Interplanetary Dust Grains Research Articles

Dynamics of dust grains near the Sun

Abstract The orbital motion of interplanetary dust grains in sublimation zone near the Sun is revised in detail for grains of obsidian, basalt, astronomical silicate and graphite. Effects of gravity, radiation pressure for a spherical source with limb darkening, and solar wind pressure on dust grains were taken into account. The influence of sputtering, thermal velocity and tangential velocity component of the solar wind particles on lifetime of the grains moving on prograde and retrograde orbits is investigated. It is obtained that β = radiation pressure/gravity is constant everywhere including the region close to the Sun. It is shown that the temperature of submicron dust grains does not exceed 1500 K for silicate grains and 2000 K for graphite ones anywhere in solar corona. Both the dust rings observed near 9r[odot] and the dust free zone near 6.5r[odot] can be explained by basalt-like grains. These dust rings and those observed earlier near 4r[odot], formed by obsidian-like grains, were not found duri...

Interplanetary dust and debris, as observed from the moon

The visible trace of the interplanetary dust cloud, so-called the zodiacal light, has already been photographed from the Moon, more than twenty years ago (part 1). The interplanetary dust grains do not only scatter solar light; they produce a thermal emission in the near infrared domain; also they may impact the Earth and Moon system as they spiral towards the Sun (part 2). The main problems which can be anticipated for Moon based observations of faint astronomical sources are likely to be due to zodiacal light and zodiacal emission; the induced contamination would however be reduced by appropriate choices in the periods of observation (part 3).

Cometary and interstellar dust grains: Analysis by ion microprobe mass spectrometry and other techniques

A survey of microanalytical measurements on interplanetary dust particles (IDPs) and interstellar dust grains from primitive meteorites is presented. Ion microprobe mass spectrometry with its capability to determine isotopic compositions of many elements on a μm spatial scale has played a special role. Examples are measurements of H, N, and O isotopes and refrectory trace elements in IDPs, and C, N, Mg, and Si isotopes in interstellar silicon carbide grains, and C and N isotopes as well as H, N, Al and Si concentrations in interstellar graphite grams. Possible future instrumental developments are also outlined.

Ultraviolet Observations of the Zodiacal Light and the Origin of Interplanetary Dust Grains

AbstractSurface 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.

The Zodiacal Cloud Complex

AbstractThe 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.

Modification of simple organic solids in space: Energetic carbon interactions with solid methane

The formation of complex organic compounds in space by high energy and radiation chemical reactions was simulated in the laboratory using solid methane as a model substance for primordial organic solids. The reactions were induced by energetic carbon atoms formed via the 12C( 3He, 4He) 11C nuclear process (high energy chemistry) and the accompanying radiolysis by the 3He-cyclotron particles (radiation chemistry). Gaschromatographic analysis of the target showed the formation of many new carbon compounds ranging from acetylene and ethylene to molecules containing up to eight carbon atoms including probably cyclic and aromatic compounds. Formation of this kind of products can only be explained by insertion of hot carbon atoms into CH bonds and bridging reactions between CH 4 molecules. The mechanisms can be responsible for the formation of organic polymers, refractories and crusts on objects in space such as interplanetary dust grains, comets and asteroids hit by particle radiation (e.g. solar wind). It may constitute a general pathway for the build-up of complex molecules in prebiotic chemical evolution.

Optical constants of the mixture of ices

The Maxwell-Garnett mixing rule (MG) was applied to estimate the optical constant m * of the mixture of ices. A fairly good agreement between the resulting values of m * and those of our laboratory measurements suggests that the MG rule becomes a powerful tool to derive the unknown optical constants of natural dirty-ice, when there are no chemical bonds between the guest and host materials. Our results would provide the knowledge of the optical constants of dirty-ice for studies of icy substances on the surface of satellites, cometary nucleus and interplanetary dust grains based on their reflectance spectra.

Random fluctuations versus Poynting–Robertson drag on interplanetary dust grains

A particle moving through a sea of stochastic impulses gains energy from the sea; this is a long-established property of brownian motion, given theoretical backing in the fluctuation–dissipation theorem1. However, this energy gain is generally neglected in describing circumstellar dust grains as slowly spiralling into the central star under Poynting–Robertson (P–R) drag. Stochastic forces on circumsolar grains arise from low-frequency fluctuations in surface charge and interplanetary fields, as has long been recognized2,3, but previous studies have treated the mean orbital energy as constant4,5 or slowly decreasing6. I show here that stochastic heating can balance and indeed overwhelm the dissipative P–R drag for small grains (≲1 µm scale radius). Furthermore, the consequent drift to the outer Solar System may cancel the strong collisional source inferred7 for micrometre and sub-micrometre fragments, explaining how their present distribution is stable in time. More generally, the stochastic heating mechanism combined with collisional fragmentation sets limits on dust accretion onto cool stars.

Helios

On December 10, 1974, Helios 1, the first of two nearly identical German‐American spacecraft designed to explore interplanetary space in the inner solar system (inside the orbit of earth), was launched into orbit with perihelion 0.3 AU from the sun. Thirteen months later the sister spacecraft, Helios 2, was launched into a similar orbit. To date these are the only spacecraft to reach this proximity to the sun. Each of the Helios spacecraft contained 10 state‐of‐the‐art experiments, variously designed to measure and analyze the solar wind plasma, the interplanetary magnetic field, plasma waves and radio waves, medium‐ and high‐energy solar and galactic cosmic rays, the zodiacal light, interplanetary dust grains, and extra‐solar system gamma ray bursts (Helios 2 only). In addition, ground monitoring of Faraday rotations, Doppler shifts, and temporal delays of the Helios radio signals provided information on the magnetic field and electron density within the solar corona close to the solar limb. Communication links with Helios 2 were maintained until March 1980, while Helios 1 continues to provide useful scientific data more than 10 years after launch. This book, written to provide an overview of the scientific, technical, and managerial triumphs of the missions, celebrates the 10th anniversary of successful Helios operations.

Some Remarks on the Density of Interplanetary Dust Grains

AbstractThe relevance of the bulk density as a physical parameter characterizing interplanetary dust grains is discussed. The various measurements which lead to a determination of this parameter are reviewed. The specific case of the collected interplanetary dust grains is considered.The bulk density of interplanetary dust grains has been and is still a matter of controversy. This quantity cannot, in general, be directly measured; it is used to relate the mass and the size of a grain. This duality stems from physics itself as there are interactions sensitive to the mass (e.g., gravitational forces) while others are sensitive to the size or the cross-section (e.g., light scattering, radiation pressure, gas and plasma interactions). The measuring technics of the grains reflect this duality as, for instance, impact sensors are generally sensitive to the kinetic energy and thus to the mass, while optical sensors are sensitive to the cross-section. One sees that the density is not strictly speaking the relevant parameter, but what is needed is a relationship between mass and average cross-section.

Secondary Emission from Interplanetary Dust Grains

AbstractSecondary emission can play an important role in the charging of dust grains. This process is very sensitive to their size and to the physical properties of the solid. It is particulary important in the case of insulators in which an intense electric field is present at the surface and can accelerate the excited electrons.As a consequence, the secondary emission yield δ does not depend on the energy of primaries and multiple solutions of the potential due to the usual non-monotonic form of δ versus the energy of primaries disappear.

The Motion of Interplanetary Dust Particles

AbstractRadial velocity measurements on the solar MgI 5183.618Å Fraunhofer absorption line in the Zodiacal Light spectrum have been made with a microprocessor-controlled servo-stabilised Fabry-Perot interferometer. Observations were made at 5 and 10 degree intervals in the ecliptic plane between morning and evening elongations of 25 degrees. These new data are of much greater precision and coverage than any previously obtained. Obtained over a two year period, the observations show a consistent evening/morning asymmetry in the radial velocity curve with the Gegenschein receding from the Earth at 4 Km/sec. These data do not support the hypothesis that the majority of interplanetary dust grains are in hyperbolic trajectories.

Electrostatic Charge of Interplanetary Dust Grains: New Results

AbstractA continuing program aimed at improving the determination of the charge of interplanetary as well as cosmic grains is presented. Recent data have been combined to generate two high-resolution solar spectra corresponding to the maximum & minimum of activity. The energy distribution of photoelectrons emitted by quartz grains under solar irradiation is calculated using the new laboratory measurements of Quemerais et al. (this volume). Finally, the method of Lafon, Millet and Lamy (Astron. Astrophys., 95,295, 1981) is used to find the electrostatic potential of these grains.

Lorentz Scattering of Interplanetary Dust Grains

AbstractThe scattering of dust grains orbits due to recurrent sectors of the interplanetary magnetic field is reinvestigated with a better formalism. Our method reveals the resonant character of the diffusion and is well suited for the problem. The spreads in the orbital parameters are found less important than believed untill now and to vary rapidly with eccentricity and semi-major axis. Only the small dielectric grains with size less than 0.5 μm may be scattered by the Lorentz force fluctuations; the main diffusion occurs in inclination and near the sun (20-60 R⊙).

21. Light of the Night Sky

The light of the night sky consists of atmospheric components (airglow, light scattered in the atmosphere) and – even in the case of spaceborne observations – of zodiacal, galactic and extragalactic light. Although all components are of similar importance, investigations on zodiacal light have profitted most by the space age since their object of research, the interplanetary dust cloud, became accessible to direct in-situ measurements. Lunar samples and measurements by micrometeoroid detectors provide individual and eventually detailed information on impact events, which however are limited in number and therefore restricted in statistical significance. Zodiacal light investigations involve scattered light of many particles in large volume elements and therefore provide global information about physical properties and spatial distribution of interplanetary dust grains, however just in terms of average values. Therefore both sources of information are complementary and a synthesis can only be achieved by synoptic interpretation of zodiacal light, micrometeoroid, and meteoroid investigations also including dynamical aspects. Measurements of zodiacal light (and emission) from rockets, manned or non manned spacecraft, and deep space probes gained drastically in importance compared to ground based observations. On the other hand investigations on airglow have become more and more a topic of geophysics Caeronomy). They remain relevant however to astronomy as far as photometric features are concerned. These general trends continued in the last triennium and have influenced the activities of our commission.

Laboratory Simulation of Chemical Interactions of Accelerated Ions with Dust and Ice Grains

AbstractEnergetic ions or atoms in space may undergo hot chemical reactions upon penetration into interplanetary or interstellar dust grains, ice layers, cometary matter, and surfaces of planetary moons. The mechanistic pathways can be different from those of classical ion molecule interactions, photolytical and radiolytical processes. The kinetic energy of the hot reactant facilitates endothermic reactions and those with high energy of activation, among them atom-molecule interactions. The conditions of hot cosmic chemistry are simulated in laboratory experiments in order to obtain insight into the nature of chemical products and the reaction mechanisms of their formation. This paper reviews the methods of ion implantation, nuclear recoil in situ, nuclear recoil implantation, secondary knock-on processes and computer simulation of collision cascades. Carbon and nitrogen impact in frozen H2O, NH3 and CH4 is shown to lead to the formation and radiolytic permutation of a series of organic molecules, among them e.g. formaldehyde, methanol, methylamine, cyanamide, formamidine and guanidine which may act as precursors for biomolecules.

Gas-rich meteorites: Probes for particle environment and dynamical processes in the inner solar system

The discovery in the early sixties of precompaction solar wind irradiation records in the gas-rich meteorites opened up the possibility of studying the solar activity at different epochs in the distant past. Subsequent studies in several meteorites have led to the discovery of the precompaction records of irradiation of constituent grains by solar wind, solar flare and galactic cosmic ray particles. There are also microcraters resulting from their collisions with interplanetary dust grains. Analyses of these records and their observed similarity with those found in the lunar samples led to the hypothesis that the precompaction records in individual components of these meteorites were imprinted while they were residing in the near surface region of their parent bodies, most probably the asteroids. Although the asteroids are the most plausible candidates for the parent bodies of gas-rich meteorites, there exist certain dynamical arguments which tend to favor a cometary origin in certain cases. Also, recent studies indicate that in the case of gas-rich carbonaceous chondrites solar flare irradiation of grains may have occurred prior to formation of the parent bodies.

Nature, Origin and Evolution of Interplanetary Dust Grains

AbstractThis contribution will attempt to give a coherent and up-to-date view of the interplanetary dust cloud as well as to delineate some of the current outstanding problems. It is largely based on studies carried out at Laboratoire d’Astronomie Spatiale during the past years.

Charged dust in the outer planetary magnetospheres

Interplanetary dust grains entering the Jovian plasmasphere become charged, and those in a certain size range get magneto-gravitationally trapped in the corotating plasmasphere. The trajectories of such dust grains intersect the orbits of one or more of the Galilean satellites. Orbital calculations of micron sized dust grains show that they impact the outermost satellite Callisto predominantly on its leading face, while they impact the inner three - Io, Europa and Ganymede - predominantly on the trailing face. These results are offered as an explanation of the observed brightness asymmetry between the leading and trailing faces of the outer three Galilean satellites. The albedo of Io is likely to be determined by its volcanism.

Collisional processes among interplanetary dust grains: An unlikely origin for the β meteoroids

The question of the collisional production of the β meteoroids is reexamined incorporating recent experimental results (A. Fugiwara, G. Kamimoto, A. Tsukamoto, 1977, Icarus 31, 277–288). The collisional model yields a flux of fragments supported by the conservation of mass flux which does not account by far for the observed flux of submicron grains. Particles larger than about 100 μm will be destroyed by collisions inside 1 AU, well before they can get near the Sun. The existence of two independent populations of interplanetary dust grains as proposed by L. B. Le Sergeant and Ph. L. Lamy (1978, Nature 266, 822–824; 1980, Icarus 43, 350–372) appears reinforced. It is proposed that the bulk of submicron grains does not necessarily travel in hyperbolic orbits and that β meteoroids may be a phenomenon—possibly transitory—of limited importance.