Elemental Mapping by Dawn Reveals Exogenic H in Vesta’s Regolith

Vesta to the Core Vesta is one of the largest bodies in the main asteroid belt. Unlike most other asteroids, which are fragments of once larger bodies, Vesta is thought to have survived as a protoplanet since its formation at the beginning of the solar system (see the Perspective by Binzel, published online 20 September). Based on data obtained with the Gamma Ray and Neutron Detector aboard the Dawn spacecraft, Prettyman et al. (p. 242, published online 20 September) show that Vesta's reputed volatile-poor regolith contains substantial amounts of hydrogen delivered by carbonaceous chondrite impactors. Observations of pitted terrain on Vesta obtained by Dawn's Framing Camera and analyzed by Denevi et al. (p. 246, published online 20 September), provide evidence for degassing of volatiles and hence the presence of hydrated materials. Finally, paleomagnetic studies by Fu et al. (p. 238) on a meteorite originating from Vesta suggest that magnetic fields existed on the surface of the asteroid 3.7 billion years ago, supporting the past existence of a magnetic core dynamo. Analysis of data from the Dawn spacecraft implies that asteroid Vesta is rich in volatiles. Using Dawn’s Gamma Ray and Neutron Detector, we tested models of Vesta’s evolution based on studies of howardite, eucrite, and diogenite (HED) meteorites. Global Fe/O and Fe/Si ratios are consistent with HED compositions. Neutron measurements confirm that a thick, diogenitic lower crust is exposed in the Rheasilvia basin, which is consistent with global magmatic differentiation. Vesta’s regolith contains substantial amounts of hydrogen. The highest hydrogen concentrations coincide with older, low-albedo regions near the equator, where water ice is unstable. The young, Rheasilvia basin contains the lowest concentrations. These observations are consistent with gradual accumulation of hydrogen by infall of carbonaceous chondrites—observed as clasts in some howardites—and subsequent removal or burial of this material by large impacts.

[1]  Y. Miura,et al.  81Kr terrestrial ages and grouping of Yamato eucrites. , 1993 .

[2]  P. Lucey,et al.  Spectral properties of angrites , 2006 .

[3]  Thomas H. Prettyman,et al.  Elemental composition of the lunar surface: Analysis of gamma ray spectroscopy data from Lunar Prospector , 2006 .

[4]  E. Gibson.  Nature of the carbon and sulfur phases and inorganic gases in the Kenna ureilite , 1976 .

[5]  Daniel J. Scheeres,et al.  Characterizing and navigating small bodies with imaging data , 2006 .

[6]  Andreas Nathues,et al.  Color and Albedo Heterogeneity of Vesta from Dawn , 2012, Science.

[7]  G. Wasserburg,et al.  Sm-Nd isotopic evolution of chondrites and achondrites. II , 1984 .

[8]  H. Wiik.  REGULAR DISCONTINUITIES IN THE COMPOSITION OF METEORITES. , 1969 .

[9]  D. Heymann,et al.  Noble gases in carbonaceous chondrites , 1970 .

[10]  R. Allen,et al.  Minor and trace elements in some meteoritic minerals , 1973 .

[11]  G. Lugmair,et al.  Early solar system timescales according to 53Mn-53Cr systematics , 1998 .

[12]  A. Turkevich,et al.  Determinations of concentrations of heavy elements in meteorites by activation analysis , 1960 .

[13]  P. N. Shukla,et al.  Piplia Kalan eucrite: Fall, petrography and chemical characteristics , 1997 .

[14]  E. Anders,et al.  Ages of calcium-rich achondrites. II - Howardites, nakhlites, and the Angra dos Reis angrite. , 1969 .

[15]  A. Masuda,et al.  Cerium anomaly in REE pattern of Antarctic eucrite , 1983 .

[16]  T. Kirsten,et al.  Edelgas- und kalium-bestimmungen an einer gröβeren zahl von steinmeteoriten , 1963 .

[17]  M. Gaffey,et al.  Spectral reflectance properties of ureilites , 2010 .

[18]  H. Wiik.  THE CHEMICAL COMPOSITION OF THE HAVERÖ METEORITE AND THE GENESIS OF THE UREILITES , 1972 .

[19]  G. Kallemeyn,et al.  Explosive volcanism and the graphite-oxygen fugacity buffer on the parent asteroid(s) of the ureilite meteorites , 1992 .

[20]  M. Zolensky,et al.  The Bholghati howardite: Petrography and mineral chemistry , 1989 .

[21]  V. K. Rai,et al.  Nitrogen components in ureilites , 2003 .

[22]  G. Wasserburg,et al.  Neon in gas-rich samples of the carbonaceous chondrites Mokoia, Murchison, and Cold Bokkeveld , 1978 .

[23]  J. Zähringer.  Ueber die Uredelgase in den Achondriten Kapoeta und Staroe Pesjanoe , 1962 .

[24]  T. Friedmann,et al.  Noble gas composition of the solar wind as collected by the Genesis mission , 2009 .

[25]  H. Wiesmann,et al.  A Sr and Nd isotopic study of five Yamato polymict eucrites and a comparison to other Antarctic and ordinary eucrites , 1983 .

[26]  A. Yamaguchi,et al.  Evidence for K‐rich terranes on Vesta from impact spherules , 2009 .

[27]  J. Kerridge.  Carbon, hydrogen and nitrogen in carbonaceous chondrites: abundances and isotopic compositions in bulk samples. , 1985, Geochimica et cosmochimica acta.

[28]  K. Keil,et al.  Petrology and shock age of the Palo Blanco Creek eucrite , 1984 .

[29]  K. Jochum,et al.  The Antarctic meteorite Yamato 74123 — a new ureilite , 1978 .

[30]  G. Wasserburg,et al.  Argon 40-argon 39 chronology of lithic clasts from the Kapoeta howardite , 1979 .

[31]  H. Takeda.  Mineralogy of Antarctic ureilites and a working hypothesis for their origin and evolution , 1987 .

[32]  J. Birck,et al.  87Rb/87Sr study of diogenites , 1981 .

[33]  M. Tatsumoto,et al.  Time Differences in the Formation of Meteorites as Determined from the Ratio of Lead-207 to Lead-206 , 1973, Science.

[34]  A. Masuda,et al.  Rare earth element distribution in the Melrose-b howardite: Pre-terrestrial negative Ce anomaly , 1980 .

[35]  E. Jarosewich,et al.  Chemical analyses with notes on one mesosiderite and seven chondrites , 1969 .

[36]  I. Franchi,et al.  Geochemistry of diogenites: Still more diversity in their parental melts , 2008 .

[37]  J. Lovering,et al.  Uranium and thorium in achondrites. , 1973 .

[38]  J. Morgan,et al.  Chemical fractionations in meteorites. V - Volatile and siderophile elements in achondrites and ocean ridge basalts. , 1972 .

[39]  M. Ma,et al.  Genesis of the cumulate eucrites Serra de Mage and Moore County - A geochemical study , 1979 .

[40]  K. Keil,et al.  Impact melting of the Cachari eucrite 3.0 Gy ago , 1985 .

[41]  Richard P. Binzel,et al.  Impact excavation on Asteroid 4 Vesta: Hubble Space Telescope results , 1997 .

[42]  L. Wilkening.  Foreign inclusions in stony meteorites—I. Carbonaceous chondritic xenoliths in the Kapoeta howardite , 1973 .

[43]  G. Wasserburg,et al.  Samarium-neodymium evolution of meteorites , 1992 .

[44]  R. Schmitt,et al.  Rare-earth, yttrium and scandium abundances in meteoritic and terrestrial matter—II , 1964 .

[45]  E. Stolper.  Experimental petrology of eucritic meteorites , 1977 .

[46]  H. Hintenberger,et al.  Radiogene, spallogene und primordiale Edelgase in Steinmeteoriten III , 1964 .

[47]  E. Jarosewich,et al.  ELEVEN NEW METEORITES FROM ANTARCTICA, 1976–1977 , 1978 .

[48]  J. Huizenga,et al.  Thorium in stone meteorites by neutron activation analysis , 1959 .

[49]  J. Zähringer.  Rare gases in stony meteorites , 1968 .

[50]  K. Lodders.  Solar System Abundances and Condensation Temperatures of the Elements , 2003 .

[51]  S. Fourcade,et al.  Rubidium-87/Strontium-87 Age of Juvinas Basaltic Achondrite and Early Igneous Activity in the Solar System , 1975, Science.

[52]  I. Franchi,et al.  Petrology and geochemistry of the fine‐grained, unbrecciated diogenite Northwest Africa 4215 , 2006 .

[53]  D. Lal,et al.  Observations on Space Irradiation of Individual Crystals of Gas-rich Meteorites , 1969, Nature.

[54]  A. Davis,et al.  The Antarctic achondrite ALHA 76005 - A polymict eucrite , 1981 .

[55]  M. Zadnik.  Noble Gases in the Bells (C2) and Sharps (H3) Chondrites , 1985 .

[56]  G. Dreibus,et al.  Camel Donga, a Eucrite with High Metal Content , 1988 .

[57]  A. V. Murali,et al.  Genesis of the Angra dos Reis and other achondritic meteorites , 1976 .

[58]  M. Lipschutz,et al.  Volatile/mobile trace elements in Bholghati howardite , 1989 .

[59]  J. Morgan,et al.  Volatile and siderophile trace elements in anorthositic rocks from Fiskenaesset. West Greenland: comparison with lunar and meteoritic analogues , 1976 .

[60]  P. W. Gast.  Terrestrial Ratio of Potassium to Rubidium and the Composition of Earth's Mantle , 1965, Science.

[61]  E. Gibson,et al.  Sulfur in achondritic meteorites. , 1985, Meteoritics.

[62]  D. C. Hess,et al.  Argon-Potassium Ages and the Isotopec Composition of Argon from Meteorites. , 1958 .

[63]  G. Wasserburg,et al.  Isotopic and chemical investigations on Angra dos Reis , 1977 .

[64]  R. Wieler,et al.  Primordial noble gases in “phase Q” in carbonaceous and ordinary chondrites studied by closed‐system stepped etching , 2000 .

[65]  B. Mason,et al.  The composition of the Barratta, Carraweena, Kapoeta, Mooresfort, and Ngawi meteorites. , 1966 .

[66]  D. Mittlefehldt,et al.  MIL 03443, a dunite from asteroid 4 Vesta: Evidence for its classification and cumulate origin , 2011 .

[67]  G. Megrue.  Rare gas chronology of hypersthene achondrites and pallasites , 1968 .

[68]  E. Helin,et al.  Determination of iron, nickel, cobalt, calcium, chromium and manganese in stony meteorites by X-ray fluorescence , 1967 .

[69]  C. Pillinger,et al.  Isotopic anomalies of Ne, Xe, and C in meteorites. I. Separation of carriers by density and chemical resistance , 1988 .

[70]  G. Kallemeyn,et al.  Siderophile and other geochemical constraints on mixing relationships among HED-meteoritic breccias , 2009 .

[71]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .

[72]  J. P. Willis,et al.  The composition of stony meteorites II. The analytical data and an assessment of their quality , 1968 .

[73]  N. Nakamura,et al.  Sm-Nd isotopic systematics and REE abundance studies of the ALH-765 eucrite , 1983 .

[74]  H. McSween,et al.  Petrologic and textural diversity among the PCA 02 howardite group, one of the largest pieces of the Vestan surface , 2012 .

[75]  R. Binzel,et al.  Chips off of Asteroid 4 Vesta: Evidence for the Parent Body of Basaltic Achondrite Meteorites , 1993, Science.

[76]  J. Huizenga,et al.  ABUNDANCES OF RUTHENIUM, OSMIUM AND URANIUM IN SOME COSMIC AND TERRESTRIAL SOURCES , 1963 .

[77]  H. Urey,et al.  Determination of alkali metals in meteorites by a distillation process , 1955 .

[78]  K. Lodders.  Solar System Abundances of the Elements , 2010, 1010.2746.

[79]  H. Mori,et al.  Antarctic howardites and their primitive crust , 1984 .

[80]  Michael T. Lee,et al.  Petrology and geochemistry of D'Orbigny, geochemistry of Sahara 99555, and the origin of angrites , 2002 .

[81]  Richard D. Starr,et al.  Analysis of gamma ray spectra measured by Mars Odyssey , 2007 .

[82]  J. Morgan,et al.  URANIUM AND THORIUM IN THE NUEVO LAREDO ACHONDRITE , 1965 .

[83]  T V Johnson,et al.  Asteroid Vesta: Spectral Reflectivity and Compositional Implications , 1970, Science.

[84]  E. Jurney,et al.  A revision of the meteorite based cosmic abundance of boron , 1980 .

[85]  E. Jarosewich,et al.  CAMEL DONGA METEORITE, A NEW EUCRITE FROM THE NULLARBOR PLAIN, WESTERN AUSTRALIA , 1986 .

[86]  H. Wiesmann,et al.  Neodymium, strontium and chromium isotopic studies of the LEW86010 and Angra dos Reis meteorites and the chronology of the angrite parent body , 1994 .

[87]  Tomoki Nakamura,et al.  Microdistribution of primordial noble gases in CM chondrites determined by in situ laser microprobe analysis: decipherment of nebular processes , 1999 .

[88]  S. Maurice,et al.  Fluxes of fast and epithermal neutrons from Lunar Prospector: evidence for water ice at the lunar poles. , 1998, Science.

[89]  L. Nittler,et al.  Bulk element compositions of meteorites: A guide for interpreting remote-sensing geochemical measurements of planets and asteroids , 2004 .

[90]  A. Masuda,et al.  REE, Ba, Sr and Rb abundances in some unique Antarctic achondrites , 1981 .

[91]  Tomoki Nakamura,et al.  Heterogeneous distribution of solar and cosmogenic noble gases in CM chondrites and implications for the formation of CM parent bodies , 1999 .

[92]  J. N. Goswami,et al.  Cosmogenic neon from procompaction irradiation OF Kapoeta and Murchison , 1983 .

[93]  J. Morgan,et al.  A “chondritic” eucrite parent body: inference from trace elements , 1977 .

[94]  W. D. Ehmann,et al.  ELEMENTAL ABUNDANCES IN THE HAVERÖ METEORITE , 1972 .

[95]  L. Ahrens,et al.  The chemical composition of the basaltic achondrites , 1971 .

[96]  R. W. Bild,et al.  Classification of and elemental fractionation among ureilites , 1976 .

[97]  M. Zolensky,et al.  Mineralogy of carbonaceous chondrite clasts in HED achondrites and the Moon , 1996 .

[98]  R. Reedy,et al.  Lunar Surface Radioactivity: Preliminary Results of the Apollo 15 and Apollo 16 Gamma-Ray Spectrometer Experiments , 1973, Science.

[99]  E. Asphaug.  Impact origin of the Vesta family , 1997 .

[100]  R. Mark,et al.  Chondrites: Initial Strontium-87/Strontium-86 Ratios and the Early History of the Solar System , 1973, Science.

[101]  F. Begemann,et al.  Rare gases and 36Cl in stony-iron meteorites: cosmogenic elemental production rates, exposure ages, diffusion losses and thermal histories , 1976 .

[102]  M. Lipschutz,et al.  Chemical studies of differentiated meteorites. I - Labile trace elements in Antarctic and non-Antarctic eucrites , 1990 .

[103]  C. Pillinger,et al.  The carbon and nitrogen isotopic composition of ureilites: Implications for their genesis , 1985 .

[104]  G. Manhès,et al.  UThPb systematics of the eucrite "Juvinas": Precise age determination and evidence for exotic lead , 1984 .

[105]  I. Franchi,et al.  The Stannern trend eucrites: Contamination of main group eucritic magmas by crustal partial melts , 2007 .

[106]  Rudolf Rieder,et al.  Refined data of Alpha Proton X-ray Spectrometer analyses of soils and rocks at the Mars Pathfinder site: Implications for surface chemistry , 2003 .

[107]  J. Birck,et al.  Chronology and chemical history of the parent body of basaltic achondrites studied by the 87Rb-87Sr method , 1978 .

[108]  J. Wasson,et al.  Compositions of chondrites , 1988, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[109]  D. Lindstrom,et al.  Petrology of the Indian eucrite Piplia Kalan , 2000 .

[110]  J. Birck,et al.  87Rb–87Sr chronology of the Binda howardite , 1979, Nature.

[111]  R. Jaumann,et al.  The Violent Collisional History of Asteroid 4 Vesta , 2012, Science.

[112]  G. Mccall.  New Stony Meteorite Finds Including Two Ureilites from the Nullarbor Plain, Western Australia , 1968 .

[113]  W. Boynton,et al.  Trace element analysis of ureilites: New constraints on their petrogenesis , 1991 .

[114]  D. Mittlefehldt,et al.  Mesosiderites and howardites: igneous formation and possible genetic relationships , 1979 .

[115]  C. Russell,et al.  Photometric mapping of Asteroid (4) Vesta’s southern hemisphere with Hubble Space Telescope , 2010 .

[116]  R. Jaumann,et al.  Vesta’s Shape and Morphology , 2012, Science.

[117]  E. Anders,et al.  Isotopic anomalies of noble gases in meteorites and their origins. VI Presolar components in the Murchison C2 chondrite , 1980 .

[118]  A. Masuda,et al.  REE patterns of eucrites and their genetic implications , 1986 .

[119]  D. Lindstrom,et al.  The South African polymict eucrite Macibini , 2000 .

[120]  M. Lindstrom,et al.  Geochemistry of eucrites: genesis of basaltic eucrites, and Hf and Ta as petrogenetic indicators for altered antarctic eucrites , 2003 .

[121]  R. Clayton,et al.  Potassium isotope cosmochemistry: Genetic implications of volatile element depletion , 1995 .

[122]  Haramura,et al.  Mineralogical Examination of the Allan Hills No.5 Meteorite , 1979 .

[123]  J. Huizenga,et al.  Scandium, chromium and europium in stone meteorites by simultaneous neutron activation analysis , 1960 .

[124]  M. A. Reynolds,et al.  Noble gases and radionuclides in Lost City and other recently fallen meteorites , 1971 .

[125]  J. H. Reynolds,et al.  Rare-gas-rich separates from carbonaceous chondrites , 1976 .

[126]  T. McCarthy,et al.  Further evidence in support of the mixing model for howardite origin , 1972 .

[127]  H. Wiesmann,et al.  Rb‐Sr and Sm‐Nd internal isochron ages of a subophitic basalt clast and a matrix sample from the Y75011 eucrite , 1986 .

[128]  E. Gibson,et al.  Total carbon and nitrogen abundances in Apollo 11 lunar samples and selected achondrites and basalts , 1970 .

[129]  H. McSween,et al.  HED Meteorites and Their Relationship to the Geology of Vesta and the Dawn Mission , 2011 .

[130]  G. Megrue.  Rare‐gas chronology of calcium‐rich achondrites , 1966 .

[131]  J. P. Willis,et al.  NEW CHEMICAL ANALYSES OF SIX ACHONDRITES AND ONE CHONDRITE , 1974 .

[132]  H. Takeda.  A layered-crust model of a Howardite parent body , 1979 .

[133]  D. J. Barber,et al.  Yamato-82042: an unusual carbonaceous chondrite with CM affinities , 1987 .

[134]  P. W. Gast.  The isotopic composition of strontium and the age of stone meteorites - I , 1962 .

[135]  B. Mason,et al.  Catalog of Antarctic Meteorites, 1977-1978 , 1980 .

[136]  D. Garrison,et al.  39Ar40Ar age of the Ibitira eucrite and constraints on the time of pyroxene equilibration , 1995 .

[137]  M. Drake,et al.  Sm-Nd and Rb-Sr isotopic systematics of ureilites , 1991 .

[138]  D. E. Fisher,et al.  Aluminum abundances in stony meteorites. , 1969 .

[139]  W. Kiesl,et al.  The Medanitos Meteorite , 1978 .

[140]  J. Morgan,et al.  URANIUM AND THORIUM ABUNDANCES IN STONY METEORITES. 2. THE ACHONDRITIC METEORITES , 1964 .

[141]  P. S. Goel,et al.  Total nitrogen in meteorites , 1974 .

[142]  D. Mittlefehldt.  Petrographic and chemical characterization of igneous lithic clasts from mesosiderites and howardites and comparison with eucrites and diogenites , 1979 .

[143]  H. McSween,et al.  Geochemistry of 4 Vesta based on HED meteorites: Prospective study for interpretation of gamma ray and neutron spectra for the Dawn mission , 2007 .

[144]  T. Osborn,et al.  ELEMENTAL ABUNDANCES IN STONE METEORITES , 1972 .

[145]  Robert L. Tokar,et al.  Fast neutron flux spectrum aboard Mars Odyssey during cruise , 2001 .

[146]  R. Schmitt,et al.  Abundances of the fourteen rare-earth elements, scandium, and yttrium in meteoritic and terrestrial matter , 1963 .

[147]  W. Feldman,et al.  A novel fast-neutron detector for space applications , 1991 .

[148]  A. Treiman,et al.  Basaltic volcanism on the eucrite parent body: Petrology and chemistry of the polymict eucrite ALHA80102 , 1985 .

[149]  E. Olsen,et al.  Chondrule-like objects and brown glasses in howardites , 1990 .

[150]  R. Wiens,et al.  Evidence for water ice near the lunar poles , 2001 .

[151]  Kim Strohbehn,et al.  The MESSENGER Gamma-Ray and Neutron Spectrometer , 2007 .

[152]  R. J. Floran,et al.  Mineralogy, petrology, and trace element geochemistry of the Johnstown meteorite: a brecciated orthopyroxenite with siderophile and REE-rich components , 1981 .

[153]  David J. Williams,et al.  The Geologically Recent Giant Impact Basins at Vesta’s South Pole , 2012, Science.

[154]  H. Stauffer.  Primordial argon and neon in carbonaceous chondrites and ureilites , 1961 .

[155]  R. Clayton,et al.  D'Orbigny: A non-igneous angritic achondrite? , 2004 .

[156]  V. Murthy,et al.  Rubidium-Strontium Age and Elemental and Isotopic Abundances of Some Trace Elements in Lunar Samples , 1970, Science.

[157]  T. Hiroi,et al.  Evidence of hydrated and/or hydroxylated minerals on the surface of asteroid 4 Vesta , 2003 .

[158]  K. Jochum,et al.  CHEMICAL COMPOSITION AND CLASSIFICATION OF 19 YAMATO METEORITES , 1980 .

[159]  Martin P. Ward,et al.  The Mars Odyssey Gamma-Ray Spectrometer Instrument Suite , 2004 .

[160]  H. Takeda,et al.  Mineralogical examination of the Yamato-79 achondrites : Polymict eucrites and ureilites , 1982 .

[161]  M. Drake.  Presidential Address: Presented 2000 August 28, Chicago, Illinois, USA The eucrite/Vesta story , 2001 .

[162]  R. Wieler,et al.  Microdistribution of primordial Ne and Ar in fine‐grained rims, matrices, and dark inclusions of unequilibrated chondrites—Clues on nebular processes , 2003 .

[163]  Thomas H. Prettyman,et al.  Composition from fast neutrons: Application to the Moon , 2001 .

[164]  M. Rao,et al.  Neon isotope studies of Fayetteville and Kapoeta meteorites and clues to ancient solar activity , 1989 .

[165]  M. Wadhwa,et al.  Age of the eucrite “Caldera” from convergence of long-lived and short-lived chronometers , 1996 .

[166]  H. Wiesmann,et al.  Age of a eucrite clast from the Bholghati howardite , 1990 .

[167]  J. Morgan,et al.  Chemical fractionations in meteorites - X. Ureilites , 1976 .

[168]  R. Wieler,et al.  Characterisation of Q-gases and other noble gas components in the Murchison meteorite , 1992 .

[169]  Masanori Kobayashi,et al.  Uranium on the Moon: Global distribution and U/Th ratio , 2010 .

[170]  R. Clayton,et al.  Paired Renazzo-type (CR) carbonaceous chondrites from the Sahara , 1993 .

[171]  P. N. Shukla,et al.  The Lohawat howardite: Mineralogy, chemistry and cosmogenic effects , 2001 .

[172]  Sherwood Chang,et al.  Carbonaceous chondrites—I. Characterization and significance of carbonaceous chondrite (CM) xenoliths in the Jodzie howardite , 1979 .

[173]  G. Wasserburg,et al.  Petrography of isotopically-dated clasts in the Kapoeta howardite and petrologic constraints on the evolution of its parent body , 1976 .

[174]  M. Zolensky,et al.  Carbonaceous chondrite clasts in the howardites Bholghati and EET87513 , 1993 .

[175]  E. Jarosewich,et al.  Chemical analyses of meteorites: A compilation of stony and iron meteorite analyses , 1990 .

[176]  H. Palme,et al.  The formation of eucrites: Constraints from metal‐silicate partition coefficients , 2007 .

[177]  K. Fredriksson,et al.  Impact glass in the Cachari eucrite , 1967 .

[178]  A. J. Easton.  SEVEN NEW BULK CHEMICAL ANALYSES OF AUBRITES , 1985 .

[179]  R. Wieler,et al.  Consequences of the non-existence of the “SEP” component for noble gas geo-and cosmochemistry , 2007 .

[180]  L. Ahrens,et al.  Association of rubidium and potassium and their abundance in common igneous rocks and meteorites , 1952 .

[181]  M. Shima.  GEOCHEMICAL STUDY OF BORON ISOTOPES , 1963 .

[182]  K. Housen,et al.  REGOLITHS ON SMALL BODIES IN THE SOLAR SYSTEM , 1982 .

[183]  Kazuyuki,et al.  Mineralogical Examination of the Allan Hills Achondrites and Their Bearing on the Parent Bodies , 1980 .

[184]  G. Kallemeyn,et al.  Siderophile geochemistry of ureilites : A record of early stages of planetesimal core formation , 2006 .

[185]  C. Desnoyers,et al.  The Malvern howardite: a petrological and chemical discussion , 1977 .

[186]  O. Eugster,et al.  Common asteroid break-up events of eucrites, diogenites, and howardites and cosmic-ray production rates for noble gases in achondrites , 1995 .

[187]  John S. Hendricks,et al.  Dawn’s Gamma Ray and Neutron Detector , 2011 .

[188]  Robert L. Tokar,et al.  Global Distribution of Neutrons from Mars: Results from Mars Odyssey , 2002, Science.

[189]  J. Huneke,et al.  Argon 40-argon 39 chronology of four calcium-rich achondrites , 1973 .

[190]  D. Mittlefehldt,et al.  Lithic components in the paired howardites EET 87503 and EET 87513: Characterization of the regolith of 4 Vesta , 2003 .

[191]  P. K. Kuroda,et al.  Iodine, uranium and tellurium contents in meteorites , 1967 .

[192]  M. Lipschutz,et al.  Trace Element Contents of Selected Antarctic Meteorites.I. Weathering Effects and ALH A77005, A77257, A77278 and A77299 , 1980 .

[193]  L. Schultz,et al.  Noble gases in enstatite chondrites I: Exposure ages, pairing, and weathering effects , 2001 .

[194]  E. Jerde,et al.  Composition and origin of Nuevo Laredo Trend eucrites , 1987 .

[195]  M. Michel-Lévy,et al.  L'eucrite de Bouvante. Chimie, pétrologie et minéralogie , 1987 .

[196]  W. Feldman,et al.  MCNPX benchmark for cosmic ray interactions with the Moon , 2006 .

[197]  William Marshall,et al.  Detection of Water in the LCROSS Ejecta Plume , 2010, Science.

[198]  G. Megrue.  Isotopic Analysis of Rare Gases with a Laser Microprobe , 1967, Science.

[199]  B. Mason.  Notes on Australian meteorites , 1974 .

[200]  A. Turkevich,et al.  Uranium and barium in stone meteorites , 1957 .

[201]  D. Garrison,et al.  Noble gases in the howardites Bholghati and Kapoeta , 1990 .

[202]  P. S. Goel,et al.  LITHIUM IN STONE METEORITES AND STONY IRONS , 1983 .

[203]  D. Mittlefehldt.  Petrology and geochemistry of the Elephant Moraine A79002 diogenite: A genomict breccia containing a magnesian harzburgite component , 2000 .

[204]  Paul G. Lucey,et al.  Lunar rare earth element distribution and ramifications for FeO and TiO2: Lunar Prospector neutron spectrometer observations , 2000 .

[205]  J. R. Vogt,et al.  Silicon abundances in stony meteorites by fast neutron activation analysis , 1965 .

[206]  W. D. Ehmann,et al.  Silicon abundances in some meteorites and standard rocks by activation analysis , 1968 .

[207]  G. Edwards.  Sodium and potassium in meteorites , 1955 .

[208]  H. Takeda,et al.  Some unique meteorites found in Antarctica and their relation to asteroids , 1979 .

[209]  Thomas H. Prettyman,et al.  Improved modeling of Lunar Prospector neutron spectrometer data: Implications for hydrogen deposits at the lunar poles , 2006 .

[210]  Meng‐Hua Zhu,et al.  Chang’E-1 gamma ray spectrometer and preliminary radioactive results on the lunar surface , 2010 .

[211]  K. Welten,et al.  Lewis Cliff 86360: An Antarctic L‐chondrite with a terrestrial age of 2.35 million years , 1997 .

[212]  R. Wieler,et al.  Noble gases in chondrules and associated metal‐sulfide‐rich samples: Clues on chondrule formation and the behavior of noble gas carrier phases , 2004 .

[213]  M. Lipschutz,et al.  Contents of eleven trace elements in ureilite achondrites , 1975 .

[214]  E. Anders,et al.  Noble gases in separated meteoritic minerals - Murchison /C2/, Ornans /C3/, Karoonda /C5/, and Abee /E4/ , 1977 .

[215]  A. Reid,et al.  The evolution of the Kapoeta howardite based on fossil track studies , 1971 .

[216]  C. Patterson.  The Pb207/Pb206 ages of some stone meteorites , 1955 .

[217]  J. Blichert‐Toft,et al.  The Tatahouine diogenite: Mineralogical and chemical effects of sixty‐three years of terrestrial residence , 1999 .

[218]  M. Lipschutz,et al.  Volatile trace elements in Antarctic ureilites , 1995 .

[219]  D. Mittlefehldt.  The genesis of diogenites and HED parent body petrogenesis , 1994 .

[220]  L. Schultz,et al.  Noble gas record, collisional history, and pairing of CV, CO, CK, and other carbonaceous chondrites , 2000 .

[221]  H. A.,et al.  Trace element analysis of ureilites : New constraints on their petrogenesis , 2002 .

[222]  G. T. Prior.  On the Mesosiderite-Grahamite Group of Meteorites: With Analyses of Vaca Muerta, Hainholz, Simondium, and Powder Mill Creek1 , 1918 .

[223]  E. Anders,et al.  Aubrites and diogenites - Trace element clues to their origin , 1983 .

[224]  R. Hutchison,et al.  Medanitos and Putinga, two South American meteorites , 1970, Mineralogical Magazine.

[225]  S. Galer,et al.  Age and isotopic relationships among the angrites Lewis Cliff 86010 and Angra dos Reis , 1992 .

[226]  Bruce Fegley,et al.  The Planetary Scientist's Companion , 1998 .

[227]  O. Müller,et al.  Chemische unterschiede bei uredelgashaltigen steinmeteoriten , 1966 .

[228]  J. Blichert‐Toft,et al.  The differentiation of eucrites: The role of in situ crystallization , 2000 .

[229]  A. Rivkin,et al.  Rotationally-resolved spectroscopy of Vesta I: 2–4 μm region , 2006 .

[230]  Richard D. Starr,et al.  Composition and structure of the Martian surface at high southern latitudes from neutron spectroscopy , 2004 .

[231]  A. Jaques,et al.  The Nilpena ureilite, an unusual polymict breccia: implications for origin , 1982 .

[232]  Shima,et al.  Mineralogical and Petrographical Studies of the Yamato Meteorites, Yamato-7301(j), -7305(k), -7308(l) and -7303(m) from Antarctica , 1978 .

[233]  W. Boynton,et al.  Chemical evidence for the genesis of the ureilites, the achondrite Chassigny and the nakhlites , 1976 .

[234]  E. Anderson,et al.  On the radioactivity of stone meteorites , 1963 .

[235]  M. Duke,et al.  Petrology of eucrites, howardites and mesosiderites☆ , 1967 .

[236]  P. A. J. Englert,et al.  Distribution of Hydrogen in the Near Surface of Mars: Evidence for Subsurface Ice Deposits , 2002, Science.

[237]  B. Mason.  The Bununu meteorite, and a discussion of the pyroxene-plagioclase achondrites* , 1967 .

[238]  K. Fredriksson.  THE MANEGAON DIOGENITE , 1982 .

[239]  H. König,et al.  Uranbestimmungen an Steinmeteoriten mittels Neutronenaktivierung über die Xenon-Isotope 133 und 135 , 1959 .

[240]  Paul G. Lucey,et al.  Iron abundances on the lunar surface as measured by the Lunar Prospector gamma‐ray and neutron spectrometers , 2002 .

[241]  L. Schultz,et al.  Helium, neon, and argon in meteorites: A data collection , 1989 .

[242]  N. C. Pant,et al.  The Vissannapeta eucrite , 2000 .

[243]  D. Stöffler,et al.  Thermal and impact metamorphism on the HED parent asteroid , 1995 .

[244]  J. F. Lovering.  THE MOAMA EUCRITE — A PYROXENE‐PLAGIOCLASE ADCUMULATE , 1975 .

[245]  Thomas H. Prettyman,et al.  Gamma-Ray, Neutron, and Alpha-Particle Spectrometers for the Lunar Prospector mission , 2004 .

[246]  K. Keil,et al.  The Kapoeta howardite: Implications for the regolith evolution of the howardite‐eucrite‐diogenite parent body , 1998 .

[247]  E. Asphaug,et al.  Mega‐ejecta on asteroid Vesta , 2011 .

[248]  N. Nakamura,et al.  History of the Pasamonte achondrite: Relative susceptibility of the SmNd, RbSr, and UPb systems to metamorphic events , 1977 .

[249]  B. N. Powell.  Petrology and chemistry of mesosiderites—II. Silicate textures and compositions and metal-silicate relationships☆ , 1971 .

[250]  H. Craig,et al.  The composition of the stone meteorites and the origin of the meteorites , 1953 .

[251]  A. Masuda,et al.  Rare-Earth Geochemistry of Antarctic Diogenites , 1979 .

[252]  Yanagisawa,et al.  40Ar-39Ar Age Studies of Four Yamato-74 Meteorites , 1979 .

[253]  J. Huizenga,et al.  Thorium Content of Stone Meteorites , 1957, Science.

[254]  J. Klein,et al.  10Be and 26Al contents of eucrites: Implications for production rates and exposure ages , 1988 .

[255]  Richard D. Starr,et al.  Elemental composition from gamma‐ray spectroscopy of the NEAR‐Shoemaker landing site on 433 Eros , 2001 .

[256]  Timothy H. McConnochie,et al.  E‐type asteroid spectroscopy and compositional modeling , 2004 .

[257]  M. Lindstrom,et al.  Geochemistry and genesis of the angrites , 1990 .

[258]  D. Mittlefehldt.  Ibitira: A basaltic achondrite from a distinct parent asteroid and implications for the Dawn mission , 2005 .

[259]  Andreas Nathues,et al.  The Dawn Topography Investigation , 2011 .

[260]  W. Feldman,et al.  Characterization of Mars' seasonal caps using neutron spectroscopy , 2009 .

[261]  H Y McSween,et al.  Spectroscopic Characterization of Mineralogy and Its Diversity Across Vesta , 2012, Science.

[262]  L. Schultz,et al.  New noble gas data of primitive and differentiated achondrites including Northwest Africa 011 and Tafassasset , 2003 .

[263]  J. H. Reynolds.  ISOTOPIC COMPOSITION OF PRIMORDIAL XENON , 1960 .

[264]  D. E. Fisher.  Uranium Content of Some Stone Meteorites and their Pu–Xe Decay Interval , 1969, Nature.

[265]  R. H. Becker,et al.  An acid‐etch study of the Kapoeta achondrite: Implications for the argon‐36/argon‐38 ratio in the solar wind , 1998 .

[266]  T. Prettyman,et al.  K‐Th‐Ti systematics and new three‐component mixing model of HED meteorites: Prospective study for interpretation of gamma‐ray and neutron spectra for the Dawn mission , 2010 .

[267]  D. Garrison,et al.  39Ar‐40Ar ages of eucrites and thermal history of asteroid 4 Vesta , 2003 .

[268]  N. Nakamura.  A Preliminary Isotopic Study on Four Yamato Diogenites-Sm-Nd and Rb-Sr Systematics- , 1979 .

[269]  Harold C. Urey,et al.  Abundances of the elements , 1956 .

[270]  D. Black.  On the origins of trapped helium, neon and argon isotopic variations in meteorites. I - Gas-rich meteorites, lunar soil and breccia. II - Carbonaceous meteorites. , 1972 .

[271]  H. McSween,et al.  Compositional constraints on the genesis of diogenites , 2012 .

[272]  V. Sautter,et al.  Petrology and geochemistry of the unbrecciated achondrite Northwest Africa 1240 (NWA 1240): An HED parent body impact melt , 2003 .

[273]  M. Zolensky,et al.  Mineralogy of carbonaceous chondritic microclasts in howardites: identification of C2 fossil micrometeorites , 2003 .

[274]  E. Jarosewich,et al.  THE COMPOSITION OF THE JOHNSTOWN METEORITE , 1971 .

[275]  J. Morgan,et al.  Ancient meteoritic component in Apollo 17 boulders. , 1975 .

[276]  William V. Boynton,et al.  Global distribution of near-surface hydrogen on Mars , 2004 .

[277]  O. Müller,et al.  Isotopenhäufigkeit und Konzentration des Lithiums in Steinmeteoriten , 1964 .

[278]  R. Schmitt,et al.  MONTICELLO: A GLASS‐RICH HOWARDITE , 1987 .

[279]  D. Heymann,et al.  Light-dark structure and rare gas content of the carbonaceous chondrite Nogoya. , 1967 .

[280]  T N Titus,et al.  Dawn at Vesta: Testing the Protoplanetary Paradigm , 2012, Science.

[281]  D. Garrison,et al.  Energetic proton irradiation history of the howardite parent body regolith and implications for ancient solar activity , 1997 .

[282]  M. Lindstrom,et al.  MAGNESIAN BASALT CLASTS FROM THE EET 92014 AND KAPOETA HOWARDITES AND A DISCUSSION OF ALLEGED PRIMARY MAGNESIAN HED BASALTS , 1997 .

[283]  Tomoko Yamamoto,et al.  Multiple nitrogen isotopic components coexisting in ureilites , 1998 .

[284]  M. R. Smith,et al.  Chemical composition of the Howardite Parent Body deduced from Kapoeta primary 'mafic' magmas , 1982 .

[285]  D. Gosselin,et al.  The Bholghati howardite: Chemical study , 1990 .

[286]  M. Shima.  The abundances of titanium, zirconium and hafnium in stony meteorites , 1979 .

[287]  Brigitte Zanda,et al.  Relative chronology of crust formation on asteroid Vesta: Insights from the geochemistry of diogenites , 2010 .

[288]  E. Gibson,et al.  Noble gas and carbon abundances of the Haverö, Dingo Pup Donga, and North Haig ureilites , 1973 .

[289]  J. Wacker.  Noble gases in the diamond-free ureilite, ALHA 78019: The roles of shock and nebular processes , 1986 .

[290]  G. Reed,et al.  Some halogen measurements on achondrites , 1969 .

[291]  D. Heymann,et al.  Meteorites with short cosmic-ray exposure ages, as determined from their Al26 content , 1967 .

[292]  H. Takeda,et al.  A Preliminary Mineralogical Examination of the Yamato-74 Achondrites , 1978 .

[293]  Masuda Akimasa,et al.  REE Abundances in the Whole Rock and Mineral Separates of the Allan Hills-765 Meteorite , 1980 .

[294]  H. Reeves,et al.  Primitive Low-energy Particle Irradiation of Meteoritic Crystals , 1969, Nature.

[295]  S. Kobayashi,et al.  Determining the Absolute Abundances of Natural Radioactive Elements on the Lunar Surface by the Kaguya Gamma-ray Spectrometer , 2010 .

[296]  E. Anders,et al.  Primordial gases in the Jodzie howardite and the origin of gas-rich meteorites. , 1967 .

[297]  R. Wieler,et al.  Solar Wind Neon from Genesis: Implications for the Lunar Noble Gas Record , 2006, Science.

[298]  R. Clayton,et al.  A New Source of Basaltic Meteorites Inferred from Northwest Africa 011 , 2002, Science.

[299]  J. P. Willis,et al.  On the origin of eucrites and diogenites , 1973 .

[300]  D. Black.  On the origins of trapped helium, neon and argon isotopic variations in meteorites—II. Carbonaceous meteorites , 1972 .

[301]  W. Kiesl,et al.  ACTIVATION ANALYTICAL DETERMINATION OF ELEMENTS IN METEORITES. , 1967 .

[302]  A. Reid,et al.  Petrology of the polymict eucrite Petersburg , 1996 .

[303]  A. Weigel,et al.  Neon-E in CM-2 chondrite LEW90500 and collisional history of CM-2 chondrites, Maralinga, and other CK chondrites , 1998 .

[304]  T. Ntaflos,et al.  Foreign meteoritic material of howardites and polymict eucrites , 2007 .

[305]  J. Laul.  The Bholghati (howardite) consortium: An overview , 1990 .

[306]  G. Dreibus,et al.  The Chemistry of the Havero Ureilite , 1972 .

[307]  E. L. Fireman,et al.  Measurement of Li6, He3, and H3 in meteorites and its relation to cosmic radiation , 1957 .