Pollack et al. [Icarus 19, 372 (1973)] have reported the optical constants for obsidian, basalt, andesite and basaltic glass over the wavelength range 0.2 to 50 μm, and Lamy [Icarus 34, 68 (1978)] reported the optical constants from 0.10 to 0.44 μ for obsidian, basalt, and basaltic glass. We have revised the former measurements for basaltic glass and extended them into the extreme UV to 0.0173 μ.

In this work, studies on relationships of chemical compositions between fusion crust and nucleus in iron spherules are reported. More than 10% of the iron spherules which were picked out from deep sea sediment, have cores and crusts. We were able to divide three of them into cores and crusts. Each cores and crusts were analyzed individually by INAA. The core mainly consists of iron and nickel. Other trace elements, especially noble metal Au and Ir were concentrated in the core. The mechanism of core formation in the iron spherules shows us the origin of them.

Studies on isotopic anomalies in cosmic meteoroids are expected to reveal the features of nuclear synthesis in various phases of star-evolution. The respective isotopes of noble metals had been produced through various reaction processes as well as in various regions of star-eruptions. However, isotopic anomalies of 0s in extremely refractory inclusions of primordial carbonaceous chondrites have not been found up to now. In this work, isotopic ratios of the elements having high condensation temperatures, such as 0s and Ir, in the cosmic spherules are examined using instrumental neutron activation analysis(INAA).

Atomic structures of amorphous silicate dusts with the MgSiO3 composition were simulated by molecular dynamics method as a function or the dust density based on the assumption that the density corresponds to cooling rate of dust formation. The SiO4 tetrahedra are more polymerized with decreasing density, suggesting phase separation between SiO2-rich and MgO-rich components in less dense dusts formed by rapid condensation. A mode of atomic vibration probably due to the Si-0 bending is different in the amorphous silicates with different densities. This may cause changes of the 20 μm bands of IR spectra of silicate dusts with different cooling rates.

Production methods of Fe3O4 grain and MgS grain have been introduced. Fe3O4 grain was produced in an Ar gas pressure range of 25 to 100 Torr by evaporating FeO powder. The growth of Fe3O4 have been discussed as the result of oxidation of Fe grains. MgS grain produced by the reaction of Mg and S vapors grew in the coagulation of tiny cubic sulfide.

The far-infrared extinction of various silicates was measured in the 27 - 400 μm range of wavelength. The SiO2 content of our samples distributes between 45 and 100 weight (wt.)%. There is no distinct absorption band in the far-infrared region and the extinction decreases in proportion to λ−1.4.

Among the various silicates proposed as components of cosmic dust grains, olivine is considered one of the most likely materials. In this work we present the infrared spectra of three different types of olivine grains: crystalline, amorphous and synthetic (also amorphous). While the first and second sample derive from the same natural mineral, the third one has been prepared in the laboratory according to the relative cosmic abundances of the elements. The experimental data are used to fit the emission feature observed in the comet Halley spectrum between 8 and 13 μm. Satisfactory results are obtained by using synthetic olivine mixed with a small amount (5%) of crystalline grains.

The physical properties of the interplanetary dust grains are, out of the ecliptic plane, mainly derived from observations of zodiacal light in the visual or infrared domains. The bulk optical properties (polarization, albedo) of the grains are demonstrated to depend upon their distance to the Sun (at least in a 0.1 AU to 1.7 AU range in the symmetry plane) and upon the inclination of their orbits (at least up to 22°). Classical models assuming the homogeneity of the zodiacal cloud are no longer acceptable. A hybrid model, with a mixture of two populations, is proposed. It suggests that various sources (periodic comets, asteroids, non periodic comets...) play an important role in the replenishment of the zodiacal cloud complex.

Within the recent years the spatial distribution of Zodiacal dust has been subject to a variety of modelling approaches. Whereas models derived from observations in the visual range tend to demand for an increase of interplanetary matter above the solar poles (bulges), models based on infrared measurements and extended to small r seem to favor a decrease there (holes). The models are reviewed, and the dynamical structure implicated in the models is outlined.

Using 3-dim density models of the zodiacal cloud, we have calculated brightness of the zodiacal light over an extended region around the anti-solar point. The isophotal contours of the model Gegenscheins differ from each other, morphologically, to the degree that they can differentiate the competing density models. The recently reduced Gegenschein observations of 2° resolution clearly favour the ellipsoid-type models to the fan-types, and also suggest that the surface of the densest dust concentration in the outer part of the cloud has its ascending node at longitude 100 ± 20° and is inclined 2 ± 0°.5 with respect to the ecliptic plane.

Surface brightness photometry of the night sky from rocket and satellite experiments shows an increase in the scattering efficiency of interplanetary dust grains in the 1500 to 3000 \ region of the spectrum. This increase is best explained by the presence of small dielectric particles with a mean radius of 0.04 microns. The most likely source of these grains is the dissolution of agglomerates of these particles which are released by comets during their perihelion passage. Many of these agglomerates have been collected in the Earth’s atmosphere by high flying aircraft. Submicron particles swept up from interplanetary space may be responsible for the high altitude haze observed in planetary atmospheres.

Photometric observations of the zodiacal light performed by Pioneer 10 indicated that there may be very little scattering by dust in the outer solar system. To shed more light on this problem we formulate explicit expressions for interpreting the brightness observed by a spacecraft travelling inside or outside a finite homogeneous cloud of scattering particles. An application is made to the ecliptic zodiacal light brightness as observed by Pioneer 10 and tabulated by Toller and Weinberg (1985). A satisfactory interpretation of these data as well as earthbound observations can be given by means of a model having a particle density distribution or mean scattering cross section which vanishes beyond 2.8 - 3.7 AU. Some implications for the nature and spatial distribution of the interplanetary dust are discussed.

The opposition effect and the reversal of linear polarization, or negative polarization, at small phase angles have been almost universally observed in light scattered from atmosphereless solar system bodies (e.g., Seeliger 1887, Lyot 1929). Recent investigations have indicated that both phenomena can be qualitatively understood as resulting from a common physical mechanism: coherent multiple backscattering (Shkuratov 1989, Muinonen 1989). These findings have cast doubt on the hitherto accepted explanation that mutual shadowing alone is responsible for the opposition effect, and for the first time offer an acceptable interpretation of the polarization reversal near opposition. As for interplanetary dust, the coherent backscattering mechanism contributes both to the Gegenschein and to the almost certainly existing negative polarization branch (Roosen 1970, Lumme and Bowell 1985).

In the following, theoretical results supporting the coherent backscattering explanation are briefly presented. As future work, we suggest modeling light scattering by a particulate medium to include the first, second and, if necessary, higher orders of scattering in the range below the typical particle size.

After briefly evaluating the observations of the Zodiacal Light and F-corona, we review the laboratory results on the light scattering by dust particles and the various theories which have been recently proposed. We then discuss the optical properties of the dust with emphasis on the phase function, the polarization, the color, the albedo and the local enhancement in the Gegenschein.

Thermal emission from interplanetary dust is the main source of diffuse radiation at λ 5-50 μm. Analysis of infrared sky maps from IRAS and ZIP lead to the result that the average optical properties of the dust change with heliocentric distance. The present uncertainties in calibration should be resolved by COBE. Existence of a dust sublimation zone at 4 solar radii awaits confirmation at the next solar eclipse.

The Barbier’s relation for the diffusely scattered airglow has been modified in such a way that it may describe, with simple changes of two parameter values, the dependence on zenith distance of the atmospheric diffuse light at any time of the night.

Applying time-dependent corrections of the atmospheric diffuse light to the observed night sky brightness, we have determined brightness of the zodiacal light over the region 40° ≤λ − λ⊙ ≤;320ΰand − 20°≤β≤20ΰ. The resulting map of equal brightness contours has an angular resolution of two degrees, and exhibits east-west and north-south asymmetries.

The optical and infrared brightness of the Fraunhofer-corona is produced by light scattering at the zodiacal dust particles and by their thermal emission (see Koutchmy and Lamy 1985). It is modelled within the ecliptic (4 Ro ≤ ε ≤ 15 Ro)taking into account investigations of the global zodiacal dust cloud due to remote sensing and in situ experiments. The input of near solar dust to the corona brightness is discussed.

The Wide-field White Light and Spectrometric Coronograph (LASCO) to be flown on SOHO in 1995 will observe the corona from just above the limb at 1.1 out to 30 solar radii (R o). In addition to the fundamental problems of coronal physics (heating of the corona, acceleration of the solar wind, coronal transients), the scientific objectives incorporate the distribution and properties of dust particles including those released from sun-grazing comets, and interactions of coronal plasma with the dust.

The Wide-Field Light and Spectrometric Coronograph (LASCO) to be flown on SOHO in 1995 is designed to perform accurate photopolarimetric observations of the solar corona. For simulation purpose but also to have a two-dimensional model of the F-corona, we have realized synthetic maps of its brightness and polarization