ORCID Profile
0000-0003-0348-2407
Current Organisation
University of Maryland
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Publisher: Elsevier BV
Date: 09-2006
Publisher: Elsevier BV
Date: 05-2015
Publisher: Springer Science and Business Media LLC
Date: 2009
DOI: 10.1038/NATURE07651
Abstract: Mechanisms for the formation of crust on planetary bodies remain poorly understood. It is generally accepted that Earth's andesitic continental crust is the product of plate tectonics, whereas the Moon acquired its feldspar-rich crust by way of plagioclase flotation in a magma ocean. Basaltic meteorites provide evidence that, like the terrestrial planets, some asteroids generated crust and underwent large-scale differentiation processes. Until now, however, no evolved felsic asteroidal crust has been s led or observed. Here we report age and compositional data for the newly discovered, paired and differentiated meteorites Graves Nunatak (GRA) 06128 and GRA 06129. These meteorites are feldspar-rich, with andesite bulk compositions. Their age of 4.52 +/- 0.06 Gyr demonstrates formation early in Solar System history. The isotopic and elemental compositions, degree of metamorphic re-equilibration and sulphide-rich nature of the meteorites are most consistent with an origin as partial melts from a volatile-rich, oxidized asteroid. GRA 06128 and 06129 are the result of a newly recognized style of evolved crust formation, bearing witness to incomplete differentiation of their parent asteroid and to previously unrecognized ersity of early-formed materials in the Solar System.
Publisher: Geological Society of America
Date: 09-2010
DOI: 10.1130/G30944.1
Publisher: Springer Science and Business Media LLC
Date: 10-07-2023
Publisher: Elsevier BV
Date: 06-2012
Publisher: Society of Economic Geologists
Date: 09-2007
Publisher: Elsevier BV
Date: 07-2011
Publisher: Elsevier BV
Date: 06-2023
Publisher: Elsevier BV
Date: 04-2008
Publisher: Springer Science and Business Media LLC
Date: 12-12-2022
Publisher: Proceedings of the National Academy of Sciences
Date: 31-05-2021
Abstract: Kimberlites are igneous rocks derived from deep mantle sources. Recent studies have suggested that certain kimberlites originated from a mantle source with relatively primitive chemical composition that was created by early Earth processes. We present W isotope data for a global suite of kimberlites with variable formation ages and find their mantle source(s) to be characterized by 182 W/ 184 W averaging ∼6 ppm lower than the upper mantle ratio. This result is consistent with derivation of some kimberlites from one or more early formed mantle reservoirs. The low 182 W/ 184 W of these kimberlites is indicative of an ancient mantle source modified by some form of core–mantle interaction, an early silicate fractionation event, an overabundance of late-accreted materials, or a combination of these.
Publisher: Wiley
Date: 28-06-2023
DOI: 10.1111/NPH.19109
Abstract: Carotenoids are photoprotectant pigments and precursors of hormones such as strigolactones (SL). Carotenoids are produced in plastids from geranylgeranyl diphosphate (GGPP), which is erted to the carotenoid pathway by phytoene synthase (PSY). In tomato ( Solanum lycopersicum ), three genes encode plastid‐targeted GGPP synthases ( SlG1 to SlG3 ) and three genes encode PSY isoforms ( PSY1 to PSY3 ). Here, we investigated the function of SlG1 by generating loss‐of‐function lines and combining their metabolic and physiological phenotyping with gene co‐expression and co‐immunoprecipitation analyses. Leaves and fruits of slg1 lines showed a wild‐type phenotype in terms of carotenoid accumulation, photosynthesis, and development under normal growth conditions. In response to bacterial infection, however, slg1 leaves produced lower levels of defensive GGPP‐derived diterpenoids. In roots, SlG1 was co‐expressed with PSY3 and other genes involved in SL production, and slg1 lines grown under phosphate starvation exuded less SLs. However, slg1 plants did not display the branched shoot phenotype observed in other SL‐defective mutants. At the protein level, SlG1 physically interacted with the root‐specific PSY3 isoform but not with PSY1 and PSY2. Our results confirm specific roles for SlG1 in producing GGPP for defensive diterpenoids in leaves and carotenoid‐derived SLs (in combination with PSY3) in roots.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-02-2023
Abstract: Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. S les of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu s les. The s les are mainly composed of materials similar to those of carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The s les consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37° ± 10°C, about 5.2 − 0.7 + 0.8 million (statistical) or 5.2 − 2.1 + 1.6 million (systematic) years after the formation of the first solids in the Solar System. After aqueous alteration, the Ryugu s les were likely never heated above ~100°C. The s les have a chemical composition that more closely resembles that of the Sun’s photosphere than other natural s les do.
Publisher: Elsevier BV
Date: 2010
Publisher: Elsevier BV
Date: 03-2012
Publisher: Wiley
Date: 05-04-2012
Publisher: Elsevier BV
Date: 07-2012
Publisher: Wiley
Date: 23-06-2015
Publisher: Elsevier BV
Date: 08-2009
Publisher: Oxford University Press (OUP)
Date: 03-09-2009
Publisher: Springer Science and Business Media LLC
Date: 14-03-2023
Publisher: American Association for the Advancement of Science (AAAS)
Date: 14-07-2023
Abstract: Preliminary analyses of asteroid Ryugu s les show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu s les that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration. The 5 to 10 times higher abundances of presolar SiC (~235 ppm), N-rich organic matter, organics with N isotopic anomalies (1.2%), and organics with C isotopic anomalies (0.2%) in the primitive clasts compared to bulk Ryugu suggest that the clasts formed in a unique part of the protoplanetary disk enriched in presolar materials. These clasts likely represent previously uns led outer solar system material that accreted onto Ryugu after aqueous alteration ceased, consistent with Ryugu’s rubble pile origin.
Publisher: Elsevier BV
Date: 2007
Publisher: Elsevier BV
Date: 09-2018
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-11-2022
Abstract: Little is known about the origin of the spectral ersity of asteroids and what it says about conditions in the protoplanetary disk. Here, we show that s les returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inward to be implanted into the Main Belt. In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune.
Publisher: Elsevier BV
Date: 11-2012
Publisher: American Association for the Advancement of Science (AAAS)
Date: 16-12-2022
Abstract: The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: 16 O-rich (associated with refractory inclusions) and 16 O-poor (associated with chondrules). Both the 16 O-rich and 16 O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the 16 O-rich to 16 O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.
Publisher: Elsevier BV
Date: 2005
Publisher: Springer Science and Business Media LLC
Date: 05-2009
DOI: 10.1038/NATURE08078
Publisher: Elsevier BV
Date: 11-2011
Publisher: Elsevier BV
Date: 10-2016
Publisher: Springer Science and Business Media LLC
Date: 28-05-2009
DOI: 10.1038/NATURE08077
Abstract: The production of terrestrial andesites in subduction zones is well established. Day et al. describe two ex les of meteorites (GRA 06128 and GRA 06129) that they claim to represent "an entirely new mode of generation of andesite crust compositions" on asteroids this suggestion has wide implications for the generation of andesitic planetary crusts in general. However, here we show that compositional data, particularly for the rare-earth elements (REEs) and other lithophile elements, presented in their paper do not substantiate this claim. We conclude that existing mechanisms for andesite generation do not need revision.
Publisher: American Astronomical Society
Date: 08-2023
DOI: 10.3847/PSJ/ACEA62
Abstract: We present oxygen isotopic analyses of fragments of the near-Earth C b -type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu s les and CI chondrites in Δ ′ 17 O can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly s led C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope 26 Al, suggests that if lithified at the time of alteration, the parent body was small (≪50 km radius). If the parent planetesimal was large ( km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.
Publisher: Informa UK Limited
Date: 07-2005
DOI: 10.1080/14763140508522866
Abstract: The aim of this study was to determine whether a constructivist approach, in particular a visit to a zoo, could be effective in consolidating mechanical concepts and applying those concepts to coaching and teaching. Ten students in their final year of their Bachelor of Physical Education at the University of Edinburgh participated in a visit to Edinburgh Zoo. During the visit students completed a worksheet of questions and engaged interactively in discussing how various animals are adapted mechanically to survive in their environments. Immediately after the visit they completed a questionnaire with four sections. The first section assessed whether they could apply the mechanical concepts discussed during the visit to human sports performance. The second canvassed their opinions on whether the visit was effective in reinforcing mechanical concepts, in developing 'lateral thinking' about mechanical concepts, and in improving their ability to apply mechanical concepts to coaching and teaching. The third canvassed their opinions on whether the visit would be effective for senior high school Physical Education and Sports Science students for developing mechanical concepts and applying them to coaching. The fourth section canvassed their opinions on when the visit should be conducted for Physical Education and Sports Science students in universities and in senior high schools. The results indicated that the visit was effective in reinforcing mechanical concepts and in applying them laterally to improve understanding of human sports performance. Participants believed that the visit would also be effective for senior high school students. All participants believed that the visit would be most beneficial after at least one course in biomechanics that covers the basic biomechanical principles.
Publisher: Informa UK Limited
Date: 08-08-2014
Publisher: Elsevier BV
Date: 11-2009
Publisher: Elsevier BV
Date: 03-2006
Publisher: American Astronomical Society
Date: 04-2023
Abstract: Rock fragments of the Cb-type asteroid Ryugu returned to Earth by the JAXA Hayabusa2 mission share mineralogical, chemical, and isotopic properties with the Ivuna-type (CI) carbonaceous chondrites. Similar to CI chondrites, these fragments underwent extensive aqueous alteration and consist predominantly of hydrous minerals likely formed in the presence of liquid water on the Ryugu parent asteroid. Here we present an in situ analytical survey performed by secondary ion mass spectrometry from which we have estimated the D/H ratio of Ryugu’s hydrous minerals, D/H Ryugu , to be [165 ± 19] × 10 −6 , which corresponds to δ D Ryugu = +59 ± 121‰ (2 σ ). The hydrous mineral D/H Ryugu ’s values for the two s ling sites on Ryugu are similar they are also similar to the estimated D/H ratio of hydrous minerals in the CI chondrites Orgueil and Alais. This result reinforces a link between Ryugu and CI chondrites and an inference that Ryugu’s s les, which avoided terrestrial contamination, are our best proxy to estimate the composition of water at the origin of hydrous minerals in CI-like material. Based on this data and recent literature studies, the contribution of CI chondrites to the hydrogen of Earth’s surficial reservoirs is evaluated to be ∼3%. We conclude that the water responsible for the alteration of Ryugu’s rocks was derived from water ice precursors inherited from the interstellar medium the ice partially re-equilibrated its hydrogen with the nebular H 2 before being accreted on the Ryugu’s parent asteroid.
Publisher: Elsevier BV
Date: 11-2005
Publisher: Elsevier BV
Date: 06-2008
Publisher: Elsevier BV
Date: 08-2009
Publisher: Elsevier BV
Date: 08-2010
Publisher: Mineralogical Society of America
Date: 10-2006
DOI: 10.2138/AM.2006.2083
Publisher: American Geophysical Union (AGU)
Date: 07-2013
DOI: 10.1002/GGGE.20152
Publisher: Elsevier BV
Date: 02-2011
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-06-1998
DOI: 10.1126/SCIENCE.280.5369.1570
Abstract: Osmium isotopic analyses of picritic lavas from Hawaii show enrichments in the osmium-186/osmium-188 ratio ( 186 Os/ 188 Os) of 0.008 to 0.018%, relative to a chondritic upper mantle, that are positively correlated with enrichments in 187 Os/ 188 Os of 5.4 to 9.0%. The most viable mechanism to produce these coupled 186 Os and 187 Os enrichments is by addition of 0.5 to 1 weight percent of outer core metal to a portion of the D" layer and subsequent upwelling of the mixture. These data suggest that some plumes originate at the core-mantle boundary and that Os isotopes may be used to distinguish plumes derived from shallow versus deep mantle sources.
Location: United States of America
Location: United States of America
Start Date: 2006
End Date: 2008
Funder: National Science Foundation - Directorate for Geosciences
View Funded ActivityStart Date: 2013
End Date: 2015
Funder: National Science Foundation - Directorate for Geosciences
View Funded ActivityStart Date: 2009
End Date: 2014
Funder: National Science Foundation - Directorate for Geosciences
View Funded ActivityStart Date: 2007
End Date: 2010
Funder: National Science Foundation - Directorate for Geosciences
View Funded Activity