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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Dust from periodic comet Encke - Large grains in short supply

A photographic observation of periodic comet Encke is analyzed which reveals the emission of large dust grains from the comet. Photometric reduction of the photographic plate is described, and a two-dimensional isodensitometer scan of P/Encke is presented. An analytical expression is obtained for the average mass-loss rate of the dust over the revolution period of about 1200 days. A comparison of the results for P/Encke with previous results for P/d'Arrest indicates that both comets shed dust at just about equal average rates. It is concluded that the current contribution of P/Encke to the interplanetary dust is quite negligible if the dust particles reflect more than 1% of light and that smaller dust grains probably tend to contribute more mass than larger grains.

Sekanina, Z.↗
NASA NTRS2006

Isotopic Analyses of Stardust Mission Samples

In January 2006 the NASA Stardust spacecraft successfully returned to Earth the first direct samples of cometary dust. Comets are considered to be the best preserved remnants of the original building blocks of the solar system, and should contain high abundances of interstellar dust. The isotopic analyses of the Stardust samples now underway will offer a sensitive measure of the relative proportions of solar system and preserved interstellar matter in comets. Though once considered to be unprocessed assemblages of interstellar materials, a minor population of crystalline silicates is apparent in some cometary spectra, suggesting that comets contain materials processed at high temperatures. Identifying and isotopically characterizing crystalline silicates among the collected Stardust materials is another high-priority goal of this mission. The results of these preliminary isotopic analyses of the Stardust mission samples will be presented.

Messenger, Scott↗
NASA NTRS2007

Analysis of Cometary Dust Impact Residues in the Aluminum Foil Craters of Stardust

In January 2006, the sample return capsule from NASA s Stardust spacecraft successfully returned to Earth after its seven year mission to comet Wild-2. While the principal capture medium for comet dust was low-density graded silica aerogel, the 1100 series aluminum foil (approximately 100 m thick) which wrapped around the T6064 aluminum frame of the sample tray assembly (STA) contains micro-craters that constitute an additional repository for Wild-2 dust. Previous studies of similar craters on spacecraft surfaces, e.g. the Long Duration Exposure Facility (LDEF), have shown that impactor material can be preserved for elemental and mineralogical characterization, although the quantity of impact residue in Stardust craters far exceeds previous missions. The degree of shock-induced alteration experienced by the Wild-2 particles impacting on foil will generally be greater than for those captured in the low-density aerogel. However, even some of the residues found in LDEF craters showed not only survival of crystalline silicates but even their solar flare tracks, which are extremely fragile structures and anneal at around 600 C. Laboratory hypervelocity experiments, using analogues of Wild-2 particles accelerated into flight-grade foils under conditions close to those of the actual encounter, showed retention of abundant projectile residues at the Stardust encounter velocity of 6.1 km/s. During the preliminary examination (PE) of the returned foils, using optical and electron microscopy studies, a diverse range in size and morphologies of micro-craters was identified. In this abstract we consider the state of residue preservation in a diverse range of craters with respect to their elemental composition and inferred mineralogy of the original projectiles.

Graham, G. A.↗
NASA NTRS1988

Optical investigation of Comet Halley

The physical properties of Comet P/Halley are being monitored from the ground using state of the art optical detectors. The long time base (1982-present) of the observations provides a unique record of the development of activity in a single comet. In addition, physical properties of other comets are measured to provide a reference against which Comet Halley may be compared. Results for the past year include: (1) publication of the first results on the surface brightness profiles of dust comets; (2) charge coupled device measurements of Comet Bowell show that the activity of comets can persist at least to heliocentric distances R = 13.6 AU; (3) a study of the back-scattering phase angle dependences of 5 comets (including Halley) shows evidence for small linear phase coefficients in each case; (4) temporal monitoring of P/Halley continues.

Jewitt, David↗
NASA NTRS1985

The dust coma of periodic Comet Churyumov-Gerasimenko (1982 VIII)

IR emission from the dust comet of Comet C-G was monitored at 1-20 microns with the 3-m NASA Infrared Telescope Facility at Mauna Kea, Hawaii during its perihelion passage from September 1982 to March 1983. The maximum dust production rate of approximately 200,000 g/sec was found to occur approximately one month after perihelion. It was also found that no obvious 1-micron silicate feature was present at 1.33 AU preperihelion, and that the ratio of dust/gas production was higher in other short-period comets observed in the infrared, particularly preperihelion. The low albedos derived for the dust grains (less than 0.05 micron) are noted to be plausible for mineral mixtures expected in cometary grains.

Hanner, M. S.↗
NASA NTRS1994

Dust evolution from comets and asteroids: Their velocities at Earth orbit intersection

In this study on the evolution of dust particles from comets and asteroids, the effects of accurate many-body planetary motion on the gravitational perturbations of the dust grains are computed. In a computer simulation, dust grains of radius 10, 30, and 100 micron were released at perihelion passage from each of 36 different celestial bodies: 16 main asteroids, 15 short period comets with perihelion greater than 1 AU, and 5 short period comets with perihelion less than 1 AU. It is found that when dust grains evolve to intersection with the earth's orbit, they nearly always retain orbital characteristics indicative of their origins. Grains from main belt asteroids differ significantly in orbital characteristics, especially orbital eccentricity, from grains that evolve from comets.

Jackson, A. A.↗
NASA NTRS1984

Coma morphology and dust-emission pattern of periodic Comet Halley. I - High-resolution images taken at Mount Wilson in 1910

A radial/rotational shift-difference algorithm has been developed to improve visibility of the May-June 1910 high-resolution images taken at Mount Wilson of Comet Halley. Dust features for a period of up to three days were identified, which consisted of discrete active areas emitting dust continuously from the sunlit hemisphere of the rotating nucleus. A lower limit of the comet's rotation period was approximated at one day, and expansion velocities of the dust features were determined to be in the range of 0.2-0.3 km/s. Based on relative photometry of a bright jet, it was proposed that the column density of dust ejecta in the jet exceeded the density in the coma by a factor greater than or approximately equal to two, and that, if narrow along the line of light, the jet might have had a particle number concentration much higher than the coma background. Also noted are numerous ion features.

Larson, S. M.↗
NASA NTRS2016

Martian Methane From a Cometary Source: A Hypothesis

In recent years, methane in the martian atmosphere has been detected by Earth-based spectroscopy, the Planetary Fourier Spectrometer on the ESA Mars Express mission, and the NASA Mars Science Laboratory. The methane's origin remains a mystery, with proposed sources including volcanism, exogenous sources like impacts and interplanetary dust, aqueous alteration of olivine in the presence of carbonaceous material, release from ancient deposits of methane clathrates, and/or biological activity. An additional potential source exists: meteor showers from the emission of large comet dust particles could generate martian methane via UV pyrolysis of carbon-rich infall material. We find a correlation between the dates of Mars/cometary orbit encounters and detections of methane on Mars. We hypothesize that cometary debris falls onto Mars during these interactions, generating methane via UV photolysis.

Fries, M.↗
NASA NTRSDate not supplied

Dust Composition of Comet 81P/Wild 2 From JWST Spectroscopy Compared to Stardust’s Fine-Grained Materials and Gems-Rich IDPS

The Stardust Mission returned samples from the coma of Jupiter Family comet 81P/Wild 2 for detailed laboratory analyses. Here we present and discuss the best-fit thermal dust model for the coma dust of comet 81P/Wild 2 as observed by JWST. Comet 81P was observed through JWST GO 018xx, using NIRSpec (2.9–5.3µm, λ/∆λ≈1000) and MRS IFU (4.9–28.1µm, λ/∆λ≈3000) on 2023-03-20 UT and 2023-03-24 UT, respectively, at a heliocentric distance of 1.85 au and JWST distance of 1.43 au (phase angle of 32 degrees). The dust coma of 81P as revealed by JWST offers a salient compliment to laboratory studies of Stardust samples that typically are bigger than 2 µm and up to 60 µm in size.

D H Wooden↗
NASA NTRS1981

A study of central cryogenic cooling system for the comet rendezvous spacecraft

Several science instruments required temperatures between 100 K and 120 K on a proposed Halley Flyby, Tempel-2 Rendezvous Mission. Significant features of the thermal environment are a large variation in heliocentric as well as comet distance, very large solar panels for a Solar Electric Propulsion stage, and the comet dust environment. The best cooling is achieved by one central radiative cooler connected by insulated cryogenic heat pipes to the instruments. The conceptual design is of a single-stage rectangular shielded radiator deployed on a boom some distance from the spacecraft bus and solar panels. Thermal modeling determined sensitivity to solar and comet distance and was used to optimize cooler geometry.

Salazar, R. P.↗
NASA NTRS1997

Modelling two dust features in comet Hale-Bopp (1995 O1)

A Monte Carlo computer simulation code for generating synthetic images of dust features in comets is applied to comet Hale-Bopp to model the diurnal evolution of a bright jet and the appearance of nearly concentric halos.

comet-Hale-Bopp diurnal evolution of a dust jet du↗
NASA NTRS1989

Comet ejection and dynamics of nonspherical dust particles and meteoroids

This paper generalizes the formalism for calculating the ejection velocity of meteoroids and dust from comets and the forces to which such objects are subject in interplanetary space, including the dust tail of comets. It is found that spheres have the smallest cross section of any geometrical figures of the same valume averaged over random orientations, so for a fixed volume and mass, both the ejection velocity and beta reaches a minimum for bodies of spherical shapes. Flakes in random orientation are ejected near 70 percent of the highest ejection velocity for any orientation. Needles in random orientation escape a comet at nearly 90 percent of their maximum velocities. Randomly oriented cylinders of finite thickness escape at lower velocities that are slightly closer to their maximum velocities. The average beta acting on spin-aligned, perfectly absorbing needles is more than half that acting on a sphere of the same material and radius.

Gustafson, Bo A. S.↗
NASA NTRS2003

Migration of Dust Particles from Comet 2P Encke

We investigated the migration of dust particles under the gravitational influence of all planets (except for Pluto), radiation pressure, Poynting-Robertson drag and solar wind drag for Beta equal to 0.002, 0.004, 0.01, 0.05, 0.1, 0.2, and 0.4. For silicate particles such values of Beta correspond to diameters equal to about 200, 100, 40, 9, 4, 2, and 1 microns, respectively. We used the Bulirsh-Stoer method of integration, and the relative error per integration step was taken to be less than lo-'. Initial orbits of the particles were close to the orbit of Comet 2P Encke. We considered initial particles near perihelion (runs denoted as Delta tsub o, = 0), near aphelion (Delta tsub o, = 0.5), and also studied their initial positions when the comet moved for Pa/4 after perihelion passage (such runs are denoted as Delta tsub o, =i 0.25), where Pa is the period of the comet. Variations in time T when perihelion was passed was varied with a step 0.1 day for series 'S' and with a step 1 day for series 'L'. For each Beta we considered N = 101 particles for "S" runs and 150 particles for "L" runs.

Ipatov, S. I.↗
NASA NTRS1998

Dust Morphology of Comet Hale-Bopp (C/1995 01). II. Introduction of a Working Model

A Monte Carlo image simulation code for dust features in comets is applied to comet Hale-Bopp in order to model the object's persistent porcupine-like appearance on high-resolution images taken between May 11 and November 2, 1996. In this scenario, the dust-emission profile is dominated by several brief flare-ups, or puffs in the production of dust from one of the sources.

comet↗
NASA NTRS1993

Long-slit ultraviolet spectroscopy of Comet Austin (1990 V)

The spatial distributions of the brightest features in the far-UV spectrum of Comet Austin were measured, and it is found that they are generally similar to those found for Comet Halley during two rocket observations in 1986. As in Halley, the CO profile can be fit to a radial outflow profile for a source whose size is smaller than the instrumental spatial resolution. Neither the shape nor the magnitude of the extended atomic carbon profiles, however, can be satisfactorily explained by the photodissociation of CO. No evidence is found for an extended source of CO in the coma; thus, suggestions that the additional carbon can come directly from grains are difficult to accept since Austin is a low-dust comet. The presence of the O I 1356 A feature implies that there is a photoelectron excitation source in the coma. The measured O I 1304 A distribution is consistent with H2O being the dominant source of oxygen in the coma. The atomic sulfur profile matches that expected for a daughter product of relatively short-lived parents.

Sahnow, David J.↗