Interplanetary dust

It is interesting to note that recent evidence shows that even extra-terrestrially formed hydrocarbons can reach the Earth. The Earth continues to receive some 40,000 tons of interplanetary dust every year. Mass-spectrometric analysis has revealed the presence of hydrocarbons attached to these dust particles, including polycyclic aromatics such as phenanthrene, chrysene, pyrene, benzopyrene, and pentacene of extraterrestrial origin indicated by anomalous isotopic ratios. 

Fig. 7. A 10-)J.m interplanetary dust particle that is not porous and contains hydrated siUcates. The particle s elemental composition is a good match to solar...

Fig. 8. A porous interplanetary dust particle collected in the stratosphere. The particle is 10 ]lni across and is composed of anhydrous...

The number of scientific articles published on meteorites has increased dramatically in the last few years few of these, however, concern themselves with small meteorites, the size of which lies between that of the normal meteorites (from centimetres to metres in size) and that of interplanetary dust particles. In the course of an Antarctic expedition, scientists (mainly from French institutions) collected micrometeorites from 100 tons of Antarctic blue ice (Maurette et al 1991). These micrometeorites were only 100 400 pm in size five samples, each consisting of 30-35 particles, were studied to determine the amount of the extraterrestrial amino acids a-aminoisobutyric acid (AIBS) and isovaline—both of which are extremely rare on Earth—which they contained. The analysis was carried out using a well-tested and extremely sensitive HPLC system at the Scripps Institute, La Jolla. Although the micrometeorites came from an extremely clean environment, the samples must have been contaminated, as they all showed traces of L-amino acids. Only one sample showed a significantly higher concentration of AIBS (about 280 ppm). The AIBS/isovaline ratio in the samples also lay considerably above that previously found in CM-chondrites. 

Flynn G. J., Keller F. P., Feser M., Wirick S. and Jacobsen C. (2003). The origin of organic matter in the solar system evidence from the interplanetary dust particles. Geochimica et Cosmochimica Acta 67 4791. 

Isotope variations found in extraterrestrial materials have been classified according to different processes such as chemical mass fractionation, nuclear reactions, nucleosynthesis, and/or to different sources such as interplanetary dust, solar materials, and comet material. Various geochemical fingerprints point to the reservoir from which the planetary sample was derived and the environment in which the sample has formed. They can be attributed to a variety of processes, ranging from heterogeneities in the early solar nebula to the evolution of a planetary body. For more details the reader is referred to reviews of Thiemens (1988), Clayton (1993, 2004), and McKeegan and Leshin (2001). 

These resnlts snggest that the interplanetary dust particles are among the most primitive samples available for laboratory stndies. Isotopically anomalous material constitutes only a small fraction of the investigated particles. Thus, it appears that the isotopic composition of these anomalons particles is not different from those observed in minor components of primitive meteorites. 

Rietmeijer FJM (1998) Interplanetary dust particles. In Planetary materials. Rev Miner 36 Chapter 2... 

Two characteristics of the light from noctilucent clouds may be observed with no more than one s eyes and a polarizing filter its color and whether or not it is strongly polarized. This enabled Ludlum (1957) to estimate the size range of noctilucent cloud particles. Because of the observed strong polarization he set 0.16 jum as their upper size limit on the basis of the observed color—white, silvery, sometimes bluish, but not sufficiently so as to indicate very small particles—he set 0.008 jam as their lower size limit. From other than optical evidence he also concluded that the particles were not ice, but were more likely to be volcanic, meteoric, or interplanetary dust. 

Cosmochemistry is the study of the chemical composition of the universe and the processes that produced those compositions. This is a tall order, to be sure. Understandably, cosmochemistry focuses primarily on the objects in our own solar system, because that is where we have direct access to the most chemical information. That part of cosmochemistry encompasses the compositions of the Sun, its retinue of planets and their satellites, the almost innumerable asteroids and comets, and the smaller samples (meteorites, interplanetary dust particles or IDPs, returned lunar samples) derived from them. From their chemistry, determined by laboratory measurements of samples or by various remote-sensing techniques, cosmochemists try to unravel the processes that formed or affected them and to fix the chronology of these events. Meteorites offer a unique window on the solar nebula - the disk-shaped cocoon of gas and dust that enveloped the early Sun some 4.57 billion years ago, and from which planetesimals and planets accreted (Fig. 1.1). 

In recent years, a new source of information about stellar nucleosynthesis and the history of the elements between their ejection from stars and their incorporation into the solar system has become available. This source is the tiny dust grains that condensed from gas ejected from stars at the end of their lives and that survived unaltered to be incorporated into solar system materials. These presolar grains (Fig. 5.1) originated before the solar system formed and were part of the raw materials for the Sun, the planets, and other solar-system objects. They survived the collapse of the Sun s parent molecular cloud and the formation of the accretion disk and were incorporated essentially unchanged into the parent bodies of the chondritic meteorites. They are found in the fine-grained matrix of the least metamorphosed chondrites and in interplanetary dust particles (IDPs), materials that were not processed by high-temperature events in the solar system. 

Bradley, J. P. (2004). Interplanetary dust particles. In Treatise on Geochemistry, Vol. 1. 

Messenger, S., Keller, L. P., Stadermann, F. J., Walker, R. M. andZinner, E. (2003) Samples of stars beyond the solar system silicate grains in interplanetary dust. Science, 300,105— 108. 

We will now describe each of the various kinds of meteoritic samples available for cosmochemical investigation, progressing from primitive materials to samples from differentiated bodies. Presolar grains extracted from meteorites have already been described in Chapter 5, and interplanetary dust particles (IDPs) and returned comet samples will be described in Chapter 12. 

Piazzarello, S., Cooper, G. W. and Flynn, G. J. (2006) The nature and distribution of the organic material in carbonaceous chondrites and interplanetary dust particles. In Meteorites and the Early Solar System II, eds. Lauretta, D. S. and McSween, H. Y., Jr. Tucson University of Arizona Press, pp. 625-651. A comprehensive, up-to-date review of organic matter in carbonaceous chondrites, but not for the faint-hearted. 

What are interplanetary dust particles (IDPs) made of, and what do they tell us about the... 

Bradley, J. P. (2004) Interplanetary dust particles. In Treatise on Geochemistry, Vol. 1. Meteorites, Comets, and Planets, ed. Davis, A. M. Oxford Elsevier, pp. 689-711. This review provides an excellent summary of the voluminous literature that describes and interprets IDPs. 

Rietmeijer, F. J. M. MacKinnon, I. D. R. 1987 Metastable carbon in two chondritic porous interplanetary dust particles. Nature, Land. 326, 162-165. 

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