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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Constraints on early events in Martian history as derived from the cratering record

Constrains on early events in Martian history are derived using the planet's cratering record. Variations in the shapes of the crater size-frequency distribution curves are interpreted as indicative of the size-frequency distribution of the production populations, thus providing information about the age of the unit relative to the end of the heavy bombardment period. Results from the analysis of craters superposed on heavily cratered units across the Martian surface provide constraints on the hemispheric dichotomy and the early erosional conditions on Mars.

Barlow, Nadine G.↗
NASA NTRS1990

Resurfacing history of Tempe Terra and surroundings

The resurfacing history of the Tempe Terra region is examined on the basis of an analysis of cumulative frequency curves for individual terrain units within Tempe Terra and its surroundings. The results of the analysis, which was carried out using the techniques of Neukum and Hiller (1981), suggest that three major resurfacing events occurred in this region, with crater retention ages N(1) (the cumulative number of craters larger than 1 km diameter per million square kilometer) of (242,100), (95,700), (20,800), and (5500). These results are interpreted as indicative of three major resurfacing events occurring in this region, ending at N(1) = (95,700), (20,800), and (5500). It is shown that it is possible to extend this technique to derive not only ages for major resurfacing events, but the minimum extent of the now-buried surfaces and the thickness of the materials involved in each major resurfacing event.

Frey, Herbert V.↗
NASA NTRS1991

X-15: the Perspective of History

The linkages between the Apollo 11 voyage to Tranquility Base and the 199 flights of the X-15 aircraft are discussed. Accomplishments of the X-15 program and a history of aircraft developments that led up to the X-15 are presented.

Hallion, Richard P.↗
NASA NTRS1991

Water on Mars: Volatile history and resource availability

The existence of water on Mars is undisputed today. Measurements of atmospheric water vapor have shown that the abundance varies with location and season in a systematic way which depends on processes of exchange with the polar caps, regolith, and atmosphere. Channels, which give the appearance of having been carved by water or of having had water involved in their formation, appear in various locations on the surface; some were formed by catastrophic outflow of water from beneath the surface, while others form valley networks which give the appearance of having formed over long periods of time primarily early in the planet's history. The north polar residual cap consists of water ice, possibly containing an amount of water equivalent to a global layer several tens of meters thick. Finally, water is observed within the regolith, as adsorbed water or as water of hydration.

Jakosky, Bruce M.↗
NASA NTRS1990

Creating a rocket-building institution - The history of the Marshall Space Flight Center

This paper will examine the early history of NASA Marshall Space Flight Center to identify major changes in the Center during the period that it was responsible for developing the Saturn family of launch vehicles. The principal conclusion is that the unique change experienced by Marshall during the Saturn era was its shift from an in-house, self-sustaining organization to an institution responsible for managing the Saturn-related performance of a nationwide network of aerospace contractors.

Wright, Michael D.↗
NASA NTRS1990

Rare earth elements in minerals of the ALHA77005 shergottite and implications for its parent magma and crystallization history

Analyses of mineral REE and selected minor and trace elements were carried out on individual grains of pyroxenes, whitlockite, maskelynite, and olivine of the Antarctic shergottite ALHA77005, and the results are used to interpret its parent magma and crystallization history. The results of mineral compositions and textural observations suggest that ALHA77005 is a cumulate with about half cumulus material (olivine + chromite) and half postcumulus phases. Most of the REEs in ALHA77005 reside in whitlockite whose modal concentration is about 1 percent. Mineral REE data support previous suggestions that plagioclase and whitlockite crystallized late, and that low-Ca pyroxene initiated crystallization before high-Ca pyroxene. The REE patterns for the intercumulus liquid, calculated from distribution coefficients for ALHA77005 pyroxene, plagioclase, and whitlockite, are in very good agreement and are similar to that of Shergotty.

Lundberg, Laura L.↗
NASA NTRS1991

Propulsion at the Marshall Space Flight Center - A brief history

The history of propulsion development at the NASA Marshall Space Flight Center is summarized, beginning with the development of the propulsion system for the Redstone missile. This course of propulsion development continues through the Jupiter IRBM, the Saturn family of launch vehicles and the engines that powered them, the Centaur upper stage and RL-10 engine, the Reactor In-Flight Test stage and the NERVA nuclear engine. The Space Shuttle Main Engine and Solid Rocket Boosters are covered, as are spacecraft propulsion systems, including the reaction control systems for the High Energy Astronomy Observatory and the Space Station. The paper includes a description of several technology efforts such as those in high pressure turbomachinery, aerospike engines, and the AS203 cyrogenic fluid management flight experiment. These and other propulsion projects are documented, and the scope of activities in support of these efforts at Marshall delineated.

Jones, L. W.↗
NASA NTRS1991

Mimas: Tectonic structure and geologic history

Mimas, the innermost of the major saturnian satellites, occupies an important place in comparative studies of icy satellites. It is the smallest icy satellite known to have a mostly spherical shape. Smaller icy objects like Hyperion and Puck are generally irregular in shape, while larger ones like Miranda and Enceladus are spherical. Thus Mimas is near the diameter where the combination of increasing surface gravity and internal heating begin to have a significant effect on global structure. The nature and extent of endogenic surface features provide important constraints on the interior structure and history of this transitional body. The major landforms on Mimas are impact craters. Mimas has one of the most heavily cratered surfaces in the solar system. The most prominent single feature on Mimas is Herschel, an unrelaxed complex crater 130 km in diameter. The only other recognized landforms on Mimas are tectonic grooves and lineaments. Groove locations were mapped by Schenk, but without analysis of groove structures or superposition relationships. Mimas' tectonic structures are remapped here in more detail than previously has been done, as part of a general study of tectonic features on icy satellites.

Croft, Steven K.↗
NASA NTRS1991

Understanding asteroid collisional history through experimental and numerical studies

Asteroids can lose angular momentum due to so called splash effect, the analog to the drain effect for cratering impacts. Numerical code with the splash effect incorporated was applied to study the simultaneous evolution of asteroid sized and spins. Results are presented on the spin changes of asteroids due to various physical effects that are incorporated in the described model. The goal was to understand the interplay between the evolution of sizes and spins over a wide and plausible range of model parameters. A single starting population was used both for size distribution and the spin distribution of asteroids and the changes in the spins were calculated over solar system history for different model parameters. It is shown that there is a strong coupling between the size and spin evolution, that the observed relative spindown of asteroids approximately 100 km diameter is likely to be the result of the angular momentum splash effect.

Davis, Donald R.↗
NASA NTRS1991

The history of lunar volcanism

The timing and extent of volcanism must have reflected the internal thermal evolution of the moon and a knowledge of the history of lunar volcanism is important for understanding the global evolution of the moon. Recent studies show that lunar volcanism began prior to formation of at least some of the major lunar basins, although the exact provenance of the earliest volcanism remains somewhat obscure. It was shown that the ferroan anorthosites are the best candidates to be remnants of the postulated lunar magma ocean. The Mg-suite rocks are the second major category of highland rocks, and highly evolved granites and quartz-monzodiorites comprise a third suite of lunar highland rocks. Basalts form the Apollo 12, 15, and 17 landing sites demonstrated that the lunar mantle is greatly depleted in LREE beneath the widely separated landing sites, an observation supportive of a global process of differentiation. Also, KREEP volcanism apparently predated basin formation in the Serenitatis region, but appears to have been contemporaneous with basin formation in the Imbrium region. Recent studies showed that the earliest lunar basaltic volcanism was of mare-like composition.

Nyquist, Laurence E.↗
NASA NTRS1992

NASA's hypersonic propulsion program: History and direction

Research into hypersonic propulsion; i.e., supersonic combustion, was seriously initiated at the Langley Research Center in the 1960's with the Hypersonic Research Engine (HRE) project. This project was designed to demonstrate supersonic combustion within the context of an engine module consisting of an inlet, combustor, and nozzle. In addition, the HRE utilized both subsonic and supersonic combustion (dual-mode) to demonstrate smooth operation over a Mach 4 to 7 speed range. The propulsion program thus concentrated on fundamental supersonic combustion studies and free jet propulsion tests for the three dimensional fixed geometry engine design to demonstrate inlet and combustor integration and installed performance potential. The developmental history of the program is presented. Additionally, the HRE program's effect on the current state of hypersonic propulsion is discussed.

Wander, Steve↗
NASA NTRS1992

Monthly mean global satellite data sets available in CCM history tape format

Satellite data for climate monitoring have become increasingly important over the past decade, especially with increasing concern for inadvertent antropogenic climate change. Although most satellite based data are of short record, satellites can provide the global coverage that traditional meteorological observations network lack. In addition, satellite data are invaluable for the validation of climate models, and they are useful for many diagnostic studies. Herein, several satellite data sets were processed and transposed into 'history tape' format for use with the Community Climate Model (CCM) modular processor. Only a few of the most widely used and best documented data sets were selected at this point, although future work will expand the number of data sets examined as well as update the archived data sets. An attempt was made to include data of longer record and only monthly averaged data were processed. For studies using satellite data over an extended period, it is important to recognize the impact of changes in instrumentation, drift in instrument calibration, errors introduced by retrieval algorithms and other sources of errors such as those resulting from insufficient space and/or time sampling.

Hurrell, James W.↗
NASA NTRS1991

COBE battery overview: History, handling, and performance

The following topics are presented in viewgraph format: Cosmic Background Explorer (COBE) mission background; battery background and specifications; cell history; battery mechanical/structural design; battery test data; and flowcharts of the various battery approval procedures.

Yi, Thomas↗
NASA NTRS1992

History of oxygen and carbon escape from the Martian atmosphere

A fraction of the oxygen in the Martian atmosphere continually escapes to space because dissociative recombination of the O2(+) ions in the ionosphere can impart sufficient energy to the product O atoms. In addition, ionization of the extended atomic oxygen corona resulting from the above process adds to escape since the solar wind can carry away O(+) ions born above a few hundred km altitude. A further by-product of this ion-pickup by the solar wind is an additional population of escaping oxygen atoms that are sputtered from the atmosphere near the exobase by pickup ions that are on reentry rather than escaping trajectories. This sputtering process can also remove carbon in the form of intact or dissociated CO2 since all atoms and molecules in the 'target' gas are subject to the collisional energy transfer that characterizes sputtering. We have estimated the present rates of escape of oxygen and carbon due to these mechanisms, as well as the rates at several epochs in the history of the solar system.

Luhmann, J. G.↗
NASA NTRS1991

Exposure histories of lunar meteorites - ALHA81005, MAC88104, MAC88105, and Y791197

The cosmogenic radionuclides Ca-41, Cl-36, Al-26, and Be-10 in the Allan Hills 81005, MacAlpine Hills 88104, MacAlpine Hills 88105, and Yamato 791197 meteorites were measured by accelerator mass spectrometry. Mn-53 in Allan Hills 81005 and Yamato 791197 was measured by neutron activation. These four lunar meteorites experienced similar histories. They were ejected from near the surface of the moon ranging in depth down to 400 g/sq cm and had very short transition times (less than 0.1 Ma) from the moon to the earth. A comparison of the cosmogenic nuclide concentrations in MacAlpine Hills 88104 and MacAlpine Hills 88105 clearly indicates that they are a pair from the same fall.

Nishiizumi, K.↗
NASA NTRS1991

Exposure histories of the lunar meteorites - MAC88104, MAC88105, Y791197, and Y86032

Four lunar meteorites were analyzed for the cosmogenic radionuclides Be-10, Al-26, Cl-36, and Ca-41. Histories of exposure to cosmic rays were modelled in terms of two-stage irradiations, each with a long first stage on the moon, lasting a time T sub 2pi greater than 5 Ma at a burial depth d sub 2pi(g/sq cm), followed by a second stage in space, i.e., the transit time between the moon and the earth, lasting a time T sub 4pi (Ma) in a body of typical metereological size. It is inferred that the production rate is of the order of 5/Ma and the arrival rate worldwide is about 3,000,000 meteorites/Ma. It is concluded that each impact event large enough to produce lunar meteorites sends a large number of them to the earth.

Vogt, S.↗
NASA NTRS1991

Thermoluminescence constraints on the metamorphic, shock, and brecciation history of basaltic meteorites

The metamorphic, shock, and brecciation history of 18 eucrites, 13 howardites, 6 diogenites, and 15 mesosiderites is investigated via induced thermoluminescence measurements performed on them. The eucrites show a 15-fold range of TL sensitivities, which correlate with petrographic indicators of metamorphic intensity. The temperature of the dominant TL peak observed for basaltic meteorites, and experiments in which four eucrites with diverse petrographic properties were annealed at various temperatures in the laboratory, suggests that the metamorphic equilibration temperatures for most basaltic meteorites were not more than 800 C. Assuming this temperature was typical of conditions during metamorphism, then burial depths for type-above-5 eucrites were greater than 350 m and less than 50 m for type-2 eucrites. Since TL peak temperatures are related to the degree of disorder in the Al, Si chain in feldspar, the present data provide independent evidence for very slow cooling rates for mesosiderites and for the slower cooling rates for some cumulate eucrites relative to equilibrated noncumulate eucrites.

Batchelor, J. D.↗