi Valley, CA, USA
| | | | | | - D Rowlands
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - E Mazarico
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - J Small
- Aerospace Corporation, Chantilly, VA, USA
| | | | - M Moreau
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - J P Emery
- University of Tennessee, Knoxville, TN, USA
| | - B Rozitis
- Planetary and Space Sciences, School of Physical Sciences, The Open University, Milton Keynes, UK
| | | | - P Sánchez
- Colorado Center for Astrodynamics Research, University of Colorado, Boulder, CO, USA
| | - S Van Wal
- Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Japan
| | - P Tricarico
- Planetary Science Institute, Tucson, AZ, USA
| | - R-L Ballouz
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - C L Johnson
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
- Planetary Science Institute, Tucson, AZ, USA
| | - M M Al Asad
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - H C M Susorney
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - O S Barnouin
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - M G Daly
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
| | - J Seabrook
- The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada
| | - R W Gaskell
- Planetary Science Institute, Tucson, AZ, USA
| | - E E Palmer
- Planetary Science Institute, Tucson, AZ, USA
| | - J R Weirich
- Planetary Science Institute, Tucson, AZ, USA
| | - K J Walsh
- Southwest Research Institute, Boulder, CO, USA
| | - E R Jawin
- Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - E B Bierhaus
- Lockheed Martin Space Systems Company, Denver, CO, USA
| | - P Michel
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - W F Bottke
- Southwest Research Institute, Boulder, CO, USA
| | - M C Nolan
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - H C Connolly
- School of Earth and Environment, Rowan University, Glassboro, NJ, USA
| | - D S Lauretta
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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10
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Barnouin OS, Daly MG, Palmer EE, Gaskell RW, Weirich JR, Johnson CL, Asad MMA, Roberts JH, Perry ME, Susorney HCM, Daly RT, Bierhaus EB, Seabrook JA, Espiritu RC, Nair AH, Nguyen L, Neumann GA, Ernst CM, Boynton WV, Nolan MC, Adam CD, Moreau MC, Risk B, D'Aubigny CD, Jawin ER, Walsh KJ, Michel P, Schwartz SR, Ballouz RL, Mazarico EM, Scheeres DJ, McMahon J, Bottke W, Sugita S, Hirata N, Hirata N, Watanabe S, Burke KN, DellaGuistina DN, Bennett CA, Lauretta DS. Shape of (101955) Bennu indicative of a rubble pile with internal stiffness. Nat Geosci 2019; 12:247-252. [PMID: 31080497 PMCID: PMC6505705 DOI: 10.1038/s41561-019-0330-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 02/15/2019] [Indexed: 05/18/2023]
Abstract
The shapes of asteroids reflect interplay between their interior properties and the processes responsible for their formation and evolution as they journey through the Solar System. Prior to the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission, Earth-based radar imaging gave an overview of (101955) Bennu's shape. Here, we construct a high-resolution shape model from OSIRIS-REx images. We find that Bennu's top-like shape, considerable macroporosity, and prominent surface boulders suggest that it is a rubble pile. High-standing, north-south ridges that extend from pole to pole, many long grooves, and surface mass wasting indicate some low levels of internal friction and/or cohesion. Our shape model indicates that, similar to other top-shaped asteroids, Bennu formed by reaccumulation and underwent past periods of fast spin leading to its current shape. Today, Bennu might follow a different evolutionary pathway, with interior stiffness permitting surface cracking and mass wasting.
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Affiliation(s)
- O S Barnouin
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - M G Daly
- The Centre for Research in Earth and Space Science, York University, Toronto, Ontario, Canada
| | - E E Palmer
- Planetary Science Institute, Tucson, AZ, USA
| | - R W Gaskell
- Planetary Science Institute, Tucson, AZ, USA
| | - J R Weirich
- Planetary Science Institute, Tucson, AZ, USA
| | - C L Johnson
- Planetary Science Institute, Tucson, AZ, USA
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - M M Al Asad
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - J H Roberts
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - M E Perry
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - H C M Susorney
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - R T Daly
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - E B Bierhaus
- Lockheed Martin Space Systems Company, Denver, CO, USA
| | | | - R C Espiritu
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - A H Nair
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - L Nguyen
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - G A Neumann
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - C M Ernst
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - W V Boynton
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - M C Nolan
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - C D Adam
- KinetX Aerospace, Inc. Simi Valley, CA, USA
| | - M C Moreau
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - B Risk
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - E R Jawin
- Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - K J Walsh
- Southwest Research Institute, Boulder, CO, USA
| | - P Michel
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
| | - S R Schwartz
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - R-L Ballouz
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E M Mazarico
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - D J Scheeres
- Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA
| | - J McMahon
- Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA
| | - W Bottke
- Southwest Research Institute, Boulder, CO, USA
| | - S Sugita
- University of Tokyo, Tokyo, Japan
| | - N Hirata
- Aizu University, Aizu-Wakamatsu, Japan
| | | | - S Watanabe
- Nagoya University, Nagoya, Japan
- Institute of Space and Astronautical Science, JAXA, Sagamihara, Japan
| | - K N Burke
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - C A Bennett
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - D S Lauretta
- Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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11
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Hergenrother CW, Maleszewski CK, Nolan MC, Li JY, Drouet d'Aubigny CY, Shelly FC, Howell ES, Kareta TR, Izawa MRM, Barucci MA, Bierhaus EB, Campins H, Chesley SR, Clark BE, Christensen EJ, DellaGiustina DN, Fornasier S, Golish DR, Hartzell CM, Rizk B, Scheeres DJ, Smith PH, Zou XD, Lauretta DS. The operational environment and rotational acceleration of asteroid (101955) Bennu from OSIRIS-REx observations. Nat Commun 2019; 10:1291. [PMID: 30890725 PMCID: PMC6425024 DOI: 10.1038/s41467-019-09213-x] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 02/26/2019] [Indexed: 11/17/2022] Open
Abstract
During its approach to asteroid (101955) Bennu, NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft surveyed Bennu's immediate environment, photometric properties, and rotation state. Discovery of a dusty environment, a natural satellite, or unexpected asteroid characteristics would have had consequences for the mission's safety and observation strategy. Here we show that spacecraft observations during this period were highly sensitive to satellites (sub-meter scale) but reveal none, although later navigational images indicate that further investigation is needed. We constrain average dust production in September 2018 from Bennu's surface to an upper limit of 150 g s-1 averaged over 34 min. Bennu's disk-integrated photometric phase function validates measurements from the pre-encounter astronomical campaign. We demonstrate that Bennu's rotation rate is accelerating continuously at 3.63 ± 0.52 × 10-6 degrees day-2, likely due to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, with evolutionary implications.
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Affiliation(s)
- C W Hergenrother
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA.
| | - C K Maleszewski
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - M C Nolan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - J-Y Li
- Planetary Science Institute, Tucson, AZ, USA
| | | | - F C Shelly
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - E S Howell
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - T R Kareta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - M R M Izawa
- Institute for Planetary Materials, Okayama University-Misasa, Misasa, Tottori, Japan
| | - M A Barucci
- LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, Meudon, France
| | | | - H Campins
- Department of Physics, University of Central Florida, Orlando, FL, USA
| | - S R Chesley
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - B E Clark
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
| | - E J Christensen
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - D N DellaGiustina
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - S Fornasier
- LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, Meudon, France
| | - D R Golish
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - C M Hartzell
- Department of Aerospace Engineering, University of Maryland, College Park, MD, USA
| | - B Rizk
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - D J Scheeres
- Smead Department of Aerospace Engineering, University of Colorado, Boulder, CO, USA
| | - P H Smith
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - X-D Zou
- Planetary Science Institute, Tucson, AZ, USA
| | - D S Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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12
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Hamilton VE, Simon AA, Christensen PR, Reuter DC, Clark BE, Barucci MA, Bowles NE, Boynton WV, Brucato JR, Cloutis EA, Connolly HC, Hanna KLD, Emery JP, Enos HL, Fornasier S, Haberle CW, Hanna RD, Howell ES, Kaplan HH, Keller LP, Lantz C, Li JY, Lim LF, McCoy TJ, Merlin F, Nolan MC, Praet A, Rozitis B, Sandford SA, Schrader DL, Thomas CA, Zou XD, Lauretta DS. Evidence for widespread hydrated minerals on asteroid (101955) Bennu. Nat Astron 2019; 3:332-340. [PMID: 31360777 PMCID: PMC6662227 DOI: 10.1038/s41550-019-0722-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 02/12/2019] [Indexed: 05/18/2023]
Abstract
Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7 μm and thermal infrared spectral features that are most similar to those of aqueously altered CM carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of meters observed to date. In the visible and near-infrared (0.4 to 2.4 μm) Bennu's spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth.
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Affiliation(s)
- V. E. Hamilton
- Department of Space Studies, Southwest Research Institute, Boulder, CO, USA
| | - A. A. Simon
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - P. R. Christensen
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | - D. C. Reuter
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - B. E. Clark
- Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
| | | | - N. E. Bowles
- Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
| | - W. V. Boynton
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - J. R. Brucato
- INAF-Astrophysical Observatory of Arcetri, Firenze, Italy
| | - E. A. Cloutis
- Department of Geography, University of Winnipeg, Winnipeg, Canada
| | - H. C. Connolly
- Department of Geology, Rowan University, Glassboro, NJ, USA
| | - K. L. Donaldson Hanna
- Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
| | - J. P. Emery
- Department of Earth and Planetary Science, University of Tennessee, Knoxville, TN, USA
| | - H. L. Enos
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | | | - C. W. Haberle
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | - R. D. Hanna
- Jackson School of Geosciences, University of Texas, Austin, TX, USA
| | - E. S. Howell
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - H. H. Kaplan
- Department of Space Studies, Southwest Research Institute, Boulder, CO, USA
| | - L. P. Keller
- ARES, NASA Johnson Space Center, Houston, TX USA
| | - C. Lantz
- Institut d’Astrophysique Spatiale, CNRS/Université Paris Sud, Orsay, France
| | - J.-Y. Li
- Planetary Science Institute, Tucson, AZ, USA
| | - L. F. Lim
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - T. J. McCoy
- Smithsonian Institution, National Museum of Natural History, Washington, D.C., USA
| | - F. Merlin
- LESIA, Observatoire de Paris, France
| | - M. C. Nolan
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
| | - A. Praet
- LESIA, Observatoire de Paris, France
| | - B. Rozitis
- Planetary and Space Sciences, The Open University, Milton Keynes, UK
| | | | - D. L. Schrader
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | - C. A. Thomas
- Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ, USA
| | - X.-D. Zou
- Planetary Science Institute, Tucson, AZ, USA
| | - D. S. Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
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Whelan TJ, Olivotto I, Ackerman I, Chapman JW, Chua B, Nabid A, Vallis KA, White JR, Rousseau P, Fortin A, Pierce LJ, Manchul L, Craighead P, Nolan MC, Bowen J, McCready DR, Pritchard KI, Levine MN, Parulekar W. NCIC-CTG MA.20: An intergroup trial of regional nodal irradiation in early breast cancer. J Clin Oncol 2011. [DOI: 10.1200/jco.2011.29.18_suppl.lba1003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
LBA1003 Background: Randomized trials have demonstrated that locoregional radiation after mastectomy reduces locoregional recurrence and improves overall survival (OS) in women with node positive breast cancer treated with adjuvant systemic therapy. MA.20 evaluated the addition of regional nodal irradiation (RNI) to whole breast irradiation (WBI) following breast conserving surgery (BCS). Methods: Women with high risk node-negative or node-positive breast cancer treated with BCS and adjuvant chemotherapy and/or endocrine therapy were stratified by positive nodes, axillary nodes removed, chemo- and endocrine therapy and randomized to WBI (50Gy in 25 fractions +/- boost irradiation) or WBI plus RNI (45Gy in 25 fractions) to the internal mammary, supraclavicular, and high axillary lymph nodes. The primary outcome was OS. The Data Safety Monitoring Committee approved the analysis plan for the protocol specified interim analysis of relapse patterns, survival and toxicity at 5 years. Upon review of the data, they recommended release of the results. Results: Between March 2000 to March 2007, 1,832 women were randomly assigned to WBI+RNI (916) or WBI (916). Median follow-up was 62 months. Characteristics of the study population were: mean age, 53.3 years; node negative, 10%; 1-3 positive nodes, 85%; > 4 positive nodes, 5%; adjuvant chemotherapy, 91%; and adjuvant endocrine therapy, 71%. WBI+RNI in comparison to WBI alone was associated with an improvement in isolated locoregional disease free survival (DFS; HR=.59, p=.02, 5 year risk: 96.8% and 94.5% respectively), distant DFS (HR=.64, p=.002, 5 year risk: 92.4% and 87.0% respectively), DFS (HR=.68, p=.003, 5 year risk: 89.7% and 84.0% respectively) and OS (HR=.76, p=.07, 5 year risk: 92.3% and 90.7% respectively). WBI+RNI in comparison to WBI was associated with an increase in grade 2 or greater pneumonitis (1.3% and 0.2% respectively, p=.01), and lymphedema (7.3% and 4.1% respectively, p=.004). Conclusions: The majority of women with node positive breast cancer are now managed by BCS followed by WBI and adjuvant systemic therapy. Results from MA.20 demonstrate that additional RNI reduces the risk of locoregional and distant recurrence, and improves DFS with a trend in improved OS.
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Affiliation(s)
- T. J. Whelan
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - I. Olivotto
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - I. Ackerman
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - J. W. Chapman
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - B. Chua
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - A. Nabid
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - K. A. Vallis
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - J. R. White
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - P. Rousseau
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - A. Fortin
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - L. J. Pierce
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - L. Manchul
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - P. Craighead
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - M. C. Nolan
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - J. Bowen
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - D. R. McCready
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - K. I. Pritchard
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - M. N. Levine
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
| | - W. Parulekar
- Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Toronto Sunnybrook Reg Cancer Center, Toronto, ON, Canada; NCIC Clinical Trials Group, Queen's University, Kingston, ON, Canada; Peter MacCallum Cancer Centre, Melbourne, Australia; Centre Hospitalier de Sherbrooke, Sherbrooke, QC, Canada; Oxford University, Oxford, England; Radiation Therapy Oncology Group and Medical College of Wisconsin, Milwaukee, WI; Centre Hopitalier
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Whelan TJ, Olivotto I, Ackerman I, Chapman JW, Chua B, Nabid A, Vallis KA, White JR, Rousseau P, Fortin A, Pierce LJ, Manchul L, Craighead P, Nolan MC, Bowen J, McCready DR, Pritchard KI, Levine MN, Parulekar W. NCIC CTG MA.20: An intergroup trial of regional nodal irradiation in early breast cancer. J Clin Oncol 2011. [DOI: 10.1200/jco.2011.29.15_suppl.lba1003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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15
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Scheeres DJ, Fahnestock EG, Ostro SJ, Margot JL, Benner LAM, Broschart SB, Bellerose J, Giorgini JD, Nolan MC, Magri C, Pravec P, Scheirich P, Rose R, Jurgens RF, De Jong EM, Suzuki S. Dynamical configuration of binary near-Earth asteroid (66391) 1999 KW4. Science 2006; 314:1280-3. [PMID: 17038588 DOI: 10.1126/science.1133599] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Dynamical simulations of the coupled rotational and orbital dynamics of binary near-Earth asteroid 66391 (1999 KW4) suggest that it is excited as a result of perturbations from the Sun during perihelion passages. Excitation of the mutual orbit will stimulate complex fluctuations in the orbit and rotation of both components, inducing the attitude of the smaller component to have large variation within some orbits and to hardly vary within others. The primary's proximity to its rotational stability limit suggests an origin from spin-up and disruption of a loosely bound precursor within the past million years.
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Affiliation(s)
- D J Scheeres
- Department of Aerospace Engineering, University of Michigan, 1320 Beal Avenue, Ann Arbor, MI 48109-2140, USA.
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16
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Margot JL, Nolan MC, Benner LAM, Ostro SJ, Jurgens RF, Giorgini JD, Slade MA, Campbell DB. Binary asteroids in the near-Earth object population. Science 2002; 296:1445-8. [PMID: 11951001 DOI: 10.1126/science.1072094] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Radar images of near-Earth asteroid 2000 DP107 show that it is composed of an approximately 800-meter-diameter primary and an approximately 300-meter-diameter secondary revolving around their common center of mass. The orbital period of 1.755 +/- 0.007 days and semimajor axis of 2620 +/- 160 meters constrain the total mass of the system to 4.6 +/- 0.5 x 10(11) kilograms and the bulk density of the primary to 1.7 +/- 1.1 grams per cubic centimeter. This system and other binary near-Earth asteroids have spheroidal primaries spinning near the breakup point for strengthless bodies, suggesting that the binaries formed by spin-up and fission, probably as a result of tidal disruption during close planetary encounters. About 16% of near-Earth asteroids larger than 200 meters in diameter may be binary systems.
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Affiliation(s)
- J L Margot
- California Institute of Technology, MC 150-21, Pasadena, CA 91125, USA.
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17
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Giorgini JD, Ostro SJ, Benner LAM, Chodas PW, Chesley SR, Hudson RS, Nolan MC, Klemola AR, Standish EM, Jurgens RF, Rose R, Chamberlin AB, Yeomans DK, Margot JL. Asteroid 1950 DA's encounter with Earth in 2880: physical limits of collision probability prediction. Science 2002; 296:132-6. [PMID: 11935024 DOI: 10.1126/science.1068191] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Integration of the orbit of asteroid (29075) 1950 DA, which is based on radar and optical measurements spanning 51 years, reveals a 20-minute interval in March 2880 when there could be a nonnegligible probability of the 1-kilometer object colliding with Earth. Trajectory knowledge remains accurate until then because of extensive astrometric data, an inclined orbit geometry that reduces in-plane perturbations, and an orbit uncertainty space modulated by gravitational resonance. The approach distance uncertainty in 2880 is determined primarily by uncertainty in the accelerations arising from thermal re-radiation of solar energy absorbed by the asteroid. Those accelerations depend on the spin axis, composition, and surface properties of the asteroid, so that refining the collision probability may require direct inspection by a spacecraft.
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Affiliation(s)
- J D Giorgini
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA.
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18
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Abstract
Radar observations of the main-belt, M-class asteroid 216 Kleopatra reveal a dumbbell-shaped object with overall dimensions of 217 kilometers by 94 kilometers by 81 kilometers (+/-25%). The asteroid's surface properties are consistent with a regolith having a metallic composition and a porosity comparable to that of lunar soil. Kleopatra's shape is probably the outcome of an exotic sequence of collisional events, and much of its interior may have an unconsolidated rubble-pile structure.
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Affiliation(s)
- SJ Ostro
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA. School of Electrical Engineering and Computer Science, Washington State University, Pullman, WA 99164-2752, USA. Arecibo Observatory, HC3 Box
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19
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Paszat L, Shenouda G, Blood P, Nolan MC, Pater JL, Whelan T. The role of palliative radiotherapy for brain metastases. Can J Oncol 1996; 6 Suppl 1:48-53. [PMID: 8853538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Brain metastases (BRM) are common complications of malignancy, frequently associated with disability and death. Clinical trials have addressed a few of the issues arising from treatment options for BRM. Phase III trials have shown superior survival for patients with solitary resectable BRM (SRBRM) when palliative radiation treatment (RT) to the brain is preceded by resection compared to brain RT alone, but no trial has explored resection plus brain RT compared to resection alone. One Phase III trial in patients with solitary unresected BRM comparing lower to higher doses of RT has shown a small survival advantage with higher-dose radiotherapy. All other trials, however, comparing different radiation doses and fractionation schedules have failed to indicate improved outcomes from treatment more intense than 2000 cGy in 5 fractions over 1 week (in any subset of patients with unresected BRM). A panel of radiation oncologists and medical oncologists discussed a literature review and results of Phase III trials of therapy for BRM. The panel was instructed to identify from these trials any evidence for the efficacy, indications, toxicity and fractionation of palliative RT for BRM. The panel concluded that unresected BRM is a possible indication for brain RT. The panel concluded that the benefits and toxicities of brain RT for unresected BRM are not characterized adequately to allow a stronger recommendation. The panel concluded that there is no evidence for superiority for any dose or schedule of brain RT for BRM more protracted or intense than 2000 cGy in 5 fractions over one week. The panel recommended further study in order to characterize the benefits and toxicities of brain RT for unresectable BRM. The panel considered the potential value of conducting a Phase III trial comparing palliative care and strategies that included brain RT to the same strategies excluding brain RT; the panel did not, however, reach consensus on the feasibility of such a trial.
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Affiliation(s)
- L Paszat
- Department of Radiation Oncology, Kingston Regional Cancer Centre, Ontario
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Abstract
We conducted a clinical audit of the recurrence-free rates and absolute survival of 146 patients who presented with T1-T3 glottic cancer and received primary radiotherapy treatment at the Nova Scotia Cancer Centre between 1984 and 1990. The outcomes are compared with a review of published results from other centres. We used stage T3 glottic cancer as an example to illustrate concepts of effectiveness research which are used to determine at what level interventions operate in the day to day practice of medicine. The actuarial recurrence-free rates at 5 years are: T1 91%, T2 73%, and T3 44%. The actuarial absolute survival rates are: T1 84%, T2 68%, and T3 52%. Effectiveness research may utilize efficacy research, clinical audit, quality of life assessment and decision making theory. Its objective is to aid the implementation of appropriate clinical management for specific individuals and defined communities. Expert computer systems may be necessary to synthesize the data and to enhance communication and decision making.
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Affiliation(s)
- S M Sagar
- Department of Radiation Oncology, Dalhousie University, Nova Scotia Cancer Centre, Halifax, Canada
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Giannousis PP, Hofmeister GE, McLaren KL, Nolan MC. (+)-3,5-O-(R)-Benzylidene-6-deoxy-6-iodo-1,2-O-isopropylidene-α-D-glucofuranose. Acta Crystallogr C 1987. [DOI: 10.1107/s0108270187088851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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