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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 91 records · Page 5
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NASA NTRS1990

The possible presence of interstellar PAHs in meteorites and interplanetary dust particles

The Raman spectra of interplanetary dust particles (IDPs) collected in the stratosphere show two bands at about 1350 and 1600 delta cm(-1) and a broader feature between 2200 and 3300 delta cm(-1) that are characteristic of aromatic molecular units with ordered domains smaller than 25A in diameter. This suggests that the carbonaceous material in IDPs may be similar to the polymeric component seen in meteorites, where this material is thought to consist of aromatic molecular units that are randomly inter-linked by short aliphatic bridges. The features in the Raman spectra of IDPs are similar in position and relative strength to interstellar infrared emission features that have been attributed to vibrational transitions in free molecular polycyclic aromatic hydrocarbons (PAHs). The Raman spectra of some IDPs also showed photoluminescence that is similar to the excess red emission from some astronomical objects and that has also been attributed to PAHs and PAH-related materials. Moreover, a part of the carbonaceous phase in IDPs contains deuterium to hydrogen ratios that are far greater than those found in terrestrial samples. Deuterium enrichment is expected in small free PAHs that are exposed to ultraviolet radiation in the interstellar medium. Taken together, these observations suggest that some fraction of the carbonaceous material in IDPs may have been produced in circumstellar dust shells and only slightly modified in interstellar space. Since many, if not most, IDPs come from comets, this supports the view that cometary material contains primitive components which can provide clues about early solar system (and perhaps even interstellar and circumstellar) processes.

Allamandola, L. J.↗
NASA NTRS1972

Heavy ions from interplanetary dust.

Most atoms that are evaporated from interplanetary dust near the sun are quickly ionized and are probably carried away by the interplanetary magnetic field and the solar wind. The contribution of these heavy ions to the solar-wind flux has been estimated by using estimates of the mass required to maintain the zodiacal cloud. This contribution appears to be small compared with the heavy-ion flux of coronal origin. Many ions from dust remain singly ionized; some of these, such as Ca(+), can resonantly scatter solar radiation. The contribution of this interplanetary glow to the background of twilight glow has been estimated. Interplanetary glow may be detectable. Some atoms from dust may be accelerated by radiation pressure before being ionized. Estimates of velocities and fluxes for Fe indicate that this acceleration is not very effective.

Nakada, M. P.↗
NASA NTRS1977

On the origin of extraterrestrial stratospheric particles: Interplanetary dust or meteor ablation debris?

Meteor ablation debris was distinguished from unablated interplanetary dust in a collection of extraterrestrial particles collected in the stratosphere using NASA U-2 aircraft. A 62 g sample of the Murchison (C2) meteorite was artificially ablated to characterize ablation debris for comparison with the stratospheric particles. By using proper experimental conditions, artificial ablation debris can be produced that is similar to natural ablation debris. Analyses of natural fusion crusts, artificial fusion crust, and artificial ablation debris of the Murchison meteorite produced criteria for recognizing debris ablated by a primitive meteoroid. Ninety-five percent of the stratospheric particles can be described as either ablation debris from a primitive meteoroid, or as very primitive interplanetary dust.

Kyte, F. T.↗
NASA NTRS1988

Interplanetary dust particles

The ways of establishing the extraterrestrial nature of different subsets of interplanetary dust collected in the stratosphere by high-altitude aircraft are discussed. Consideration is given to microanalytic techniques which make it possible to obtain detailed experimental information on the mineralogical and petrographic characteristics, the mid-IR absorption spectra, the Raman spectra, and the isotopic properties of individual particles. The implications of data obtained by these techniques for the origin of interplanetary dust are examined, showing that the particles are less altered than those solar-system material samples found in meteorites. It is suggested that many of the particles come from comets, although an unknown fraction originate from asteroids. Small regions of isotopically distinct material suggest that part of the dust consists of interstellar-cloud material that predates the solar system.

Bradley, John P.↗
NASA NTRS1992

Suitability of silica aerogel as a capture medium for interplanetary dust

Impact experiments using silica aerogel as a deceleration and capture medium for interplanetary dust are reported. A rough correlation is noted between increasing particle track lengths and decreasing aerogel density, and there is a poor correlation of track lengths with impact velocity at laboratory attainable velocities of 5-7 km/s. It is concluded that aerogel track lengths should not be used as velocity indicators. Chemical analyses are also reported of aerogel samples used in this study in order to assess the risks concerning contamination of interplanetary dust particles by the silica aerogel capture medium. It is demonstrated that this material is impressively clean.

Barrett, R. A.↗
NASA NTRS1989

Tin in a chondritic interplanetary dust particle

Submicron platey Sn-rich grains are present in chondritic porous interplanetary dust particle (IDP) W7029 A and it is the second occurrence of a tin mineral in a stratospheric micrometeorite. Selected Area Electron Diffraction data for the Sn-rich grains match with Sn2O3 and Sn3O4. The oxide(s) may have formed in the solar nebula when tin metal catalytically supported reduction of CO or during flash heating on atmospheric entry of the IDP. The presence of tin is consistent with enrichments for other volatile trace elements in chondritic IDPs and may signal an emerging trend toward nonchondritic volatile element abundances in chondritic IDPs. The observation confirms small-scale mineralogical heterogeneity in fine-grained chondritic porous interplanetary dust.

Rietmeijer, Frans J. M.↗
NASA NTRS1978

Zodiacal light as an indicator of interplanetary dust

The most striking feature of the night sky in the tropics is the zodiacal light, which appears as a cone in the west after sunset and in the east before sunrise. It is caused by sunlight scattered or absorbed by particles in the interplanetary medium. The zodiacal light is the only source of information about the integrated properties of the whole ensemble of interplanetary dust. The brightness and polarization in different directions and at different colors can provide information on the optical properties and spatial distribution of the scattering particles. The zodiacal light arises from two independent physical processes related to the scattering of solar continuum radiation by interplanetary dust and to thermal emission which arises from solar radiation that is absorbed by interplanetary dust and reemitted mainly at infrared wavelengths. Attention is given to observational parameters of zodiacal light, the methods of observation, errors and absolute calibration, and the observed characteristics of zodiacal light.

Weinberg, J. L.↗
NASA NTRS1980

The plane of symmetry of interplanetary dust in the inner solar system

Observations of the zodiacal light from the space probes Helios 1 and 2 between 1.0 and 0.3 AU show - superimposed on the general radial dependence - a systematic variation of brightness and brightness distribution with position in the orbit which is caused by the inclination of the symmetry plane of interplanetary dust with respect to the ecliptic. By suitable choice of the observing geometry, the inclination and the ascending node of the symmetry plane can be determined directly from the data without recourse to model calculations. The resulting values of i equals 3.0 plus or minus 0.3 deg, Omega equals 87 plus or minus 4 deg are not compatible with a concentration of interplanetary dust to the invariable plane of the solar system. The data support the simple view that the distribution of interplanetary dust in the inner solar system is characterized throughout by one plane of symmetry and suggest that this plane extends to at least 1 AU.

Leinert, C.↗
NASA NTRS1969

Interplanetary dust

Physical properties, origin, and evolution of interplanetary dust particles

Bandermann, L. W.↗
NASA NTRS1982

Laboratory studies of interplanetary dust

The paper summarizes laboratory studies of interplanetary dust samples that have been collected from the stratosphere in the form of micrometeorites between 2 and 50 microns in size and from the sea floor in the form of particles between 100 and 3000 microns in size. Experimental results are reviewed for analyses of bulk elemental and isotopic compositions, measurements of noble gases, structure, and mineralogy. The results are shown to suggest that many of the collected particles are probably of cometary origin and that, if so, comets are fine-grained aggregates of nonvolatile building blocks and ice. Possible reasons for the lack of solar-flare tracks in the particles are briefly discussed.

Fraundorf, P.↗
NASA NTRS1984

Discovery of nuclear tracks in interplanetary dust

Nuclear tracks have been identified in interplanetary dust particles (IDP's) collected from the stratosphere. The presence of tracks unambiguously confirms the extraterrestrial nature of IDP's, and the high track densities (10 to the 10th to 10 to the 11th per square centimeter) suggest an exposure age of approximately 10,000 years within the inner solar system. Tracks also provide an upper temperature limit for the heating of IDP's during atmospheric entry, thereby making it possible to distinguish between pristine and thermally modified micrometeorites.

Bradley, J. P.↗
NASA NTRS1987

Interstellar polycyclic aromatic hydrocarbons and carbon in interplanetary dust particles and meteorites

Raman spectra of interplanetary dust particles (IDPs) and meteorites containing material similar to polycyclic aromatic hydrocarbons (PAHs) show features that are similar in position and relative strength to interstellar IR emission features attributable to vibrational transitions in free molecular-sized PAHs. In addition, these spectra sometimes show red photoluminescence that has elsewhere been attributed to PAHs, and a part of the carbonaceous phase in IDPs and meteorites contain a degree of deuterium enrichment anticipated in small, free PAHs that are exposed to ISM UV radiation. These observations suggest that some of the IDPs' carbonaceous material may have been produced in circumstellar dust shells, and only slightly modified in interstellar space.

Allamandola, L. J.↗
NASA NTRS1991

Ion microprobe elemental analyses of impact features on interplanetary dust experiment sensor surfaces

Hypervelocity impact features on several of the electro-active dust sensors utilized in the Interplanetary Dust Experiment (IDE) were subjected to elemental analysis using an ion microprobe. The negatively biased dust sensor surfaces acted as ion traps for cations produced in the plasma plumes of impacting particles. Impactor residue surrounds most impact features to two or three feature diameters. After etching away a layer of carbonaceous/silicaceous surface contamination, low mass resolution elemental survey scans are used to tentatively identify the presence of impactor debris. High mass resolution two-dimensional elemental maps and three dimensional depth profiling of the feature and surrounding area show the distribution and relative composition of the debris. The location of these sensors on the six primary Long Duration Exposure Facility (LDEF) sides provides a unique opportunity to further define the debris environment. Researchers applied the same techniques to impact and contaminant features on a set of ultra-pure, highly polished single crystal germanium wafer witness plates that were mounted on row 12 and exposed to the environment during the entire mission.

Hunter, Jerry L.↗
NASA NTRS1992

Ion microprobe elemental analyses of impact features on interplanetary dust experiment sensor surfaces

Hypervelocity impact features from very small particles (less than 3 microns in diameter) on several of the electro-active dust sensors used in the Interplanetary Dust Experiment (IDE) were subjected to elemental analysis using an ion microscope. The same analytical techniques were applied to impact and containment features on a set of ultra-pure, highly polished single crystal germanium wafer witness plates that were mounted on tray B12. Very little unambiguously identifiable impactor debris was found in the central craters or shatter zones of small impacts in this crystalline surface. The surface contamination, ubiquitous on the surface of the Long Duration Exposure Facility, has greatly complicated data collection and interpretation from microparticle impacts on all surfaces.

Simon, Charles G.↗
NASA NTRS1980

Four years of zodiacal light observations from the Helios space probes - Evidence for a smooth distribution of interplanetary dust

Zodiacal light experiments on Helios 2 that has been operating continually since January 1976 are discussed, with the purpose of elucidating the distribution of interplanetary dust. Results for the observed gradient of zodiacal light intensity between 1 A.U. and perihelion at 0.3 A.U. show that for all elongations, from 17.5 deg to 135 deg from the sun, the exponent of intensity increase is -2.3 plus or minus 0.1. Color investigations show no systematic variation with heliocentric distance, but a slight reddening is present, increasing towards small elongations. The degree of polarization is found to be higher at 1 A.U. than given previously and decreases towards the sun, even if no correction for electron scattering is made. All results thus fit the hypothesized power law for radial distribution of dust. It is concluded from the stability of zodiacal intensity that the distribution of interplanetary dust is rather simple in space and quite constant in time.

Leinert, C.↗
NASA NTRS2003

Mid-Infrared Spectrum of the Zodiacal Emission: Detection of Crystalline Silicates in Interplanetary Dust

Within a few astronomical units of the Sun the solar system is filled with interplanetary dust, which is believed to be dust of cometary and asteroidal origin. Spectroscopic observations of the zodiacal emission with moderate resolution provide key information on the composition and size distribution of the dust in the interplanetary space. They can be compared directly to laboratory measurements of candidate materials, meteorites, and dust particles collected in the stratosphere. Recently mid-infrared spectroscopic observations of the zodiacal emission have been made by two instruments on board the Infrared Space Observatory; the camera (ISOCAM) and the spectrophotometer (ISOPHOT-S). A broad excess emission feature in the 9-11 micron range is reported in the ISOCAM spectrum, whereas the ISOPHOT-S spectra in 6-12 microns can be well fitted by a blackbody radiation without spectral features.

Ootsubo, T.↗
NASA NTRS1981

Infrared spectroscopy of interplanetary dust in the laboratory

A mount containing three crushed chondritic interplanetary dust particles (IDPs) collected in the earth's stratosphere and subjected to infrared spectroscopic measurements shows features near 1000 and 500/cm, suggesting crystalline pyroxene rather than crystalline olivine, amorphous olivine, or meteoritic clay minerals. Chondritic IDP structural diversity and atmospheric heating effects must be considered when comparing this spectrum with interplanetary and cometary dust astrophysical spectra. TEM and infrared observations of one member of the rare subset of IDPs resembling hydrated carbonaceous chondrite matrix material shows a close infrared spectrum resemblance between 4000 and 400/cm to the C2 meteorite Murchison. TEM observations suggest that this class of particles may be used as an atmospheric entry heating-process thermometer.

Fraundorf, P.↗
NASA NTRS1994

Collection and curation of interplanetary dust particles recovered from the stratosphere

Since May 1981, the National Aeronautics and Space Administration (NASA) has used aircraft to collect interplanetary dust particles (IDP's) from Earth's stratosphere. Specially designed dust collectors are prepared for flight and processed after flight in an ultraclean (Class-100) laboratory constructed for this purpose at the Lyndon B. Johnson Space Center (JSC) in Houston, Texas. Particles are individually retrieved from the collectors, examined, and cataloged, and then made available to the scientific community for research. Interplanetary dust thereby joins lunar samples and Antarctic meteorites as a critical extraterrestrial material being curated at JSC.

Zolensky, Michael E.↗