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Now showing items 1 - 16 of 38337

  • Evidence for widespread hydrated minerals on asteroid (101955) Bennu

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

    Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRISREx) 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 mu m and thermal infrared spectral features that are most similar to those of aqueously altered CM-type 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 metres observed to date. In the visible and near-infrared (0.4 to 2.4 mu m) 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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  • Experimental insights into Stannern-trend eucrite petrogenesis

    Crossley, S. D.   Lunning, N. G.   Mayne, R. G.   McCoy, T. J.   Yang, S.   Humayun, M.   Ash, R. D.   Sunshine, J. M.   Greenwood, R. C.   Franchi, I. A.  

    The incompatible trace element-enriched Stannern-trend eucrites have long been recognized as requiring a distinct petrogenesis from the Main Group-Nuevo Laredo (MGNL) eucrites. Barrat etal. () proposed that Stannern-trend eucrites formed via assimilation of crustal partial melts by a MGNL-trend magma. Previous experimental studies of low-degree partial melting of eucrites did not produce sufficiently large melt pools for both major and trace element analyses. Low-degree partial melts produced near the solidus are potentially the best analog to the assimilated crustal melts. We partially melted the unbrecciated, unequilibrated MGNL-trend eucrite NWA 8562 in a 1atm gas-mixing furnace, at IW-0.5, and at temperatures between 1050 and 1200 degrees C. We found that low-degree partial melts formed at 1050 degrees C are incompatible trace element enriched, although the experimental melts did not reach equilibrium at all temperatures. Using our experimental melt compositions and binary mixing modeling, the FeO/MgO trend of the resultant magmas coincides with the range of known Stannern-trend eucrites when a primary magma is contaminated by crustal partial melts. When experimental major element compositions for eucritic crustal partial melts are combined with trace element concentrations determined by previous modeling (Barrat etal. ), the Stannern-trend can be replicated with respect to both major, minor, and trace element concentrations.
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  • Shape of (101955) Bennu indicative of a rubble pile with internal stiffness

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

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

    Yamashita, N.   Prettyman, T. H.   Mittlefehldt, D. W.   Toplis, M. J.   McCoy, T. J.   Beck, A. W.   Reedy, R. C.   Feldman, W. C.   Lawrence, D. J.   Peplowski, P. N.   Forni, O.   Mizzon, H.   Raymond, C. A.   Russell, C. T.  

    We have completed a mapping study of 7.6MeV gamma rays produced by neutron capture by Fe at the surface of the main belt asteroid 4 Vesta as measured by the bismuth germanate scintillator of the Gamma Ray and Neutron Detector (GRaND) on the Dawn spacecraft. The procedures used to determine Fe counting rates are presented, along with a global map, constituting the necessary initial step to quantify Fe abundances. While the final calibration of orbital data to absolute concentrations has not been determined, the range of fully corrected Fe counting rates is compared with that of Fe in howardites. We find that the global distribution of corrected Fe counting rates is generally consistent with mineralogy and composition determined independently by other instruments on the Dawn spacecraft, including measurements of pyroxene absorption bands by the Visible and Infrared Spectrometer and Framing Camera, and an index of diogenitic materials provided by neutron absorption measurements by GRaND. In addition, there is a distinctive low Fe region in the western hemisphere that was not reported by reflectance or optical observations, possibly indicating the presence of a cumulate eucrite component in Vesta's regolith.
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  • The origin of Vesta's crust: Insights from spectroscopy of the Vestoids

    Mayne, R. G.   Sunshine, J. M.   McSween, H. Y., Jr.   Bus, S. J.   McCoy, T. J.  

    High quality VNIR spectra of 15 Vestoids, small asteroids that are believed to originate from Vesta, were collected and compared to laboratory spectra and compositional data for selected HED meteorites. A combination of spectral parameters such as band centers, and factors derived from Modified Gaussian Model fits (band centers, band strengths, calculation of the low to high-Ca pyroxene ratio) were used to establish if each Vestoid appeared most like eucrite or diogenite material, or a mixture of the two (howardite). This resulted in the identification of the first asteroid with a ferroan diogenite composition, 2511 Patterson. This asteroid can be used to constrain the size of diogenite magma chambers within the crust of Vesta. The Vestoids indicate that both large-scale homogeneous units (>5 km) and smaller-scale heterogeneity (<1 km) exist on the surface of Vesta, as both monomineralogic (eucrite or diogenite material alone) and mixed (both eucrite and diogenite) spectra are observed. The small-scale of the variation observed within the Vestoid population is predicted by the partial melting model, which has multiple intrusions penetrating into the crust of Vesta. It is much more difficult to reconcile the observations here with the magma ocean model, which would predict much more homogeneous layers on a large-scale both at the surface and with depth. (C) 2011 Elsevier Inc. All rights reserved.
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  • Combining meteorites and missions to explore Mars

    McCoy, T. J.   Corrigan, C. M.   Herd, C. D. K.  

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  • Petrology of the unbrecciated eucrites

    Mayne, R. G.   McSween, H. Y., Jr.   McCoy, T. J.   Gale, A.  

    Twenty-nine unbrecciated eucrites have been thoroughly characterized in terms of the petrologic factors that affect their spectra, such as mineral chemistry, modal adundances, grain sizes, and textures. We have conducted a combined petrologic and spectral Study designed to provide insight into the petrogenesis of the basaltic crust of Vesta and the variety of rock-types that exist within it, as well as aid in the petrologic interpretation of spectra to be collected by the Dawn orbiting spacecraft. This paper details the petrology part of the study. Unbrecciated eucrite samples were selected to avoid the complications of lithologic mixing in the accompanying spectral study. A wide variety of textural types are seen within the basaltic eucrites, encompassing quenched, coarse-grained, and granoblastic samples. Zoned pyroxenes in eucrites and those that preserve a history of initial rapid cooling are rare. Nearly all eucrite samples have been thermally metamorphosed and would commonly be classified as equilibrated; however, this term reflects only the quadrilateral (Mg, Fe, and Ca) compositions of pyroxenes, and considerable variations are seen within the minor elements (Al, Ti, and Cr) in pyroxenes as well as plagioclase compositions. Determination of both pyroxene and plagioclase compositions together with pyroxene geothermometry provides a better estimate for the relative degree of thermal metamorphism a eucrite has experienced. The petrologic differences observed here might allow different eucrites to be distinguished spectrally. This is especially true for the varying pyroxene compositions as the spectra of eucrites are dominated by absorption features attributed to pyroxene. (C) 2008 Elsevier Ltd. All rights reserved.
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  • Detection of silica-rich deposits on Mars RID B-8961-2008

    Squyres, S. W.   Arvidson, R. E.   Ruff, S.   Gellert, R.   Morris, R. V.   Ming, D. W.   Crumpler, L.   Farmer, J. D.   Des Marais, D. J.   Yen, A.   McLennan, S. M.   Calvin, W.   Bell, J. F., III   Clark, B. C.   Wang, A.   McCoy, T. J.   Schmidt, M. E.   de Souza, P. A., Jr.  

    Mineral deposits on the martian surface can elucidate ancient environmental conditions on the planet. Opaline silica deposits ( as much as 91 weight percent SiO(2)) have been found in association with volcanic materials by the Mars rover Spirit. The deposits are present both as light- toned soils and as bedrock. We interpret these materials to have formed under hydrothermal conditions and therefore to be strong indicators of a former aqueous environment. This discovery is important for understanding the past habitability of Mars because hydrothermal environments on Earth support thriving microbial ecosystems.
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  • The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements

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

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

    Sunshine, J. M.   Connolly, H. C., Jr.   McCoy, T. J.   Bus, S. J.   La Croix, L. M.  

    Although the exact abundance of phases in carbonaceous chondrites remains debatable, a potentially lower absolute abundance of calcium- and aluminum- rich inclusions (CAIs) in the Allende meteorite does not change our fundamental conclusion. In a relative comparison, CAI- rich asteroids contain two to three times as many CAIs as the most CAI- rich meteorites. These asteroids are therefore greatly enriched in the earliest solar system materials and remain enticing targets for future exploration.
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  • Meteorites on Mars observed with the Mars Exploration Rovers RID B-8961-2008

    Schroeder, C.   Rodionov, D. S.   McCoy, T. J.   Jolliff, B. L.   Gellert, R.   Nittler, L. R.   Farrand, W. H.   Johnson, J. R.   Ruff, S. W.   Ashley, J. W.   Mittlefehldt, D. W.   Herkenhoff, K. E.   Fleischer, I.   Haldemann, A. F. C.   Klingelhoefer, G.   Ming, D. W.   Morris, R. V.   de Souza, P. A., Jr.   Squyres, S. W.   Weitz, C.   Yen, A. S.   Zipfel, J.   Economou, T.  

    Reduced weathering rates due to the lack of liquid water and significantly greater typical surface ages should result in a higher density of meteorites on the surface of Mars compared to Earth. Several meteorites were identified among the rocks investigated during Opportunity's traverse across the sandy Meridiani plains. Heat Shield Rock is a IAB iron meteorite and has been officially recognized as "Meridiani Planum." Barberton is olivine-rich and contains metallic Fe in the form of kamacite, suggesting a meteoritic origin. It is chemically most consistent with a mesosiderite silicate clast. Santa Catarina is a brecciated rock with a chemical and mineralogical composition similar to Barberton. Barberton, Santa Catarina, and cobbles adjacent to Santa Catarina may be part of a strewn field. Spirit observed two probable iron meteorites from its Winter Haven location in the Columbia Hills in Gusev Crater. Chondrites have not been identified to date, which may be a result of their lower strengths and probability to survive impact at current atmospheric pressures. Impact craters directly associated with Heat Shield Rock, Barberton, or Santa Catarina have not been observed, but such craters could have been erased by eolian-driven erosion.
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  • Craters,boulders and regolith of (101955) Bennu indicative of an old and dynamic surface

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

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

    McSween, H. Y.   Ruff, S. W.   Morris, R. V.   Bell, J. F., III   Herkenhoff, K.   Gellert, R.   Stockstill, K. R.   Tornabene, L. L.   Squyres, S. W.   Crisp, J. A.   Christensen, P. R.   Mccoy, T. J.   Mittlefehldt, D. W.   Schmidt, M.  

    [ 1] Irvine, Backstay, and Wishstone are the type specimens for three classes of fine-grained or fragmental, relatively unaltered rocks with distinctive thermal emission spectra, found as float on the flanks of the Columbia Hills. Chemical analyses indicate that these rocks are mildly alkaline basalt, trachybasalt, and tephrite, respectively. Their mineralogy consists of Na- and K-rich feldspar(s), low- and high-Ca pyroxenes, ferroan olivine, Fe-Ti ( and possibly Cr) oxides, phosphate, and possibly glass. The texture of Wishstone is consistent with a pyroclastic origin, whereas Irvine and Backstay are lavas or possibly dike rocks. Chemical compositions of these rocks plot on or near liquid lines of descent for most elements calculated for Adirondack class rocks (olivine-rich basalts from the Gusev plains) at various pressures from 0.1 to 1.0 GPa. We infer that Wishstone-, Backstay-, and Irvine-class magmas may have formed by fractionation of primitive, oxidized basaltic magma similar to Adirondack-class rocks. The compositions of all these rocks reveal that the Gusev magmatic province is alkaline, distinct from the subalkaline volcanic rocks thought to dominate most of the planet's surface. The fact that differentiated volcanic rocks were not encountered on the plains prior to ascending Husband Hill may suggest a local magma source for volcanism beneath Gusev crater.
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  • Craters, boulders and regolith of (101955) Bennu indicative of an old and dynamic surface

    Walsh, K. J.   Jawin, E. R.   Ballouz, R.-L.   Barnouin, O. S.   Bierhaus, E. B.   Connolly, H. C.   Molaro, J. L.   McCoy, T. J.   Delbo’, M.   Hartzell, C. M.   Pajola, M.   Schwartz, S. R.   Trang, D.   Asphaug, E.   Becker, K. J.   Beddingfield, C. B.   Bennett, C. A.   Bottke, W. F.   Burke, K. N.   Clark, B. C.   Daly, M. G.   DellaGiustina, D. N.   Dworkin, J. P.   Elder, C. M.   Golish, D. R.   Hildebrand, A. R.   Malhotra, R.   Marshall, J.   Michel, P.   Nolan, M. C.   Perry, M. E.   Rizk, B.   Ryan, A.   Sandford, S. A.   Scheeres, D. J.   Susorney, H. C. M.   Thuillet, F.   Lauretta, D. S.  

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  • Re-187-Os-187 isotopic and highly siderophile element systematics of pallasites

    Lee, S. R.   Walker, R. J.   McCoy, T. J.   McDonough, W. F.  

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  • Nickel on Mars: Constraints on meteoritic material at the surface RID B-3870-2009

    Yen, A. S.   Mittlefehldt, D. W.   McLennan, S. M.   Gellert, R.   Bell, J. F., III   McSween, H. Y., Jr.   Ming, D. W.   McCoy, T. J.   Morris, R. V.   Golombek, M.   Economou, T.   Madsen, M. B.   Wdowiak, T.   Clark, B. C.   Jolliff, B. L.   Schroeder, C.   Brueckner, J.   Zipfel, J.   Squyres, S. W.  

    Impact craters and the discovery of meteorites on Mars indicate clearly that there is meteoritic material at the Martian surface. The Alpha Particle X-ray Spectrometers (APXS) on board the Mars Exploration Rovers measure the elemental chemistry of Martian samples, enabling an assessment of the magnitude of the meteoritic contribution. Nickel, an element that is greatly enhanced in meteoritic material relative to samples of the Martian crust, is directly detected by the APXS and is observed to be geochemically mobile at the Martian surface. Correlations between nickel and other measured elements are used to constrain the quantity of meteoritic material present in Martian soil and sedimentary rock samples. Results indicate that analyzed soils samples and certain sedimentary rocks contain an average of 1% to 3% contamination from meteoritic debris.
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