Early Solar Nebula Grains – Interplanetary Dust Particles

Early Solar Nebula Grains – Interplanetary Dust Particles

1.8 Early Solar Nebula Grains – Interplanetary Dust Particles JP Bradley, Institute of Geophysics and Planetary Physics, Livermore, CA, USA ã 2014 E...

3MB Sizes 0 Downloads 8 Views

1.8

Early Solar Nebula Grains – Interplanetary Dust Particles

JP Bradley, Institute of Geophysics and Planetary Physics, Livermore, CA, USA ã 2014 Elsevier Ltd. All rights reserved.

1.8.1 Introduction 1.8.2 Particle Size, Morphology, Porosity, and Density 1.8.3 Mineralogy 1.8.3.1 CPIDPs 1.8.3.2 Glass with Embedded Metal and Sulfides 1.8.3.3 CSIDPs 1.8.4 Optical Properties 1.8.5 Compositions 1.8.5.1 Major Elements 1.8.5.2 Trace Elements 1.8.5.3 Isotopes 1.8.5.4 Noble Gases 1.8.6 Conclusions Acknowledgments References

How can you appreciate a castle if you don’t cherish all the building blocks? (Stephen Jay Gould)

1.8.1

Introduction

One of the fundamental goals of the study of meteorites is to understand how the solar system and planetary systems around other stars formed. It is known that the solar system formed from preexisting (presolar) interstellar dust grains and gas. The grains originally formed in the circumstellar outflows of other stars and in the interstellar medium (ISM) itself. They were modified to various degrees, ranging from negligible modification to complete destruction and reformation during their 100 Ma lifetimes in the ISM (Jones and Nuth, 2011; Mathis, 1993; Seab et al., 1987). Finally, they were incorporated into the solar system. Submicrometer-sized silicates and carbonaceous material are the most common grains in the ISM (Mathis, 1993; Sandford, 1996), but it is not known to what extent these presolar grains survive in the solar system and whether they can be unambiguously distinguished from solar-system grains. Spatially resolved observations of (the surfaces of) accretion disks around some young stars indicate significant variation in the distribution and properties of grains as a function of heliocentric distance. For example, in some disks, grains close to the hot stars are melted and recrystallized, and in outer cold disks regions, they remain amorphous with properties similar to (silicate) dust in the ISM (van Boekel et al., 2004). Although it is unknown whether a similar environment existed in the solar accretion disk, the logical place to find surviving grains from the presolar molecular cloud is in samples of small primitive bodies like comets and asteroids that have undergone little, if any, parent-body alteration. Interplanetary dust particles (IDPs) include such samples.

Treatise on Geochemistry 2nd Edition

287 289 289 290 294 297 298 299 299 301 303 304 304 306 306

Trace quantities of mostly refractory presolar grains survive in the matrices of the most primitive carbon-rich chondritic meteorites (Anders and Zinner, 1993; Bernatowicz and Walker, 1997; Bernatowicz and Zinner, 1996; Clayton and Nittler, 2004; Davis, 2011; Hoppe and Zinner, 2000; Lodders and Amari, 2005; Lugaro, 2005; Chapter 1.4). Chondritic meteorites are believed to be from the asteroid belt, a narrow region between 2.5 and 3.5 astronomical units (AU) that marks the transition from the terrestrial planets to the giant gasrich planets. The spectral properties of the asteroids (Chapter 2.14) suggest a gradation in properties with some inner and main-belt C and S asteroids (the source region of most meteorites and polar micrometeorites) containing layer silicates indicative of parent-body aqueous alteration and the more distant anhydrous P and D asteroids exhibiting no evidence of (aqueous) alteration (Gradie and Tedesco, 1982). This gradation in spectral properties presumably extends several hundred AU out to the Kuiper belt, the source region of most short-period comets, where the distinction between comets and outer asteroids may simply be one of the orbital parameters (Brownlee, 1994; Jessberger et al., 2001; Luu, 1993; Chapter 2.13). The mineralogy and petrography of meteorites provide direct confirmation of aqueous alteration, melting, fractionation, and thermal metamorphism among the inner asteroids (Brearley and Jones, 1998; Dobrica˘ and Brearley, 2012; Farinella et al., 1993; Zolensky and McSween, 1988). Because the most common grains in the ISM (silicates and carbonaceous matter) are not as refractory as those found in meteorites, it is unlikely that they have survived in significant quantities in meteorites. To date, only a few presolar silicates have been identified in meteorites (Floss and Stadermann, 2012; Chapter 1.4). IDPs are the smallest and most fine-grained meteoritic objects available for laboratory investigation (Figure 1).

http://dx.doi.org/10.1016/B978-0-08-095975-7.00114-5

287

288

Early Solar Nebula Grains – Interplanetary Dust Particles

1 mm 20KV

X9400

0136

1.0U

Oct82

(a)

(b)

Chondritic material

20KV X9400

0185

1.0U

100 mm

Jul81

(c)

(d)

Figure 1 (a–c) Secondary electron images. (a) Anhydrous CPIDP. (b) Hydrated CSIDP (RB12A44). (c) Single-mineral forsterite grain with adhering chondritic material. (d) Optical micrograph (transmitted light) of giant cluster IDP (U220GCA) in silicone oil on ER2 collection flag.

In contrast to meteorites, IDPs are derived from a broad range of dust-producing bodies extending from the inner main belt of the asteroids to the Kuiper belt (Dermott et al., 1994; Flynn, 1990, 1996; Liou et al., 1996). After release from their asteroidal or cometary parent bodies, the orbits of IDPs evolve by Poynting–Robertson (PR) drag, the combined influence of light pressure and radiation drag (Dermott et al., 2001). Irrespective of the location of their parent bodies, nearly all IDPs can eventually reach Earth-crossing orbits under the influence of PR drag. IDPs are collected by impaction onto silicone oilcoated substrates (‘flags’) in the stratosphere at 20–25 km altitude using NASA ER2 aircraft (Sandford, 1987; Warren and Zolensky, 1994) and, more recently, from Antarctic snow and ice (Dobrica˘ et al., 2011; Noguchi et al., 2008). Laboratory measurements of implanted rare gases, solar flare tracks (Figure 2), and isotope abundances have confirmed that the collected particles are indeed extraterrestrial and that, prior to atmospheric entry, they spent 10–100 ka as small particles orbiting the Sun (Bradley et al., 1984a; Hudson et al., 1981; McKeegan et al., 1985; Messenger, 2000; Rajan et al., 1977). During atmospheric entry, most IDPs are frictionally heated to within 100  C of their peak heating temperature for 1 s and, to a first-order approximation, the smallest particles are the least strongly heated. Although some IDPs may experience thermal pulses in excess of 1000  C for up to 10 s, depending on particle size, mass, entry angle, and speed (Love and

Brownlee, 1991, 1996), the presence of solar flare tracks in an IDP establishes that it was not heated above 650  C (Bradley et al., 1984a). Since IDPs decelerate from cosmic velocities at altitudes >90 km, where the maximum aerodynamic ram pressure is a factor of 103 less than that exerted on conventional meteorites, extremely fragile meteoritic materials that cannot survive as large objects can survive as small IDPs (Figure 1(a)) (Brownlee, 1994). Such fragile materials are suspected to be among the most primitive objects and potentially the most informative regarding early solar system and presolar processes. Conventional meteorites penetrate deep into the atmosphere such that only relatively well-indurated rocks can survive. Collected IDPs are briefly exposed to the terrestrial environment, but since their residence time in the stratosphere is short (2 weeks), they are not subjected to longer-term weathering that affects the surfaces of most meteorites (Flynn, 1994a). This chapter examines the compositions, mineralogy, sources, and geochemical significance of IDPs. Additional reading can be found in reviews by Fraundorf (1981), Brownlee (1985), Sandford (1987), Bradley et al. (1988), Jessberger et al. (2001), Rietmeijer (1998), and the book edited by Zolensky et al. (1994). Despite their micrometer-scale dimensions and nanogram masses, it is now possible, primarily as a result of advances in small particle handling techniques and analytical instrumentation, to examine IDPs at close to

Early Solar Nebula Grains – Interplanetary Dust Particles

289

Solar flare tracks

Solar wind and solar flare effects

Sputtered rim

100 nm

100 nm

(a)

(b)

Figure 2 Dark-field transmission electron micrographs. (a) Solar-wind sputtered rim on exterior surface plus implanted solar flare tracks in chondritic IDP U220A19 (from Bradley and Brownlee, 1986). (b) Solar flare tracks in a forsterite crystal in chondritic IDP U220B11 (from Bradley et al., 1984a). The track densities in both IDPs are 1010–1011cm2 corresponding to an orbital exposure age of 10 ka.

atomic-scale resolution. The most widely used instruments for IDP studies are presently the analytical electron microscope, synchrotron facilities, and the ion microprobe. These laboratory analytical techniques are providing fundamental insights about IDP origins, mechanisms of formation, and grain processing phenomena that were important in the early solar system and presolar environments. At the same time, laboratory data from IDPs are being compared with astronomical data from dust in comets, circumstellar disks, and the ISM. The direct comparison of grains in the laboratory with grains in astronomical environments defines the relatively new discipline of ‘astromineralogy’ (Bradley et al., 1999a,b; Flynn et al., 2002; Henning, 2010; Jaeger et al., 1998; Keller et al., 2001; Molster et al., 2001).

1.8.2 Particle Size, Morphology, Porosity, and Density Individual IDPs span the diameter range 1–50 mm, although most are between 5 and 15 mm (Figure 1(a)–1(c)). Larger 50– 500 mm diameter particles (10–20% of collected IDPs) that fragment into many pieces when they impact the flags are known as giant ‘cluster’ particles (Figure 1(d)). Two principal morphological groups of IDPs are recognized, porous and smooth (Figure 1(a) and 1(b)). Since their bulk compositions are similar to chondritic meteorites (of types CI and CM), they are referred to as chondritic porous (CP) and chondritic smooth (CS) IDPs. CP and CSIDPs are also mineralogically distinct classes of materials (see Section 1.8.3). The morphologies of CP particles resemble a bunch of grapes (Figure 1(a)).

Porosities as high as 70% and densities ranging between 0.3 and 6.0 g cm3 have been measured, although IDPs with densities above 3.5 g cm3 typically contain a large FeNi sulfide grain (Fraundorf et al., 1982a; Love et al., 1994). Such low densities, high porosities, and fragile microstructures are consistent with the particulate matter in cometary meteors (Bradley and Brownlee, 1986). Most cluster particles belong to the CP class, presumably because their fragile microstructures predispose them to fragmentation during impact onto the collection substrates. Less common low-porosity CPIDPs are referred to as chondritic filled (Schramm et al., 1989). The CSIDPs are mostly solid objects with platy and/or fibrous surface textures (Figure 1(b)). It is important to note that although there are many particles that fall neatly into this category, some particles have characteristics of more than one particle type or they have unique characteristics. Some IDPs are composed mostly of refractory calcium-, aluminum-, and silicon-rich minerals (Zolensky, 1987), and others are singlemineral grains like olivine, pyroxene, and iron-rich sulfide, some of which have adhering fine-grained chondritic material. Their morphologies are defined, to a large extent, by the shape of the mineral grain (Figure 1(c)).

1.8.3

Mineralogy

It has been established using infrared (IR) and electron microscopic studies that there are three principal mineralogical classes of chondritic IDPs (Figure 3). They are referred to as ‘pyroxene,’ ‘olivine,’ and ‘layer silicate’ after their most abundant silicate minerals. In a study of 26 IDPs, Sandford and

290

Early Solar Nebula Grains – Interplanetary Dust Particles

SI

W7027 -H14

PY OL

8.0

9.0 10.0 11.0 12.0 Wavelength (mm)

(a)

MG (d)

FE

SI

U22OA14

cpx

PY

ol OL

7.0

8.0

ol 9.0 10.0 11.0 12.0

Wavelength (mm) (b)

MG (e)

FE

U230A43 SI

Carbonate Layer silicate 7.0 8.0 9.0 10.0 11.0 12.0 Wavelength (mm) (c)

MG (f)

FE

Figure 3 (a–c) IR spectra from thin sections of pyroxene-rich CPIDP W7027H14, olivine-rich CPIDP U220A14, and layer silicate-rich CSIDP U230A43. (d–f) Corresponding x-ray point count analyses obtained from the thin sections on a two-dimensional grid using a 200 keV electron probe with <50 nm spatial resolution at each point. Solid boxed area in (f) shows Mg–Fe–Si composition of the layer silicate and dotted boxed area shows carbonate Mg–Fe composition. Reproduced from Bradley JP, Humecki HJ, and Germani MS (1992) Combined infrared and analytical electron microscope studies of interplanetary dust particles. The Astrophysics Journal 394: 643–651.

Walker (1985) classified 25% as ‘pyroxene,’ 25% as ‘olivine,’ and 50% as ‘layer lattice silicate’ IDPs. The pyroxene and olivine classes are usually porous CPIDPs and contain only anhydrous minerals, while the layer silicate classes are usually smooth CSIDPs and contain hydrous silicates (clays). Most IDPs fall into this mineralogical classification scheme, although IDPs with intermediate morphology and mineralogy are relatively common. Examples include anhydrous IDPs with similar amounts of pyroxene and olivine (Bradley et al., 1989, 1992; Sandford and Walker, 1985), porous IDPs containing

minor amounts of hydrated layer silicates (Thomas et al., 1995), and smooth layer silicate particles containing large anhydrous silicate grains (Germani et al., 1990).

1.8.3.1

CPIDPs

This class of IDPs has been most intensively examined primarily because their high porosities and fluffy microstructures are unique among other known classes of extraterrestrial materials. IR spectra indicate that silicates are the most abundant

Early Solar Nebula Grains – Interplanetary Dust Particles

Chondritic porous (CP)

291

Chondritic smooth (CS)

1 µm

1 µm

(a)

(b) Chondritic smooth (CS)

Chondritic porous (CP) FeS Carbonaceous material

Enstatite

Saponite FeNi metal (kamcite) 0.1 µm

Saponite FeS 0.1 µm

FeS

GEMS (c)

Di

(d)

Figure 4 Bright-field electron micrographs of ultramicrotome thin sections: (a) CPIDP U222B42, (b) CSIDP U230A43, (c) CPIDP U222B42 with carbonaceous material, GEMS, crystalline silicates (enstatite), and sulfides (FeS), and (d) CSIDP U222C29 with fibrous layer lattice silicate (saponite), pyrrhotite (FeS), and the pyroxene diopside (Di).

minerals in CPIDPs and that the absence of hydrous silicates is a fundamental distinguishing property (Bradley et al., 1992; Sandford and Walker, 1985). Transmission electron microscopy studies of electron-transparent thin sections confirm the absence of hydrous minerals and reveal that CPIDPs are heterogeneous aggregates of predominantly submicrometer-sized crystalline mineral grains (olivine, pyroxenes, iron-rich sulfides, and FeNi metal), polycrystalline aggregates (e.g., glass with embedded metal and sulfides (GEMS); see Section 1.8.3.2), silicate glasses, and carbonaceous material (Bradley, 1994a) (Figure 4(a) and 4(b)). Enstatite and forsterite with <5 mol% forsterite and fayalite, respectively, are the most common crystalline silicates, although pyroxene and olivine with up to 30 mol% of these components are also observed (Bradley et al., 1989, 1999b; Christoffersen and Buseck, 1986). Enstatite-rich IDPs are the most fine-grained with a mean crystal size <50 nm diameter, although enstatite, sulfide, and sometimes forsterite crystals up to several micrometer or more in diameter are common. These IDPs contain 40% enstatite by volume, 40% FeNi sulfides, 70% GEMS plus (organic) carbonaceous material, and sometimes minor forsterite and FeNi metal. Olivine-rich particles have a significantly larger mean grain size, 0.1–1 mm diameter, and often contain 25–50% olivine and pyroxene and lower amounts of FeNi sulfides and glassy phases (see Bradley et al., 1989). Solar

flare tracks have been observed in both enstatite-rich and forsterite-rich IDPs, confirming that they are indeed extraterrestrial and that they were not strongly heated during atmospheric entry. However, while tracks are observed in most enstatite-rich IDPs, they are conspicuously absent in most but not all forsteriterich IDPs. Some forsterite-rich IDPs exhibit melt textures, equilibrated silicate mineralogy, and surfaces that are decorated with magnetite that almost certainly formed from frictional heating during atmospheric entry (Germani et al., 1990). Therefore, it is likely that the olivine-rich subset of CPIDPs includes and is perhaps dominated by particles that were thermally modified during atmospheric entry. The morphologies, crystal structures, and compositions of some enstatite and forsterite crystals in (track-rich) CPIDPs suggest that they formed by vapor-phase growth. (Gas-tosolid condensation is the fundamental mechanism by which grains are formed from nebular gases throughout the galaxy.) Enstatite (MgSiO3) crystals in IDPs have distinctive ultrathin platelet morphologies, while others are whiskers with crystallographic screw dislocation characteristic of vapor-phase growth (Figure 5) (Bradley et al., 1983). Forsterite and enstatite grains in some IDPs contain up to 5 wt% MnO, in contrast to pyroxenes and olivines in meteorites that typically contain <0.5% MnO. Since iron and manganese are coupled during

292

Early Solar Nebula Grains – Interplanetary Dust Particles

800

600 a a 400

500 Å

Enstatite whiskers

200

1 µm

(a)

(b)

1 2 100 nm 3 100 nm

4

5

(c)

(d)

Figure 5 (a) Secondary electron image of a CPIDP with embedded enstatite whiskers (and a platelet, upper left). (b) (Left) Bright-field transmission electron micrograph of a segment of a clinoenstatite rod viewed down the b crystallographic axis. The two features parallel to the axis of the rod are screw dislocations and the features cutting across the rod are (100) stacking faults. (Right) Selected area electron diffraction pattern showing the (h00) reciprocal lattice row from the rod. The side bands (splitting) of the diffracted beams, especially visible for the 600 and 800, are related to the helical lattice distortions arising from the dislocations (see Bradley et al., 1983). (c) Bright-field electron micrograph of five ultrathin enstatite ribbons and platelets. (d) Dark-field electron micrograph of an enstatite ribbon. Striations in the crystal result from extreme stacking disorder associated with unit cell-scale intergrowths of orthorhombic, orthoenstatite, and monoclinic clinoenstatite. All of enstatite crystals are likely condensates from a nebular gas.

crystallization from a liquid melt and decoupled during vaporphase condensation, Klo¨ck et al. (1989) propose that the lowiron, manganese-enriched forsterite and enstatite grains in IDPs are vapor-phase condensates. CPIDPs contain more silicate glass than any other class of chondritic materials. Nonstoichiometric magnesium-rich silicate glass is most common, although other glass compositions with highly variable amounts of oxygen, magnesium, aluminum, silicon, calcium, titanium, and iron are also observed. The glasses occur as discrete grains, rims on silicate crystals, and within GEMS (Section 1.8.3.2) (Bradley, 1994a,b; Brownlee et al., 1999). Sulfides are the second most abundant class of minerals in CPIDPs (Figure 6). The most common sulfide is pyrrhotite with up to 20 at% Ni and a hexagonal unit cell (Dai and Bradley, 2001; Fraundorf, 1981; Zolensky and Thomas, 1995). Some crystals exhibit superlattice reflections. Grain sizes span a huge range from 10 nm to 5 mm. Rare troilite, pentlandite, sphalerite, and NiS crystals have also been observed or reported (Christoffersen and Buseck, 1986; Zolensky and Thomas, 1995). A cubic ‘spinel-like’ sulfide with a composition similar to the hexagonal pyrrhotite has also been identified in CPIDPs

(Dai and Bradley, 2001). Both polymorphs are sometimes coherently intergrown on a unit cell scale. The cubic polymorph is metastable and it transforms into hexagonal pyrrhotite when it is heated in the electron beam (Figure 6(c) and 6(d)). Since most IDPs are pulse heated above 200  C during atmospheric entry (Love and Brownlee, 1991; Sandford and Bradley, 1989), it is possible that much of the hexagonal pyrrhotite in IDPs is a secondary thermal alteration product of the cubic sulfide. Although cubic spinel-like sulfides with pyrrhotite compositions have not been reported in nature, a crystallographically similar nickel-free pentlandite was synthesized in the laboratory by lowtemperature (<200  C), low-pressure vapor-phase growth (Nakazawa et al., 1973). Therefore, it is possible that some or all of the sulfides in IDPs, like the pyroxene whiskers and platelets (Figure 5), formed by direct condensation from a nebular gas. Alternatively, the sulfides may have formed by gaseous sulfidization of preexisting FeNi metal grains (Lauretta and Fegley, 1994; Lauretta et al., 1995, 1996; Zolensky and Thomas, 1995). Since the cubic sulfide has not been found in chondritic meteorites, it is likely that some sulfides in IDPs formed under conditions significantly different from those in

Early Solar Nebula Grains – Interplanetary Dust Particles

U222B28

293

2560

0006 0226 0220

1/6

200 nm [2110] (a)

(b)

0001

111

0111

111 0110 200

[011]C (c)

[2110]H (d)

Figure 6 Bright-field electron micrograph of a pyrrhotite crystal in a thin section of CPIDP U222B28. (b) Selected area electron diffraction pattern from the pyrrhotite crystal in (a) exhibiting prominent superlattice reflections consistent with the a ¼ 2A, c ¼ 6C superstructure. Inset lower right is a magnified view of the central region of the pattern showing the 6C reciprocal lattice periodicity. (c–d) Electron microdiffraction patterns from a pyrrhotite crystal in CPIDP W2070-8D before and after extended electron irradiation. The initial pattern (c) shows two reciprocal lattice nets, the stronger indexed as hexagonal pyrrhotite viewed along [010] (thick-line box) and the weaker as cubic spinel-like sulfide viewed along [011] (thin-line box). After the grain was illuminated in electron beam for several tens of seconds (c) only the strong reflections remain, indicating that the cubic sulfide has transformed into hexagonal pyrrhotite. Reproduced from Dai ZR and Bradley JP (2001) Iron nickel sulfides in anhydrous interplanetary dust particles. Geochimica et Cosmochimica Acta 65: 3601–3612.

conventional meteorites. Flynn (2000) observed selenium levels in IDPs 60% higher than those in meteoritic sulfides and concluded that IDP sulfides may have formed in a different environment than the sulfides in meteorites. Carbonaceous material is widespread throughout CPIDPs, both as discrete inclusions of noncrystalline material and as a semicontinuous matrix with embedded mineral grains. Several textural and morphological forms are observed, including a vesiculated form consistent with an organic component (Figure 7(a)). Ubiquitous hydrogen, nitrogen, and rare carbon isotope anomalies are consistent with primitive carbonaceous matter inherited from or formed within from the presolar molecular cloud (Matrajt et al., 2012). The bulk abundance of carbon in CPIDPs varies from 4% to 45 wt% with an average of 13 wt% (Keller et al., 1994). In contrast to the fine-grained matrices of carbonaceous chondrites, ordered (graphitic) carbon exhibiting 3.4 A˚ lattice fringes is rare in chondritic IDPs where it is rarely observed as rims on the surfaces of FeNi metal and FeNi carbide grains (e.g., Bradley et al., 1984b). The carbonaceous material is present in clumps or as a semicontinuous matrix throughout which submicrometer-sized grains (e.g., GEMS and sulfides) are distributed. While elemental carbon is almost certainly a major component, IR spectra showing prominent C–H stretching resonances establish the presence of an

aliphatic organic component in chondritic IDPs (Figure 7(b)) (Flynn et al., 2000). Using two-step laser desorption mass spectroscopy, Clemett et al. (1993) have shown that both porous and smooth IDPs contain polyaromatic hydrocarbons (PAHs). Nitrogen may be associated with the PAHs because the mass spectra of the PAHs are dominated by odd mass species in the intermediate molecular weight range from 200 to 300 amu. This is in contrast to the results previously obtained from PAHs in primitive meteorites using the same analytical technique. The odd mass peaks could be due to the substitution of functional groups containing odd numbers of nitrogen atoms, such as cyano (–CN) and amino (–NH2) groups. Spatially correlated 13C depletion and 15N enrichments were observed in one IDP (Floss and Stadermann, 2003). Nanodiamonds have been identified in large cluster CPIDPs but not so far in smaller noncluster CPIDPs (Figure 7(c) and 7(d)) (Dai et al., 2002). The nanodiamonds are similar in size distribution and abundance to those found within carbonaceous chondrites, although in one IDP (U220GCA, Figure 1 (d)) their abundance appears to be 10 higher. Defect structures in meteoritic nanodiamonds suggest that they formed by a vapor deposition process as opposed to shock metamorphism (Daulton et al., 1996). The carrier of nanodiamonds in IDPs is a disordered (amorphous) carbonaceous material that may

294

Early Solar Nebula Grains – Interplanetary Dust Particles

Nanodiamond

Fe sulfide

100 nm

Carbonaceous material

(a)

5 nm

(c)

Orqueil acid residue

Nanodiamond

IDP W7207A3

3.2

3.3

3.5 3.6 3.4 Wavelength (µm)

3.7

(b)

0.206 nm (d)

Figure 7 (a) Bright-field transmission electron micrograph of vesiculated amorphous carbonaceous material (in CPIDP W7027A1) that likely contains organic and inorganic carbon. (b) Comparative IR spectra from Orgueil (CI) meteorite acid residue and CPIDP W7207A3 showing prominent C–H stretch features at 3.4–3.5 mm indicative of aliphatic hydrocarbons (Brownlee et al., 2000). (c) Nanodiamond embedded in a carbonaceous mantle on the surface of a sulfide crystal at the edge of a GEMS (cluster IDP U220GCA). (d) A single nanodiamond within an acid-etched residue of cluster IDP W7110A-2E-D.

contain organic components, for example, PAHs (Dai et al., 2003). It is unclear why nanodiamonds are found in cluster IDPs and depleted or absent in smaller noncluster IDPs. Moreover, the relationship and distinction between large cluster and smaller noncluster IDPs are also unclear. It has been suggested that cluster IDPs are more isotopically primitive (Messenger, 2000), but their compositions, mineralogy, and petrography appear identical to those of smaller noncluster CPIDPs. Despite their large sizes, cluster IDPs appear less strongly heated than is predicted by atmospheric entry heating models, implying that they are captured from low-speed asteroidal or Kuiper belt orbits (Brownlee et al., 1995; Flynn, 1996; Liou et al., 1996; Thomas et al., 1995). Since (asteroidal) chondritic meteorites contain nanodiamonds, it is not unexpected that cluster IDPs also contain nanodiamonds, assuming they are from asteroids. Irrespective of the origins of cluster IDPs, the absence or depletion of nanodiamonds in smaller carbon-rich chondritic IDPs, some or all of which may be cometary, suggests that nanodiamonds are heterogeneously distributed throughout the solar system and that they may actually be more abundant in asteroids than in comets. Therefore, it is possible that most meteoritic nanodiamonds formed within the inner solar system in the vicinity of asteroid accretion and not in a presolar environment as is widely believed, although xenon and tellurium isotopes indicate that at least a small fraction of them must be of presolar origin (Hoppe and Zinner, 2000). A solar-system origin could explain the

anomalously high abundance of nanodiamonds relative to other types of presolar grains in meteorites (Hoppe and Zinner, 2000). The recent detection by the Infrared Space Observatory of nanodiamonds formed in situ within the accretion disks of young stars confirms that nanodiamonds could indeed have formed in the inner solar system (Van Kerckhoven et al., 2002).

1.8.3.2

Glass with Embedded Metal and Sulfides

GEMS are smallest and most exotic class of primitive meteoritic ‘rocks’ yet encountered (Figure 8). They are 0.1–0.5 mm spheroids that are ubiquitous throughout the matrices of CPIDPs. Their bulk compositions are approximately chondritic, although individual element abundances vary by an order of magnitude (Ishii et al., 2009). Terminology used to describe GEMS has evolved as increasingly sophisticated instruments have been used to analyze them, particularly those capable of highest spatial resolution and light element (carbon and oxygen) analyses. GEMS have been described as ‘tar balls,’ ‘granular units,’ ‘microcrystalline aggregates,’ ‘unequilibrated aggregates,’ and ‘polyphase units’ (Bradley, 1988; Klo¨ck and Stadermann, 1994; Rietmeijer, 1989, 1997). They are mineralogically unequilibrated, in that they contain nanometer-sized inclusions of FeNi alloy (kamacite) and iron-rich sulfide (pyrrhotite) embedded in oxygen-rich, low-iron magnesium silicate glass.

Early Solar Nebula Grains – Interplanetary Dust Particles

C

100 nm

295

100 nm

C

C C (a)

(b)

100 nm

10 nm

Relict FeS (c)

Relict forsterite (d)

Figure 8 Transmission electron micrographs of GEMS within CPIDPs. (a) Bright-field image of GEMS embedded within amorphous carbonaceous material (labeled ‘C’). The inclusions are FeNi metal (kamacite) and Fe sulfides. (b) Dark-field image. Bright inclusions are metal and sulfides; matrix is magnesium silicate glass. (c, d) Dark-field images of GEMS with ‘relict’ sulfide and forsterite (Mg2SiO4) inclusions. Reproduced from Bradley JP, Keller LP, Snow TP, et al. (1999a) An infrared spectral match between GEMS and interstellar grains. Science 285: 1716–1718.

Figure 8 shows a bright-field and several dark-field images of GEMS. Typically, GEMS are found embedded within amorphous carbonaceous matrix (Figure 8(a)). In Figure 8(b), the bright inclusions are 2–100 nm diameter FeNi metal (kamacite) and pyrrhotite nanocrystals and the uniform gray matrix is magnesium-rich silicate glass. Some GEMS contain deeply eroded ‘relict’ pyrrhotite, forsterite, or enstatite grains toward their cores (Figure 8(c) and 8(d)). Experiments with irradiated mineral standards and observations of the surfaces of lunar soil grains exposed to the solar wind (SW) indicate that the mineralogy and petrography of GEMS were shaped primarily by exposure to ionizing radiation and the exposure occurred prior to the accretion of the host CPIDPs (Bradley, 1994b; Bradley et al., 1996a). Nonequilibrium vapor-phase condensation has been proposed as an alternative mechanism of GEMS formation (Keller and Messenger, 2011). Both the irradiation and vapor-phase growth mechanisms have been evaluated using valence electron energyloss spectroscopy, an electron-beam technique that enables examination of the electronic (valence band) structure of amorphous silicates formed by different mechanisms (Bradley et al., 2012; Erni et al., 2005). Figure 9 compares VEEL spectra from amorphous magnesium-rich silicates formed by irradiation, nonequilibrium vapor-phase condensation and a VEEL spectrum from the magnesium-rich silicate matrix of GEMS. The fine structure in the GEMS VEEL spectrum matches irradiated silicates but does not match (amorphous) silicates formed by nonequilibrium condensation (Figure 9). The most intriguing property of GEMS is their physical similarity to ‘amorphous silicate’ grains that are ubiquitous throughout interstellar space. The presence of silicate grains in the ISM is revealed by spectral features at 1030 and 525 cm1 (9.7 and 19 mm) corresponding to the Si–O stretching and Si–O–Si bending modes of silicates (Aitken

et al., 1989; Millar and Duley, 1980). The features are observed both in absorption and emission along various lines-of-sight, and they generally lack fine structure, which suggests that the silicates are predominantly amorphous (i.e., glasses). The size range of the grains inferred from extinction is between 0.1 and 0.5 mm (Kim et al., 1994). These grains are believed to have originally formed in the atmospheres and outflows of oxygenrich post-main-sequence AGB stars (Henning, 1999; Mathis, 1993). With the exception of carbon, most of the condensed rock-forming elements in ISM are associated with these silicate grains (Snow and Witt, 1996). Immediately prior to the collapse of the solar nebula, most of the condensed atoms in the solar system were carried within these interstellar amorphous silicate grains. The physical and chemical properties of interstellar silicates inferred from astronomical observations match the exotic properties of GEMS. For example, it has been proposed that polarization of starlight caused by alignment of IS amorphous silicates in the galactic magnetic can be explained by nanometer-sized inclusions of superparamagnetic FeNi metal (Jones and Spitzer, 1967). Other properties of GEMS including their bulk compositions and size distribution match those of IS amorphous silicates (Bradley et al., 1997). The presolar interstellar origins of several GEMS have been confirmed by detection of nonsolar oxygen isotope abundances (Floss and Stadermann, 2003; Keller and Messenger, 2011; Messenger et al., 2003). However, most GEMS do not have detectable isotope anomalies even though they are otherwise indistinguishable from the anomalous GEMS in terms of composition, mineralogy, and petrography. The lack of detectable anomalies must be due in part to their small sizes because most of the isotopically anomalous GEMS are unusually large. The mean diameter of GEMS is 180 nm and the lower limit for reliable isotope measurements is currently 250 nm (Messenger et al.,

296

Early Solar Nebula Grains – Interplanetary Dust Particles

10.9

8000

6000

1000

6000

10.9

4000 4000 2000

Counts

2000

4.4 6.0

14.9

8.1

500 12.6

12.6 4.4

0

0

2000

−2000

6.0

14.9

8.1

−0

−500

4000

−4000

6000

5

(a)

−1000

−6000

8000 10 eV

15

5

10

(b)

eV

5

15

(c)

10

15

eV

Electron energy Figure 9 Second derivative valence electron energy-loss (VEEL) spectra of amorphous silicates formed by (a) nonequilibrium vapor-phase condensation, (b) proton irradiation of the surface of San Carlos olivine, and (c) GEMS in CPIDP U220A19. The relatively featureless spectrum in (a) is typical of amorphous silicates formed by condensation and melting. The surface plasmon features at 4.4, 6, 8.1, 10.9, 12.6, and 14.9 eV, due principally to valence band transitions of electrons from surface states, are characteristic of nanoporous irradiated materials with high defect densities (from Bradley et al., 2012).

2007). Alternatively, most GEMS may be isotopically normal (solar) because they formed in the solar system, although the chemical (elemental), mineralogical, and petrographic properties of anomalous GEMS are identical to those of the isotopically normal GEMS. Furthermore, if GEMS truly are interstellar amorphous silicates, it is not entirely clear that they should have nonsolar isotopic compositions, because grains undergo considerable processing during their 0.1–1 Ga lifetimes in the ISM such that the chemical and isotopic compositions of most grains are likely homogenized (Jones and Nuth, 2011; Mathis, 1993; Seab et al., 1987). This dilemma was best articulated by the late R.M. Walker: It is (also) true that preexisting interstellar grains might not, on the average, be very different from solar-system material. Although there is strong evidence that some circumstellar grains with distinctive isotopic signatures have survived intact in meteorites, theoretical calculations indicate that most grains are quickly destroyed in the diffuse interstellar medium. Thus, the grains found in a protostellar gas/dust cloud may themselves consist of interstellar dust grains whose compositions have been homogenized in the interstellar medium to give compositions similar to those of solar-system values. In this connection, it is interesting to note that the isotopic compositions of galactic cosmic rays is, with some exceptions, not strikingly different from average solar-system material (Bradley et al., 1988).

The finding that some GEMS are presolar confirms they are interstellar ‘amorphous silicates’ and that during their ISM lifetimes these tiny rocks acquired constituents that formed in circumstellar and supernovae environments (see Flynn, 1994b; Goodman and Whittet, 1995; Keller and Messenger, 2011; Martin, 1995). The consensus view is that isotopic composition is the only reliable means of distinguishing between a solar and extrasolar origin, but it has recently been proposed that regardless of isotopic compositions, the chemical (elemental) compositions alone prove that most GEMS formed in the solar system Keller and Messenger (2011). The argument is that the element/silicon ratios in GEMS, for example, Mg/Si,

S/Si, Ca/Si, and Fe/Si, differ significantly from those of amorphous silicate grains in the ISM. Mg/Si, Fe/Si, and Ca/Si are too low and S/Si is too high. However, if iron is used as the ratio element (i.e., Mg/Fe, Si/Fe, S/Fe, and Ca/Fe), as has been used historically in element abundance quantification by synchrotron x-ray fluorescence, the systematic element depletions in GEMS disappear and only a single element, silicon, is anomalously enriched (Bradley et al., 2011; Flynn et al., 2008) (Figure 10(a)). Silicone oil in which IDPs are collected and stored (for >20 years in some cases) is responsible for at least some of the excess silicon. Although the degree of contamination varies from one IDP to another, oil residue is sequestered in most IDPs, especially GEMS- and carbon-rich IDPs, even after repetitive cleaning with solvents (Bradley et al., 2011; Fraundorf, 1981; Rietmeijer, 1987; Rost et al., 1999; Sandford and Walker, 1985). Another cause of the measured excess silicon may be GEMS’ chemical stability. GEMS formed by irradiation processing in a cold environment (Bradley, 2012; Brownlee et al., 2005). Like other irradiated materials, they are highly reactive, as evidenced by atmospheric entry heating-induced  FeS/Fe3O4 rims on GEMS in solar flare track-rich IDPs, the order-of-magnitude variations in their compositions, and high element mobility and loss under electron irradiation, all of which lower measured element/silicon ratios and produce an apparent excess of silicon (Bradley and Dai, 2009; Keller and Messenger, 2011). Finally, although solar-system element abundances are well defined, ISM abundances are not because they vary widely along different lines-of-sight. For example, Mg/Si and Fe/Si vary by 50%. Sulfur (i.e., S/Si) is especially uncertain because of the ‘formidable’ observational selection bias (Jenkins, 2009; Voshchinnikov and Henning, 2010). The order-of-magnitude variations in GEMS compositions coupled with the uncertainty in ISM abundances rule out a statistically significant distinction between solar system, ISM, and GEMS element abundances (Figure 10(b)). In addition to GEMS, there are other types of polycrystalline aggregates in CPIDPs. Rietmeijer (1997, 1998) described

Early Solar Nebula Grains – Interplanetary Dust Particles

EI/Fe

et al., 1984b). Since all of these aggregates have undergone an accretional event and processing prior to accretion of the IDPs in which they reside, they are older than the IDPs. Therefore, the study of aggregates in CPIDPs provides a window back to times predating the accretion of interplanetary dust. Whether the accretion occurred in the early solar system or presolar interstellar environments is unknown at this time.

EI/Si

1.8.3.3

(EI/SiGEMS)/(EI/SiSolar)

2

1

0 Mg 2

1

297

Si

GEMS

S

Ca

Fe

ISM grains

Solar

0 Mg

Si

S

Ca

Fe

Figure 10 (a) Comparison of element/Si and element/Fe ratios in GEMS. GEMS are systematically depleted from solar abundances when silicon is used as the ratio element. When iron is used as the ratio element, the systematic element depletions disappear and a single element, silicon, is anomalously enriched over solar abundances. Silicon and sulfur are significant contaminants associated with collection of (GEMS-rich) IDPs (data from Keller and Messenger, 2011). (b) Average (hexagonal spots) and range (vertical lines) of element/silicon abundances in GEMS (black) and interstellar dust (red) normalized to solar (CI) element abundance (horizontal line). The wide range in GEMS’ measured compositions and variability and uncertainty of interstellar abundances along different lines-of-sight mean complicate distinction between the three populations (from Bradley, 2012).

course-grained and ultrafine-grained ‘polyphase units’ composed of glass, iron-bearing olivine and pyroxene, oxides, sulfides, and metal. Other submicrometer grains described as ‘equilibrated aggregates’ also have bulk compositions that are approximately chondritic (Bradley, 1994a). But in contrast to GEMS that have highly unequilibrated compositions and mineralogy, ‘equilibrated aggregates’ contain iron-bearing olivine and pyroxene grains with equilibrated Fe/Mg ratios and iron sulfides embedded in aluminosilicate glass. Their textures and petrography suggest that they have an igneous origin, for example, formation by collisional shock melting. ‘Reduced aggregates’ are yet another component of chondritic IDPs. These carbon-rich aggregates contain FeNi metal, FeNi carbide, and FeNi sulfide crystals embedded in carbonaceous matrix (Bradley, 1994a). Some of the metal grains are rimmed with a thin (<10 nm) rim of graphitic carbon (Bradley

CSIDPs

CSIDPs are low-porosity objects composed predominantly of hydrated layer lattice silicates (clays) (Figures 1(b) and 11). IR spectra indicate that silicates are the most abundant minerals in CSIDPs, some of them contain carbonates, and that the presence of hydrous silicates (clays) is a fundamental distinguishing property (Bradley et al., 1992; Germani et al., 1990; Sandford and Walker, 1985). Transmission electron microscopy studies of electron-transparent thin sections confirm the presence of hydrous layer lattice silicates and carbonates. Their mineralogical and petrographic similarity to the fine-grained matrices of type CI and CM carbonaceous chondrites is unmistakable, but there are important differences. Whereas serpentine is the dominant layer lattice silicate in CI and CM chondrites, smectite is the dominant layer silicate in CSIDPs, suggesting that there were significant differences in the parent bodies of the IDPs and meteorites (Brearley and Jones, 1998; Germani et al., 1990; Zolensky and McSween, 1988). In contrast to the layer silicates in CI/CM chondrites, those in CSIDPs are poorly crystallized, the predominant basal spacing is 10 A˚, and they are compositionally more heterogeneous on a scale of 50 nm than the fine-grained matrices of carbonaceous chondrites (Germani et al., 1990). Most of the layer silicates in CI and CM chondrites are serpentine with a 7 A˚ basal spacing, and they formed mostly from crystalline silicates like olivine and pyroxene. The layer silicates in CSIDPs formed in situ by aqueous alteration of silicate glasses and their compositions plus the 10 A˚ spacing suggest that they are smectites. A variety of other minerals have been reported in CSIDPs. They include the anhydrous crystalline silicates diopside (Figure 4(d)), enstatite, fassaite, and forsterite; amorphous silicates (glasses) with variable amounts of magnesium, calcium, aluminum, and iron; the sulfides pyrrhotite, troilite, and nickel sulfide; the oxides magnetite and chromite; and a phosphide, schreibersite. The sulfide mineralogy of CSIDPs differs from that of CPIDPs. Whereas low-nickel pyrrhotite ([Fe,Ni]1xS) is the dominant sulfide in CSIDPs (Dai and Bradley, 2001), nickel-rich sulfides with compositions ranging from low-nickel pyrrhotite compositions up to and including pentlandite ([Fe,Ni]9S8) are more abundant in CSIDPs (Zolensky and Thomas, 1995). A ‘low-nickel pentlandite’ has been reported in a hydrated CSIDP (Tomeoka and Buseck, 1984). The composition and crystal structure of the low-nickel pentlandite are similar to those of the cubic spinel-like sulfide identified in CSIDPs (Dai and Bradley, 2001). To confirm whether they are one and the same mineral requires more study. CSIDPs are, on average, significantly enriched in carbon relative to CI chondrites and contain disordered carbonaceous material similar to that found in CPIDPs. Carbon abundances vary from 5% to >20 wt% with an average of 13 wt% (Keller et al., 1994). The hydrated silicate mineralogy of CSIDPs indicates that they are derived from parent bodies in which aqueous

298

Early Solar Nebula Grains – Interplanetary Dust Particles

RB12A44−1 10.8 Å 7A 7 5 11 7 7 7 7

7.3 Å

5.4 Å (a)

(b)

10.8 Å

20 nm

(c)

(d)

Figure 11 Lattice-fringe images of cronstedite and tochilinite in CSIDP RB12A44 (see also Figure 1(b)). (a) Mixture of iron-rich serpentine cronstedite (7.3 A˚ spacing) and tochilinite (5.4 and 10.8 A˚ spacings). (b) Unit cell intergrowth of cronstedite and tochilinite. (c) Pseudo-rectangular tochilinite ‘prototube’ nucleated in a cronstedite plate. (d) Tochilinite tube. Reproduced from Bradley JP and Brownlee DE (1991) An interplanetary dust particle linked directly to type CM meteorites and an asteroidal origin. Science 251: 549–552.

alteration has occurred. High-nickel sulfides (e.g., pentlandite) are also consistent with formation during asteroidal parent-body aqueous alteration because nickel-rich sulfides form at relatively high oxygen fugacities (Godlevskiy et al., 1971). Asteroids are the logical parent bodies, since it is well established that aqueous alteration is an important parent-body process within at least some regions of the asteroid belt (Brearley and Jones, 1998). The mineralogy of several CSIDPs provides a direct connection to the asteroids. Tochilinite, an ordered mixed-layer mineral containing magnesium, aluminum, iron, nickel, sulfur, and oxygen, identified in CSIDP RB12A44, has been found in only one other class of meteorites, the type CM carbonaceous chondrites (Bradley and Brownlee, 1991). Similarly, unit cell-scale intergrowths of serpentine and saponite observed in CSIDP W7013F5 are also found within the fine-grained matrices of type CI chondrites (Keller et al., 1992). The presence of these distinctive secondary mineral assemblages provides direct petrogenetic links between some IDPs and specific classes of meteorites and thus confirms that some IDPs collected in the stratosphere do indeed have an asteroidal origin (Rietmeijer, 1996). But the scarcity of these IDPs suggests that CSIDPs sample a broad range of hydrous parent bodies and that materials with CM and CI mineralogy are not abundant among the hydrous dust-producing asteroids.

1.8.4

Optical Properties

The optical properties of chondritic IDPs have been measured in the IR and visible spectral regions (Figures 3, 12, and 13).

Most IR measurements have been acquired in transmission over the 2–25 mm IR region using microscope spectrophotometers equipped with globar sources (Figure 3). More recently, highbrightness synchrotron light sources have proved to be ideal for spectral microanalysis of IDPs and even subcomponents of IDPs (e.g., GEMS and sulfides). Synchrotron sources can deliver an apertured beam with a spot as small as 3 mm in diameter and >100 brighter than globar sources. The 2–25 mm region includes the important 10 and 20 mm silicate features. Almost all chondritic IDPs exhibit a dominant 10 mm silicate feature, the position and shape of which have been used to classify particles as ‘pyroxene,’ ‘olivine,’ or ‘layer silicate’ IDPs. The 10 mm feature of pyroxene-rich CPIDPs typically consists of principal bands at 9.1–9.4 mm (1064–1099 cm1) and 10.5– 10.75 mm (930–953 cm1) that are consistent with monoclinic pyroxene. Olivine-rich CPIDPs exhibit an intense band at 11.2– 11.3 mm (885–892 cm1) with less intense bands at 10.1, 10.75, and 11.9 mm (840, 930, and 990 cm1). Hydrated CSIDPs usually produce a single featureless band at 9.7– 9.8 mm (see Bradley et al., 1992; Sandford and Walker, 1985). The 10 mm feature of chondritic IDPs has been compared with the 10 mm feature of astronomical silicates. No particular IDP IR class consistently matches the 10 mm feature of solarsystem comets or silicate dust in the ISM (Sandford and Walker, 1985). However, the 10 mm features of CPIDPs composed mostly of GEMS and submicrometer enstatite and forsterite crystals generally resemble those of comets and latestage Herbig Ae/Be stars in support of the hypothesis that some CPIDPs are of cometary origin (Figure 14).

11.2 µm

9.6 µm

Intensity (arb. units)

(a)

299

(a)

9.7 µm

Intensity (arb. units)

Early Solar Nebula Grains – Interplanetary Dust Particles

(b) (b)

Emissivity (arb. units)

Emissivity (arb. units)

(c)

(c)

(d)

(d)

(e)

8

9 10 11 12 Wavelength (µm)

13

8

9 10 11 12 Wavelength (µm)

13

Figure 12 Comparison of the 10 mm Si–O stretch bands of a ‘GEMS-rich’ IDP and astronomical silicates. (Left) (a) CPIDP L2008V42A, profile derived from transmittance spectrum; (b) Comet Halley (Campins and Ryan, 1989); (c) Comet Hale–Bopp (Hanner et al., 1997); (d) late-stage Herbig Ae/Be star HD163296 (Sitko et al., 1999). (Right) (a) GEMS (in IDP L2011*B6); (b) Elias 16 molecular cloud (Bowey et al., 1998); (c) Trapezium molecular cloud (Hanner et al., 1995); (d) pre-main-sequence T Tauri YSO DI Cephei (Hanner et al., 1998); (e) post-main-sequence M-type supergiant m-Cephei (Aitken et al. (1988). Reproduced from Bradley JP, Keller LP, Snow TP, et al. (1999a) An infrared spectral match between GEMS and interstellar grains. Science 285: 1716–1718.

The IR spectral features of individual subcomponents of chondritic IDPs have also been measured. A measurement of the 10 mm silicate feature of GEMS produced a broad featureless band at 9.7 mm that matches the spectra of interstellar molecular cloud dust, providing further evidence in support of the controversial hypothesis that GEMS are interstellar amorphous silicates (Figure 14) (Bradley et al., 1999a). This hypothesis was confirmed by the discovery of GEMS with oxygen isotopic compositions indicating that they are indeed presolar silicates (Keller and Messenger, 2011; Messenger et al., 2003). Some chondritic IDPs exhibit a broad feature at 23.5 mm and a similar broad feature is seen in the IR spectra of young stellar objects. Detailed mineralogical analyses of the IDPs in conjunction with IR spectroscopy of mineral standards established that iron sulfides are responsible for the 23.5 mm feature (Keller et al., 2001). Reflectance spectra have been collected from chondritic IDPs over the visible 450–800 nm wavelength range (Figure 13). Interpretation of the indigenous reflectance characteristics of IDPs can be complicated because of spurious scattering effects from large mineral grains, secondary magnetite formed on the surfaces of some IDPs during atmospheric entry, and other small particle light scattering artifacts. In general, chondritic IDPs are spectrally dark objects with <15% reflectivity over the 400–800 nm range. Most anhydrous CPIDPs dominated by enstatite, forsterite, and GEMS exhibit spectral characteristics similar to those of smaller,

more primitive solar-system objects (e.g., P and D asteroids). Carbon-rich CPIDPs are spectrally red with a redness comparable to the comet-like outer asteroid Pholus (Binzel, 1992). Hydrated CSIDPs that contain layer lattice silicates exhibit spectral characteristics similar to carbonaceous chondrites and main-belt C-type asteroids (Bradley et al., 1996b).

1.8.5 1.8.5.1

Compositions Major Elements

The bulk compositions of several hundred IDPs like those shown in Figure 1 have been measured using electron-induced energy-dispersive x-ray spectroscopy (EDS), synchrotron x-ray fluorescence, proton-induced x-ray emission, and instrumental neutron activation analysis. The benchmark standard of comparison is with CI chondrite meteorites. The CI meteorites are considered to be the most chemically primitive class of meteoritic materials, because their bulk compositions, more than any other class of meteorites, closely correspond to the composition of the solar corona (see Chapter 1.1). Within a factor of 2–3, the element ratios for most chondritic CP and CSIDPs match those of the CI chondrites. Carbon is an exception with abundances as high as 5  higher than CI chondrites (Keller et al., 1994). The compositions of CPIDPs are chondritic (solar) on a scale of less than 1 mm, indicating that they

300

Early Solar Nebula Grains – Interplanetary Dust Particles

20

Reflectance (%)

W7030A15

Mg

0,0

Al

0,0

S

1,1

Ca

0,1

Fe

1,0

15

10

5 0 300

400

500

600

700

800

900

Wavelength (nm)

(a)

10 W7030A5 Reflectance (%)

8 6 4 2 0 300 (b)

400

500 600 700 Wavelength (nm)

800

900

Figure 13 Reflectance spectra of (a) CSIDP W7030A15 and (b) CPIDP W7030A5. Reproduced from Bradley JP, Keller LP, Brownlee DE, and Thomas KL (1996b) Reflectance spectroscopy of interplanetary dust particles. Meteoritics and Planetary Science 31: 394–402.

are mineralogically heterogeneous on a submicrometer scale (Bradley et al., 1989). CSIDPs are less heterogeneous, presumably as a result of in situ aqueous alteration (Germani et al., 1990). IDPs dominated by a single-mineral grain (e.g., forsterite or pyrrhotite) typically have nonchondritic compositions reflecting the composition of the grain. Other stratospheric particles identified as IDPs include the so-called refractory IDPs, which are rich in the elements calcium, aluminum, and titanium (Zolensky, 1987). The major-element compositions of 200 chondritic IDPs were measured by EDS (Table 1 and Figure 14). All of the particles were identified as extraterrestrial because they have approximately chondritic compositions or consist predominantly of a single-mineral grain like forsterite or pyrrhotite (commonly found within chondritic IDPs): 37% of the particles are CSIDPs, 45% are CPIDPs, and 18% IDPs composed predominantly of a single mineral. Table 1 summarizes the compositions of the IDPs. Within a factor of 2, the abundances of oxygen, magnesium, aluminum, sulfur, calcium, chromium, manganese, iron, and nickel are approximately chondritic. CPIDPs are a closer match to CI carbonaceous chondrites than CSIDPs, and they are closer to CI bulk than to CI or CM matrix. Anhydrous CPIDPs are the only known meteoritic materials that have a composition at the nanometer scale that is similar to CI bulk. Despite the compositional similarities between CP and CS particles, there are significant differences. While CPIDPs are a

0 0

1

2

3

Figure 14 CI chondrite normalized element to silicon ratios for CS and CPIDPs. The solid line represents frequency of CSIDPs and the dotted line frequency of CPIDPs. Numbers in upper right of each histogram are the number of CS and CPIDPs, respectively, with element to silicon ratios >3 CI. CSIDPs are systematically depleted in calcium and magnesium, while CPIDPs are only slightly depleted in calcium, aluminum, sulfur, and iron relative to CI (vertical dotted line). Reproduced from Schramm LS, Brownlee DE, and Wheelock MM (1989) Major element composition of stratospheric micrometeorites. Meteoritics 24: 99–112.

close match to CI abundances (they are a closer match to CI bulk than to CI or CM matrix), the CS group shows systematic magnesium and calcium depletions and a stoichiometric ‘excess’ of oxygen. The mean Mg/Si ratio for CPIDPs is 6% below the CI mean but the Mg/Si ratio of CSIDPs is 25% below the CI mean. The Ca/Si ratio shows a large range with a mean for all IDPs that is depleted by 15% relative to CI. Like Mg/Si, there is a clear difference between the CP and CS particles, with the former containing normal calcium and the latter depleted in calcium (see also Fraundorf et al., 1982b). These element patterns are consistent with the presence of hydrous layer silicates in CSIDPs and the loss of magnesium and calcium by the formation of secondary magnesium–calcium carbonates on the parent bodies. Similar magnesium depletions in the fine-grained matrices of CI (and CM) meteorites also have been attributed to leaching during aqueous alteration. Thus, the magnesium concentrations in the smooth group of chondritic IDPs suggest that they too have been processed by aqueous alteration, which is an important clue regarding their

Early Solar Nebula Grains – Interplanetary Dust Particles

Table 1

301

Mean atomic element/Si ratios for stratospheric micrometeorites versus those of various chondritic meteorite classes Ca

Type

O

Na

Mg

Al

S

Ca

Cr

Fe

Ni

4.17 4.49 3.98 3.81

0.052 0.051 0.056 0.043

0.980 0.824 1.015 1.203

0.075 0.082 0.070 0.075

0.356 0.341 0.417 0.231

0.052 0.021 0.047 0.125

0.015 0.014 0.016 0.013

0.697 0.742 0.705 0.585

0.027 0.032 0.024 0.019

7.64 4.38 3.49

0.057 0.029 0.046

1.040 1.023 0.928

0.083 0.088 0.067

0.444 0.201 0.099

0.061 0.070 0.050

0.013 0.012 0.011

0.868 0.804 0.594

0.048 0.048 0.032

0.920 0.957

0.094 0.121

0.129 0.194

0.011 0.029

0.012 0.010

0.539 0.935

0.047 0.057

b

Chondritic IDPs All CS CP Coarse

1.75 1.32 2.39 1.31

Chondritic meteorites (bulk) CIc CMd Ld

0.70 0.35 0.02

Chondritic meteorites (fine-grained matrices) CIe CMe

NA NA

NA NA

0.016 0.038

a

C and O analyses were done for only 30 IDPs. IDP data from Schramm et al. (1989). c CI chondrite average; Palme et al. (Chapter 2.2). d CM and L chondrite averages calculated from Jarosewich (1990). e CI and CM matrix compositions from McSween and Richardson (1977). b

origin. Conversely, CPIDPs are not significantly depleted in either magnesium or calcium suggesting that they have not been exposed to aqueous alteration. The lack of hydrous minerals in most CPIDPs supports this assertion. The mean Al/Si ratio relative to CI varies among IDPs by an amount similar to that seen for Mg/Si. Again, there is a systematic difference between CP and CSIDPs with the latter being enriched in aluminum. CS particles contain secondary layer lattice silicates (clays) with a high percentage of aluminum (Germani et al., 1990). The S/Si ratio shows a large range, although there is no systematic difference between CS and CP particles. Although it is depleted from the CI ratio by 30%, it is still higher than any other chondrite group except CIs. Sulfur is the most volatile major element in IDPs, and its measured abundance is complicated by the potential for sulfur loss by frictional heating during atmospheric entry and possible contamination of IDPs from stratospheric sulfate aerosols. Because pyrrhotite (FeS) is the major carrier of iron in chondritic IDPs, iron correlates strongly with sulfur (Figure 14). The correlated depletion of iron and sulfur is likely due to exclusion of singlemineral FeS-dominated grains from the data set. Fe/Si is depleted by 20% relative to CI chondrites, and there is no significant difference in the Fe/Si ratio between CP and CS particles. Iron and aluminum are correlated in CSIDPs but not in CPIDPs. The average Fe/Al value for CS particles is 9.05, which is further from the solar-system value of 10.50 (see Chapter 2.2) than the 10.13 Fe/Al mean value for CPIDPs. This same iron–aluminum correlation was seen in point count area analyses of a CSIDP that contains abundant layer lattice silicates. The correlation in CSIDPs almost certainly reflects the abundance of aluminum and iron-containing layer lattice silicates. The C/Si ratio in chondritic IDPs is systematically higher than all classes of chondritic meteorites. The mean carbon abundance is 10 versus 3.22 wt% for CI (see Chapter 2.3). Nitrogen has been detected in chondritic IDPs but as yet not quantified, although Keller et al. (1995) report that the C/N

ratio is approximately chondritic. Electron energy-loss spectra show that nitrogen is carried in amorphous carbonaceous material and that it is heterogeneously distributed as ‘hot spots.’ There is indirect evidence that the nitrogen is associated with PAHs (Section 1.8.3.1).

1.8.5.2

Trace Elements

Most chondritic IDPs have ‘chondrite-like’ trace-element compositions (Arndt et al., 1996). Abundances in individual chondritic IDPs generally scatter from 0.3  CI to 3  CI and that enrichments are more common than depletions (Flynn and Sutton, 1992a,b,c). Volatile elements tend to be enriched relative to CI meteorites (Ganapathy and Brownlee, 1979; Sutton, 1994). Enrichments of bromine measured in some IDPs probably reflect stratospheric contamination (Flynn, 1994a; Flynn et al., 1996; Van der Stap et al., 1986), and zinc depletions probably reflect loss of zinc by heating during atmospheric entry heating. Some low-zinc IDPs are also depleted in other volatile elements (copper, gallium, germanium, and selenium) (Flynn and Sutton, 1992a; Flynn et al., 1992). The most important trace-element trends in chondritic IDPs are illustrated in Figure 15. Element ratios for two different elements are plotted on the x- and y-axes, and the reference lines are where CI-normalized element ratios are 1. Nickel and chromium do not show a trend and are scattered about the CI reference lines and average Cr/Fe and Ni/Fe are similar to CI (Figure 15(a) and 15(b)). Calcium is depleted in most of the IDPs in accordance with Schramm et al. (1989) (Figure 15(b)), and titanium appears to be enriched (Figure 15(c)). Volatile trace elements are plotted in Figure 15(d) and 15(e). There are both enrichments and depletions of zinc (Figure 15(d)). Figure 15(e) shows the relationship between selenium and zinc. Low-zinc IDPs tend to also have low selenium and selenium deficiencies, like zinc deficiencies, and are more common in chondritic IDPs than selenium enrichments.

302

0.01

1000.

1000.

100.

100.

10.

10.

0.10

10.

100.

Cr/Fe/Cl

Cr/Fe/Cl

Early Solar Nebula Grains – Interplanetary Dust Particles

0.10

0.01

0.001

1000.

1000.

100.

100.

10.

10.

0.10

10.

100.

0.01

0.10 0.100

0.100

0.010

0.010

0.001 Ni/Fe/Cl

0.001 Ni/Fe/Cl

(d)

1000.

100.

10. Zn/Fe/Cl

(c)

0.01

0.10

10. 0.100

0.010

0.001 (e)

100.

0.001 Ni/Fe/Cl

(b)

Zn/Fe/Cl

Ti/Fe/Cl

0.01

10.

0.010

IDPs Average Logarithmic average

Ni/Fe/Cl

(a)

100.

0.100

0.100

0.010

10.

Se/Fe/Cl

100.

Early Solar Nebula Grains – Interplanetary Dust Particles

1.8.5.3

15

Isotopes

Because a single 10 mm IDP can contain several tens of thousands of submicrometer grains, and the ion microprobe has traditionally measured isotopic composition on a scale of 10 mm, large isotopic anomalies in individual grains within IDPs may not be recognized because they were averaged out on a scale of 10 mm. With this caveat in mind, the hydrogen, carbon, nitrogen, oxygen, magnesium, and silicon isotopic compositions of chondritic IDPs have been measured. Esat et al. (1979) first measured the magnesium isotopic compositions of four chondritic IDPs and calcium in one IDP. They found that the magnesium compositions were very close to normal isotopic composition but their normalized isotopic ratios appeared to show nonlinear effects of 3–4%, which at that time was near the limit of detection. The isotopic composition of calcium was found to be normal (solar) within 2%. Esat et al. recommended that it might prove useful to measure individual 1 mm components of IDPs. Significant enrichments and depletions in D/H have been found in IDPs (McKeegan, 1987; McKeegan et al., 1985; Zinner et al., 1983). The carrier of the D/H anomalies is believed to be the carbonaceous matrix within IDPs and, since the highest D/H enrichments (up to 30 000%) are found in large cluster IDPs that likely maintain a thermal gradient during atmospheric entry (i.e., their interiors remain cool), the carrier is presumably organic (Messenger, 2000). Enrichments of 15N (up to d15N ¼ 1280%) have also been found. Many but not all of the

N-enriched particles also show D/H enrichments, but the converse is not true (Stadermann et al., 1989). Both the D/H and 14N/15N often vary significantly within a given particle, in some cases displaying a pronounced ‘hot spot.’ The D and 15N anomalies have been attributed to organic materials produced by ion–molecule reactions in cold interstellar molecular clouds (Messenger, 2000), although the same processes might equally work in the outer fringes of the solar nebula. PAHs, believed to be important constituents of interstellar molecular clouds, were found in only two (of seven measured) IDPs that had large D anomalies. D and N enrichments have been observed in both the CP and CS particles. The NanoSIMS ion microprobe has extended detection limits for isotope anomalies in chondritic IDPs to 250 nm (Busemann et al., 2009; Floss and Stadermann, 2003; Messenger et al., 2003, 2007). Six silicate grains identified by Messenger et al. in nine chondritic IDPs have isotopic compositions confirming their presolar origins. Three of the grains exhibit elevated 17O/16O ratios and solar 18O/16O ratios consistent with origins in red giant and asymptotic giant branch stars, one is 16 O-rich consistent with formation in a low-metallicity star, and two of uncertain stellar origin are 16O depleted. One of the grains is a forsterite crystal and two others are GEMS. Floss and Stadermann (2003) measured carbon, nitrogen, and oxygen enrichments in two IDPs using the NanoSIMS (Figure 16). Two 17O-enriched presolar grains (of unknown mineralogy) but with isotopic compositions similar to those of the presolar

Benavente (L2036-G36)

Benavente (L2036-G16) 1500 1400 1200 1000 800

+ 1280‰

600 400 + 1430‰

200 0 −200 −300

Image area: 10 ⫻ 10 µm2 (a)

303

d 17O

Image area: 10 ⫻ 10 µm2

1500 1400 1200 1000 800 600 400 200 0 −200 −300 −600 d 15N

(b)

Figure 16 (a) d O image of portion of Benavente (L2036-G16) showing a O-rich subgrain within the IDP. The grain is 300 nm2 in size. The extremely anomalous O isotopic composition indicates that this grain is of presolar origin. (b) d15N image of a portion of Benavente (L2036-G36) showing a strongly 15N-enriched portion of the IDP. The ‘hot spot’ is 0.6  1.8 mm in size. The bulk IDP is also 15N-enriched with an average d15N of about 230% (data courtesy of Floss C and Stadermann F, Washington University). 17

17

Figure 15 Trace-element ratios in IDPs. Data from synchrotron x-ray fluorescence analyses are plotted on ‘three element’ diagrams. Element ratios are normalized to bulk CI abundances: (element/Fe)sample/(element/Fe)CI also denoted ‘element/Fe/CI.’ CI composition lies at the point element/Fe/CI ¼ 1 on each plot. Averages, assuming data are normally distributed (open squares) and assuming the data are log normally distributed (open diamonds), are also shown. Plots (a–c) exhibit the behavior of some more refractory elements chromium, calcium, and titanium with respect to nickel, while (d) and (e) show the behavior of zinc (relatively volatile) with respect to nickel (relatively refractory) and selenium (relatively volatile). Reproduced from Kehm K, Flynn GJ, Sutton SR, and Hohenberg CM (2002) Combined noble gas and trace element measurements on individual stratospheric interplanetary dust particles. Meteoritics and Planetary Science 37: 1323–1335.

304

Early Solar Nebula Grains – Interplanetary Dust Particles

silicates were observed as well in a region with a modest but significant depletion in 13C (d13C ¼  75%) and spatially associated with a nitrogen ‘hot spot’ with d15N ¼ 1280%. Although hints of depletions of 13C (with large errors) have previously been reported (McKeegan, 1987), the NanoSIMS measurements provide the first indication of correlated carbon and nitrogen isotope anomalies.

1.8.5.4

elemental ratios in Figure 17 indicate that the IDPs contain SW noble gases diffusively fractionated either in solar orbit or by heating during atmospheric entry with helium and neon depleted with respect to argon. An observed correlation between helium and zinc abundances in the IDPs suggests that it is more likely that helium is lost by frictional heating during atmospheric entry (Flynn and Sutton, 1992a; Kehm et al., 2002). Implanted helium is released from IDPs during pulsed stepwise heating in a furnace that mimics frictional heating during atmospheric entry. The helium release profile can be used to estimate the peak frictional heating temperatures and speeds experienced by individual IDPs during atmospheric entry (Nier, 1994). Stepwise heating has been used to distinguish high-speed cometary IDPs from low-speed asteroidal IDPs (Brownlee et al., 1995). In summary, the abundances and isotopic compositions of noble gases in chondritic IDPs are consistent with a SW origin, although fractionations due to cosmogenic spallation reactions and ‘secondary’ diffusive processes are evident (e.g., heating during atmospheric entry). The SW gases are implanted in IDPs during their lifetimes in solar orbit, and they may also contain a primordial (preaccretional) noble-gas component.

Noble Gases

Rajan et al. (1977) first measured the noble gases in chondritic IDPs and found SW 4He concentrations comparable to those observed in lunar soil grains. The measured concentrations were consistent with the 10 ka calculated exposure ages of small particles in solar orbit. Hudson et al. (1981) measured 20 Ne/22Ne in 13 combined IDPs and observed a ratio of 13  3, which is within the range of SW neon. Nier and Schlutter (1990) measured 3He/4He and 20Ne/22Ne in 16 individual IDPs. The average helium content was 0.027  0.01 cm3 STP g1 (in the same range reported by Rajan et al., 1977), and the average 3 He/4He ratio of 15 of the IDPs was (2.4  0.3) 104 (one IDP had a 3He/4He ratio of (1.45  0.3)  103). But using stepwise heating, Pepin et al. (2000) measured 3He/4He ratios up to 40 the SW ratio in several cluster particles, which they attribute to either cosmic-ray-induced spallogenic reactions during prolonged exposures of the IDPs in space or irradiation of the IDPs on their parent-body regoliths prior to their release into the interplanetary medium. The average 20Ne/22Ne value for 10 of the 16 IDPs measured by Nier and Schlutter (1990) was 12.0 0.3, and the average 21Ne/22Ne value for three of the 16 IDPs was 0.035  0.006. Noble-gas ratios (4He/36Ar vs. 20Ne/36Ar) in 31 IDPs are plotted in Figure 17. Plotted uncertainties are 1s. Also plotted is the noble-gas elemental composition of the CI carbonaceous chondrite Orgueil (‘planetary’) and the ‘SW.’ The observed

1.8.6

Conclusions

Chondritic IDPs are an important resource of extraterrestrial materials because they sample a much broader range of primitive solar-system bodies than do conventional meteorites and micrometeorites. Technical difficulties that limit interest in IDP research are being mitigated to some extent as a result of rapid advances in microparticle handling and microanalytical instrumentation. The atmospheric entry speeds of IDPs suggest that some hydrated CSIDPs are from asteroids and some anhydrous CPIDPs are from comets (Brownlee et al., 1995). The

5

10

SW Pyx

104

IIm

I12

Olv

D10 H21 C3 H14 L20 C21 H8 F32 I3 I24 F24 F12 D3 J13 B19 B1 M20 Plag O16 G8 I14 F9 G14 I8 G19 E15 G13 G11 H25 G2

4

He/36Ar

103 Planetary

102

101

100 10−1

B9

100

101 20

102

36

Ne/ Ar

Figure 17 Noble-gas elemental ratios in IDPs compared with CI meteorites and solar-wind (star) noble-gas compositions are also plotted. Closed and open diamonds represent ‘unheated’ IDPs and Zn-depleted IDPs, respectively. Square and circle represent lunar mineral separates (Signer et al., 1977) and planetary bulk CI chondrite (Jeffery and Anders, 1970), respectively (data courtesy of Kehm K). See also Kehm et al. (2002).

Early Solar Nebula Grains – Interplanetary Dust Particles

will increasingly be compared with in situ spacecraft measurements and ground-based observational data from dust in space. Future comet and asteroid sample return missions will undoubtedly provide new insight about stratospheric IDPs. Modeling will likely become increasingly important in understanding grain behavior in the outer solar nebula environment and its relevance to observed properties of IDPs (Ciesla and Sandford, 2012; Nuth and Johnson, 2012). The Stardust mission successfully returned a sample of comet 81P/Wild 2 to Earth in January 2006 (Chapter 2.13). The returned sample was expected to be similar to CPIDPs, and although there are mineralogical similarities, there are also perplexing differences. For example, carbonaceous material is conspicuously rare in the 81P/Wild 2 sample. ‘GEMS-like’ amorphous silicates with metal and sulfide inclusions are abundant in the impact tracks in aerogel, but it is unclear at this early stage whether they are relatively pristine GEMS (impact) modified GEMS, or melt residues produced during hypervelocity impact and unrelated to GEMS (Ishii et al., 2009). A fundamentally important result is the finding of calcium aluminum inclusions in comet 81P/Wild 2 (Simon et al., 2008), proving that material formed at high temperatures in the inner nebula was transported over the full radial extent of solar nebula. The overall mineralogy and grain size in the P81/Wild 2 sample may be a better match to the finegrained matrices of some chondritic meteorites from the asteroid belt than to ‘cometary’ CPIDPs, underscoring the arbitrary distinction between (some) asteroids and comets (Chapter 2.13). Observed differences in the grain size distributions in CPIDPs and the comet 81P/Wild 2 could be evidence that CPIDPs are from comets that accreted at significantly greater heliocentric

250 Comet 81P/Wild 2

200 ate

r silic

91

rsulfide (nm)

mineralogy and petrography of CSIDPs clearly indicate that they were derived from hydrous objects where parent-body aqueous alteration occurred. Given their similarity to the fine-grained matrices of CI and CM meteorites, asteroids are the logical sources. In a few cases, the mineralogy and petrography of chondritic CSIDPs link them directly to CI- or CM-like hydrous asteroids. The mineralogy and petrography of anhydrous CPIDPs suggest that they are from either anhydrous objects or very low-temperature hydrous objects where parent-body alteration was either minimal or nonexistent. Comets or ‘comet-like’ outer asteroids are the likely sources of CPIDPs (see Chapter 2.13). But it is also likely that some CPIDPs are from asteroids and some CSIDPs are from comets. Since studies of IDPs are equivalent to a limited sample return, clarification of the source(s) of the different classes of IDPs is a high priority of future research. Anhydrous CPIDPs are highly unusual in that they are mineralogically heterogeneous at the nanometer scale and unusual among known meteoritic materials in that they have not been subjected to significant postaccretional (parent-body) processing. They differ fundamentally from even the most primitive chondritic meteorites and micrometeorites. Some enstatite and forsterite crystals exhibit preserved evidence of condensation from nebular gases. Others have nonsolar isotopic compositions indicating that grain condensation occurred in the atmospheres of other stars. GEMS are perhaps the most enigmatic component of CPIDPs. Although they are cosmically primitive, they have been extensively processed by ionizing radiation as free-floating objects in space. Material removed by sputtering has been thoroughly mixed and redeposited on grain surfaces producing GEMS with approximately cosmic (chondritic) elemental compositions. The oxygen isotopic compositions of some GEMS establish that they acquired presolar components from AGB stars and supernovae during their lifetimes in the ISM. The ratio of presolar-to-solar-system components in CPIDPs is unknown. Some and possibly all GEMS-rich CPIDPs are probably well-preserved aggregates inherited from the presolar molecular cloud, the ‘common stuff’ of the ISM. New sample collection methods and analytical technologies will positively impact the future direction of interplanetary dust research. Alternatives to silicone oil for stratospheric IDP collections and organic solvents to remove the oil are needed to improve the accuracy of element abundance measurements and to better investigate the organic (molecular) chemistry of IDPs. Although it has recently been demonstrated that IDPs can be collected in the stratosphere without using silicone oil, additional thermal effects associated with impact onto dry substrates need to be evaluated (Messenger et al., 2012). The new source of IDPs recovered from Antarctica snow and ice will be complimentary to the stratospheric collections providing it can be shown that terrestrial alteration is minimal (Dobrica˘ et al., 2011; Noguchi et al., 2008), and the feasibility of sea-level collection of IDPs from oceanic aerosols is under investigation (Wozniakiewicz et al., 2011). Emerging analytical methods like resonant ionization mass spectrometry may lead to improved spatial resolution and sensitivity for detection of isotope anomalies in IDPs (Stephan et al., 2012). Similarly, advances in electron microscopy are enabling new kinds of spectroscopic measurements at close to atomic spatial scales (Bradley, 2012; Bradley and Dai, 2009). Laboratory analytical data from IDPs

305

150

=

9 0.6

ide

r sulf

2

R

100

95

.96

=0

CP IDP U220GCA CP IDP U211B6

50 CP IDP U212A34A

0 50

100

150

200

250

300

rsilicate (nm)

Figure 18 Comparison of mean radii of crystalline Mg silicates and sulfides from outer solar-system objects: comet 81P/Wild 2 and CPIDPs U2-11B6, SP-75, and C-11. Each CPIDP has significantly different average silicate and sulfide grain sizes that are smaller than the average grain size of comet 81P/Wild 2. All data points fall on or near the 1:1 line of aerodynamic silicate and sulfide equivalence indicative of grain sorting prior to parent body accretion. The standard errors of the means lie within the symbols on the plot, with the exception of comet 81P/Wild 2 where they are represented by error bars. The deviation about each mean is indicated by the shaded areas surrounding the mean data points (from Wozniakiewicz et al., 2012).

306

Early Solar Nebula Grains – Interplanetary Dust Particles

distances than comet 81P/Wild 2 (Figure 18) (Wozniakiewicz et al., 2012).

Acknowledgments This work was funded in part by a grant from NASA’s Cosmochemistry program. Portions of this work were performed under the auspices of the US Department of Energy by LLNL under contract DE-AC52-07NA27344.

References Aitken DK, Smith CH, James SD, Roche PF, and Hough JH (1988) Infrared spectropolarimetry of AFGL 2591 – Evidence for an annealed grain component. Monthly Notices of the Royal Astronomical Society 230: 629–638. Aitken DK, Smith CH, and Roche PF (1989) 10 and 20 mm spectropolarimetry of the BN object. Monthly Notices of the Royal Astronomical Society 236: 919–927. Anders E and Zinner E (1993) Interstellar grains in primitive meteorites: Diamond, silicon carbide, and graphite. Meteoritics 28: 490–514. Arndt P, Bohsung J, Maetz M, and Jessberger EK (1996) The elemental abundances in interplanetary dust particles. Meteoritics and Planetary Science 31: 817–834. Bernatowicz TJ and Walker RM (1997) Ancient stardust in the laboratory. Physics Today 50: 26–32. Bernatowicz TJ and Zinner E (1996) Astrophysical Implications of the Laboratory Study of Presolar Materials. AIP Conference Proceedings, vol. 402. New York: American Institute of Physics 750 p. Binzel RP (1992) The optical spectrum of 5145 Pholus. Icarus 99: 238–240. Bowey JE, Adamson AJ, and Whittet DCB (1998) The 10 mm profile of molecular-cloud and diffuse ISM silicate dust. Monthly Notices of the Royal Astronomical Society 298: 131–138. Bradley JP (1988) Analysis of chondritic interplanetary dust thin sections. Geochimica et Cosmochimica Acta 52: 889–900. Bradley JP (1994a) Nanometer-scale mineralogy and petrography of fine-grained aggregates in anhydrous interplanetary dust particles. Geochimica et Cosmochimica Acta 58: 2123–2134. Bradley JP (1994b) Chemically anomalous, preaccretionally irradiated grains in interplanetary dust from comets. Science 265: 925–929. Bradley JP (2013) How and where did GEMS form?. Geochimica et Cosmochimica Acta 107: 336–340. Bradley JP and Brownlee DE (1986) Cometary particles: Thin sectioning and electron beam analysis. Science 231: 1542–1544. Bradley JP and Brownlee DE (1991) An interplanetary dust particle linked directly to type CM meteorites and an asteroidal origin. Science 251: 549–552. Bradley JP, Brownlee DE, and Fraundorf P (1984a) Discovery of nuclear tracks in interplanetary dust. Science 226: 1432–1434. Bradley JP, Brownlee DE, and Fraundorf P (1984b) Carbon compounds in interplanetary dust particles: Evidence for formation by heterogeneous catalysis. Science 223: 56–58. Bradley JP, Brownlee DE, and Germani MS (1989) Automated thin-film analyses of anhydrous interplanetary dust particles in the analytical electron microscope. Earth and Planetary Science Letters 93: 1–13. Bradley JP, Brownlee DE, and Snow TP (1997) GEMS and other preaccretionally irradiated grains in interplanetary dust particles. In: Pendleton YJ and Tielens AGGM (eds.) From Stardust to Planetesimals. ASP Conference Series, Vol. 122, pp. 217–225. San Francisco: Astronomical Society of the Pacific. Bradley JP, Brownlee DE, and Veblen DR (1983) Pyroxene whiskers and platelets in interplanetary dust particles: Evidence of vapor phase growth. Nature 301: 473–477. Bradley JP and Dai ZR (2009) An analytical SuperSTEM for extraterrestrial materials research. Meteoritics and Planetary Science 44: 1627–1642. Bradley JP and Dia ZR (2006) Analytical SuperSTEM for extraterrestrial materials research. Meteoritics and Planetary Science 44: 1627–1642. Bradley JP, Dukes C, Baragiola R, McFadden L, Johnson RE, and Brownlee DE (1996) Lunar and Planetary Science 27: 149–150. Bradley JP, Humecki HJ, and Germani MS (1992) Combined infrared and analytical electron microscope studies of interplanetary dust particles. The Astrophysical Journal 394: 643–651.

Bradley JP, Ishii HA, Aguiar J, Borg LE, and Shearer CK (2012) Amorphous silicates produced during space weathering: Insight from monochromated valence electron energy-loss spectroscopy. Lunar and Planetary Science 43: #1659. Bradley JP, Keller LP, Brownlee DE, and Thomas KL (1996) Reflectance spectroscopy of interplanetary dust particles. Meteoritics and Planetary Science 31: 394–402. Bradley JP, Keller LP, Snow TP, et al. (1999) An infrared spectral match between GEMS and interstellar grains. Science 285: 1716–1718. Bradley JP, Sandford SA, and Walker RM (1988) Interplanetary dust particles. In: Kerridge JF and Matthews MS (eds.) Meteorites and the Early Solar System, pp. 861–895. Tucson: University of Arizona Press. Bradley JP, Snow TP, Brownlee DE, and Hanner MS (1999) Mg-rich olivine and pyroxene grains in primitive meteoritic materials: comparison with crystalline silicate data from ISO. In: d’Hendecourt L, Joblin C, and Jones A (eds.) Solid Interstellar Matter: The ISO Revolution. Les Houches No. 11pp. 297–315. Les Ullis: EDP Sciences. Bradley JP, Wozniakiewicz PJ, and Ishii HA (2011) Constraints on the cosmochemical significance of element/Si ratios and oxygen isotopic compositions of GEMS from IDPs collected in silicone oil. Lunar and Planetary Science 42: # 1320. Brearley AJ and Jones RH (1998) Chondritic meteorites. In: Papike JJ (ed.) Planetary Materials. Rev. Mineral., vol. 36, pp. 3.1–3.398. Washington, DC: Mineralogical Society of America. Brownlee DE (1985) Cosmic dust—collection and research. Annual Review of Earth and Planetary Sciences 13: 147–173. Brownlee DE (1994) The origin and role of dust in the early solar system. In: Zolensky ME, Wilson TL, Rietmeijer FJM, and Flynn GJ (eds.) Analysis of Interplanetary Dust. AIP Conference Proceedings, vol. 310, pp. 5–8. New York: American Institute of Physics. Brownlee DE (1996) STARDUST: Comet and interstellar dust sample return mission. In: Gustafson BA˚S and Hanner MS (eds.) Physics, Chemistry, and Dynamics of Interplanetary Dust, pp. 223–226. New York: American Institute of Physics. Brownlee DE, Flynn G, Ho¨rz F, et al. (2006) Comet samples returned by the Stardust mission. Lunar and Planetary Science 37: #2286. Brownlee DE, Joswiak DJ, and Bradley JP (1999) High spatial resolution analyses of GEMS and other ultrafine grained IDP components. Lunar and Planetary Science 30: #2031. Brownlee DE, Joswiak DJ, Bradley JP, Gezo JC, and Hill HGM (2000) Spatially resolved acid dissolution of IDPs: The state of carbon and the abundance of diamonds in the dust. Lunar and Planetary Science 31: #1921. Brownlee DE, Joswiak DJ, Bradley JP, Matrajt G, and Wooden D (2005) Cooked GEMS – Insights into the hot origins of crystalline silicates in circumstellar disks and the cold origins of GEMS. Lunar and Planetary Science 36: #2391. Brownlee DE, Joswiak DJ, Schlutter DJ, Pepin RO, Bradley JP, and Love SJ (1995) Identification of individual cometary IDPs by thermally stepped He release. Lunar and Planetary Science 26: 183–184. Busemann H, Nguyen AN, Cody GD, et al. (2009) Ultra-primitive interplanetary dust particles from the comet 26P/Grigg-Skjellerup dust stream collection. Earth and Planetary Science Letters 288: 44–57. Campins H and Ryan E (1989) The identification of crystalline olivine in cometary silicates. The Astrophysical Journal 341: 1059–1066. Christoffersen R and Buseck PR (1986) Mineralogy of interplanetary dust particles from the “olivine” infrared class. Earth and Planetary Science Letters 78: 53–66. Ciesla F and Sandford S (2012) Organic synthesis via irradiation and warming of ice grains in the solar nebula. Science 236: 452–454. Clayton DD and Nittler LR (2004) Astrophysics with presolar stardust. Annual Review of Astronomy and Astrophysics 42: 39–78. Clemett SJ, Maechling CR, Zare RN, Swan PD, and Walker RM (1993) Identification of complex aromatic molecules in individual: Interplanetary dust particles. Science 262: 721–725. Dai ZR and Bradley JP (2001) Iron nickel sulfides in anhydrous interplanetary dust particles. Geochimica et Cosmochimica Acta 65: 3601–3612. Dai ZR, Bradley JP, Brownlee DE, and Joswiak DJ (2003) The petrography of meteoritic nano-diamonds. Lunar and Planetary Science 34: #1121. Dai ZR, Bradley JP, Joswiak DJ, Brownlee DE, Hill HGM, and Genge MJ (2002) Possible in situ formation of nanodiamonds in the early solar system. Nature 418: 157–159. Daulton TL, Eisenhour DD, Bernatowicz TJ, Lewis RS, and Buseck PR (1996) Genesis of presolar diamonds: Comparative high-resolution transmission electron microscopy study of meteoritic nano-diamonds. Geochimica et Cosmochimica Acta 60: 4853–4872. Davis AM (2011) Stardust in meteorites. Proceedings of the National Academy of Sciences 108: 19142–19146. Dermott SF, Grogan K, Durda DD, et al. (2001) Orbital evolution of interplanetary dust. In: Gru¨n E, Gustafson BA˚S, Dermott SF, and Fechtig H (eds.) Interplanetary Dust, pp. 569–640. Berlin: Springer. Dermott SF, Jayaraman S, Xu X-L, Gustafson BA˚S, and Liou J-C (1994) A circumsolar ring of asteroidal dust in resonant lock with the Earth. Nature 369: 719–723.

Early Solar Nebula Grains – Interplanetary Dust Particles

Dobrica˘ E and Brearley A (2012) Complex heterogeneous aqueous alteration in the matrices of unequilibrated ordinary chondrites by low temperature hydrothermal solutions. Lunar and Planetary Science 43: #2212. Dobrica˘ E, Engrand C, Leroux H, Rouzaud J-N, and Duprat J (2011) Transmission electron microscopy of CONCORDIA ultracarbonaceous Antarctic micrometeorites (UCAMMs): Mineralogical properties. Geochimica et Cosmochimica Acta 76: 68–82. Erni R, Browning ND, Dai ZR, and Bradley JP (2005) Analysis of extraterrestrial particles using monochromated electron energy-loss spectroscopy. Micron 36: 369–379. Esat TM, Brownlee DE, Papanastassiou DA, and Wasserburg GJ (1979) Magnesium isotopic composition of interplanetary dust particles. Science 206: 190–197. Farinella P, Gonzi R, and Froeschl C (1993) The injection of asteroid fragments into resonances. Icarus 101: 174–187. Floss C and Stadermann FJ (2003) Complimentary carbon, nitrogen, and oxygen isotopic imaging of interplanetary dust particles: Presolar grains and an indication of a carbon isotope anomaly. Lunar and Planetary Science 34: #1238. Floss C and Stadermann FJ (2012) Presolar silicate and oxide abundances and compositions in the ungrouped carbonaceous chondrite Adelaide and the K chondrite Kakangari: The effects of secondary processing. Meteoritics and Planetary Science 47: 992–1009. Flynn GJ (1990) The near-Earth enhancement of asteroidal over cometary dust. In: Proceedings of the 20th Lunar and Planetary Science Conference 363–371. Flynn GJ (1994a) Interplanetary dust—the common stuff of stardust. Nature 371: 287–288. Flynn GJ (1994b) Changes in the composition and mineralogy of interplanetary dust particles be terrestrial encounters. In: Zolensky ME, Wilson TL, Rietmeijer FJM, and Flynn GJ (eds.) Analysis of Interplanetary Dust. AIP Conference Proceedings, vol. 310, pp. 127–143. New York: American Institute of Physics. Flynn GJ (1996) Sources of 10 micron interplanetary dust: The contribution from the Kuiper belt. In: Gustafson BA˚S and Hanner MS (eds.) Physics, Chemistry, and Dynamics of Interplanetary Dust, pp. 171–175. New York: American Institute of Physics. Flynn GJ (2000) A comparison of the selenium contents of sulfides from interplanetary dust particles and meteorites. Meteoritics and Planetary Science 35: A54. Flynn GJ, Bajt S, and Sutton SR (1996) Evidence for weakly bound bromine in large interplanetary dust particles collected from the stratosphere. Lunar and Planetary Science 27: 367–368. Flynn GJ, Henning T, Keller LP, and Mutschke H (2002) Infrared spectroscopy of cosmic dust. In: Videen G and Kocifaj M (eds.) Optics of Cosmic Dust. NATO Science Series, vol. 79, pp. 37–56. Dordrecht: Kluwer. Flynn GJ, Keller LP, Jacobsen C, Wirick S, and Miller MA (2000) Organic carbon in interplanetary dust particles. In: Lemarchand G and Meech K (eds.) A New Era in Bioastronomy. ASP Conference Series, vol. 213, pp. 191–194. San Francisco: Astronomical Society of the Pacific. Flynn GJ, Lanzirotti A, and Sutton SR (2008) Elemental compositions of large cluster IDPs. Lunar and Planetary Science 39: #1391. Flynn GJ and Sutton SR (1992a) Elemental abundances in stratospheric cosmic dust: Indications for a new chemical type of chondritic material. Lunar and Planetary Science 23: 373–374. Flynn GJ and Sutton SR (1992b) Trace elements in chondritic cosmic dust: Volatile correlation with Ca abundance. Meteoritics 27: 220. Flynn GJ and Sutton SR (1992c) Trace elements in chondritic stratospheric particles: Zinc depletion as a possible as a possible indicator of atmospheric entry heating. In: Proceedings of the 22nd Lunar and Planetary Science Conference 171–184. Flynn GJ, Sutton SR, Thomas KL, Keller LP, and Klo¨ck W (1992) Zinc depletions and atmospheric entry heating in stratospheric cosmic dust particles. Lunar and Planetary Science 23: 375–376. Fraundorf P (1981) Interplanetary dust in the transmission electron microscope: Diverse materials from the early solar system. Geochimica et Cosmochimica Acta 45: 915–943. Fraundorf P, Brownlee DE, and Walker RM (1982) Laboratory studies of interplanetary dust. In: Wilkening LL (ed.) Comets, pp. 383–409. Tucson: University of Arizona Press. Fraundorf P, Hintz C, Lowry O, McKeegan KD, and Sandford SA (1982) Determination of the mass, surface density, and volume density of individual interplanetary dust particles. Lunar and Planetary Science 13: 225–226. Ganapathy R and Brownlee DE (1979) Interplanetary dust: Trace element analyses of individual particles by neutron activation. Science 206: 1075–1077. Germani MS, Bradley JP, and Brownlee DE (1990) Automated thin-film analyses of hydrated interplanetary dust particles in the analytical electron microscope. Earth and Planetary Science Letters 101: 162–179. Godlevskiy MN, Likhachev AP, Chuvikina NG, and Andronov AD (1971) Hydrothermal synthesis of pentlandite. Doklady Akademii Nauk SSSR 196: 146–149. Goodman AA and Whittet DCB (1995) A point in favor of the superparamagnetic grain hypothesis. The Astrophysical Journal 455: L181–L184.

307

Gradie J and Tedesco E (1982) Compositional structure of the asteroid belt. Science 216: 1405–1407. Hanner MS, Brooke TY, and Tokunaga AT (1995) 10 micron spectroscopy of younger stars in the rho Ophiuchi cloud. The Astrophysical Journal 502: 250–258. Hanner MS, Brooke TY, and Tokunaga AT (1998) Micron spectroscopy of young stars. The Astrophysical Journal 502: 871–882. Hanner MS, Gehrz RD, Harker DE, et al. (1997) Thermal emission from the dust coma of Comet Hale–Bopp and the composition of the silicate grains. Earth, Moon, and Planets 79: 247–264. Henning T (1999) Grain formation and evolution in the interstellar medium. In: d’Hendecourt L, Joblin C, and Jones A (eds.) Solid Interstellar Matter: The ISO Revolution. Les Houches No. 11pp. 247–262. Les Ullis: EDP Sciences. Henning T (ed.) (2010) Astromineralogy. In: Lecture Notes in Physics, vol. 815. Berlin: Springer. Hoppe P and Zinner E (2000) Presolar dust grains from meteorites and their stellar sources. Journal of Geophysical Research 105: 10371–10398. Hudson B, Flynn GJ, Thomas KL, Keller LP, Fraundorf CM, and Shirck J (1981) Noble gases in stratospheric dust particles: Confirmation of extraterrestrial origin. Science 211: 383–386. Ishii HA, Bradley JP, Dai ZR, et al. (2009) Comparison of comet 81P/Wild 2 with interplanetary dust from comets. Science 319: 447–450. Jaeger C, Molster FJ, Dorschner J, Henning T, Mutschke H, and Waters LBFM (1998) Steps toward interstellar silicate mineralogy: IV. The crystalline revolution. Astronomy and Astrophysics 339: 904–916. Jarosewich E (1990) Chemical analyses of meteorites: A compilation of stony and iron meteorite analyses. Meteoritics 25: 323–337. Jeffery PM and Anders E (1970) Primordial noble gases in separated meteoritic minerals: I. Geochimica et Cosmochimica Acta 34: 1175–1198. Jenkins EB (2009) A unified representation of gas-phase element depletions in the interstellar medium. The Astrophysical Journal 700: 1299–1348. Jessberger EK, Stephan T, Rost D, et al. (2001) Properties of interplanetary dust: Information from collected samples. In: Gru¨n E, Gustafson BA˚S, Dermott SF, and Fechtig H (eds.) Interplanetary Dust, pp. 253–294. Berlin: Springer. Jones AP and Nuth JA III (2011) Dust destruction in the ISM: A re-evaluation of dust lifetimes. Astronomy and Astrophysics 530: (12 pp) A44. Jones RV and Spitzer L Jr. (1967) Magnetic alignment of interstellar grains. The Astrophysical Journal 147: 943–964. Kehm K, Flynn GJ, Sutton SR, and Hohenberg CM (2002) Combined noble gas and trace element measurements on individual stratospheric interplanetary dust particles. Meteoritics and Planetary Science 37: 1323–1335. Keller LP, Hony S, Bradley JP, et al. (2001) Sulfides in space: A possible match to the 23 mm feature detected by the Infrared Space Observatory. Nature 417: 148–150. Keller LP and Messenger S (2011) On the origins of GEMS. Geochimica et Cosmochimica Acta 75: 5336–5365. Keller LP, Thomas KL, Bradley JP, and McKay DS (1995) Nitrogen in interplanetary dust particles. Meteoritics 30: 526–527. Keller LP, Thomas KL, and McKay DS (1992) An interplanetary dust particle with links to CI chondrites. Geochimica et Cosmochimica Acta 56: 1409–1412. Keller LP, Thomas KL, and McKay DS (1994) Carbon in primitive interplanetary dust particles. In: Zolensky ME, Wilson TL, Rietmeijer FJM, and Flynn GJ (eds.) Analysis of Interplanetary Dust. AIP Conference Proceedings, vol. 310, pp. 51–87. New York: American Institute of Physics. Kim S-H, Martin PG, and Hendry PD (1994) The size distribution of interstellar dust particles as determined from extinction. The Astrophysical Journal 422: 164–175. Klo¨ck W and Stadermann FJ (1994) Mineralogical and chemical relationships of interplanetary dust particles, micrometeorites and meteorites. In: Zolensky ME, Wilson TL, Rietmeijer FJM, and Flynn GJ (eds.) Analysis of Interplanetary Dust. AIP Conference Proceedings, vol. 310, pp. 159–164. New York: American Institute of Physics. Klo¨ck W, Thomas KL, McKay DS, and Palme H (1989) Unusual olivine and pyroxene composition in interplanetary dust and unequilibrated ordinary chondrites. Nature 339: 126–128. Lauretta DS and Fegley B Jr. (1994) Troilite formation kinetics and growth mechanism in the solar nebula. Meteoritics 29: 490. Lauretta DS, Kremser DT, and Fegley B Jr. (1995) Nickel fractionation during troilite formation in the solar nebula. Lunar and Planetary Science 26: 831–832. Lauretta DS, Kremser DT, and Fegley B Jr. (1996) The rate of iron sulfide formation in the solar nebula. Icarus 122: 288–315. Liou JC, Zook HA, and Dermott SF (1996) Kuiper belt dust grains as a source of interplanetary dust. Icarus 124: 429–440. Lodders K and Amari S (2005) Presolar grains from meteorites: Remnants from the early times of the solar system. Chemie der Erde 65: 93–166.

308

Early Solar Nebula Grains – Interplanetary Dust Particles

Love SG and Brownlee DE (1991) Heating and thermal transformation of micrometeoroids entering Earth’s atmosphere. Icarus 89: 26–43. Love SG and Brownlee DE (1996) Peak atmospheric entry heating temperatures of micrometeorites. Meteoritics and Planetary Science 31: 394–402. Love SG, Joswiak DJ, and Brownlee DE (1994) Densities of stratospheric micrometeorites. Icarus 111: 227–236. Lugaro M (2005) Stardust from Meteorites. Singapore: World Scientific Publishing 209 p. Luu JX (1993) Spectral diversity among the nuclei of comets. Icarus 104: 138–148. Martin PG (1995) On the value of GEMS (glass with embedded metal and sulfides). The Astrophysical Journal 445: L63–L66. Mathis JA (1993) Observations and theories of interstellar dust. Reports on Progress in Physics 56: 605–652. Matrajt G, Messenger S, Brownlee DE, and Joswiak DJ (2012) Diverse forms of primordial organic matter identified in interplanetary dust particles. Meteoritics and Planetary Science 47: 525–549. McKeegan KD (1987) Ion Microprobe Measurements of H, C, O, Mg, and Si Isotopic Abundances in Individual Interplanetary Dust Particles. PhD Thesis, Washington University. McKeegan KD, Zinner E, and Walker RM (1985) Ion microprobe isotopic measurements of individual interplanetary dust particles. Geochimica et Cosmochimica Acta 49: 1971–1987. McSween HY Jr. and Richardson SM (1977) The composition of carbonaceous chondrite matrix. Geochimica et Cosmochimica Acta 41: 1145–1161. Messenger S (2000) Identification of molecular-cloud material in interplanetary dust particles. Nature 404: 968–971. Messenger S, Keller LP, Nakamura-Messenger K, and Clemett SJ (2012) Pristine stratospheric collection of cosmic dust. Lunar and Planetary Science 43: #2696. Messenger S, Keller L, Nakamura-Messenger K, and Ito M (2007) The abundance and distribution of presolar materials in cluster IDPs. Lunar and Planetary Science 38: #2122. Messenger S, Keller LP, Stadermann FJ, Walker RM, and Zinner E (2003) Samples of stars beyond the solar system: Silicate grains in interplanetary dust. Science 300: 105–108. Millar TJ and Duley WW (1980) Interstellar grains: Constraints on composition from infrared observations. Monthly Notices of the Royal Astronomical Society 191: 641–649. Molster FJ, Bradley JP, Sitko ML, and Nuth JA (2001) Astromineralogy: The comparison of infrared spectra from astrophysical environments with those from interplanetary dust particles (IDPs). Lunar and Planetary Science 32: #1391. Nakazawa H, Osaka T, and Sakaguchi K (1973) A new cubic iron sulphide prepared by vacuum deposition. Nature 242: 13–14. Nier AO (1994) Helium and neon in interplanetary dust particles. In: Zolensky ME, Wilson TL, Rietmeijer FJM, and Flynn GJ (eds.) Analysis of Interplanetary Dust. AIP Conference Proceedings, vol. 310, pp. 115–126. New York: American Institute of Physics. Nier AO and Schlutter DJ (1990) Helium and neon isotopes in stratospheric particles. Meteoritics 25: 263–267. Noguchi T, Ohashi N, Nishida S, et al. (2008) Discovery of Antarctic micrometeorites containing GEMS and enstatite whiskers. Meteoritics and Planetary Science 43: #5129. Nuth JA III and Johnson NM (2012) Complex protostellar chemistry. Science 336: 424–425. Pepin RO, Palma RL, and Schlutter DJ (2000) Noble gases in interplanetary dust particles: I. The excess helium-3 problem and estimates of the relative fluxes of solar wind and solar energetic particles in interplanetary space. Meteoritics 35: 495–504. Rajan RS, Brownlee DE, Tomandl D, Hodge PW, Farrar H, and Britten RA (1977) Detection of 4He in stratospheric particles gives evidence of extraterrestrial origin. Nature 267: 133–134. Rietmeijer FJM (1987) Silicone oil: A persistent contaminant in chemical and spectral micro-analyses of interplanetary dust particles. Lunar and Planetary Science 18: 386–387. Rietmeijer FJM (1989) Ultrafine-grained mineralogy and matrix chemistry of olivine-rich chondritic interplanetary dust particles. In: Proceedings of the 19th Lunar and Planetary Science Conference 513–521. Rietmeijer FJM (1996) CM-like interplanetary dust particles in the lower stratosphere during 1989 October and 1991 June/July. Meteoritics and Planetary Science 31: 278–288. Rietmeijer FJM (1997) Interplanetary dust petrology, principal components analysis, chondrites, chemical composition, grain size, porosity, magnesium compounds, iron compounds, minerals. Lunar and Planetary Science 28: #1301. Rietmeijer FJM (1998) Interplanetary dust particles. In: Papike JJ (ed.) Planetary Materials. Rev. Mineral., vol. 36, pp. 2.1–2.95. Washington, DC: Mineralogical Society of America. Rost D, Stephan T, and Jessberger E (1999) Surface analysis of stratospheric dust particles. Meteoritics and Planetary Science 34: 637–646.

Sandford SA (1987) The collection and analysis of extraterrestrial dust particles. Fundamentals of Cosmic Physics 12: 1–73. Sandford SA (1996) The inventory of interstellar materials available for the formation of the solar system. Meteoritics and Planetary Science 31: 449–476. Sandford SA and Bradley JP (1989) Interplanetary dust particles collected in the stratosphere: Observations of atmospheric heating and constraints on their interrelationships and sources. Icarus 82: 146–166. Sandford SA and Walker RM (1985) Laboratory infrared transmission spectra of individual interplanetary dust particles from 2.5 to 25 microns. The Astrophysical Journal 291: 838–851. Schramm LS, Brownlee DE, and Wheelock MM (1989) Major element composition of stratospheric micrometeorites. Meteoritics 24: 99–112. Seab CG, Hollenbach DJ, and Thronson HA (1987) Interstellar Processes. Dordrecht: Reidel 491 p. Signer P, Baur H, and Derksen U (1977) Helium, neon, and argon records of lunar soil evolution. In: Proceedings of the 8th Lunar and Planetary Science Conference 3657–3683. Simon SB, Joswiak DJ, Ishii HA, et al. (2008) A refractory inclusion returned by Stardust from comet 81P/Wild 2. Meteoritics and Planetary Science 43: 1861–1877. Sitko ML, Grady CA, Lynch DK, Russell RW, and Hanner MS (1999) Cometary dust in the debris disks of HD 31648 and HD 163296: Two “baby” beta Pictoris stars. The Astrophysical Journal 510: 408–412. Snow TP and Witt AN (1996) Interstellar depletions updated: Where all the atoms went. The Astrophysical Journal 468: L65–L68. Stadermann FJ, Walker RM, and Zinner E (1989) Ion microprobe measurements of nitrogen and carbon isotopic variations in individual IDPs. Meteoritics 24: 327. Stephan T, Davis AM, Pellin MJ, et al. (2012) CHILI – Approaching the final frontiers in lateral resolution and sensitivity – A progress report. Lunar and Planetary Science 43: #2660. Sutton SR (1994) Chemical compositions of primitive solar system particles. In: Zolensky ME, Wilson TL, Rietmeijer FJM, and Flynn GJ (eds.) Analysis of Interplanetary Dust. AIP Conference Proceedings, vol. 310, pp. 145–157. New York: American Institute of Physics. Thomas KL, Blanford GE, Clemett SJ, et al. (1995) An asteroidal breccia: The anatomy of a cluster IDP. Geochimica et Cosmochimica Acta 59: 2797–2815. Tomeoka K and Buseck PR (1984) Transmission electron microscopy of the “LOW-CA” hydrated interplanetary dust particle. Earth and Planetary Science Letters 69: 243–254. Tsou P, Brownlee DE, Flynn GJ, et al. (2006) STARDUST’s comet Wild 2 and contemporary interstellar stream sample analysis. Lunar and Planetary Science 37: #2286. van Boekel R, Min M, Leinert Ch, et al. (2004) The building blocks of planets within the ‘terrestrial’ region of protoplanetary disks. Nature 432: 479–482. Van der Stap CCGM, Vis RD, and Verheul H (1986) The Lunar and Planetary Institute, Houston. Lunar and Planetary Science 17: 1013–1014. Van Kerckhoven C, Tielens AGGM, and Waelkens C (2002) Nanodiamonds around HD 97048 and Elias: 1. Astronomy and Astrophysics 384: 568–584. Voshchinnikov NV and Henning Th (2010) From interstellar abundances to grain composition: The major dust constituents Mg, Si, and Fe. Astronomy and Astrophysics 517: A45–A60. Warren JL and Zolensky ME (1994) Collection and curation of interplanetary dust particles recovered from the stratosphere by NASA. In: Zolensky ME, Wilson TL, Rietmeijer FJM, and Flynn GJ (eds.) Analysis of Interplanetary Dust. AIP Conference Proceedings, vol. 310, pp. 245–253. New York: American Institute of Physics. Wozniakiewicz PJ, Bradley JP, Zolensky ME, Brownlee DE, and Ishii HA (2011) Kwajalein Atoll: A new collection site for micrometeorites. Meteoritics and Planetary Science 46: #5206. Wozniakiewicz PJ, Ishii HA, Bradley JP, Kearsley AT, Burchell M, and Price MC (2012) Grain size sorting in cometary dust from the outer nebula. The Astrophysical Journal 760: (6pp) #L23. Zinner E, McKeegan KD, and Walker RM (1983) Laboratory measurements of D/H ratios in interplanetary dust. Nature 305: 119–121. Zolensky ME (1987) Refractory interplanetary dust particles. Science 237: 1466–1468. Zolensky ME and McSween HY Jr. (1988) Aqueous alteration. In: Kerridge JF and Matthews MS (eds.) Meteorites and the Early Solar System, pp. 114–143. Tucson: University of Arizona Press. Zolensky ME and Thomas KL (1995) Iron and nickel sulfides in chondritic interplanetary dust. Geochimica et Cosmochimica Acta 59: 4707–4712. Zolensky ME, Wilson TL, Rietmeijer FJM, and Flynn GJ (eds.) (1994) Analysis of Interplanetary Dust. In: AIP Conference Proceedings, vol. 310. New York: American Institute of Physics.