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Scheller EL, Ehlmann BL. Composition, Stratigraphy, and Geological History of the Noachian Basement Surrounding the Isidis Impact Basin. JOURNAL OF GEOPHYSICAL RESEARCH. PLANETS 2020; 125:e2019JE006190. [PMID: 34422533 PMCID: PMC8378244 DOI: 10.1029/2019je006190] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 02/11/2020] [Indexed: 05/29/2023]
Abstract
The western part of the Isidis basin structure hosts a well-characterized Early Noachian to Amazonian stratigraphy. The Noachian Basement comprises its oldest exposed rocks (Early to Mid-Noachian) and was previously considered a single low-Ca pyroxenes (LCP)- and Fe/Mg-smectite-bearing unit. Here, we divide the Noachian Basement Group into five distinct geological units (Stratified Basement Unit, Blue Fractured Unit, Mixed Lithology Plains Unit, LCP-bearing Plateaus Unit, and Fe/Mg-smectite-bearing Mounds Unit), two geomorphological features (megabreccia and ridges), and a mineral deposit (kaolinite-bearing bright materials), based on geomorphology, spectral characteristics, and stratigraphic relationships. Megabreccia contain four different pre-Isidis lithologies, possibly including deeper crust or mantle materials, formed through mass wasting associated with transient crater collapse during Isidis basin formation. The Fe/Mg-smectite-bearing Stratified Basement Unit and LCP-bearing Blue Fractured Unit likewise represent pre-Isidis units within the Noachian Basement Group. Multiple Fe/Mg-smectite-bearing geological units with different stratigraphic positions and younger kaolinite-bearing bright materials indicate several aqueous alteration episodes of different ages and styles. Units with slight changes in pyroxene spectral properties suggest a transition from low-Ca pyroxene-containing materials to those with higher proportions of pyroxenes higher in Ca and/or glass that could be related to different impact and/or igneous processes, or provenance. This long history of Noachian and potentially Pre-Noachian geological processes, including impact basin formation, aqueous alteration, and multiple igneous and sedimentary petrogeneses, records changing ancient Mars environmental conditions. All units defined by this study are available 20 km outside of Jezero crater for in situ analysis and sampling during a potential extended mission scenario for the Mars 2020 rover.
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Affiliation(s)
- Eva L Scheller
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Bethany L Ehlmann
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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Joy KH, Snape JF, Nemchin AA, Tartèse R, Martin DM, Whitehouse MJ, Vishnyakov V, Pernet-Fisher JF, Kring DA. Timing of geological events in the lunar highlands recorded in shocked zircon-bearing clasts from Apollo 16. ROYAL SOCIETY OPEN SCIENCE 2020; 7:200236. [PMID: 32742691 PMCID: PMC7353986 DOI: 10.1098/rsos.200236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 05/05/2020] [Indexed: 06/11/2023]
Abstract
Apollo 16 soil-like regolith breccia 65745,7 contains two zircon-bearing clasts. One of these clasts is a thermally annealed silica-rich rock, which mineralogically has affinities with the High Alkali Suite (Clast 1), and yields zircon dates ranging from 4.08 to 3.38 Ga. The other clast is a KREEP-rich impact melt breccia (Clast 2) and yields zircon dates ranging from 3.97 to 3.91 Ga. The crystalline cores of both grains, which yield dates of ca 3.9 Ga, have undergone shock pressure modification at less than 20 GPa. We interpret that the U-Pb chronometer in these zircon grains has been partially reset by the Imbrium basin-forming event when the clasts were incorporated into the Cayley Plains ejecta blanket deposit. The zircon grains in Clast 1 have been partially decomposed, resulting in a breakdown polymineralic texture, with elevated U, Pb and Th abundances compared with those in the crystalline zircon. These decomposed areas exhibit younger dates around 3.4 Ga, suggesting a secondary high-pressure, high-temperature event, probably caused by an impact in the local Apollo 16 highlands area.
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Affiliation(s)
- K. H. Joy
- Department of Earth and Environmental Sciences, School of Natural Sciences, The University of Manchester, Manchester, UK
| | - J. F. Snape
- Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
| | - A. A. Nemchin
- Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
- Department of Applied Geology, Curtin University, Perth, Australia
| | - R. Tartèse
- Department of Earth and Environmental Sciences, School of Natural Sciences, The University of Manchester, Manchester, UK
| | - D. M. Martin
- European Centre for Satellite Applications and Telecommunications (ECSAT), European Space Agency, Fermi Avenue, Harwell Campus, Didcot, Oxfordshire OX11 0FD, UK
| | - M. J. Whitehouse
- Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
| | - V. Vishnyakov
- School of Computing and Engineering, University of Huddersfield, Huddersfield, UK
| | - J. F. Pernet-Fisher
- Department of Earth and Environmental Sciences, School of Natural Sciences, The University of Manchester, Manchester, UK
| | - D. A. Kring
- Center for Lunar Science and Exploration, Lunar and Planetary Institute, Universities Space Research Association, Houston, TX 77058, USA
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History of the Terminal Cataclysm Paradigm: Epistemology of a Planetary Bombardment That Never (?) Happened. GEOSCIENCES 2019. [DOI: 10.3390/geosciences9070285] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study examines the history of the paradigm concerning a lunar (or solar-systemwide)terminal cataclysm (also called “Late Heavy Bombardment” or LHB), a putative, brief spikein impacts at ~3.9 Ga ago, preceded by low impact rates. We examine origin of the ideas, why theywere accepted, and why the ideas are currently being seriously revised, if not abandoned. Thepaper is divided into the following sections:1. Overview of paradigm.2. Pre-Apollo views (1949-1969).3. Initial suggestions of cataclysm (ca. 1974).4. Ironies.5. Alternative suggestions, megaregolith evolution (1970s).6. Impact melt rocks “establish” cataclysm (1990).7. Imbrium redux (ca. 1998).8. Impact melt clasts (early 2000s).9. Dating of front-side lunar basins?10. Dynamical models “explain” the cataclysm (c. 2000s).11. Asteroids as a test case.12. Impact melts predating 4.0 Ga ago (ca. 2008-present.).13. Biological issues.14. Growing doubts (ca. 1994-2014).15. Evolving Dynamical Models (ca. 2001-present).16. Connections to lunar origin.17. Dismantling the paradigm (2015-2018).18. “Megaregolith Evolution Model” for explaining the data.19. Conclusions and new directions for future work.The author hopes that this open-access discussion may prove useful for classroom discussionsof how science moves forward through self-correction of hypotheses.
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Liu J, Sharp M, Ash RD, Kring DA, Walker RJ. Diverse impactors in Apollo 15 and 16 impact melt rocks: evidence from osmium isotopes and highly siderophile elements. GEOCHIMICA ET COSMOCHIMICA ACTA 2015; 155:122-153. [PMID: 34531613 PMCID: PMC8442830 DOI: 10.1016/j.gca.2015.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Concentrations of highly siderophile elements (HSE) and 187Os/188Os isotopic compositions for eleven impact related rocks from the Apollo 15 and 16 landing sites are reported and combined with existing geochronological data to investigate the chemical nature and temporal changes in the large impactors implicated in the formation of the lunar basins. Data for the samples all define linear trends on plots of HSE versus Ir concentrations, whose slopes likely reflect the relative HSE compositions of the dominant impactors that formed the rocks. The inferred Imbrium basin impactor that generated Apollo 15 impact melt rocks 15445 and 15455 was characterized by modestly suprachondritic 187Os/188Os, Ru/Ir, Pt/Ir and Pd/Ir ratios. Diverse impactor components are revealed in the Apollo 16 impact melt rocks. The 187Os/188Os and HSE/Ir ratios of the impactor components in melt rocks 60635, 63595 and 68416, with reported ages < 3.84 Ga, are within the range of chondritic meteorites, but slightly higher than ratios characterizing previously studied granulitic impactites with reported ages > 4.0 Ga. By contrast, the impactor components in melt rocks 60235, 62295 and 67095, with reported ages of ~3.9 Ga, are characterized by suprachondritic 187Os/188Os and HSE/Ir ratios similar to the Apollo 15 impact melt rocks, and may also sample the Imbrium impactor. Three lithic clasts from regolith breccias 60016 and 65095, also with ~3.9 Ga ages, contain multiple impactor components, of which the dominant composition is considerably more suprachondritic than those implicated for Imbrium and Serenitatis (Apollo 17) impactors. The dominant composition recorded in these rocks was most likely inherited from a pre-Imbrium impactor. Consideration of composition versus age relations among lunar impact melt rocks reveals no discernable trend. Virtually all lunar impact melt rocks sampled by the Apollo missions, as well as meteorites, are characterized by 187Os/188Os and HSE/Ir ratios that, when collectively plotted, define linear trends ranging from chondritic to fractionated compositions. The impact melt rocks with HSE signatures within the range of chondritic meteorites are interpreted to have been derived from impactors that had HSE compositions similar to known chondrite groups. By contrast, the impact melt rocks with non-chondritic relative HSE concentrations could not have been made by mixing of known chondritic impactors. These signatures may instead reflect contributions from early solar system bodies with bulk chemical compositions that have not yet been sampled by primitive meteorites present in our collections. Alternately, they may reflect the preferential incorporation of evolved metal separated from a fractionated planetesimal core. Pre-3.9 Ga ages for at least some impactor components with both chondritic and fractionated HSE raise the possibility that the bulk of the HSE were added to the lunar crust prior to the later-stage basin-forming impacts, such as Imbrium and Serenitatis, as proposed by Fischer-Gödde and Becker (2012). For this scenario, the later-stage basin-forming impacts were more important with respect to mixing prior impactor components into melt rocks, rather than contributing much to the HSE budgets of the rocks themselves.
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Affiliation(s)
- Jingao Liu
- Department of Geology, University of Maryland, College Park MD 20742 USA
- Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton AB T6G 2E3 Canada
| | - Miriam Sharp
- Department of Geology, University of Maryland, College Park MD 20742 USA
| | - Richard D. Ash
- Department of Geology, University of Maryland, College Park MD 20742 USA
| | - David A. Kring
- Center for Lunar Science and Exploration, Lunar and Planetary Institute, Universities Space Research Association, 3600 Bay Area Boulevard, Houston, Texas 77058, USA
| | - Richard J. Walker
- Department of Geology, University of Maryland, College Park MD 20742 USA
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Jerde EA, Warren PH, Morris RV, Heiken GH, Vaniman DT. A potpourri of regolith breccias: “New” samples from the Apollo 14, 16, and 17 landing sites. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/jb092ib04p0e526] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lindstrom MM, Lindstrom DJ. Lunar granulites and their precursor anorthositic norites of the early lunar crust. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/jb091ib04p0d263] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Warren PH, Haack H, Rasmussen KL. Megaregolith insulation and the duration of cooling to isotopic closure within differentiated asteroids and the Moon. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/90jb02333] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ryder G. Mass flux in the ancient Earth-Moon system and benign implications for the origin of life on Earth. ACTA ACUST UNITED AC 2002. [DOI: 10.1029/2001je001583] [Citation(s) in RCA: 176] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Halekas JS, Mitchell DL, Lin RP, Frey S, Hood LL, Acuña MH, Binder AB. Mapping of crustal magnetic anomalies on the lunar near side by the Lunar Prospector electron reflectometer. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000je001380] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Stratigraphy and Isotope Ages of Lunar Geologic Units: Chronological Standard for the Inner Solar System. SPACE SCIENCES SERIES OF ISSI 2001. [DOI: 10.1007/978-94-017-1035-0_2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Cohen BA, Swindle TD, Kring DA. Support for the lunar cataclysm hypothesis from lunar meteorite impact melt ages. Science 2000; 290:1754-6. [PMID: 11099411 DOI: 10.1126/science.290.5497.1754] [Citation(s) in RCA: 243] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Lunar meteorites represent a more random sampling of lunar material than the Apollo or Luna collections and, as such, lunar meteorite impact melt ages are the most important data in nearly 30 years with which to reexamine the lunar cataclysm hypothesis. Within the lunar meteorite breccias MAC 88105, QUE 93069, DaG 262, and DaG 400, seven to nine different impact events are represented with 40Ar-39Ar ages between 2.76 and 3.92 billion years ago (Ga). The lack of impact melt older than 3.92 Ga supports the concept of a short, intense period of bombardment in the Earth-moon system at approximately 3.9 Ga. This was an anomalous spike of impact activity on the otherwise declining impact- frequency curve.
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Affiliation(s)
- B A Cohen
- The University of Arizona, Tucson, AZ 85721, USA.
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Korotev RL. The great lunar hot spot and the composition and origin of the Apollo mafic (“LKFM”) impact-melt breccias. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001063] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Bussey DBJ, Spudis PD. Compositional studies of the Orientale, Humorum, Nectaris, and Crisium lunar basins. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001130] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Morris RV, See TH, Hörz F. Composition of the Cayley formation at Apollo 16 as inferred from impact melt splashes. ACTA ACUST UNITED AC 1986. [DOI: 10.1029/jb091ib13p00e21] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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