Can be retrieved at: http://www.amara.com/ftpstuff/dustevolve.txt
Copyright Amara Graps 1996-2000. All rights reserved.
Cosmic dust used to be an annoyance to astronomers because of the way that the dust obscures the object that they wish to observe. When the field of infrared astronomy begin, those annoying little dust particles were observed to be significant constituents of the Universe and found to be vital components of astrophysical processes.
For example, the dust can drive the mass loss that occurs when a star is nearing the end of its life, those particles are an essential parts of the early stages of star formation, and they form planets around other stars. In our own solar system, dust plays a major role in the zodiacal light, Saturn's B ring spokes, the outer diffuse planetary rings at Jupiter, Saturn, Uranus and Neptune, the resonant dust ring at the Earth, and the overall behavior of comets.
The study of dust is one of those many-faceted research topics that brings together different scientific fields. In this case, physics (solid-state, electromagnetic theory, surface physics, statistical physics, thermal physics), math (fractal math), chemistry (chemical reactions on grain surfaces), meteoritics, as well as every branch of astronomy and astrophysics.
Dust evolves in the Universe. Dust forms in dusty clouds, cycles through solar systems (even comets), through a star's late evolution and back into a nebula.
First, there is no such thing as a "standard cloud of gas and dust". There are different types of nebulae with different physical causes and processes. One might see the following classifications:
Some distinctions between those types of nebula are that very different radiation processes are at work. For example, HII regions, like the Orion Nebula, where a lot of star-formation is taking place, are characterized as thermal emission nebulae. Supernova remnants, on the other hand, like the Crab Nebula, are characterized as nonthermal emission (synchrotron radiation).
Some of the better known dusty regions in the Universe are the diffuse nebula in the Messier catalog: M1, M8, M16, M17, M20, M42, M43, for example. You can see these online at:
http://seds.lpl.arizona.edu/messier/Messier.html
Some larger 'dusty' catalogs that you can access from the NSSDC, CDS, and perhaps other places are:
The processing of dust in the Galaxy is a wonderfully rich study. The dust grains evolve cyclically- chemically, physically and dynamically. There are at least four kinds of dust populations (Dorschner, J., (1996), pg. 487-8)):
The scenario that I describe here originated with J. Mayo Greenberg and has been expanded upon by many people since then. It is called the grain "core-mantle" model. It has some pretty good observational and theoretical arguments supporting it.
The dust processing cycle, in brief, looks like the following (Dorschner, J., (1996), pg. 487-8). From the stellar winds of evolved stars, new dust is formed and is injected into interstellar space. Young stardust is mixed with old, heavily-processed, diffuse ISM dust, and is subject to passing supernova shocks and ultraviolet radiation. Dusty clouds form. The protostar environment is a fertile ground for solids on all size scales from dust grains to planets (Hanner, M.S. 1995) to form. Star formation in cool molecular clouds become both a *sink* of old dust and well as a *source* of new dust.
Before I start with details of the evolutionary aspects of dust, I answer:
Cosmic dust is dust grains and agreggates of dust grains. These particles are irregularly-shaped with porosity ranging from fluffy to compact. The composition, size, and other properties depends on where the dust is found. General diffuse interstellar medium dust should be distinguished from dust grains in dense clouds, which should be distinguished from planetary rings dust, which should be distinguished from circumstellar dust etc. For example, grains in dense clouds have acquired a mantle of ice and the average dimensions are larger than those dust particles in the diffuse interstellar medium. Interplanetary dust particles (IDPs) are generally larger still.
Other dust composition variances are the following.
The densities of most stratospheric-captured IDPs range between 1 and 3 g/cm^3, with an average density at about 2.0 g/cm^3 (Love, Joswiak, and Brownlee, 1994).
Typical IDPs are fine-grained mixtures of thousands to millions of mineral grains and amorphous components. We can picture an IDP as a "matrix" of material with embedded elements which were formed at different times and places in the solar nebula and before our solar nebula's formation. I would like to point to GEMS, chondrules, and CAIs, in particular.
GEMS (Glass with Embedded Metal and Sulfides) are tiny submicrometer spheroids with bulk compositions that are approximately chondritic. They form the building blocks of anhydrous IDPs in general, and cometary IDPs, in particular. Their compositions, minerology and petrography appear to have been shaped by exposure to ionizing radiation. Since the exposure occurred prior to the accretion of cometary IDPs, and therefore comets themselves, GEMS are likely either solar nebula or presolar interstellar grains. The properties of GEMS (size, shape, mineralogy) bear a strong resemblance to those of interstellar silicate grains as inferred from astronomical observations (Bradley and Ireland, 1996).
Chondrules are millimeter-sized spherical "drops" suspended in the younger matrix of dust grain material of chondritic meteorites and chondritic interplanetary dust particles. Chondrules are leftover chaff from the time period of the collapse of the solar nebula. Chondrules were once molten, which required temperatures in excess of 1500 to 1900 K. The chondrules must have cooled very rapidly, in about an hour (Wood, 1999). They could not have been formed in the ambient temperature of the innermost solar nebula, instead, they were formed as the result of a quick, high-energy event, for example, a lightning discharge, an accretion shock, or a magnetic nebular flare (Excell, S., 1998).
CAIs are the "Calcium-Aluminum-Inclusions" that one sometimes finds between the chondrules. CAIs were formed at much higher temperatures than the temperatures at which chondrules formed, and CAIs may have survived many multiple high-temperature events, while most chondrules are the product of a single, transient melting event. The isotopic anomalies of CAIs give us a good clue about some of the events of our solar system's formation because the isotopic anomalies infer that the solar nebula collapsed shortly after a _nearby supernova event_. In addition, radiactive dating methods show that the formation of CAIs preceded the formation of chondrules by about 2 million years (Excell, 1998). (Therefore, CAIs are one nice trail from a supernova to "us" via dust.)
In the book: The Dusty Universe by Aneurin Evans, the author makes a nice argument that the gas-to-dust ratio in the interstellar medium suggests that a large fraction of heavy elements (other then hydrogen and helium) must be tied up in dust grains, the assembled elements for the molecules most likely being carbon, nitrogen, oxygen, magnesium, silicon, sulphur, iron, and compounds of these.
A dust particle interacts with electromagnetic radiation in a way that depends on its cross-section, the wavelength of the electromagnetic radiation, and on the nature of the grain: its refractive index, size, etc. The radiation process for an individual grain is called its "emissivity," dependent on the grain's "efficiency factor". Furthermore, we have to specify whether the emissivity process is extinction, scattering, or absorption. In the radiation emission curves, several important signatures identify the composition of the emitting or absorbing dust particles.
Dust particles can scatter light nonuniformly. Forward-scattered light means that light is redirected slightly by diffraction off its path from the star/sunlight, and back-scattered light is reflected light.
The scattering and extinction ("dimming") of the radiation gives useful information about the dust grain sizes. For example, if the object(s) in one's data is many times brighter in forward-scattered visible light than in back-scattered visible light, then we know that a significant fraction of the particles are about a micrometer in diameter.
The scattering of light from dust grains in long exposure visible photographs is quite noticeable in "reflection nebulas", and gives clues about the individual particle's light-scattering properties. In x-ray wavelengths, many scientists are investigating the scattering of x-rays by interstellar dust, and some have suggested that astronomical x-ray sources would possess diffuse haloes, due to the dust.
By utilizing the radiative properties of cosmic dust, one is learning about dust by indirect means. What about learning of dust by utilizing direct means, i.e. collecting and analyzing dust?
An average of 40 tons per day of cosmic dust falls to the Earth (Leinert and Gruen, 1990). Some dust particles are swept up by the Earth, and collected by research aircraft that fly high in the stratosphere. Other interplanetary dust particles are collected on the large Earth ice-masses (Antartica and Greenland and Arctic) and in deep-sea sediments. These stratospheric and polar ice melt interplanetary dust particles are then examined in the laboratory.
Laboratory experiments to measure dust impacts and to study the evolution of dust mantles on top of ice-dust mixtures (to simulate comet environments) have been performed, yielding useful results.
Dust detectors on planetary spacecraft have been built, and are being built. Space experiments to determine velocity, charge (from which masses are derived), and flight direction of cosmic dust particles by impacting dust on a target have produced good results. Dust detectors are now currently flying on the Galileo, Ulysses, Cassini, Gorid, and the Stardust spacecraft. In addition to Gorid, which is flying in earth orbit, the LDEF satellite and the Eureca satellite, also detected, in-situ, natural and man-made debris.
Some of the interesting results from the last few years of dust detector experiments are the "dust streams", detected by instruments on the Ulysses and Galileo spacecraft, dust that is confirmed to mostly originate from the volcanoes on Io. Dust scientists now know that some origins of the in-situ dust is interstellar, as well as interplanetary, deduced by arguments that the particles have hyperbolic orbit trajectories that are compatible with the flow of interstellar gas. In Spring 2000, Stardust scientists presented provocative results that the Stardust CIDA dust instrument detected in-situ tar-like macro-molecules.
The magnetic field embedded in the solar wind and light pressure forces combine to act like a giant mass spectrometer for dust particles traveling in the solar system. The smaller interstellar dust particles are hard to detect because radiation pressure and interaction of the charged grains with the interplanetary magnetic field prevent these small grains from penetrating down to the distance where the spacecraft can detect them (for example Ulysses near the Sun or Galileo near Jupiter), but spacecraft dust detectors have been able to detect the larger mass particles (say 30 times larger than the average diffuse medium dust grain).
The large grains start with the silicate particles forming in the atmospheres of cool stars, and carbon grains in the atmospheres of cool carbon stars. Stars, which have evolved off the main sequence, and which have entired the giant phase of their evolution, are a major source of dust grains in the Galaxy.
How do we know that that dust is formed in the envelopes of late-evolved stars? We have some good observations. An observed (infrared) 9.7 micron emission silicate signature for cool evolved (oxygen-rich giant) stars. And an observed (infrared) 11.5 micron emission silicon carbide signature for cool evolved (carbon-rich giant) stars. These help provide evidence that the small silicate particles in space came from the outer envelopes (ejecta) of these stars. (See Humphreys et al, (1972) ApJ 172, 75, and Evans, A. The Dusty Universe, pg 164-167)
How do we know that dust wasn't formed in interstellar space? We know because the conditions in interstellar space are generally not suitable for the formation of silicate cores. The arguments are that: given an observed typical grain diameter a, the time for a grain to attain a, and given the temperature of interstellar gas, it would take considerably longer than the age of Universe for interstellar grains to form (see pg 147-148 of Evans' book). Evans says in his book that grains are seen to form in the vicinity of nearby stars in real time. "Real time" meaning a) nova and supernova ejecta, and b) R Coronae Borealis, which seems to eject discrete clouds containing both gas and dust.
For condensation from gas to solid to occur depends on the values of the gas pressure P_gas and the vapour pressure P_vap. Once P_gas exceeds P_vap, then condensation should occur. If one neglects curvature of the grain surface (which is an effect that must be considered for tiny grains), then
P_vap ~ P_0 exp[-T_0/T]
where P_0 and T_0
are pressure and temperature constants specfic to
the astronomical material. You can plug in the following numbers and
get some idea for the vapour pressure (from Anueurin Evans, Dusty
Universe, page 85.):
Material P_0(N m^{-2}) T_0 (K)
Graphite 1.68E13 88880
Silicates 5.31E13 60560
Water ice 2.16E5 6160
Hydrogen 2.66E7 104
Then supernovae/novae explosions of the star eject that material out into space. The dust that you see in supernovae remnants (like from M1, the Crab nebula) was mostly not produced in the supernovae. It was present in the star's outer envelope before the supernovae explosion. The explosion just pushed that material outwards.
Note that new grains can form in the debris of the supernovae explosion (even easier in the debris of a novae explosion) but that material has to be quite cool, so it takes some time (say, on the order of a year) after an explosion for the debris to be cool enough for grains to form. It's a race between dropping temperature, which favors grain formation, and dropping density, which opposes it.
When the grains have cooled down to about 15K, those silicates are the cores for the growth of mantles of ices. The mantles are formed by accretion of (gas phase) atoms and molecules of oxygen, carbon, nitrogen, sulfur, along with hydrogen. The grains are nonspherical, and various sticking processes cause other simple molecules (H2O, CO, H2S, CH3OH, OCS, OCN- etc.) to stick. The mantle ices are always being photoprocessed by ultraviolet (UV) radiation from either distant stars or by UV created by cosmic rays or from local hot stars and/or stellar winds. The photoprocessing changes the basic composition of the ices and causes some complex organic refractory residues to form.
So now the heavily photoprocessed material is out in a diffuse environment (diffuse cloud). That cloud may eventually become a denser molecular cloud. In the denser clouds, more organic mantle formation occurs, layering the silicate core- like the rings in a tree trunk. The innermost layers of the dust grain have been the most irradiated, and the outermost layers are the result of the most recent processes.
Then, within those molecular clouds, critical densities lead to star formation, and that dust gets captured and becomes part of the new star, and the cycle stars all over again. A typical grain anywhere in space will have undergone at least 20 cycles (And remember that, in addition, new grains are formed.)
Dust is an important driving force in the development of a protostar's accretion disk. In particular, it has a large effect on the turbulence and convection in the disk. Before the dust grains settle into a midplane region, (and before the T-Tauri phase of the protostar) the homogenized distribution of the grains are a primary cause of opacity, leading to steep temperature gradients and convection and turbulence. (Other driving forces for turbulence in this early stage may be the angular momentum in the solar nebula by infalling matter, and the thermal energy liberated by gravitational collapse.)
How are the interstellar grains destroyed? There are some ultraviolet processes which lead to grain "explosions" (d'Hendecourt et al., 1985 Astr Ap, 152, 130; Greenberg, J.M., 1976, Ap. Space Sci, 39, 9). Evans' book also describes evaporation, sputtering (when an atom or ion strikes the surface of a solid with enough momentum to eject atoms from it), and grain-grain collisions, which have a major influence on the grain size distribution, as well.
These destructive processes happen in a variety of places. Some grains are destroyed in the supernovae/novae explosion (and then some grains form sometime afterwards). Some of the dust is ejected out of the protostellar disk in the strong stellar winds that occur during a protostar's active T Tauri phase. Plus there are some pretty complicated gas-phase processes in a dense cloud where ultraviolet photons eject energetic electrons from the grains into the gas.
Dust grains incorporated into stars are also destroyed, but only a relatively small fraction of the mass of a star-forming cloud actually ends up in stars. This means a typical grain goes through many molecular clouds and has mantles added and removed many times before the grain core is destroyed.
I said previously that a typical grain anywhere in space will have undergone at least 20 cycles. How does this work, since a typical star lives for 5+ billion years, and the time since the Big Bang is only 15 billion years (say)?
Mayo Greenberg explains (in Greenberg's chapter of the IAU Symposium #135: Interstellar Dust book) : "The mean star production rate of 12 solar masses per year implies an interstellar medium turnover time of ~5*10^9 years, so that this is the absolute maximum lifetime of a dust particle no matter how resistant to destruction. If we use a mean molecular cloud-diffuse cloud period of 2*10^8 years (10^8 years in each), then a typical grain anywhere in space will have undergone at least 20 cycles so that, for example, the typical diffuse cloud dust particle age is greater than 10^9 years and consists of a mix of particles which have undergone a wide variety of photoprocessing."
So the grain recycling works through molecular clouds with the formation and destruction of grain mantles. One time in 20 or so, the grain core gets incorporated into a star, and is destroyed. The other times, the grain gets ejected, and only the mantle is destroyed.
I found an interesting table in Gehrz's chapter (pg 447) of the IAU #135 Interstellar Dust book: "Types of Dust Grains in Stellar Outflows".
Stellar Type Input to Interstellar Medium, Relative to all Stars M Stars (Miras) 35% RLOH/IR stars 32% Carbon stars 20% Supernovae 8% M supergiants 4% Wolf-Rayet stars 0.5% Planetary Nebulae 0.2% Novae 0.1% RV Tauri stars 0.02% O,B stars 0
Gehrz concludes in his last section titled: "The Ecology of Stardust in the Galaxy" that:
Studies of the local interstellar medium (LISM) during the last 20 years have yielded a picture of the Sun located in a cool (~7000 K according to Axford), low-density region (Ferlet, R., et al. 1991) flowing past our solar system, this region being immersed in an irregular, very hot (~million degree K), and tenuous (~0.05/cm^3), larger, local bubble of tens to hundreds of parsecs in size. (Axford and Suess, 1995). The larger local bubble is thought to have been produced by a combination of one or more supernovae and stellar winds associated with a group of O and B stars. A map of our galactic neighborhood can be seen at: http://galileo.mpi-hd.mpg.de/dune/content/map.htm
An interesting interdisciplinary paper about dust embedded in the interstellar cloud flowing through the solar system appeared in late 1999 (P. C. Frisch, et all), measuring elemental abundances and the dust-to-gas ratio towards two directions in our local interstellar environment: towards eps CMa and alpha Sco, and comparing those dust properties to Galileo and Ulysses dust detector interstellar dust measurements. Included in the paper are the following conclusions:
Closer to home, the interplanetary dust cloud has been studied for many years in order to understand its nature, origin, and relationship to solar systems (our own, as well as extrasolar systems).
The interplanetary dust particles (IDPs) not only scatter solar light (called the "zodiacal light", which is confined to the ecliptic plane), the IDPs also produce thermal emission, which is the most prominent feature of the night sky light in the 5-50 micron wavelength domain (Levasseur-Regourd, A.C. 1996). The grains characterizing the infrared emission near the earth's orbit have typical sizes of 10-100 microns (Backman, D., 1997). The total mass of the interplanetary dust cloud is about the mass of an asteroid of radius 15 km (with density of rho=2.5).
The sources of IDPs include at least: asteroid collisions, cometary activity and collisions in the inner solar system, Kuiper Belt collisions, and ISM grains (Backman, D., 1997). Indeed, one of the longest-standing controversies debated in the interplanetary dust community revolves around the relative contributions to the interplanetary dust cloud from asteroid collisions and cometary activity.
The main physical processes "affecting" (destruction or expulsion mechanims) IDPs are: expulsion by radiation pressure, inward Poynting-Robertson (PR) radiation drag, solar wind pressure (with significant electromagnetic effects), sublimation, mutual collisions, and the dynamical effects of planets (Backman, D., 1997).
The lifetimes of these dust particles are very short compared to the lifetime of the Sun. If one finds grains around a star that is older than 10^8 years, then the grains *must* have been from recently released fragments of larger objects, i.e. they cannot be leftover grains from the protoplanetary nebula (Backman, private communication). Therefore, the grains would be "later-generation" dust. The zodiacal dust in our solar sytem is 99.9% later-generation dust, 0.1% intruding ISM dust, and 0% primodial grains from the Solar Sytem's formation.
The interplanetary dust cloud has a complex structure (Reach, W., 1997). It has:
The isotope ratios of comet and interstellar dust are very similar, indicating a common origin (see R.F. Knacke chapter: "Comet Dust" in IAU Symposium No. 135, Interstellar Dust ed. Allamandola and Tielens, publ. by Kluwer, 1989). Interplanetary dust particle isotope ratios are quite different.
In this section I expand on the dusty link between the molecular clouds and comets in a solar system.
Long-period comets are often thought to be pristine, unaltered relics since their formation. They may be the best probes of ancient solar system (and pre-solar) processes available to us. (However, some experts with good observational evidence are challenging this view. See recent work by S.A. Stern)
A long-period comet in a highly eccentric orbit with a perihelion distance of only a few solar radii will experience a range of diverse conditions as it traverses its orbit (Lewis, 1995). Almost all of the time it will be so far from the Sun that it will be too cold for evaporation of ices to occur. When it passes through the terrestrial planet region, evaporation will be rapid enough to blow away small grains, but the largest grains may resist entrainment and stay behind on the comet nucleus, beginning the formation of a dust layer. Near perihelion, the heating and evaporation rate will be so great, that no dust can be retained.
Therefore, the thickness of dust layers covering the nuclei of a comet can indicate how closely and how often a comet's perihelion travels are to the Sun. If a comet has an accumulation of thick volatile-depleted dust layers, it may have frequent perihelion passages that don't approach the Sun too closely.
This thick accumulation of dust layers is actually a good description of virtually all of the periodic short-period comets. The general conclusion of studies by David Brin (UCSD), Harry Houpis (UCSD), Asoka Mendis (UCSD), Fraser Fanale (U HI), James Salvail (U HI), Paul Weissman (JPL), Hugh Keiffer (USGS), and others has been that dust layers with thicknesses of order meters may accumulate on the surfaces of short-period comet nuclei.
Note that the accumulation of dust layers over time would change the physical character of the short-period comet. A dust layer both inhibits the heating of the cometary ices by the Sun (the dust is very opaque and a poor conductor of heat), and slows the loss of gases from below. A comet nucleus in an orbit typical of short period comets would quickly decrease its evaporation rate to the point that neither a coma or tail would be detectable. Such a body may be described by terrestrial astronomers as a low-albedo near-Earth asteroid. It would be able to retain much of its ices over its entire dynamical lifetime (of ~100 M yr).
Comet dust can provide clues to comets' orgin, and the formation of our solar system. There are two main models about where comets came from: 1) the interstellar model and 2) the solar system model. The remaining portion of this essay came from information in Science News 149, June 1, 1996, pg. 346-347.
The interstellar model is the following. It says that ices formed on dust grains in the dense cloud that preceded the Sun. The mix of ice and dust then gathers together into a comet without appreciable chemical modification. J. Mayo Greenberg first proposed this idea in 1986.
In the solar system model, the ices that formed in the interstellar cloud didn't initially gather together, but vaporized as the ices to become part of the accretion disk of gas and dust around the protosun. The vaporized ices later resolidified and assembled into comets. So the comets in this model would have a little bit different composition than those comets that were made directly from interstellar ice.
Comet Hyakutake data has been very good so far for providing some clues to the above.
Michael Mumma's et al's IR observations from the IRTF detected ethane in the comet. Now investigators think that the comet originated directly from a chilly part of the interstellar cloud (which can't exceed 20K). They have some confirming evidence for this theory from the fact that Hyakutake's nucleus has very little carbon monoxide, which makes chemical sense if the carbon is tied up in heavier molecules like ethane.
The giant Hale-Bopp, on the other hand, may have formed in our solar system.
Note: Some other models for comet formation are: 1) primordial rubble piles which agglomerate in the region where Jupiter was forming, 2) aggregatation of planetisimals in the dust disk around the Uranus-Neptune region 3) cold shells of material swept out by the protostellar wind. I honestly don't know how seriously people take these latter models. The ones that I hear about the most are the "interstellar model" and the "solar system model."
See, I'll bet you didn't know before that those annoying little dust particles are significant constituents of the Universe and vital components of astrophysical processes.
I condensed parts of this essay from three or four shorter dust essays and one long thread titled "Supernovae Distribution" running on sci.astro in January 1996. I want to thank Steve Willner in particular for his comments on that sci.astro thread.
The interplanetary dust sections were derived, in part, from reports given at the Exozody Workshop, NASA-Ames Research Center, Mountain View, California, October 23-25, 1997, and from discussions with the participants before, during, and after the Workshop. In particular, I want to thank Dana Backman for many of those discussions. Other parts of this essay were derived in part from discussions with my colleagues Harald Krueger, (Max-Planck-Institut fuer Kernphysik, Heidelberg), Antal Juhasz, (KFKI, Budapest), and with Eberhard Gruen, head of the MPI-K, Heidelberg dust group.
You are welcome to visit the Max-Planck-Institut fuer Kernphysik Cosmic Dust group web site: http://galileo.mpi-hd.mpg.de to learn more about results from in-situ solar system dust detector experiments.
Allamandola, Lou and A.G.G.M Tielens eds., IAU Symposium 135: Interstellar Dust, 1989, Kluwer Press. (I used Mayo Greenberg's chapter: "The Core-Mantle Model of Interstellar Grains and the Cosmic Dust Connection" as a source for the sections of "Dust Grain Formation" and "Dust Grain Recycling" above.)
Axford, W.I. and S.T. Suess, "The Heliosphere," http://web.mit.edu/afs/athena.mit.edu/org/s/space/www/helio.review/axford.suess.html
Backman, Dana, Extrasolar Zodiacal Emission - NASA Study Panel Report, 1997 for Exozody Workshop, NASA-Ames, October 23-25, 1997. http://astrobiology.arc.nasa.gov/workshops/zodiac/backman/backman.txt
Bradley, John and Ireland, Trevor, I, "The Search for Interstellar Components in Interplanetary Dust Particles," Physics, Chemistry, and Dynamics of Interplanetary Dust, ASP Conference Series, Vol 104, 1996, B.A.S. Gustafson, and Martha Hanner, eds.
Dermott, S.F. Jayaraman, S., Xu, Y.L., Gustafson, A.A.S., Liou, J.C., (1994), "A circumsolar ring of asteroid dust in resonant lock with the Earth," Nature 369, June 30, 1994, pg. 79.
Dermott, S.F., in talk titled "Signatures of Planets in Zodiacal Light," Exozody Workshop, NASA-Ames, October 23, 1997.
Dorschner, Johann, "Properties of Interstellar Dust," Physics, Chemistry and Dynamics of Interplanetary Dust, Gustafson, Bo A.S. and Martha Hanner, ed., , ASP Conference series, Vol 104, 1996, p 487-506.
Evans, Aneurin, The Dusty Universe , Ellis Horwood, 1994. (excellent reference)
Excell, Steven, 1998, Web page: "The Nature and Origin of Chondrules -- A Survey of the Classic and Current Models of Chondrule Formation", http://www.arachnaut.org/meteor/chondrules.html
Ferlet, R., A. Vidal-Madjar, et al. (1991). Structure of the local interstellar medium. (Astrophysics at FUV and EUV wavelengths; Proceedings of the Topical Meeting of the Interdisciplinary Scientific Commission E /Meeting E3/ of the COSPAR 28th Plenary Meeting, The Hague, Netherlands, June 25-July 6, 1990. A92-19151 06-90) Advances in Space Research (ISSN 0273-1177) 11(11, 1991): 81-86.
Flynn, G. "Sources of 10 micron Interplanetary Dust: The Contribution from the Kuiper Belt", from _Physics, Chemistry, and Dynamics of Interplanetary Dust_, ASP Conference Series, Gustafson, B.A.S. and Hanner, M.S. ed., Vol 104, 1996, pg. 171-175.
Gruen, E. "Interplanetary Dust and the Zodiacal Cloud", _Encyclopedia of the Solar System_, Academic Press, 1999 who uses this reference for Table III: Jessberger, E.K. et al., (1992), Earth Planet. Sci. Lett. 112, 91-99.
Greenberg, J. Mayo and J.I. Hage, (1990) "From Interstellar Dust to Comets: A Unification of Observational Constraints," ApJ 361, 260-274.
Hanner, M.S. 1995, Highlights Astron. 10, 351.
Leinert C. and Gruen E, 1990 "Interplanetary Dust," in _Physics and Chemistry in Space_ (R. Schwenn and E. Marsch eds.) Space and Solar Physics, Springer, Berlin: 204--275.
Levasseur-Regourd, A.C., 1996, "Optical and Thermal Properties of Zodiacal Dust," _Physics, Chemistry and Dynamics of Interplanetary Dust_, ASP Conference series, Vol 104, 1996., p. 301.
John S. Lewis, Physics and Chemistry of the Solar System, Academic Press, 1995, pp. 285, 292-293
Love S. G., Joswiak D. J., and Brownlee D. E., (1994) "Densities of stratospheric micrometeorites," Icarus 111: 227--236.
P. C. Frisch, J. Dorschner, J. Geiss, J. M. Greenberg, E. Gruen, M. Landgraf, P. Hoppe, A. P. Jones, W. Kraetschmer, T. J. Linde, G. E. Morfill, W. T. Reach, J. Slavin, J. Svestka, A. Witt, and G. P. Zank, "Dust in the local interstellar wind" (1999), Astrophysical Journal, 525 , 492-516.
Reach, W., in talk titled "General Structure of the Zodiacal Dust Cloud," Exozody Workshop, NASA-Ames, October 23, 1997.
Wood, J.A. "Origin of the Solar System," in The New Solar System Beatty, Petersen, and Chaikin, eds., Sky Publishing, 1999, pg. 13-22.