Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “early Solar System”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Characterization Of Early Solar System Aqueous Fluids

The most direct and convincing evidence for the presence of water and organic molecules on protoplanetary bodies is provided by fluid inclusions trapped in secondary minerals. Our research has demonstrated that early solar system fluids have survived as fluid inclusions in a few astromaterials that escaped significant shock, terrestrial alteration, and invasive sample handling. Our long-term goal is to measure bulk molecular and isotopic composition of individual fluid inclusions in meteorites and samples collected directly from asteroids to provide ground truth regarding the nature and evolution of aqueous fluids in the early solar system. Our current protocol is to locate candidate fluid inclusions using X-Ray Computed Tomography, and then make compositional measurements of individual fluid inclusions by coordinated Raman spectrometry, Transmission Electron Microscopy and, most recently, Time of Flight – Secondary Ion Mass Spectrometry.

Michael Zolensky↗
DOE OSTI2020

Carbon isotope evidence for the substrates and mechanisms of prebiotic synthesis in the early solar system

Meteorites contain prebiotic, bio-relevant organic compounds including amino acids. Their syntheses could result from diverse sources and mechanisms and provide a window on the conditions and materials present in the early solar system. Here we constrain alanine’s synthetic history in the Murchison meteorite using site-specific 13 C/ 12 C measurements, reported relative to the VPDB standard. The δ 13 C VPDB values of -29 ± 10‰, 142 ± 20‰, and -36 ± 20‰ for the carboxyl, amine-bound, and methyl carbons, respectively, are consistent with Strecker synthesis of interstellar-medium-derived aldehydes, ammonia, and low-δ 13 C nebular or interstellar-medium-derived CN. We report experimentally measured isotope effects associated with Strecker synthesis, and use them to constrain the δ 13 C values of the alanine precursors, which we then use to construct a model that predicts the molecular-average δ 13 C values of 19 other organic compounds of prebiotic significance found in Murchison if they were made by our proposed synthetic network. Finally, most of these predictions agree with previous measurements, suggesting that interstellar-medium-derived aldehydes and nebular and/or pre-solar CN could have served as substrates for synthesis of a wide range of prebiotic compounds in the early solar system.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1983

Hf chronometer for the early solar system

It is now widely believed that Al-26 (half-life, 7.2 x 10 to the 5th yr) and Pd-107 (half-life, 6.5 x 10 to the 6th yr) were present in the early solar system. The nucleosynthetic event responsible for the production of these nuclei must therefore have occurred no more than a few million years before the formation of solid bodies. It is possible that this event also gave a rise to the I-129 believed to be present in the early solar system. The last event to contribute Pu-244 to the solar system, however, occurred approximately 10 to the 8th yr before the time of solidification. It is noted that this latter time scale is also consistent with the lack of evidence for a Cm-247 chronometer. It is proposed that Hf-182 (half-life, 9 x 10 to the 6th yr) can resolve the question whether heavy-element nonactinide nucleosynthesis occurred during the (Al-26)-producing event. It is believed that an answer to this question will help to clarify the chronology of the formation of the solar system and will help to determine the astrophysical sites of heavy-element nucleosynthesis.

Norman, E. B.↗
NASA NTRS2011

Evolution of Planetesimals Accreted in the Early Solar System

The purpose of this presentation is to point out that the origins and abundances of short-lived nu-clides in the early solar system had important conse-quences for "icy planetesimals". It is believed that these planetesimals, composed of ice and rock, were once very abundant in the early, outer solar system. Today, spacecraft can visit remnants of that popula-tion and measure their properties. Cassini's flyby of Saturn's satellite Phoebe may have been the first visit to an object related to this population.

Saturn satellites↗
NASA NTRS1985

Short-lived nuclides in the early solar system and general isotopic anomalies in meteorites

Evidence for short-lived nuclides in the early solar system is reviewed. The presence of these nuclides requires the addition to the interstellar medium, from which the solar system formed, of freshly synthesized materials just prior to the formation of the solar system. The best evidence is obtained for Al26. The time scale implied by the Al26 effects is equated with the free-fall time for the collapse of the protosolar cloud. From the observation of ratios of short-lived parent to stable isotopes for nuclides with different half-lives, it is apparent that addition of exotic material to the solar system occurred just prior to its formation. Evidence for a diffuse galactic gamma-ray line emission attributed to Al26 provides support for the existence of Al26 in the protosolar cloud. The time scale for isolation of the protosolar cloud would still be restricted on a timescale comparable to tau 1/2 (Al26).

Papanastassiou, D. A.↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Early Solar System Chronology

The titles in this section discuss: 1) Mg Isotopic Systematics in Eutectites; 2) Diffusion Kinetics of Cr in Olivine; 3) The W Isotope Composition of Eucrite Metals; 4) U-Pb and Hf-W Chronometry; 5) Fe-60 in Silicate from a Semarkona Chondrule; 6) The Isotope Geochemistry of Nickel in Chondrites and Iron Meteorites; 7) Iron-60 in the Early Solar System; 8) Endemic Mo Isotopic Anomalies in Iron and Carbonaceous Meteorites; 9) Solar System Iron and Tungsten Isotope Abundances; 10) Li and B Isotope Variations in CAI; 11) Short-lived Radionuclides and Early Solar System Irradiation; Ru Endemic Isotope Anomalies in Meteorites; 12) Cl-36 in Ca-Al rich inclusions from a carbonaceous chondrite.

Source record↗
NASA NTRS1974

The movement of small particulate matter in the early solar system and the formation of satellites

The motions of the abundant small particulate matter in the early solar system are discussed. The effects of gas drag and resonance effects of perturbing forces could have led to accretion and differentiation of the matter. The composition of the moon and the existence of the rings of Saturn can be explained on the basis of the assembly of small particulate matter in satellite orbits around the planets.

Gold, T.↗
NASA NTRS1993

Energetic particle environment in the early solar system - Extremely long pre-compaction meteoritic ages or an enhanced early particle flux

Individual mineral grains from meteorites have been exposed to energetic particles prior to inclusion in the host meteorite matrix, an event which occurred quite early in solar system history. Spallation-produced noble gases in such grains are observed to be orders of magnitude greater in abundance than could be produced after meteorite formation and thus provide a record of precompaction irradiation by energetic particles. If attributed to the contemporary particle environment (current galactic and solar cosmic rays) a minimum exposure time for these grains in the CM parent-body regolith of 150 Myr is obtained, with more realistic models suggesting an active parent body regolith for 300 Myr. Constraints on when meteorite compaction occurred and current models for meteorite evolution suggest that this is unreasonably long, that the time available for exposure to energetic particles on the surface of the parent-body regolith is much less than this. Pre-compaction exposure, compressed into a shorter span of time by constraints on the compaction times of carbonaceous meteorites, would require energetic particle fluxes in excess of those in the contemporary solar system and point toward an active early (T Tauri) sun as its source.

Woolum, Dorothy S.↗
NASA NTRS1973

Deuterium in the early solar system.

An attempt is made to construct a self-consistent picture of the deuterium abundance in the early solar system based on the assumption of chemical equilibrium in the solar nebula. A recent determination of the D/H ratio for the atmosphere of Jupiter is consistent with a previous estimate of the D/H ratio for the protosun. The high (greater than .00015) D/H ratios determined from analyses of carbonaceous meteorites imply an equilibrium temperature less than 270 K, in marked disagreement with the equilibrium temperature determined for the same material by oxygen isotope cosmothermometry.

Black, D. C.↗
NASA NTRS1993

Development of a molecular beam technique to study early solar system silicon reactions

Silicon monoxide is one of the major gas phase silicon bearing components observed in astronomical environments. Silicon oxide serves as the major rock forming material for terrestrial and meteoritic bodies. It is known that several gas phase reactions produce mass independent isotopic fractionations which possess the same delta(O-17)/delta(O-18) ratio observed in Allende inclusions. The general symmetry dependence of the chemically produced mass independent isotopic fractionation process suggests that there are several plausible reactions which could occur in the early solar system which may lead to production of the observed meteoritic oxygen isotopic anomalies. An important component in exploring the role of such processes is the need to experimentally determine the isotopic fractionations for specific reactions of relevance to the early solar system. It has already been demonstrated that atomic oxygen reaction with CO, a major nebular oxygen bearing species, produces a large (approximately 90 percent), mass independent isotopic fractionation. The next hurdle regarding assessing the involvement of symmetry dependent isotopic fractionation processes in the pre-solar nebula is to determine isotopic fractionation factors associated with gas phase reactions of metallic oxides. In particular, a reaction such as O + SiO yields SiO2 is a plausible nebular reaction which could produce a delta(O-17) is approximately delta(O-18) fractionation based upon molecular symmetry considerations. While the isotopic fractionations during silicate evaporation and condensation have been determined, there are no isotopic studies of controlled, gas phase nucleation processes. In order to carefully control the reaction kinetics, a molecular beam apparatus has been constructed. This system produces a supersonic, collimated beam of SiO molecules which is reacted with a second beam of oxygen atoms. An important feature of molecular beams is that they operate at sufficiently low pressures and high temperatures in the jet that avalanche nucleation and clustering processes may be avoided.

Dong, Q. W.↗
NASA NTRS1983

Samarium-146 in the early solar system - Evidence from neodymiun in the Allende meteorite

A carbon-chromite fraction from the Allende C3V chondrite shows strikingly large isotopic enrichments of neodymium-142 (0.47 percent) and neodymium-143 (36 percent). Both apparently formed by alpha decay of samarium-146 and samarium-147 (half-lives 1.03 x 10 to the 8th and 1.06 x 10 to the 11th years), but the isotopic enrichment was greatly magnified by recoil of residual nuclei into a carbon film surounding the samarium-bearing grains. These data provide an improved estimate of the original abundance of extinct samarium-146 in the early solar system, Sm-146/Sm-144 = (4.5 + or - 0.5) x 10 to the -3rd, higher than predicted by some models of p-process nucleosynthesis. It may be possible to use this isotopic pair as a chronometer of the early solar system.

Lugmair, G. W.↗
NASA NTRS1977

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.↗
NASA NTRS1985

Short-lived nuclei in the early solar system

An overview is given of the existence and abundance of short-lived nuclei that were present in the early solar system. It is shown that there are excesses of certain isotopes that may be assigned to the decay of short-lived radioactive nuclei corresponding to an abundance of about 0.0001 relative to a neighboring stable isotope. This abundance is roughly similar to the level of general nonlinear isotopic anomalies present in meteoritic material (excluding oxygen) which are not attributable to short-lived nuclei. If these results are representative of the bulk solar system, they indicate that about 0.0001 solar mass of freshly synthesized material of peculiar composition was added to the protosolar nebula as it was formed from the interstellar medium. This material must have been synthesized about three million yr before the formation of the solar system.

Wasserburg, G. J.↗
DOE OSTI2022

Absolute Decay Counting of $$^{146}$$Sm and $$^{147}$$Sm for Early Solar System Chronology

Sm-Nd chronometers use 146 Sm and 147 Sm to determine the ages of major events in the early Solar System. Their half-lives are the most important nuclear parameters deter mining the accuracy of chronometry. However, the 146 Sm half-life is not well-established: the published values differ by ~30%, which results in significant uncertainties in the So lar System timeline. We are re-measuring the half-lives of 146 Sm and 147 Sm using decay energy spectroscopy and metallic magnetic calorimeters to improve the accuracy of the Sm Nd chronometers. We report recent experimental results from our first measurement of a 147 Sm source, as well as status and plans for experiments on 146 Sm.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1977

Pre-mare cratering and early solar system history

An evaluation of the application of the high extralunar flux in pre-mare times to more general problems of early solar system history is attempted by combining the results of dynamic studies with lunar chronological data. There is a twofold to fourfold contrast in the integral impact flux between the Apollo 14 and 16 sites and the older mare surfaces. This is judged insufficient to account for the contrasting lithology between these two sites: basalts and soil breccias in the maria, annealed breccias and impact melts in the highlands. Therefore, these rocks and their ages (3.9-4.0 b.y.) are thought to predate the surfaces in which they are found. Estimation of the flux needed to produce these lithologies, and difficulties associated with extrapolating this further back in lunar history give support to the "cataclysm" hypothesis of Tera, Papanastassiou, and Wasserburg. Dynamical studies permit separate evaluation of the possible sources for both the "normal" flux during the first 600 million years of lunar history and the "peak" that apparently occurred 4.0 billion years ago. The most likely sources for the normal flux are comets from the vicinity of Uranus and Neptune. The most promising source for the peak is tidal disruption by Earth or Venus of a Ceres-size asteroid initially in a Mars-crossing orbit. Alternative possibilities are suggested.

Wetherill, G. W.↗
NASA NTRS2011

Progress in the Early Solar System Chronology: A Sketch of an Ever-Changing Landscape

The years since the Workshop on the Chronology of Meteorites and the Early Solar System, are marked with ongoing progress in cosmochronology. Rapid improvements in techniques, discovery of new meteorites unlike any previously known, and findings that what was deemed well established constants are actually variables, will be reflected in an updated review of the solar system chronology we are currently preparing. Along with updating the database of meteorite ages, it will involve development of a set of criteria for evaluation of accuracy and consistency of isotopic dates across the entire range of meteorite classes and isotope chronometer systems. Here we present some ideas on what we think is important in meteorite chronology, and invite the cosmochemistry community to discuss them.

Amelin, Yuri↗
NASA NTRSDate not supplied

Direct Analysis of Early Solar System Aqueous Fluids by TOF-SIMS

We lack fundamental information related to the location and timing of the aqueous alteration in the early solar system, and the detailed nature of the aqueous fluid itself [1,2,3]. Two thermally-metamorphosed ordinary chondrite regolith breccias (Monahans 1998, hereafter simply “Monahans” (H5) and Zag (H3-6)) contain fluid inclusion-bearing halite (NaCl) crystals [4,5]. The halites were dated by K-Ar, Rb-Sr and I-Xe systematics to be ~4.5 billion years old [4,6,7] and thus the trapped aqueous fluids are at least as ancient. Through previously-published O, H, Cr isotopic work we have established that the fluid-bearing halite originated in the outer solar system[8].

M Zolensky↗
NASA NTRS1974

Pre-mare cratering and early solar system history

An evaluation of the application of the high extra-lunar flux in pre-mare times to more general problems of early solar system history is attempted by combining the results of dynamic studies with lunar chronological data. Dynamical studies permit separate evaluation of the possible sources for both the normal flux during the first 600 m.y. years of lunar history as well as the peak which apparently occurred 4.0 b.y. ago. Dynamical studies have been carried out in order to determine the extent to which a heliocentric flux could be confined to the Moon (and Earth). A Monte Carlo method has been used to calculate the relative impact rates of planet-crossing bodies with the moon and the terrestrial planets. It is concluded that the time-variation of the flux on these planets is closely related to that on the moon.

Wetherill, G. W.↗