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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 109 records · Page 6
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NASA NTRS1982

Noble gases in planetary atmospheres - Implications for the origin and evolution of atmospheres

The radiogenic and primordial noble gas contents of the Venus, earth, and Mars atmospheres are compared with one another and with the noble gas content of other extraterrestrial samples, particularly meteorites. Key trends in the primordial noble gas content of terrestrial planetary atmospheres are shown to include: (1) a several-orders-of-magnitude decrease in Ne-20 and Ar-36 from Venus to earth to Mars; (2) a nearly constant Ne-20/Ar-36 ratio, which is comparable to that found in the more primitive carbonaceous chondrites and which is two orders of magnitude smaller than the solar ratio; (3) a sizable fractionation of Ar, Kr, and Xe from their solar ratios, though the degree of fractionation (especially for Ar-36/Xe-132) appears to decrease systematically from carbonaceous chondrites to Mars to earth to Venus; and (4) large differences in Ne and Xe isotopic ratios among earth, meteorites, and the sun. It is suggested that the grain-accretion hypothesis can explain all four trends, though the assumptions needed to achieve this agreement are far from proven.

Pollack, J. B.↗
NASA NTRS1990

Coupling of the quasi-biennial oscillation and the extratropical circulation in the stratosphere through planetary wave transport

The effects of tropical winds on the extratropical circulation are examined using calculations of eddy transport with tropical flow that is representative of the easterly and westerly phases of the quasi-biennial oscillation (QBO). A dependence of extratropical circulation on tropical winds and the QBO is shown to originate in planetary wave transport. Also, the effects of low latitude flow on high latitude circulation and the behavior of the vortex in opposite phases of the QBO are examined.

O'Sullivan, Donal↗
NASA NTRS1987

The case for planetary sample return missions. I - Origin of the solar system

The scientific aims and proposed scenarios of sample-return missions (SRMs) to Mars, Venus, comets, and asteroids are reviewed. SRMs are currently being evaluated as natural follow-ons to the NASA remote-sensing orbiter missions of the 1990s. The technological advantages of ground laboratory analysis of returned samples are discussed; and it is argued that SRMs to large evolved bodies can provide a record of (1) the composition of the solar system at different heliocentric distances and (2) the nature of the processes that led to the accretion of small objects (preserved as comets and asteroids) into large planetary bodies. Also considered are NASA research and analysis programs needed to support studies of solar-system origin. It is recommended that planning of SRMs be begun immediately, although they may not be feasible before the year 2000.

Drake, Michael J.↗
NASA NTRS1993

Trapping of water vapor from an atmosphere by condensed silicate matter formed by high-temperature pulse vaporization

The origin of planetary atmospheres is thought to be the result of bombardment of a growing planet by massive planetesimals. According to some models, the accumulation of released water vapor and/or carbon dioxide can result in the formation of a dense and hot primordial atmosphere. Among source and sink processes of atmospheric water vapor the formation of hydroxides was considered mainly as rehydration of dehydrated minerals (foresterite and enstatite). From our point of view, the formation of hydroxides is not limited to rehydration. Condensation of small silicate particles in a spreading vapor cloud and their interaction with a wet atmosphere can also result in the origin of hydrated phases which have no genetic connections with initial water bearing minerals. We present results of two experiments of a simulated interaction of condensed silicate matter which originated during vaporization of dry clinopyroxene in a wet helium atmosphere.

Gerasimov, M. V.↗
NASA NTRS1999

Observational Studies of the Clearing Phase in Proto-Planetary Disks Surrounding Intermediate Mass Stars

A detailed study of circumstellar gas associated with young, intermediate-mass stars has demonstrated that, far from being unique or an infrequently occurring phenomenon, beta Pic-like infall activity is routinely observed in stars younger than 10-50 Myr when the observer's line of sight lies within 15 degrees of the disk mid-plane. Detailed studies of 2 Herbig Ae/Be stars, AB Aur and HD 163296 demonstrate that enhanced infall episodes last 20-60 hours, comparable to the duration of similar episodes in beta Pictoris. The infall activity is consistent with detection of the comae of swarms of star-grazing bodies of asteroidal to cometary composition. Episodic fluctuations in the infall activity are clearly present by approximately 6 Myr, and may indicate the presence of massive planets within the disk. This study has therefore, directly contributed to NASA's Origins of Planetary Systems theme by identifying under what conditions extra-solar planetesimals can be remotely sensed, indicating that such bodies appear to be routinely detectable among young stars in the 1-10 Myr range, and suggesting that temporal studies of spectroscopic variability may provide a means of identifying those systems harboring massive planets. This study has resulted in 2 refereed review papers, 13 other refereed papers, and 17 conference papers.

Grady, Carol A.↗
NASA NTRS1996

Recommendations for Technology Development and Validation Activities in Support of the Origins Program

The Office of Space Science (OSS) has initiated mission concept studies and associated technology roadmapping activities for future large space optical systems. The scientific motivation for these systems is the study of the origins of galaxies, stars, planetary systems and, ultimately, life. Collectively, these studies are part of the 'Astronomical Search for Origins and Planetary Systems Program' or 'Origins Program'. A series of at least three science missions and associated technology validation flights is currently envisioned in the time frame between the year 1999 and approximately 2020. These would be the Space Interferometry Mission (SIM), a 10-meter baseline Michelson stellar interferometer; the Next Generation Space Telescope (NGST), a space-based infrared optimized telescope with aperture diameter larger than four meters; and the Terrestrial Planet Finder (TPF), an 80-meter baseline-nulling Michelson interferometer described in the Exploration of Neighboring Planetary Systems (ExNPS) Study. While all of these missions include significant technological challenges, preliminary studies indicate that the technological requirements are achievable. However, immediate and aggressive technology development is needed. The Office of Space Access and Technology (OSAT) is the primary sponsor of NASA-unique technology for missions such as the Origins series. For some time, the OSAT Space Technology Program has been developing technologies for large space optical systems, including both interferometers and large-aperture telescopes. In addition, technology investments have been made by other NASA programs, including OSS; other government agencies, particularly the Department of Defense; and by the aerospace industrial community. This basis of prior technology investment provides much of the rationale for confidence in the feasibility of the advanced Origins missions. In response to the enhanced interest of both the user community and senior NASA management in large space optics, OSAT is moving to improve the focus of its sensor, spacecraft, and interferometer/telescope technology programs on the specific additional needs of the OSS Origins Program. To better define Origins mission technology and facilitate its development, OSAT and OSS called for a series of workshops with broad participation from industry, academia and the national laboratory community to address these issues. Responsibility for workshop implementation was assigned jointly to the two NASA field centers with primary Origins mission responsibility, the Goddard Space Flight Center and the Jet Propulsion Laboratory. The Origins Technology Workshop, held at Dana Point, California between June 4 and 6, 1996 was the first in the series of comprehensive workshops aimed at addressing the broad technological needs of the Origins Program. It was attended by 64 individuals selected to provide technical expertise relevant to the technology challenges of the Origins missions. This report summarizes the results of that meeting. A higher level executive summary was considered inappropriate because of the potential loss of important context for the recommendations. Subsequent to the Origins Technology Workshop and prior to publication of this report, NASA Headquarters reorganized the activities of the Of fice of Space Access and Technology. It appears likely that responsibility for the technology programs recommended in this document will move to the Office of Space Science.

Capps, Richard W.↗
NASA NTRS1965

Chromium isotopes in meteorites.

Isotopic composition of Cr in meteorites indicates lack of high energy proton irradiation in early solar system

RADIOACTIVE DATING↗
NASA NTRS1969

Fundamental problems of the solar system.

Boundary conditions for theory of solar system origin, discussing planetary atmospheres, surfaces, magnetic fields, composition and early solar wind

Cameron, A. G. W.↗
NASA NTRS1979

The origins and early histories of planetary atmospheres

Ancient dry river beds detected on Mars by the Viking spacecraft suggest that the early Martian atmosphere may have been much more massive than at present. Degassing of a late-accreting, volatile-rich veneer may account for the primitive atmosphere of both Mars and earth. The primitive earth atmosphere could have produced a greenhouse effect sufficient to maintain temperatures above 273 K without NH3 and with low solar luminosity. The Venutian veneer, according to preliminary Pioneer results, was probably richer in noble gases relative to carbon and nitrogen than were the Martian and earth veneers. The highly evolved atmosphere of Titan, the large satellite of Saturn, is also discussed.

Owen, T.↗
NASA NTRS1979

Some new results on spherical dynamos

Small-scale motions in the earth's liquid core are likely to be highly anisotropic because of the effects of rotation. Guided by physical considerations, the 'alpha-effect' described by an anisotropic tensor alpha sub ik is formulated and the corresponding boundary value problem for a sphere is solved for a variety of boundary conditions. A converged solution has been obtained only in the case of the Fermi condition of an infinitely conducting exterior of the sphere. Some remarks are made on the hypothetical upper bound on magnetic field strengths in planetary cores originally proposed by Busse (1976).

Busse, F. H.↗
NASA NTRS1980

Physical studies of the planetary rings

In this review paper, the physical properties of the Saturnian and Uranian rings as derived from ground-based observations are first discussed. Focus is then shifted to the study of the orbital dynamics of the ring particles. Numerical simulations of the evolutionary history of a system of colliding particles in differential rotation together with theoretical modeling of the inelastic collision processes are surveyed. In anticipation of the information returned from in situ measurements by space probes, interactions of the planetary rings with the interplanetary meteoroids and planetary magnetospheres are briefly considered. Finally, models of planetary ring origin are examined. In this connection, some recent work on the satellite resonant perturbation effects on the ring structure are also touched upon.

Ip, W.-H.↗