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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

The Violent Early Solar System, as Told by Lunar Sample Geochronology

One of the legacies of the samples collected by the Apollo and Luna missions is the link forged between radiometric ages of rocks and relative ages according to stratigraphic relationships and impact crater size-frequency distributions. Our current understanding of the history of the inner solar system is based on the relative chronology of individual planets, tied to the absolute geochronology of the Moon via these important samples. Samples from these nearside locations reveal a preponderance of impact-disturbed or recrystallized ages between 3.75 and 3.95 billion years. Argon and lead loss (and correlated disturbances in the Rb-Sr system) have been attributed to metamorphism of the lunar crust by an enormous number of impacts in a brief pulse of time, called the Lunar Cataclysm or Late Heavy Bombardment. Subsequent high-precision geochronometric analyses of Apollo samples and lunar highlands meteorites show a wider range of ages, but very few older than 4 Ga. The paucity of ancient impact melt rocks has been interpreted to mean that either that most impact basins formed at this time, or that ejecta from the large, near-side, young basins dominates the Apollo samples. Selenochronology is getting more complicated: new results question meaning of sample ages, crater counts, crater production functions, and the solar system itself. Improved geological mapping of lunar geologic units and boundaries using multiple remote sensing datasets. High-resolution image-based crater counting of discrete geologic units and relating them to location. Improved understanding of the regolith thickness and its global variation (GRAIL). Tying the sampling of impact-melt rocks to the lunar impact flux. Using improved techniques (magnetic fields, diffusion studies, isotopic analysis) on existing samples. New sample return from benchmark craters, particularly SPA, which appears in 2013 Decadal Survey.

Cohen, Barbara↗
NASA NTRS2013

Corundum-Hibonite Inclusions and the Environments of High Temperature Processing in the Early Solar System

Calcium, Aluminum-rich inclusions (CAIs) are composed of the suite of minerals predicted to be the first to condense from a cooling gas of solar composition [1]. Yet, the first phase to condense, corundum, is rare in CAIs, having mostly reacted to form hibonite followed by other phases at lower temperatures. Many CAIs show evidence of complex post-formational histories, including condensation, evaporation, and melting [e.g. 2, 3]. However, the nature of these thermal events and the nebular environments in which they took place are poorly constrained. Some corundum and corundum-hibonite grains appear to have survived or avoided these complex CAI reprocessing events. Such ultra-refractory CAIs may provide a clearer record of the O isotopic composition of the Sun and the evolution of the O isotopic composition of the planet-forming region [4-6]. Here we present in situ O and Mg isotopic analyses of two corundum/hibonite inclusions that record differing formation histories.

Needham, A. W.↗
NASA NTRS2013

The Violent Early Solar System, as Told by Sample Geochronology

One of the legacies of the samples collected by the Apollo and Luna missions is the link forged between radiometric ages of rocks and relative ages according to stratigraphic relationships and impact crater size-frequency distributions. Our current understanding of the history of the inner solar system is based on the relative chronology of individual planets, tied to the absolute geochronology of the Moon via these important samples. Sample ages have enabled us to infer that impact-melt breccias from Apollo 14 and 15 record the formation of the Imbrium Basin, those from the highland massifs at Apollo 17 record the age of Serenitatis, those from the KREEP-poor Apollo 16 site record the age of Nectaris, and materials from Luna 24 record the age of Crisium. Ejecta from smaller and younger craters Copernicus and Tycho were sampled at Apollo 12 and 17, respectively, and local craters such as Cone at Apollo 14, and North Ray and South Ray at Apollo 16 were also sampled and ages determined for those events. Much of what we understand about the lunar impact flux is based on these ages. Samples from these nearside locations reveal a preponderance of impact-disturbed or recrystallized ages between 3.75 and 3.95 billion years. Argon and lead loss (and correlated disturbances in the Rb-Sr system) have been attributed to metamorphism of the lunar crust by an enormous number of impacts in a brief pulse of time, called the Lunar Cataclysm or Late Heavy Bombardment. Subsequent high-precision geochronometric analyses of Apollo samples and lunar highlands meteorites show a wider range of ages, but very few older than 4 Ga. The paucity of ancient impact melt rocks has been interpreted to mean that either that most impact basins formed at this time, or that ejecta from the large, near-side, young basins dominates the Apollo samples.

Cohen, Barbara↗
NASA NTRS2013

Early Solar System Cryovolcanics in the Laboratory

Two thermally-metamorphosed ordinary chondrite regolith breccias, Monahans 1998 (H5) and Zag (H3-6) contain fluid inclusion-bearing halite (NaCl) crystals, dated by K-Ar, Rb-Sr and I-Xe systematics to be approx. 4.5 billion years old. Heating/freezing studies of the aqueous fluid inclusions demonstrated that they were trapped near 25 C, and their continued presence in the halite grains requires that their incorporation into the H chondrite asteroid was post metamorphism.

Zolensky, M.↗
NASA NTRS2015

Assemblage of Presolar Materials and Early Solar System Condensates in Chondritic Porous Interplanetary Dust Particles

Anhydrous chondritic porous inter-planetary dust particles (CP IDPs) contain an assortment of highly primitive solar system components, molecular cloud matter, and presolar grains. These IDPs have largely escaped parent body processing that has affected meteorites, advocating cometary origins. Though the stardust abundance in CP IDPs is generally greater than in primitive meteorites, it can vary widely among individual CP IDPs. The average abundance of silicate stardust among isotopically primitive IDPs is approx. 375 ppm while some have extreme abundances up to approx. 1.5%. H and N isotopic anomalies are common in CP IDPs and the carrier of these anomalies has been traced to organic matter that has experienced chemical reactions in cold molecular clouds or the outer protosolar disk. Significant variations in these anomalies may reflect different degrees of nebular processing. Refractory inclusions are commonly observed in carbonaceous chondrites. These inclusions are among the first solar system condensates and display 16O-rich isotopic compositions. Refractory grains have also been observed in the comet 81P/Wild-2 samples re-turned from the Stardust Mission and in CP IDPs, but they occur with much less frequency. Here we conduct coordinated mineralogical and isotopic analyses of CP IDPs that were characterized for their bulk chemistry by to study the distribution of primitive components and the degree of nebular alteration incurred.

Nguyen, A. N.↗
NASA NTRS2017

Utilizing Stable Isotopes and Isotopic Anomalies to Study Early Solar System Formation Processes

Chondritic meteorites contain a diversity of particle components, i.e., chondrules and calcium-, aluminum-rich refractory inclusions (CAIs), that have survived since the formation of the Solar System. The chemical and isotopic compositions of these materials provide a record of the conditions present in the protoplanetary disk where they formed and can aid our understanding of the processes and reservoirs in which solids formed in the solar nebula, an important step leading to the accretion of planetesimals. Isotopic anomalies associated with nucleosynthetic processes are observed in these discrete materials, and can be compared to astronomical observations and astrophysical formation models of stars and more recently proplyds. The existence and size of these isotopic anomalies are typically thought to reflect a significant state of isotopic heterogeneity in the earliest Solar System, likely left over from molecular cloud heterogeneities on the grain scale, but some could also be due to late stellar injection. The homogenization of these isotopic anomalies towards planetary values can be used to track the efficiency and timescales of disk wide mixing,

Simon, Justin↗
NASA NTRS2018

Fluid Inclusions in Astromaterials: Direct Samples of Early Solar System Aqueous Fluids

We have become increasingly aware of the fundamental importance of water, and aqueous alteration, on primitive solar-system bodies. All classes of astromaterials studied show some degree of interaction with aqueous fluids. We have direct observations of cryovolcanism of several small solar system bodies (e.g. Saturnian and Jovian moons), and indirect evidence for this process on the moons Europa, Titan, Ganymede, and Miranda, and the Kuiper Belt object Charon, and so are certain of the continuing and widespread importance of aqueous processes across the solar system. Nevertheless, we are still lacking fundamental information such as the location and timing of the aqueous alteration and the detailed nature of the aqueous fluid itself.

Zolensky, Michael↗
NASA NTRSDate not supplied

Ryugu and the Quest for Unaltered CI-Like Materials From the Early Solar System

Samples of C-type asteroid (162173) Ryugu returned by the Hayabusa2 mission of JAXA [1-3] have been found to be mineralogically, chemically, and isotopically similar to CI carbonaceous chondrites [3-6]. The rare CI meteorites have bulk chemical compositions closely matching the solar photosphere in all but the most volatile elements, and so are considered to represent the starting composition of the solar system. Paradoxically, however, all known CI have been extensively altered by aqueous fluids (i.e., they are CI1), so that their primary mineralogy, textures, and oxygen isotope compositions have been obscured. Thus, one of the most exciting discoveries from Ryugu samples is that they contain “less-altered” (CI2) areas, which have substantial abundances of anhydrous silicates (olivine and pyroxene) and Ca-Al-rich phases that may be remnants of primordial CI3 materials [4-11]. This discovery has motivated new investigations of CIs that show higher abundances of anhydrous silicate grains than previously recognized [9,12,13]. Such studies are an important step in the search for unaltered CI-like material, a so-called “holy grail” of meteoriticists [14]. To further this goal, we are studying Ryugu samples in the context of a previously unrecognized, potentially Ryugu-like, population of C2 materials that occur as xenoliths in polymict ureilites.

C A Goodrich↗
NASA NTRS2024

Distribution of -92 Nb in the Early Solar System

Constraining the initial abundances of short-lived radionuclides in planetary materials helps determine the spatial and temporal distribution of interstellar material added during the initial stages of Solar System formation.

short-lived chronometer↗
NASA NTRSDate not supplied

New Directions in the Quest for Unaltered Ci-Like Material From the Early Solar System

CI meteorites have bulk chemical compositions closely matching the solar photosphere (except volatiles) and thus are considered to represent the starting composition of the Solar System. The return of CI-like samples from asteroid (162173) Ryugu by Hayabusa2 has greatly bolstered studies of CI. However, both CI and the Ryugu samples are CI1, i.e., they were extensively altered by aqueous fluids on their parent bodies so the mineralogy, textures, and oxygen isotope compositions of their CI3 precursors have been obscured. Fortunately, they contain rare remnants of primordial minerals in the form of small anhydrous silicate and Ca-Al-rich grains, and detailed petrologic and isotopic studies of these grains have helped elucidate the nature of their precursors. Here, we continue our work on petrologic and isotopic studies of such phases in Ryugu particle C0137.

C A Goodrich↗
DOE OSTI2021

Isotopic signatures as tools to reconstruct the primordial architecture of the Solar System

The significant reorganization of the early Solar System due to giant planet migration has hampered our understanding of where planetary bodies formed. Previously employed proxies for reconstructing the primordial planetary architecture, such as water content or oxidation state, are complicated by post-accretionary processes. Furthermore we investigate basaltic achondrites for their nucleosynthetic isotope signatures in the elements neodymium (Nd) and zirconium (Zr) and show that they are—similar to previously investigated chondritic meteorites—characterized by a relative deficit in isotopes produced by the s-process of nucleosynthesis. Importantly, these data are well correlated with nucleosynthetic signatures observed in other elements, demonstrating that s-process matter was heterogeneously distributed throughout the early Solar System. By comparing these isotopic signatures with potential proxies for Solar System reconstruction and computer modeling, we here argue that this isotopic heterogeneity in bulk meteoritic materials is linked to the original heliocentric distance of formation. Such scaling of nucleosynthetic signatures with heliocentric distance could permit reconstruction of the primordial architecture of the Solar System by ‘cosmolocating’ the accretion orbits of meteoritic parent bodies as a function of incorporated s-process matter.

58 GEOSCIENCES↗
NASA NTRS2004

Chondrites and the Protoplanetary Disk, Part 1

The papers discussed the following: The Formation Process of Adhering and Consorting Compound Chondrules Inferred Their Petrology and Major-Element Composition. The Prospect of High-Precision Pb Isotopic Dating of Meteorites. Evolution of UV-Irradiated Protoplanetary Disks. A Model for the Formation of E Chondrites. Oxygen Isotopic Diffusion and Exchange Experiments on Olivine and Chondrule Melts: Preliminary Results. Shock Heating: Origin of Shock Waves in the Protoplanetary Disk. Thermal Structures of Protoplanetary Disks. Meteoritical Astrophysics: A New Subdiscipline. Origin and Thermal History of FeNi-Metal in Primitive Chondrites. The Collisions of Chondrules Behind Shock Waves. Primary Signatures of the Nebular Dust Preserved in Accretionary Rims and Matrices of CV Chondrites. History of Thermally Processed Solids in the Protoplanetary Disk: Reconciling Theoretical Models and Meteoritical. Evidence Evaporation and Condensation During CAI and Chondrule Formation. Shock Heating: Effects on Chondritic Material. Rhounite-bearing Inclusions E201 and E202 from Efremovka: Constraints from Trace. Element Measurements Element Mapping in Anhydrous IDPs: Identification of the Host Phases of Major/Minor Elements as a Test of Nebula Condensation Models. Theoretical Studies of Disk Evolution Around Solar Mass Stars. Chemical Effects of High-Temperature Processing of Silicates. I-Xe and the Chronology of the Early Solar System. The Effects of X-Rays on the Gas and Dust in Young Stellar Objects. Origin of Short-lived Radionuclides in the Early Solar System. On Early Solar System Chronology: Implications of an Initially Heterogeneous Distribution of Short-lived Radionuclides. The Origin of Short-lived Radionuclides and Early Solar System Irradiation. Disequilibrium Melting and Oxygen Isotope Exchange of CAIs and Chondrules in the Solar Nebula. Mineralogy and Chemistry of Fine-grained Matrices, Rims, and Dark Inclusions in the CR Carbonaceous Chondrites Acfer/El Djouf 001 and the Ungrouped Carbonaceous Chondrites Acfer 094 and Adelaide. Oxygen Isotopes of Aluminum-rich Chondrules from Unequilibrated Enstatite Chondrites.

Source record↗
DOE OSTI2026

Chronology of ungrouped achondrites Northwest Africa 11119 and 7325/8486: implications for early evolution of a heterogeneous crust on a differentiated planetesimal

The chronology of ungrouped achondrites provides key insights into the timeline of igneous activity in the early Solar System. Two ungrouped achondrites – Northwest Africa (NWA) 11119 (andesite-dacite) and NWA 8486 and its pair NWA 7325 (olivine gabbro) – are the focus of this study, where their chronologies are investigated using multiple high-resolution techniques. Here we report the lead-lead (207Pb-206Pb) and manganese-chromium (53Mn-53Cr) systematics of NWA 11119, as well as the 207Pb-206Pb systematics of NWA 8486 alongside aluminum-magnesium (26Al-26Mg) systematics for NWA 7325. The U-corrected 207Pb-206Pb ages of NWA 11119 and the combined ages of NWA 7325/8486 are 4566.4 ± 0.8 Ma and 4563.8 ± 1.9 Ma, respectively. Additionally, we report the 53Mn-53Cr age of NWA 11119 to be 4564.4 ± 2.5 Ma and the 26Al-26Mg age of NWA 7325/8486 to be 4563.1 ± 0.3 Ma. The formation of NWA 11119 requires partial melting of a (likely chondritic) source reservoir leading to eruption of Si rich, alkali depleted magmas, while NWA 7325/8486 likely formed from a chemically fractionated reservoir with superchondritic Al/Mg. The clear geochemical and isotopic similarities of these achondrites, combined with the chronology reported here, is suggestive of formation of these two ungrouped achondrites on a common parent body which likely formed in the inner Solar System and experienced early differentiation under reducing conditions. If these achondrites did share a parent body, it would suggest that primary asteroids in the early Solar System commonly produced mineralogically and geochemically heterogeneous crusts. While mineralogical and geochemical heterogeneity is known to exist in the (mostly mafic) crust of asteroid Vesta, our findings show that even more significant crustal heterogeneity (representing felsic and mafic compositions) may exist on other asteroids.

Cartwright, Julia [University of Leicester, UK]↗