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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Expected characteristics of large dust particles in periodic Comet Halley

Observational evidence is presented for dust particles heavier than 0.01 millionth of a gram expelled from Comet Halley. Dust emitted around 1.5 AU pre-perihelion, the point in orbit where a probe would fly through the comet in 1985, should have contributed to an anomalous tail that could have been observed in 1910. From positions of the trailing boundary of the ordinary dust tail at that time, it is concluded that the production of dust started to increase steeply at 0.7 to 0.8 AU before perihelion. Observations in late January 1836 are used to derive the production of dust vs. time and the the expected number of large-particle impacts on the protective shield of the 1985 flythrough probe. From data on other comets, it is estimated that the size distribution for large particles is likely to vary inversely according to the fourth or slightly higher power of the size.

Sekanina, Z.↗
NASA NTRS2004

First Report of Taenite in an Asteroidal Interplanetary Dust Particle: Flash-heating Simulates Nebular Dust Evolution

Metallic iron with a taenite structure rimmed by Fe3C carbide, kamacite with a magnetite rim, both approximately 200 nm in size, and les than 15 nm kamacite crystals embedded in equilibrated aggregates (or GEMS) were reported in IDPs. Here I report the first g-(Fe,Ni), taenite, in sulfide fragment -F6 particle with adhered patches of thermally modified aggregate IDP-like material belonging to cluster IDP L2011#21.

Rietmeijer, F. J. M.↗
NASA NTRS1972

Collective excitations and dust particles in space

It is shown that observed bands at 2200 A and in the 10 micron region are most probably due to collective excitations of dust particles. The following specific conclusions are drawn: (1) the 2200 A interstellar band is very likely due to graphite particles; (2) these graphite particles should be very small, approximately spherical, and should have no coating whatsoever; (3) the identification of circumstellar and interstellar silicates from the observations in the 10 micron region does not seem to be correct; (4) very valuable information about the shape of the circumstellar and interstellar dust particles can be obtained directly from observations; and (5) narrow band polarization measurements in the spectral regions of these bands will be very helpful in determining the shape of the particles.

Gilra, D. P.↗
NASA NTRS1989

What if chondritic porous interplanetary dust particles are not the real McCoy

To select a target comet for a Comet Nucleus Sample Return Mission (CNSRM) it is necessary to have an experimental data base to evaluate the extent of diversity and similarity of comets. For example, the physical properties (e.g., low density) of chondritic porous (CP) interplanetary dust particles (IDPs) are believed to resemble these properties of cometary dust although it is yet to be demonstrated that the porous structure of CP IDPs is inherent to presolar dust particles stored in comet nuclei. Porous structures of IDPs could conceivably form during sublimation at the surface of active comet nuclei. Porous structures are also obtained during annealing of amorphous Mg-SiO smokes which initially forms porous aggregates of olivine + platey tridymite and which, upon continued annealing, react to fluffy enstatite aggregates. It is therefore uncertain that CP IDPs are entirely composed of unmetamorphosed presolar dust. Conceivably, new minerals and textures may form in situ in nuclei of active comets as a function of their individual thermal history. Unmetamorphosed comet dust is probably structurally amorphous. Thermal annealing of this dust can produce ultra fine-grained minerals and this ultrafine grain size of CP IDPs should be considered in assessments of aqueous alterations that could affect presolar dust in comet nuclei between 200 and 400 K. Devitrification and hydration may occur in situ in ice-dust mixtures and the mantle of active comet nuclei. Devitrification, or uncontrolled crystallization, of amorphous precursor dust can produce a range of chemical compositions of ultrafine-grained minerals and (non-equilibrium) mineral assemblages and textures in dust contained in comet nuclei as a function of period and trajectory of orbit and number of perihelion passages (not considering internal heating). Thus, experimental data on relevant processes and reaction rates between 200 and 400 K are needed in order to evaluate comet selection, penetration depth for sampling device and curation of samples for CNSRM.

Rietmeijer, Frans J. M.↗
NASA NTRS1994

Plasma produced by impacts of fast dust particles on a thin film

The thin-film impact plasma detector was pioneered by Berg for detecting small cosmic dust particles and measuring their approximate velocities in a time-of-flight configuration. While Berg's device was highly successful in establishing the flux of interplanetary dust, the accuracy of measuring the velocities of individual particles was a moderate 18 percent in magnitude and 27 degrees in angle. A much greater accuracy of less than or equal to 1 percent in determining the velocity components appears desirable in order to associate a particle with its parent body. In order to meet that need, research was initiated to determine if a thin-film detector can be designed to provide such accurate velocity measurements. Previous laboratory investigations of the impact plasma uncovered two difficulties: (1) solid or liquid spray is ejected from a primary impact crater and strikes neighboring walls where it produces secondary impact craters and plasma clouds; as a result, both quantity and time of detection of the plasma can vary significantly with the experiment configuration. Particles from an accelerator rarely have speeds v greater than or equal to 10-15 km/s, while cosmic dust particles typically impact at v = 10-72 km/s. The purpose of the tests discussed in this paper was to resolve the two difficulties mentioned. That is, the experiment configuration was designed to reduce the contribution of plasma from secondary impacts. In addition, most particles with v less than or equal to 25 km/s and all particles with v less than or equal to 10 km/s were eliminated from the beam.

Auer, Siegfried↗
NASA NTRS1983

Epsilon carbide - A low-temperature component of interplanetary dust particles

Transmission electron microscope study of a chondritic interplanetary dust particle has revealed the presence of epsilon iron-nickel carbide, a low-temperature carbide previously encountered only in metallurgical studies. In these studies epsilon-carbide was synthesized by carburization of iron or nickel grains in a stream of carbon monoxide or carbon monoxide plus hydrogen. Similar carburization of an iron-nickel metal in situ may have produced epsilon-carbide during particle heating on atmospheric entry or in solar orbit. Alternatively, the epsilon-carbide may be a by-product of Fischer-Tropsch reactions in the solar nebula. Such reactions have been proposed as the mechanism of hydrocarbon formation in the early solar system.

Christoffersen, R.↗
NASA NTRS1988

The spectral properties of interplanetary dust particles

The observed spectral and mineralogical properties of interplanetary dust particles (IDP) allows the conclusion that: (1) the majority of IDP infrared spectra are dominated by olivine, pyroxene, or layer lattice silicate minerals, (2) to the first order the emission spectra of comets Halley and Kohoutek can be matched by mixtures of these IDP infrared types, implying that comets contain mixtures of these different crystalline silicates and may vary from comet to comet and perhaps even within a single comet, (3) do not expect to observe a single 20 micron feature in cometary spectra, (4) carbonaceous materials dominate the visible spectra properties of the IDPs even though the mass in these particles consists primarily of silicates, and (5) the particle characteristics summarized need to be properly accounted for in future cometary emission models.

Sandford, Scott A.↗
NASA NTRS1988

The spectral properties of collected interplanetary dust particles

The observed spectral and mineralogical properties of interplanetary dust particles (IDP) allows the conclusion that: (1) the majority of IDP infrared spectra are dominated by olivine, pyroxene, or layer lattice silicate minerals, (2) to the first order the emission spectra of comets Halley and Kohoutek can be matched by mixtures of these IDP infrared types, implying that comets contain mixtures of these different crystalline silicates and may vary from comet to comet and perhaps even within a single comet, (3) do not expect to observe a single 20 micron feature in cometary spectra, (4) carbonaceous materials dominate the visible spectra properties of the IDPs even though the mass in these particles consists primarily of silicates, and (5) the particle characteristics summarized need to be properly accounted for in future cometary emission models.

Sandford, S. A.↗
NASA NTRS2019

A Kuiper Belt Source for Solar Flare Track-Rich Interplanetary Dust Particles

The presence of solar flare particle tracks in mineral grains within interplanetary dust particles (IDPs) has long been accepted as proof of their extraterrestrial origin [e.g. 1]. The 10-20 micrometers diameter IDPs released by dust producing objects in the solar system (mainly comets and asteroids) spiral in towards the Sun under the influence of Poynting-Robertson (PR) drag forces [2] and accumulate solar flare energetic particle tracks during their journey. The number of IDPs with well-constrained track density measurements is small, owing to the difficulty in the measurements and the lack of appropriatelysized crystals in which to image them. In order to use track densities as a chronometer of space exposure, the track production rate must be known. All previous work relied on track production rates determined by chemical etching techniques [e.g. 3], but tracks in IDPs are measured using TEM imaging. Here we report measurements of track densities in IDPs from both the anhydrous and hydrated IDP groups. Using the track production calibration determined from TEM observations of anorthite and olivine in lunar rock 64455 [4] we estimate space exposure times for these IDPs to constrain their parent body sources.

Keller, L. P.↗
NASA NTRS1994

Interplanetary dust particles collected from the stratosphere: Physical, chemical, and mineralogical properties and implications for their sources

The suggestion that significant quantities of interplanetary dust are produced by both main-belt asteroids and comets is based on the Infrared Astronomical Satellite (IRAS) detection of dust trails or bands associated with these objects. Gravitational focusing strongly biases all near-Earth collections of interplanetary dust in favor of particles with the lowest geocentric velocities, that is the dust from main-belt asteroids spiraling into the Sun under the influence of Poynting-Robertson radiation drag. The major dust bands in the main-belt appear to be associated with the catastrophic disruptions which produced the Eos, Themis and Koronis families of asteroids. If dust particles are produced in the catastrophic collision process, then Poynting-Robertson radiation drag is such an efficient transport mechanism from the main-belt to 1 AU that near-Earth collections of interplanetary dust should include, and perhaps be dominated by, this material. Interplanetary dust particles from 5 to 100 micrometers in diameter have been recovered from the stratosphere of the Earth by NASA sampling aircraft since the mid-1970s. The densities of a large fraction of these interplanetary dust particles are significantly lower than the densities of their constituent silicate mineral phases, indicating significant porosites. The majority of the particles are chemically and mineralogically similar to, but not identical to, the carbonaceous chondrite meteorites. Most stony interplanetary dust particles have carbon contents exceeding those of Allende, a carbonaceous chondrite meteorite having a low albedo. Higher albedo particles corresponding to S-type asteroids are underrepresented or absent from the stratospheric collections, and primitive carbonaceous particles seem to be overrepresented in the stratospheric collections compared to the fraction of main-belt asteroids classified as primitive. This suggests that much of the interplanetary dust may be generated by a stochastic process, probably preferentially sampling a few most recent collisional events.

Flynn, George J.↗
NASA NTRS1974

Mariner 4 - A study of the cumulative flux of dust particles over a heliocentric range of 1-1.56 AU 1964-1967

Between December 1964 and December 1967, the Mariner 4 dust particle experiment obtained data concerning the distribution of minute zodiacal dust cloud particles over a heliocentric range of 1-1.56 AU. The first measurement was over the complete heliocentric range, while the two additional measurements were made between 1.1 and 1.25 AU in 1966, and between 1.2 and 1.5 AU in 1967. The initial results of these measurements presented the mean cumulative flux for the respective data periods. The results of a detailed study and comparison of the three measurements are presented, with particular emphasis on the variation of the flux as a function of heliocentric range. A small, but statistically significant, increase in the flux is observed between 1.15 and 1.4 AU. The initial reports showed a lower cumulative flux for the latter two measurements. However, a detailed analysis containing corrections for spacecraft attitude indicate that all three measurements yield similar results, and that the particles detected were in low inclination orbits.

Alexander, W. M.↗
NASA NTRS2020

Aqueous Alteration in the Kuiper Belt: Evidence from Hydrated Interplanetary Dust Particles

Edgeworth-Kuiper belt objects (EKBOs) formed in the outer reaches of the protoplanetary disk and thus avoided much of the high tempera-ture processing experienced by bodies in the inner solar system. For this reason, they contain a wealth of information on the nature of nebular solids and the chemical conditions in the earliest solar system. Astronomical observations of EKBOs have been limited largely to the surface chemistry of the ices covering these small and difficult to observe bodies. The mineralogy of EKBO objects are poorly known, but clues regarding their mineralogical makeup come from studies of samples from short period comets (e.g. Wild2), and interplanetary dust particles (IDPs) produced by collisions in the Kuiper belt. Interplanetary dust particles from objects in the solar system (mainly comets and asteroids) spiral in to-wards the Sun under the influence of Poynting-Robertson (PR) drag forces and accumulate solar flare energetic particle tracks. Recent work has shown that the observed solar flare track densities (~1010-1011/sq.cm) in these IDPs are ~two orders of magnitude higher than expected if they were derived from main belt asteroids or Jupiter family comets and thus require an origin from outer solar system source bodies such as EKBOs. The track-rich IDPs include representatives from the two major groups of IDPs: the chondritic-porous, anhydrous IDPs and the chondritic-smooth, hydrated IDPs, although rare IDPs with mineralogies intermediate between these two groups are known. Here, we report on the mineralogy, composition, organic matter content, and isotopic characteristics of track-rich hydrated IDPs, and implications for aqueous alteration in outer solar system bodies.

Keller, L. P.↗
NASA NTRS2005

Origins and Dynamics of Interplanetary Dust Particles

This is a final report for research supported by the National Aeronautics and Space Administration issued through the Office of Space Science Planetary Geology and Geophysics Program, covering all relevant activities during its 3-year period of funding from 02/01/2002 through to 01/31/2005. The ongoing aim of the research supported through this grant, and now through a successor award, is to investigate the origin of interplanetary dust particles (IDPs) and their dynamical and collisional evolution, in order to: (1) understand the provenance of zodiacal cloud particles and their transport from their source regions to the inner solar system; (2) produce detailed models of the zodiacal cloud and its constituent components; (3) determine the origin of the dust particles accreted by the Earth; (4) ascertain the level of temporal variations in the dust environment of the inner solar system and the accretion rate of IDPs by the Earth, and evaluate potential effects on global climate; and to (5) exploit this research as a basis for interpreting the structure observed in exozodiacal clouds that may result from the collisional evolution of planetesimals and the presence of unseen planets.

Dermott, Stanley F.↗
NASA NTRS2011

Discovery of Brownleeite: a New Manganese Silicide Mineral in an Interplanetary Dust Particle

The Earth accretes approximately 40,000 tons of cosmic dust annually, originating mainly from the disintegration of comets and collisions among asteroids. This cosmic dust, also known as interplanetary dust particles (IDPs), is a subject of intense interest since it is made of the original building blocks of our Solar System. Although the specific parent bodies of IDPs are unknown, the anhydrous chondritic-porous IDPs (CP-IDPs) subset has been potentially linked to a cometary source. The CP-IDPs are extremely primitive materials based on their unequilibrated mineralogy, C-rich chemistry, and anomalous isotopic signatures. In particular, some CP-IDPs escaped the thermal, aqueous and impact shock processing that has modified or destroyed the original mineralogy of meteorites. Thus, the CP-IDPs represent some of the most primitive solar system materials available for laboratory study. Most CP-IDPs are comprised of minerals that are common on Earth. However, in the course of an examination of one of the CP-IDPs, we encountered three sub-micrometer sized grains of manganese silicide (MnSi), a phase that has heretofore not been found in nature. In the seminar, we would like to focus on IDP studies and this manganese silicide phase that has been approved as the first new mineral identified from a comet by the International Mineralogical Association (IMA) in 2008. The mineral is named in honour of Donald E. Brownlee, an American astronomer and a founder of the field of cosmic dust research who is the principal investigator of the NASA Stardust Mission that collected dust samples from Comet 81P/Wild-2 and returned them to Earth. Much of our current view and understanding of the early solar system would not exist without the pioneering work of professor Don Brownlee in the study of IDPs.

Keller, Lindsay P.↗
NASA NTRS1999

Photoelectric Charging of Dust Particles

Laboratory experiments have been performed on the photoelectric charging of dust particles which are either isolated or adjacent to a surface that is also a photoemitter. We find that zinc dust charges to a positive potential of a few volts when isolated in vacuum and that it charges to a negative potential of a few volts when passed by a photoemitting surface. The illumination is an arc lamp emitting wavelengths longer than 200 nm and the emitting surface is a zirconium foil.

Sickafoose, A.↗
NASA NTRS1980

Radiation induced rotation of interplanetary dust particles - A feasibility study for a space experiment

Irregular interplanetary dust particles may acquire a considerable spin rate due to two non-statistical dynamical mechanisms induced by solar radiation. These arise from variations in surface albedo discussed by Radzievskii (1954) and from irregularities in surface geometry discussed by Paddack (1969). An experiment is reported which will lead to an evaluation in space of the effectiveness of these two spin mechanisms. The technique of optical levitation in an argon laser beam provides a stable trap for particles 10-60 microns in diameter. The objective is to design an optical trap for dielectric particles in vacuum to study these rotation mechanisms in the gravity-free environment of a Spacelab experiment.

Ratcliff, K. F.↗