Comet interplanetary dust particles

This chapter provides an overview of available noble gas data for solar system bodies apart from the Earth, Mars, and asteroids. Besides the Sun, the Moon, and the giant planets, we will also discuss data for the tenuous atmospheres of Mercury and the Moon, comets, interplanetary dust particles and elementary particles in the interplanetary medium and beyond. In addition, we summarize the scarce data base for the Venusian atmosphere. The extensive meteorite data from Mars and asteroidal sources are discussed in chapters in this volume by Ott (2002), Swindle (2002a,b) and Wieler (2002). Data from the Venusian and Martian atmospheres are discussed in more detail in chapters by Pepin and Porcelli (2002) and Swindle (2002b). Where appropriate, we will also present some data for other highly volatile elements such as H or N. 

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). 

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. 

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. 

The dust of the early Solar System accreted to form the planets, moons, asteroids, and comets that are seen today. However, most of the bodies of the present-day Solar System have experienced significant thermal or aqueous processing, which modified the original dust, overprinting the record of early solar nebular events. A few primitive bodies, including some meteorites, interplanetary dust particles (see Fig. 6.1), and comets, are relatively unmetamorphosed. The examination of these samples provides the opportunity to examine relatively well-preserved dust from the early Solar System. 

Fortunately, and perhaps surprisingly, the Universe provides a means to address these important questions. Today we are witnessing as the answers emerge to these age-old questions. We now know that asteroids and comets of the Solar System have preserved a detailed record of the dramatic events that four billion years ago gave birth to our planetary system in only a few million years. Gravity and radiation pressure conspire to deliver almost pristine samples of the early Solar System to Earth in the form of meteorites and interplanetary dust particles. We have also taken this process one step further with the successful return of particles from the coma of comet Wild 2 by NASA s Stardust mission. Detailed chemical and mineralogical analyses of these materials allow for the reconstruction of the history of our planetary system. 

Bradley J. P. (1994) Chemically anomalous, preaccretionary irradiated grains in interplanetary dust particles from comets. Science 265, 925-929. 

Rietmeijer, F.J.M. Mackinnon, I.D.R. Cometary evolution Clues from chondritic interplanetary dust particles. In Symposium on the Diversity and Similarity of Comets, European Space Agency SP-278. Rolfe E.J. Battrick, B., Eds. ESTEC, Noordwijk, The Netherlands, 1987, 363-367. 

This demonstrates that those amino acids present in the Murchison meteorite, which also play the role of protein monomers, are indeed of extraterrestrial origin. In addition, chemical analysis has demonstrated the presence of a variety of amino acids in the Ivuna and Orgueil meteorites (Ehrenfreund et al., 2001). If the presence of biomolecules on the early earth is due in part to the bombardment of interplanetary dust particles, comets, and meteorites, then the same phenomenon could be taking place in any other solar system. 

Below we will see that meteorites, smaller rocks from asteroidal objects delivered to Earth, provide important information for solar system abundances of non-volatile elements. Other sources to refine solar system abundances are analysis of other solar system objects such as the gas-giant planets, comets and the interplanetary dust particles from comets. Outside the solar system, the compositions of hot B stars, planetary nebulae, Galactic cosmic rays (GCR), the nearby interstellar medium (ISM) and H II regions have been employed to amend the solar system abundances of some elements. 

The importance of exogenous delivery of organic matter to the early Earth is critically dependent on the survivability of organic compounds during the delivery process. It is presently unclear exactly how much organic material would escape destruction during asteroid, comet and interplanetary dust particle infall to the Earth s surface. 

A determination of the HDO/H2O ratio in comet C/1995 01 (Hale-Bopp). Science 279 842-844 Messenger S (2000) Identification of molecular-cloud material in interplanetary dust particles. Nature 404 968-971... 

Interplanetary dust particles, micrometeorites Mass spectrometry, laboratory Dust from asteroids comets, collected in near Earth space, ice, sediments. Nier and Schlutter 1992 Olinger et al. 1990. ... 

Other information about comets is potentially contained in interplanetary dust particles, which are discussed in the next section. Note that some workers also presume that the chemically most primitive meteorites, the Cl- and CM carbonaceous chondrites, originate from comets (Lodders and Osborne 1999 Ehrenfreund et al. 2001). However, as these claims are controversial, we do not discuss noble gas data from CECM chondrites from a cometary perspective. 

Accretion of icy cometary matter has been widely viewed as a plausible source for Earth s water. The D/H ratio in seawater, however, is substantially lower—by a factor of -2—than in the few comets where D/H has been measured (Laufer et al. 1999). A significant contribution of terrestrial water by comets would still be permitted if their high D/H ratio were appropriately lowered by accretion of additional, deuterium-poor materials. Suggested possibilities for low D/H carriers include rocky planetary accretional components (Laufer et al. 1999), or a high influx during the heavy bombardment epoch of interplanetary dust particles heavily loaded with implanted solar-wind hydrogen (Pavlov et al. 1999). 

Farley KA, Maier-Reimer E, Schlosser P, Broecker WS (1995) Constraints on mantle He fluxes and deep-sea circulation from an oceanic general circulation model. J Geophys Res 100(B3) 3829-3839 Farley KA, Love SG, Patterson DB (1997) Atmospheric entry heating arrd hehum retentivity of interplanetary dust particles. Geochim Cosmochim Acta 61 2309-2316 Farley KA, Montanari A, Shoemaker EM, Shoemaker CS (1998) Geochemical evidence for a comet shower in the Late Eocene. Science 280 1250-1253... 

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