Mineralogy of chondritic interplanetary dust particles

Abstract

From a mineralogical survey of approximately 30 chondritic micrometeorites collected from the lower stratosphere and studied in detail using current electron microscopy techniques, it is concluded that these particles represent a unique group of extraterrestrial materials. These micrometeorites differ significantly in form and texture from components of carbonaceous chondrites and contain some mineral assemblages which do not occur in any meteorite class. Electron microscope investigations of chondritic micrometeorites have established that these materials (1) are extraterrestrial in origin, (2) existed in space as small objects, (3) endured minimal alteration by planetary processes since formation, and (4) can suffer minimal pulse heating (<600øC) on entering earth's atmosphere. The probable sources for chondritic interplanetary dust particles (IDPs) are cometary and asteroidal debris and, perhaps to a lesser extent, interstellar regions. These sources have not been conclusively linked to any specific mineralogical subset of IDP, although the chondritic porous (CP) aggregate is considered of likely cometary origin. Chondritic IDPs occur in two predominant mineral assemblages:(1) carbonaceous phases and phyllosilicates and (2) carbonaceous phases and nesosilicates or inosilicates, although particles with both types of silicate assemblages are observed. Olivines, pyroxenes, layer silicates, and carbon-rich phases are the most commonly occurring minerals in many chondritic IDPs. Other phases often observed in variable proportions include sulphides, spineIs, metals, metal carbides, carbonates, and minor amounts of sulphates and phosphates. Individual mineral grain sizes range from micrometers (primarily pyroxenes and olivines) to nanometers, with the predominant size for all phases less than 100 nm. Specific mineral characteristics for particular chondritic IDPs provide an indication of processes which may have occurred prior to collection in the earth's stratosphere. For example, pyroxene mineralogy in some chondritic aggregates is consistent with condensation from a vapor phase and, we consider, with condensation in a turbulent solar nebula at relatively low temperatures (<1000øC). Carbonaceous phases present in other CP aggregates have been used to imply low-temperature formation processes such as Fischer-Tropsch synthesis (-530øC) or carbonization and graphitization (--•315øC). Alteration processes have been implicated in the formation of some layer silicates in CP aggregates and may have involved hydrocryogenic alteration at <0øC. In general, interpretations of transformation processes on submicrometer-size minerals in chondritic IDPs are consistent with formation at a radius equivalent to the asteroid belt or greater during the later stages of solar nebula evolution using currently available models.

Grain growth in the inner regions of Herbig Ae/Be star disks

“…Demyk et al 2000) but are a substantial component in (some) comets and in interplanetary Send offprint requests to: R. van Boekel, e-mail: rvanboek@eso.org Based on observations obtained at the European Southern Observatory (ESO), La Silla, and on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA. dust particles (IDPs) found in the solar system (MacKinnon & Rietmeijer 1987;Bradley et al 1992). Clearly, the refractory material in the proto-solar cloud went through large changes as the solar system was formed.…”

Location and sizes of forsterite grains in protoplanetary disks

“…In our own solar system, comets and interplanetary dust particles also include crystalline silicates (MacKinnon & Rietmeijer 1987;Bradley et al 1992). Silicate grains in long-period comets such as Hale-Bopp can be A&A 574, A140 (2015) crystalline (Crovisier et al 1997;Wooden et al 1999;.…”

Dynamic pyrometamorphism during atmospheric entry of large (˜10 micron) pyrrhotite fragments from cluster IDPs

“…1). Reviewing the petrology, mineralogy, and textures of chondritic aggregate IDPs, Mackinnon and Rietmeijer (1987) concluded they are uniquely different from any other materials found among the collected meteorites. Subsequent research supported this conclusion with new data on aggregate IDPs, e.g., principal components (PCs) (Rietmeijer 2002a) and GEMS (Bradley 1994;Bradley et al 1999), and on stable isotope chemistry (Keller et al 2000;Messenger 2000;Messenger et al 2003).…”