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Start Over Author "Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW)" Publisher american geophysical union (agu)
7 results on '"Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW)"'

1. Finding SEIS North on Mars: Comparisons Between SEIS Sundial, Inertial and Imaging Measurements and Consequences for Seismic Analysis

Author

P. H. Lognonné, D. Savoie, K. J. Hurst, John Clinton, Nathan R. Williams, Eléonore Stutzmann, M. Goutaudier, William B. Banerdt, Justin N. Maki, Matthew P. Golombek, David Mimoun, A. Richard, M. van Driel, Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), NASA, California Institute of Technology (CALTECH), Institute of Geophysics [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Swiss Seismological Service [ETH Zurich] (SED), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)-Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), and Institut Supérieur de l'Aéronautique et de l'Espace (ISAE-SUPAERO)

Subjects
Inertial frame of reference, 010504 meteorology & atmospheric sciences, lcsh:Astronomy, lcsh:QE1-996.5, True north, Mars, Sundial, Mars Exploration Program, Environmental Science (miscellaneous), 010502 geochemistry & geophysics, Geodesy, 01 natural sciences, Seismic analysis, lcsh:QB1-991, lcsh:Geology, Gnomon, [SDU]Sciences of the Universe [physics], 13. Climate action, General Earth and Planetary Sciences, Seismology, Geology, InSight, 0105 earth and related environmental sciences
Abstract

International audience; In this paper, we present the results obtained in the determination of the true north direction on Mars by using a gnomon on the InSight mission and compare the measurements with either the North determination from the Inertial Measurement Unit and imaging analysis. The obtained measurement has been used to populate the SEIS orientation information in the archived SEIS data. Images taken during December 2018 and January 2019 allow to determine the gnomon shadow position and length over a target. By calculating the Sun local coordinates using planetary ephemeris VSOP87, the images are used to estimate the true North direction on the landing site. By using eight different images selected, we obtain the true North direction with an accuracy up to 2.5°, which is confirmed by the IMU and imaging analysis. The true North direction is also confirmed by an image taken near local noon, when the sun crosses the meridian. The North determination precision is then discussed in view of the seismic determination of the back azimuth.

Published
2021
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2. Contrasting Export of Particulate Organic Carbon From Greenlandic Glacial and Nonglacial Streams

Author

L. Bröder, C. Hirst, S. Opfergelt, M. Thomas, J. E. Vonk, N. Haghipour, T. I. Eglinton, J. Fouché, Swiss Federal Institute of Technology (ETH) - Geological Institute, Department of Earth Sciences, UCL - SST/ELI/ELIE - Environmental Sciences, Geological Institute [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Earth and Life Institute [Louvain-La-Neuve] (ELI), Université Catholique de Louvain = Catholic University of Louvain (UCL), Ion Beam Physics [ETH Zürich], Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Laboratoire d'étude des Interactions Sol - Agrosystème - Hydrosystème (UMR LISAH), Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro Montpellier, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), The authors received funding for the field campaign from INTERACT under the European Union H2020 Grant 871120 to L.B. Further funding for this work came from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (ERC Starting Grant,714617) to S.O. and (ERC Starting Grant,Thawsome, Grant 676982) to J.V. Lastbut not least, Earth and Climate, Department of Earth Sciences [Amsterdam], and Vrije Universiteit Amsterdam [Amsterdam] (VU)

Subjects
particulate organic carbon, glacier, [SDV]Life Sciences [q-bio], [SDE.MCG]Environmental Sciences/Global Changes, stream, Greenland, particulate organic carbonGreenlandglacierstreamradiocarbonpermafrost, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, Geophysics, radiocarbon, General Earth and Planetary Sciences, SDG 14 - Life Below Water, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, permafrost
Abstract

On-going shrinkage of Greenland's icecap, permafrost thaw, and changes in precipitation are exposing its landscapes to erosion and remobilization of ancient organic carbon (OC) held in soils and sedimentary rocks. The fate of this OC and potential feedbacks to climate are still unclear. Here, we show that the glacial Zackenberg river (Northeastern Greenland) exports aged particulate OC (POC, uncalibrated radiocarbon ages of ∼4,000 years). Many of the smaller periglacial streams affected by abrupt permafrost thaw transport substantially older POC (up to 32,000 years), especially with enhanced discharge following intense precipitation. Mineralogical analysis, and density and size fractionation of soils and both glacial and nonglacial river sediments reveal that OC is largely associated with phyllosilicate minerals, suggesting stabilization against microbial processing. Enhanced export of ancient, mineral-associated OC as a consequence of summer rainfall may accelerate translocation of OC from terrestrial to marine environments, but could have limited consequences for climate., Geophysical Research Letters, 49 (21), ISSN:0094-8276, ISSN:1944-8007

Published
2022
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3. Vortex‐Dominated Aeolian Activity at InSight's Landing Site, Part 1: Multi‐Instrument Observations, Analysis, and Implications

Author

Alexander E. Stott, L. M. Sotomayor, Constantinos Charalambous, John A. Grant, Sebastien Rodriguez, Nicholas H. Warner, Veronique Ansan, Don Banfield, William T. Pike, Naomi Murdoch, Aymeric Spiga, Maria E. Banks, Daniel Viúdez-Moreiras, William B. Banerdt, P. H. Lognonné, Ernst Hauber, Jorge Pla-Garcia, Matthew P. Golombek, Clément Perrin, Ralph D. Lorenz, Justin N. Maki, T. Warren, Anna Mittelholz, Claire E. Newman, Antoine Lucas, Matthew E. Baker, Catherine L. Johnson, J. B. Garvin, Ingrid Daubar, Mark T. Lemmon, Sara Navarro, Catherine M. Weitz, J. B. McClean, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Department of Electrical and Electronic Engineering [London] (DEEE), Imperial College London, MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Johns Hopkins University (JHU), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Space Science Institute [Boulder] (SSI), Laboratoire de Planétologie et Géosciences [UMR_C 6112] (LPG), Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ), Institut de Physique du Globe de Paris (IPG Paris), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), NASA Goddard Space Flight Center (GSFC), Institut Supérieur de l'Aéronautique et de l'Espace (ISAE-SUPAERO), Planetary Science Institute [Tucson] (PSI), Smithsonian Institution, State University of New York at Geneseo (SUNY Geneseo), State University of New York (SUNY), Brown University, German Aerospace Center (DLR), University of British Columbia (UBC), Institute of Geophysics [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), University of Oxford, Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Cornell University [New York], Aeolis Research, ANR-19-CE31-0008,MAGIS,MArs Geophysical InSight(2019), Rodriguez, Sébastien, and MArs Geophysical InSight - - MAGIS2019 - ANR-19-CE31-0008 - AAPG2019 - VALID

Subjects
Convection, Seismometer, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mars, 01 natural sciences, Wind speed, Physics::Geophysics, aeolian changes at the InSight landing site on Mars, convective vortices as a primary driver of particle motion, dust lifting and saltation, multi-instrument measurements constrain the timing and atmospheric conditions of aeolian changes, passing vortices lifting dust are correlated with magnetic signatures, surface creep, surface tracks, particle transport, Geochemistry and Petrology, Planet, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), wind, 14. Life underwater, 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, InSight, 0105 earth and related environmental sciences, Mars landing, Mars Exploration Program, Geophysics, Vortex, Planetengeologie, [PHYS.ASTR.EP] Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 13. Climate action, Space and Planetary Science, Aeolian processes, Astrophysics::Earth and Planetary Astrophysics, Geology, camera
Abstract

International audience; We report the aeolian changes observed in situ by NASA's InSight lander during the first 400 sols of operations: Granule creep, saltation, dust removal, and the formation of dark surface tracks. Aeolian changes are infrequent and sporadic. However, on sols, when they do occur, they consistently appear between noon to 3 p.m., and are associated with the passage of convective vortices during periods of high vortex activity. Aeolian changes are more frequent at elevated locations, such as the top surfaces of rocks and lander footpads. InSight observed these changes using, for the first time, simultaneous insitu and orbital imaging and high-frequency meteorological, seismological, and magnetic measurements. Seismometer measurements of ground acceleration constrain the timing and trajectory of convective vortex encounters, linking surface changes to source vortices. Magnetometer measurements show perturbations in magnetic field strength during the passage of convective vortices consistent with chargedparticle motion. Detachment of sand-scale particles occurs when high background winds and vortexinduced turbulence provide a peak surface friction wind speed above the classic saltation fluid threshold. However, detachment of dust-and granule-scale particles also occurred when the surface friction wind speed remained below this threshold. This may be explained by local enhancement of the surface roughness and other effects described here and further studied in Part 2 (Baker et al., 2021). The lack of saltation and bright dust-coated surfaces at the InSight landing site implies surface stability and the onset of particle motion may be suppressed by dust "cushioning." This differentiates the InSight landing site from other areas on Mars that exhibit more aeolian activity. Plain Language Summary Aeolian activity, the movement of dust and sand by the wind, is common on Earth and has been observed on other planets, including Mars. A new Mars lander, InSight, has for the first time monitored aeolian changes by combining imaging with weather, seismic and CHARALAMBOUS ET AL.

Published
2021
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4. Listening for the Landing: Seismic Detections of Perseverance's Arrival at Mars With InSight

Author

Foivos Karakostas, N. Wójcicka, Tarje Nissen-Meyer, Nicholas A Teanby, Eleanor K. Sansom, Carene Larmat, Gareth S. Collins, Ross Maguire, Bruce Banerdt, Kuangdai Leng, Marouchka Froment, Benjamin Fernando, Aymeric Spiga, Özgür Karatekin, Philippe Lognonné, Taichi Kawamura, Lucie Rolland, Ingrid Daubar, Simon Stähler, Domenico Giardini, University of Oxford, Imperial College London, Los Alamos National Laboratory (LANL), Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), University of Maryland [College Park], University of Maryland System, Michigan State University [East Lansing], Michigan State University System, Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Royal Observatory of Belgium [Brussels] (ROB), Curtin University [Perth], Planning and Transport Research Centre (PATREC), University of Bristol [Bristol], Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), California Institute of Technology (CALTECH), Brown University, ANR-19-CE31-0008,MAGIS,MArs Geophysical InSight(2019), University of Oxford [Oxford], Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris)

Subjects
QE1-996.5, 010504 meteorology & atmospheric sciences, seismoacoustics, Astronomy, Mars, QB1-991, Geology, Mars Exploration Program, Environmental Science (miscellaneous), seismology, 01 natural sciences, impacts, InSight, 13. Climate action, [SDU]Sciences of the Universe [physics], 0103 physical sciences, General Earth and Planetary Sciences, Active listening, 010303 astronomy & astrophysics, Seismology, 0105 earth and related environmental sciences
Abstract

International audience; The entry, descent, and landing (EDL) sequence of NASA's Mars 2020 Perseverance Rover will act as a seismic source of known temporal and spatial localization. We evaluate whether the signals produced by this event will be detectable by the InSight lander (3,452 km away), comparing expected signal amplitudes to noise levels at the instrument. Modeling is undertaken to predict the propagation of the acoustic signal (purely in the atmosphere), the seismoacoustic signal (atmosphere-to-ground coupled), and the elastodynamic seismic signal (in the ground only). Our results suggest that the acoustic and seismoacoustic signals, produced by the atmospheric shock wave from the EDL, are unlikely to be detectable due to the pattern of winds in the martian atmosphere and the weak air-to-ground coupling, respectively. However, the elastodynamic seismic signal produced by the impact of the spacecraft's cruise balance masses on the surface may be detected by InSight. The upper and lower bounds on predicted ground velocity at InSight are 2.0 × 10 −14 and 1.3 × 10 −10 m s −1. The upper value is above the noise floor at the time of landing 40% of the time on average. The large range of possible values reflects uncertainties in the current understanding of impact-generated seismic waves and their subsequent propagation and attenuation through Mars. Uncertainty in the detectability also stems from the indeterminate instrument noise level at the time of this future event. A positive detection would be of enormous value in constraining the seismic properties of Mars, and in improving our understanding of impact-generated seismic waves.

Published
2021
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5. Provenance analysis using Raman spectroscopy of carbonaceous material: A case study in the Southern Alps of New Zealand

Author

Simon C. Cox, Olivier Beyssac, Lukas Nibourel, Jérôme Lavé, Frédéric Herman, Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Institute of Geological Sciences [Bern], University of Bern, Université de Lausanne = University of Lausanne (UNIL), Dunedin Research Centre, GNS Science, Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Université de Lausanne (UNIL), and Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
geography, Provenance, geography.geographical_feature_category, Lithology, Bedrock, Metamorphic rock, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Metamorphism, 15. Life on land, Flume, Geophysics, Denudation, [SDU]Sciences of the Universe [physics], 13. Climate action, Erosion, Cartography, Earth-Surface Processes
Abstract

International audience; Detrital provenance analyses in orogenic settings, in which sediments are collected at the outlet of a catchment, have become an important tool to estimate how erosion varies in space and time. Here we present how Raman Spectroscopy on Carbonaceous Material (RSCM) can be used for provenance analysis. RSCM provides an estimate of the peak temperature (RSCM‐T) experienced during metamorphism. We show that we can infer modern erosion patterns in a catchment by combining new measurements on detrital sands with previously acquired bedrock data. We focus on the Whataroa catchment in the Southern Alps of New Zealand and exploit the metamorphic gradient that runs parallel to the main drainage direction. To account for potential sampling biases, we also quantify abrasion properties using flume experiments and measure the total organic carbon content in the bedrock that produced the collected sands. Finally, we integrate these parameters into a mass‐conservative model. Our results first demonstrate that RSCM‐T can be used for detrital studies. Second, we find that spatial variations in tracer concentration and erosion have a first‐order control on the RSCM‐T distributions, even though our flume experiments reveal that weak lithologies produce substantially more fine particles than do more durable lithologies. This result implies that sand specimens are good proxies for mapping spatial variations in erosion when the bedrock concentration of the target mineral is quantified. The modeling suggests that highest present‐day erosion rates (in Whataroa catchment) are not situated at the range front but around 10 km into the mountain belt.

Published
2015
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6. Combined147,146Sm-143,142Nd constraints on the longevity and residence time of early terrestrial crust

Author

Martin Guitreau, John F. Rudge, Antoine S.G. Roth, Bernard Bourdon, Janne Blichert-Toft, Stephen J. Mojzsis, Institute of Geochemistry and Petrology, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Sciences de la Terre (LST), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Institute of Geochemistry and Petrology [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Acasta Gneiss, Felsic, Hadean, Archean, Geochemistry, Crust, sub-02, Mantle (geology), Paleontology, Geophysics, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Geochemistry and Petrology, Geology, Zircon, Gneiss
Abstract

International audience; Primordial silicate differentiation controlled the composition of Earth's oldest crust. Inherited Nd-142 anomalies in Archean rocks are vestiges of the mantle-crust differentiation before ca. 4300 Ma. Here we report new whole-rock Sm-147,Sm-146-Nd-143,Nd-142 data for the Acasta Gneiss Complex (AGC; Northwest Territories, Canada). Our Sm-147-Nd-143 data combined with literature data define an age of 3371 +/- 141 Ma (2 SD) and yield an initial epsilon Nd-143 of -5.6 +/- 2.1. These results are at odds with the Acasta zircon U-Pb record, which comprises emplacement ages of 3920-3960 Ma. Ten of our thirteen samples show Nd-142 deficits of -9.6 +/- 4.8 ppm (2 SD) relative to the modern Earth. The discrepancy between Nd-142 anomalies and a mid-Archean Sm-147-Nd-143 age can be reconciled with Nd isotope reequilibration of the AGC during metamorphic perturbations at ca. 3400 Ma. A model age of ca. 4310 Ma is derived for the early enrichment of the Acasta source. Two compositional end-members can be identified: a felsic component with Nd-142/Nd-144 identical to the modern Earth and a mafic component with Nd-142/Nd-144 as low as -14.1 ppm. The ca. 4310 Ma AGC source is similar to 200 Myr younger than those estimated for Nuvvuagittuq (northern Quebec) and Isua (Itsaq Gneiss Complex, West Greenland). The AGC does not have the same decoupled Nd-Hf isotope systematics as these other two terranes, which have been attributed to the crystallization of an early magma ocean. The Acasta signature rather is ascribed to the formation of Hadean crust that was preserved for several hundred Myr. Its longevity can be linked to Nd-142 evolution in the mantle and does not require slow mantle stirring times nor modification of its convective mode.

Published
2014
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7. On the predictability limit of convection models of the Earth's mantle

Author

Paul J. Tackley, Tobias Rolf, Nicolas Coltice, Léa Bello, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Institut Universitaire de France, Ecole Normale Supérieure de Lyon, European Research Council within the framework of the SP2-Ideas Program ERC-2013-CoG, un- der ERC Grant agreement number 617588, European Project: 617588,EC:FP7:ERC,ERC-2013-CoG,AUGURY(2014), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Convection, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Chaotic, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Geophysics, Rayleigh number, Mantle (geology), Physics::Geophysics, Lyapunov time, Mantle convection, 13. Climate action, Geochemistry and Petrology, Astrophysics::Solar and Stellar Astrophysics, Hindcast, Astrophysics::Earth and Planetary Astrophysics, Predictability, Physics::Atmospheric and Oceanic Physics, Geology
Abstract

International audience; Reconstructing convective flow in the Earth's mantle is a crucial issue for a diversity of disciplines, from seismology to sedimentology. The common and fundamental limitation of these reconstructions based on geodynamic modelling is the unknown initial conditions. Because of the chaotic nature of convection in the Earth's mantle, errors in initial conditions grow exponentially with time and limit forecasting and hindcasting abilities. In this work we estimate for the first time the limit of predictability of Earth's mantle convection. Following the twin experiment method, we compute the Lyapunov time (i.e. e-folding time) for state-of-the art 3D spherical convection models, varying rheology and Rayleigh number. Our most Earth-like and optimistic solution gives a Lyapunov time of 136±13 My. Rough estimates of the uncertainties in best guessed initial conditions are around 5%, leading to a limit of predictability for mantle convection of 95 My. Our results suggest that error growth could produce unrealistic convective structures over timescales shorter than that of Pangea dispersal.

Published
2014
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