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At least 199 records · Page 11

Titanium and chromium isotopic compositions of calcium-aluminum-rich inclusions: Implications for the sources of isotopic anomalies and the formation of distinct isotopic reservoirs in the early Solar System

As the earliest-dated solids in our Solar System, calcium-aluminum-rich inclusions (CAIs) provide a record of their formation environment near the young Sun and hold clues to the formation of planetary-scale isotopic reservoirs in the solar protoplanetary disk. Although CAIs from several CV, CK, CM, CO, and ordinary chondrites have been analyzed previously for their Ti isotopic compositions, CAIs from just three CV chondrites have been analyzed for their Cr isotopic compositions, and only a handful of CAIs have been measured for both their Ti and Cr isotopic compositions. We report mass-independent Ti and Cr isotopic anomalies in several CAIs from CV and CK chondrites; this is the first report of the Cr isotopic composition of a CAI from a CK chondrite. With this data, we aim to better constrain the compositional range of CAIs in ε 50 Ti versus ε 54 Cr space, thereby facilitating the isotopic characterization of the material inherited by the solar protoplanetary disk and the role of CAIs in the formation of distinct planetary-scale isotopic reservoirs in our early Solar System. The narrow range in isotopic anomalies in CAIs when compared to other early-formed refractory inclusions such as platy hibonite crystals (PLACs) and spinel-hibonite inclusions (SHIBs) suggests that CAIs record the mixing of these precursor materials and the averaging of their larger isotopic anomalies. The isotopic composition of CAIs is therefore likely the result of a combination of factors, including mixing of material inherited from their formation region, heterogeneous carrier phase distribution, and thermal processing in the disk. The ε 50 Ti and ε 54 Cr isotopic compositions of CAIs are not correlated, further demonstrating that these isotopic anomalies have different carrier phases. The Ti and Cr isotopic compositions of CAIs additionally show that CAIs alone cannot be responsible for the compositional difference between the non-carbonaceous chondritic (NC) and carbonaceous chondritic (CC) isotopic reservoirs but nevertheless do play a role in the formation of these large-scale isotopic reservoirs in the early Solar System.

58 GEOSCIENCES↗

Cosmogony as an extrapolation of magnetospheric research

A theory of the origin and evolution of the Solar System which considered electromagnetic forces and plasma effects is revised in light of information supplied by space research. In situ measurements in the magnetospheres and solar wind can be extrapolated outwards in space, to interstellar clouds, and backwards in time, to the formation of the solar system. The first extrapolation leads to a revision of cloud properties essential for the early phases in the formation of stars and solar nebulae. The latter extrapolation facilitates analysis of the cosmogonic processes by extrapolation of magnetospheric phenomena. Pioneer-Voyager observations of the Saturnian rings indicate that essential parts of their structure are fossils from cosmogonic times. By using detailed information from these space missions, it is possible to reconstruct events 4 to 5 billion years ago with an accuracy of a few percent.

Alfven, H.↗

Cosmogony as an extrapolation of magnetospheric research

A theory of the origin and evolution of the Solar System which considered electromagnetic forces and plasma effects is revised in light of information supplied by space research. In situ measurements in the magnetospheres and solar wind can be extrapolated outwards in space, to interstellar clouds, and backwards in time, to the formation of the solar system. The first extrapolation leads to a revision of cloud properties essential for the early phases in the formation of stars and solar nebulae. The latter extrapolation facilitates analysis of the cosmogonic processes by extrapolation of magnetospheric phenomena. Pioneer-Voyager observations of the Saturnian rings indicate that essential parts of their structure are fossils from cosmogonic times. By using detailed information from these space missions, it is possible to reconstruct events 4 to 5 billion years ago with an accuracy of a few percent.

Alfven, H.↗

Conference on Protostars and Planets, University of Arizona, Tucson, Ariz., January 3-7, 1978, Proceedings

These papers deal with star formation, the origin of the solar system, and the possible formation of planets associated with other stars. Specific topics include chemical and isotopic anomalies in meteorites, laboratory analogs of interstellar dust, properties of dark globules, locations of newly formed stars in molecular clouds, O-star formation, observations of star-formation regions near supernova remnant W44, and equilibrium condensation of supernova ejecta. Other contributions discuss radio observations of molecular clouds associated with T Tauri stars, rotational velocities of pre-main-sequence stars, observational studies of star formation, characteristics of a possible preplanetary disk around the pre-main-sequence star MWC 349, calculations of the collapse of a rotating dusty protostellar cloud, a theory on the dynamics of dust particles in an incompressible turbulent fluid, and an analysis of the dynamical collapse of a model presolar nebula.

Gehrels, T.↗

The Vapor Pressure of Palladium at Temperatures up to 1973K

Understanding high-temperature processes is imperative for modeling the formation of the solar system. It is unfortunate that since the 1950 s little has been done in the area of thermodynamics to continue gaining information on metals such as iron (Fe), nickel (Ni), cobalt (Co), palladium (Pd) and many others. Although the vapor pressures of these metals can be extrapolated to higher temperatures, the data is often limited to temperature ranges too low to be applicable to processes that occur during the formation of the solar system (T approx. 2000K). Experimental techniques inhibited the data in the past by restricting the testing of metals to temperatures below their melting point. Today, higher temperature testing is possible by using a Thermo- Cahn Thermogravimetric system that is able to reach temperatures up to 1973K in vacuo and measure a 10 gram change in a sample with mass of up to 100 grams.

Gardner, K. G.↗

Amino Acid Chemistry as a Link Between Small Solar System Bodies and Carbonaceous Chondrites

Establishing chemical links between meteorites and small solar system bodies, such as comets and asteroids, provides a tool for investigating the processes that occurred during the formation of the solar system. Carbonaceous meteorites are of particular interest, since they may have seeded the early Earth with a variety of prebiotic organic compounds including amino acids, purines and pyrimidines, which are thought to be necessary for the origin of life. Here we report the results of high-performance liquid chromatography (HPLC) based amino acid analyses of the acid-hydrolyzed hot water extracts from pristine interior pieces of the CI carbonaceous chondrites Orgueil and Ivuna and the CM meteorites Murchison and Murray. We found that the CI meteorites Orgueil and Ivuna contained high abundances of beta-alanine and glycine, while only traces of other amino acids like alanine, alpha-amino-n-butryic acid (ABA) and alpha-aminoisobutyric acid (AIB) were detected in these meteorites. Carbon isotopic measurements of beta-alanine and glycine in Orgueil by gas chromatography combustion-isotope ratio mass spectrometry clearly indicate an extraterrestrial origin of these amino acids. The amino acid composition of Orgueil and Ivuna was strikingly different from the CM chondrites Murchison and Murray. The most notable difference was the high relative abundance of B-alanine in Orgueil and Ivuna compared to Murchison and Murray. Furthermore, AIB, which is one of the most abundant amino acids found in Murchison and Murray, was present in only trace amounts in Orgueil and Ivuna. Our amino acid data strongly suggest that the CI meteorites Orgueil and Ivuna came from a different type of parent body than the CM meteorites Murchison and Murray, possibly from an extinct comet. It is generally thought that carbonaceous meteorites are fragments of larger asteroidal bodies delivered via near Earth objects (NEO). Orbital and dynamic studies suggest that both fragments of main belt asteroids and comets replenish the NEO population, therefore extinct comets may contribute up to half of all NEO's. A comparison of an amino acid analysis of a returned NEO sample to CI and CM carbonaceous chondrites would help establish a link between small solar system bodies and meteorites. Based on our amino acid measurements of CI and CM chondrites, amino acid chemistry can be included as an additional set of criteria to constrain the nature of meteorite parent bodies.

Glavin, Daniel P.↗

Interstellar silicon carbide - How much older than the solar system?

The SiC grains in C2 chondrites have large isotopic anomalies in Si, C, N, Ne, and Xe, and thus are virtually undegraded interstellar matter that survived formation of the solar system. They also contain excess Ne-21, of which only a minor part can have formed during the recent, 1 Myr cosmic-ray exposure of the meteorite. If the excess Ne-21 is cosmogenic, then the presolar exposure age of the SiC is 41 + 20 or - 14 Myr. This age is surprisingly short compared to the predicted lifetime of refractory interstellar grains, 500-1000 Myr. Possible explanations are: (1) the predicted grain lifetime is wrong, (2) the age of SiC has been falsified by neon losses, or (3) the solar system formed in part from atypically young material.

Ming, Tang↗

Early Solar System Alkali Fractionation Events Recorded by K-Ca Isotopes in the Yamato-74442 LL-Chondritic Breccia

Radiogenic ingrowth of Ca-40 due to decay of K-40 occurred early in the solar system history causing the Ca-40 abundance to vary within different early-former reservoirs. Marshall and DePaolo ] demonstrated that the K-40/Ca-40 decay system could be a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [3,4] determined 40K/40Ca ages of lunar granitic rock fragments and discussed the chemical characteristics of their source materials. Recently, Yokoyama et al. [5] showed the application of the K-40/Ca-40 chronometer for high K/Ca materials in ordinary chondrites (OCs). High-precision calcium isotopic data are needed to constrain mixing processes among early solar system materials and the time of planetesimal formation. To better constrain the solar system calcium isotopic compositions among astromaterials, we have determined the calcium isotopic compositions of OCs and an angrite. We further estimated a source K/Ca ratio for alkali-rich fragments in a chondritic breccia using the estimated solar system initial Ca-40/Ca-44.

Tatsunori, T.↗

Proceedings of Protostars and Planets V

Oral presentation sessions in this conference include: Clouds and cores; Star formation and protostars; Binaries and multiples; Newborn massive stars; jets and outflows; Clusters and associations; T Tauri stars and disks; Brown dwarfs; Planet formation and evolution; Extrasolar planets; Dust and protoplanetary disks; Early solar system and Astrobiology. Poster presentations included: Clouds and Cores. Collapse and Protostars, Binaries and Multiples, Clusters, Associations, and the IMF, Jets and Outflows, T Tauri Stars and Other Young Stars, Disks and Disk Accretion, Brown Dwarfs, Herbig Ae/Be Stars and Massive Stars, Solar System Objects, Planet Formation, Extrasolar Planets and Planet Detection, Properties of Protoplanetary Disks, Migration and Planetary Orbits and Meteoritics and Astrobiology

Source record↗

The Non-carbonaceous–Carbonaceous Meteorite Dichotomy

The isotopic dichotomy between non-carbonaceous (NC) and carbonaceous (CC) meteorites indicates that meteorite parent bodies derive from two genetically distinct reservoirs, which presumably were located inside (NC) and outside (CC) the orbit of Jupiter and remained isolated from each other for the first few million years of the solar system. Here we review the discovery of the NC–CC dichotomy and its implications for understanding the early history of the solar system, including the formation of Jupiter, the dynamics of terrestrial planet formation, and the origin and nature of Earth’s building blocks. The isotopic difference between the NC and CC reservoirs is probably inherited from the solar system’s parental molecular cloud and has been maintained through the rapid formation of Jupiter that prevented significant exchange of material from inside (NC) and outside (CC) its orbit. The growth and/or migration of Jupiter resulted in inward scattering of CC bodies, which accounts for the co-occurrence of NC and CC bodies in the present-day asteroid belt and the delivery of presumably volatile-rich CC bodies to the growing terrestrial planets. Earth’s primitive mantle, at least for siderophile elements like Mo, has a mixed NC–CC composition, indicating that Earth accreted CC bodies during the final stages of its growth, perhaps through the Moon-forming giant impactor. The late-stage accretion of CC bodies to Earth is sufficient to account for the entire budget of Earth’s water and highly volatile species.

58 GEOSCIENCES↗

Turbulent transport in the solar nebula

It is likely that turbulence played a major role in the evolution of the solar nebula, which is the flattened disk of dust and gas out of which our solar system formed. Relevant turbulent processes include the transport of angular momentum, mass, and heat, which were critically important to the formation of the solar system. This research will break ground in the modeling of compressible turbulence and its effects on the evolution of the solar nebula. The computational techniques which were developed should be of interest to researchers studying other astrophysical disk systems (e.g., active galactic nuclei), as well as turbulence modelers outside the astrophysics community.

Thompson, Kevin W.↗

What does the fine-scale petrography of IDPs reveal about grain formation and evolution in the early solar system?

The 'pyroxene' interplanetary dust particles (IDP's) may be the best samples for investigation of primordial grain-forming reactions because they appear to have experienced negligible post-accretional alteration. They are likely to continue to yield information about gas-to-solid condensation and other grain-forming reactions that may have occurred either in the solar nebular or presolar interstellar environments. An immediate challenge lies in understanding the nanometer-scale petrography of the ultrafine-grained aggregates in 'pyroxene' IDP's. Whether these aggregates contain components from diverse grain-forming environments may ultimately be answered by systematic petrographic studies using electron microscopes capable of high spatial resolution microanalysis. It may be more difficult to decipher evidence of grain formation and evolution in 'olivine' and 'layer silicate' IDP's because they appear to have experienced post-accretional alteration. Most of the studied 'olivine' IDPs have been subjected to heating and equilibration, perhaps during atmospheric entry, while the 'layer silicate' IDP's have experienced aqueous alteration.

Bradley, John↗

Triple F - A Comet Nucleus Sample Return Mission

The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA s Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three samples of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-and-go sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.

Kueppers, Michael↗

Triple F - A Comet Nucleus Sample Return Mission

The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA's Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three sample cores of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-andgo sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.

Kueppers, Michael↗

Aluminum-26 in the early solar system - Fossil or fuel

The isotopic composition of Mg was measured in different phases of a Ca-Al-rich inclusion in the Allende meteorite. Large excesses of Mg-26 of up to 10% were found. These excesses correlate strictly with the Al-27/Mg-24 ratio for four coexisting phases with distinctive chemical compositions. Models of in situ decay of Al-26 within the solar system and of mixing of interstellar dust grains containing fossil Al-26 with normal solar system material are presented. The observed correlation provides definitive evidence for the presence of Al-26 in the early solar system. This requires either injection of freshly synthesized nucleosynthetic material into the solar system immediately before condensation and planet formation, or local production within the solar system by intense activity of the early sun. Planets promptly produced from material with the inferred Al-26/Al-27 would melt within about 300,000 years.

Lee, T.↗

15N Fractionation in Star-Forming Regions and Solar System Objects

A central issue for understanding the formation and evolution of matter in the early Solar System is the relationship between the chemical composition of star-forming interstellar clouds and that of primitive Solar System materials. The pristinemolecular content of comets, interplanetary dust particles and carbonaceous chondrites show significant bulk nitrogen isotopic fractionation relative to the solar value, 14N15N 440. In addition, high spatial resolution measurements in primitive materials locally show even more extreme enhancements of 14N15N 100.

pristine molecular content↗