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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.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Chronology and Petrology of Silicates From IIE Iron Meteorites: Evidence of a Complex Parent Body Evolution

IIE iron meteorites contain silicate inclusions whose characteristics suggest a parent body similar to that of H-chondrites. However, these silicates show a wide range of alteration, ranging from Netschadvo and Techado, whose inclusions are little altered. to highly differentiated silicates like-those in Kodaikanal, Weekeroo Station and Colomera, which have lost metal and sulfur and are enriched in feldspar. We find these inclusions to show varying degrees of shock alteration. Because only a limited amount of data on - isotopic ages of HE silicates were available, we made Ar-39 - Ar-40 age determinations of Watson, Techado, miles Colomera, and Sombrerete. Watson has an Ar-Ar age of 3.653 +/- 0.012 Gyr, similar to previously reported ages for Kodaikanal and Netschadvo. We suggest that the various determined radiometric ages of these three meteorites were probably reset by a common impact event. The space exposure ages for these three meteorites are also similar to each other and are considerably younger than exposure ages of other IIEs. Ar-39 - Ar-40 ages inferred for the other four meteorites analyzed are considerably older than Watson and are: Techado =4.49 +/- 0.01 Gyr, Miles =4.412 +/- 0.016 Gyr, Colomera =4.469 +/- 0.012 Gyr, and Sombrerete =4.535 +/- 0.005 Gyr. These ages are in fair agreement with previously reported Rb-Sr isochron ages for Colomera and Weekeroo Station. Although several mechanisms to form HE meteorites previously were suggested, it is not obvious that a single mechanism could produce a suite of meteorites with very different degrees of silicate differentiation and with isotopic ages that differ by >0.8 Gyr. We suggest that those IIEs with older isotopic ages are a product of partial melting and differentiation within the parent body, followed by mixing of silicate and metal while both were relatively hot. Netschadvo and Watson may have formed by this same process or by impact mixing about 4.5 Gyr ago, but their isotopic ages were subsequently reset by shock heating. Kodaikanal apparently is required to have formed more recently, in which case impact melting and differentiation seems the only viable process. We see no compelling reasons to believe that IIE silicate and metal derived from different parent bodies or that the parent body of IIEs was the same as that of H-chondrites.

Bogard, Donald D.↗
NASA NTRS2000

Chronology of KSC and KSC Related Events for 1999

This document is intended to serve as a record of Kennedy Space Center (KSC) events and is a reference source for historians and other researchers. Arrangement is by day and month and individual articles are attributed to published sources. Materials were researched and described by the KSC Library Archivist for KSC Library Services Contractor InDyne, Inc.

Liston, Elaine E.↗
NASA NTRS2001

Chronology of KSC and KSC Related Events for 2000

This document is intended to serve as a record of Kennedy Space Center (KSC) events and is a reference source for historians and other researchers. Arrangement is by day and month and individual articles are attributed to published sources. Materials were researched and described by the KSC Library Archivist with assistance from KSC Library Librarians for KSC Library Services Contractor InDyne, Inc.

Liston, Elaine E.↗
NASA NTRS2000

SERM Forest Fire Chronology of Saskatchewan in Vector Format

The BOReal Ecosystem-Atmosphere Study (BOREAS) staff personnel worked with several Canadian agencies to obtain various GIS data for use in the research efforts. This data set is a series of ARC/INFO export files of the fire history of Saskatchewan by year from 1945 to 1996, with a few missing years. The data set was compiled and provided by the Saskatchewan Environment and Resource Management (SERM) Wildlife Branch.

Naelapea, Ott↗
NASA NTRS2001

Mars: Chronological Studies of the Large Volcanoes in Tharsis

We are beginning a study of age and morphology relations among Tharsis volcanics, with crater counts using new age calibrations. On Olympus Mons, averages over large areas give characteristic ages of a few hundred My, but youngest flows have ages in range 5-50 My. Additional information is contained in the original extended abstract.

Grier, Jennifer↗
NASA NTRS2001

A Chronology of Annual-Mean Effective Radii of Stratospheric Aerosols from Volcanic Eruptions During the Twentieth Century as Derived From Ground-based Spectral Extinction Measurements

Stratospheric extinction can be derived from ground-based spectral photometric observations of the Sun and other stars (as well as from satellite and aircraft measurements, available since 1979), and is found to increase after large volcanic eruptions. This increased extinction shows a characteristic wavelength dependence that gives information about the chemical composition and the effective (or area weighted mean) radius of the particles responsible for it. Known to be tiny aerosols constituted of sulfuric acid in a water solution, the stratospheric particles at midlatitudes exhibit a remarkable uniformity of their column-averaged effective radii r(sub eff) in the first few months after the eruption. Considering the seven largest eruptions of the twentieth century, r(sub eff) at this phase of peak aerosol abundance is approx. 0.3 micrometers in all cases. A year later, r(sub eff) either has remained about the same size (almost certainly in the case of the Katmai eruption of 1912) or has increased to approx. 0.5 micrometers (definitely so for the Pinatubo eruption of 1991). The reasons for this divergence in aerosol growth are unknown.

Strothers, Richard B.↗
NASA NTRS2003

Chronology of KSC and KSC Related Events for 2002

This document is intended to serve as a record of KSC events and is a reference source for historians and other researchers. Arrangement is by day and month and individual articles are attributed to published sources. Materials were researched and described by the KSC Library Archivist for KSC Library Services Contractor, InDyne, Inc.

Liston, Elaine E.↗
NASA NTRS2003

The Initial W-182/W-183 and Hf-182/Hf-180 of the Solar System and a Consistent Chronology with Pb-Pb Ages

The utility of the Hf-182 (bar-tau ==13 x 10(exp 6) yr) -W-182 chronometer for early solar system processes is now well established. At the 2002 LPSC meeting we first reported new Hf-W data for chondritic meteorites showing that some crucial data as well as interpretations of Lee and Halliday for chondrites were incorrect. Our results were confirmed by reports of two other groups. This new data imply a much-shorter timescale for the early Solar System evolution and the formation of the Earth s core more consistent with the original conclusions of Harper and Jacobsen. Thus, the chondritic Hf-W evolution is now well established as beginning with epsilon(sub W)(0) = -3.45 +/- 0.25 at the time of origin of the solar system and evolving to -2.2 by 20 Myr and -1.9 +/- 0.20 at present. However, there are a number of iron meteorite data that suggest the existence of initial W lower than those measured for chondrites. If the low epsilon(sub W)(0) of -4 to -5 are correct then we face an embarrassing dilemma of differentiated iron meteorites being older than the primitive chondrites, or we would have to conclude that there is an additional pre-history of 5-10 Myr in primitive chondritic meteorites prior to the closure of the Hf-182 - W-182 system. Such a prolonged early time does not seem reasonable to us. We have therefore initiated a study to resolve this issue.

Yin, Qingzhu↗
NASA NTRS2004

Chronology of KSC and KSC Related Events for 2003

This document is intended to serve as a record of KSC events and is a reference source for historians and other researchers. Arrangement is by day and month and individual articles are attributed to published sources. Materials were researched and described by the KSC Library Archivist for KSC Library Services Contractor, InDyne, Inc.

Liston, Elaine E.↗
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 NTRS1989

The post-Paleozoic chronology and mechanism of 13C depletion in primary marine organic matter

Carbon-isotopic compositions of geoporphyrins have been measured from marine sediments of Mesozoic and Cenozoic age in order to elucidate the timing and extent of depletion of 13C in marine primary producers. These results indicate that the difference in isotopic composition of coeval marine carbonates and marine primary photosynthate was approximately 5 to 7 permil greater during the Mesozoic and early Cenozoic than at present. In contrast to the isotopic record of marine primary producers, isotopic compositions of terrestrial organic materials have remained approximately constant for this same interval of time. This difference in the isotopic records of marine and terrestrial organic matter is considered in terms of the mechanisms controlling the isotopic fractionation associated with photosynthetic fixation of carbon. We show that the decreased isotopic fractionation between marine carbonates and organic matter from the Early to mid-Cenozoic may record variations in the abundance of atmospheric CO2.

Non-NASA Center↗
NASA NTRS2006

Chronology of KSC and KSC Related Events for 2005

This document is intended to serve as a record of KSC events and is a reference source for historians and other researchers. Arrangement is by day and month and individual articles are attributed to published sources. Materials were researched and described by the KSC Library .Archivist for KSC Library Services Contractor, InDyne, Inc.

Liston, Elaine E.↗