Solar nebula primitive

Carbonaceous chondrites (C-chondrites) account for only 2-3% of the meteorites so far found, but the amount of research carried out on them is considerable. C-chondrites contain carbon both in elemental form and as compounds. They are without doubt the oldest relicts of primeval solar matter, which has been changed only slightly or not at all by metamorphosis. C-chondrites contain all the components of the primeval solar nebula, apart from those which are volatile they are often referred to as primitive meteorites . 

The Earth s crust, mantle and core are strongly influenced by differentiation processes which could have resulted from gravitational separation ( smelting ) in an early molten phase of the planet, or from the sequence in which different chemical species condensed from the primitive solar nebula and were subsequently accreted. Seismology indicates that there is a liquid core (with a solid inner core) with radius 3500 km consisting mainly of iron (with some Ni and FeS) surrounded by a plastic (Fe, Mg silicate) mantle of thickness 2900 km. 

Grossman, L. (1972). Condensation in the primitive solar nebula. Geochim. Cosmochim. 

Busfield A, Gilmour JD, Whitby JA, Turner G (2004) Iodine-xenon analysis of ordinary chondrite halide implications for early solar system water. Geochim Cosmochim Acta 68 195-202 Busso M, Gallino R, Wasserburg GJ (1999) Nucleosynthesis in asymptotic giant branch stars relevance for galactic enrichment and solar system formation. Annu Rev Astronom Astrophys 37 239-309 Cameron AGW (1969) Physical conditions in the primitive solar nebula. In Meteorite Research. Millman PM (ed) Reidel, Dordrecht, p 7-12... 

Extraterrestrial materials consist of samples from the Moon, Mars, and a variety of smaller bodies such as asteroids and comets. These planetary samples have been used to deduce the evolution of our solar system. A major difference between extraterrestrial and terrestrial materials is the existence of primordial isotopic heterogeneities in the early solar system. These heterogeneities are not observed on the Earth or on the Moon, because they have become obliterated during high-temperature processes over geologic time. In primitive meteorites, however, components that acquired their isotopic compositions through interaction with constituents of the solar nebula have remained unchanged since that time. 

Cosmochemistry is the study of the chemical compositions of various solar system materials. Chondrites are the most abundant primitive samples. They are essentially sedimentary rocks composed of mechanical mixtures of materials with different origins (chondrules, refractory inclusions, metal, sulfide, matrix), which we will call components. Chondrites formed by the accretion of solid particles within the solar nebula or onto the surfaces of growing planetesimals. They are very old (>4.5 billion years, as measured by radioactive chronometers) and contain some of the earliest formed objects in the solar system. Chondrites have bulk chemical compositions very similar to the solar photosphere, except... 

Grossman, L. (1972) Condensation in the primitive solar nebula. Geochimica et Cosmochimica Acta, 36, 597-619. This paper describes the first comprehensive calculations of equilibrium condensation under nebula conditions. 

It was soon discovered that there were other solar system objects that were older and had more primitive strontium than the basaltic achondrites. Table 8.3 compares the (87Sr/86Sr)o value determined for BABI with those from some other important samples from the early solar system. If Allende, Angra dos Reis, and the basaltic achondrites formed directly from the solar nebula, then the time intervals shown in the right-hand column of Table 8.3 are valid. Note that the uncertainties on these time intervals, a few million years, are much smaller than the uncertainty in the eucrite isochron shown in Figure 8.9 ( 260 Myr). However, the validity of the time intervals determined from the initial ratios depends completely on the validity of the idea that they all formed directly from the bulk material of the solar nebula. 

C60 has not yet been detected in primitive meteorites, a finding that could demonstrate its existence in the early solar nebular or as a component of presolar dust. However, other allotropes of carbon, diamond and graphite, have been isolated from numerous chondritic samples. Studies of the isotopic composition and trace element content and these forms of carbon suggest that they condensed in circumstellar environments. Diamond may also have been produced in the early solar nebula and meteorite parent bodies by both low-temperature-low-pressure processes and shock events. Evidence for the occurrence of another carbon allotrope, with sp hybridized bonding, commonly known as carbyne, is presented. 

Noble gas clathrates will not now form on the Earth, as can be seen from the air pressure decomposition temperatures in Table 2.7. They might, however, form in cooler regions of the primitive solar nebula (see Limine Stevenson, 1985). Sill and Wilkening (1978) note that for pressures in a plausible model nebula, pure ice clathrates of Ar, Kr, and Xe could form at 40, 45, and 62 K, respectively. 

Besides water, the above evolution could occur for silicates (Cuzzi et al. 2003), organics, or more volatile ices in the outer solar nebula. The effects of these changes in abundances on the composition of primitive materials remains to be studied. 

Several types of the early Solar System materials are available for laboratory analysis (see Chapter 1 and Table 1.1 and Fig. 1.1). Each material has unique characteristics and provides specific constraints on the chemistry of the solar nebula. Major components of this sample are meteorites, fragments of asteroids, that serve as an excellent archive of the early Solar System conditions. Primitive chondritic meteorites contain glassy spherical inclusions termed chondrules, some of the oldest solids in the Solar System. Most chondrites were modified by aqueous alteration or metamorphic processes in parent bodies but there are some chondrites that are minimally altered (un-equilibrated chondrites, UCs). They have yielded a wealth of information on the chemistry, physics, and evolution of the young Solar System. 

Llorca Casanova (2000) demonstrated thatFischer-Tropsch-type (FIT ) catalytic reactions (see Fig. 5.6) occur under low pressures typical of the primitive solar nebula, converting CO and H2 into hydrocarbons. The Haber-Bosch-type (HBT) reaction converts N2 and H2 into reduced nitrogen compounds such as NH3. New... 

In order to consider the processes of dust coagulation in the early Solar System, we first review the characteristics of this material. Of considerable importance is the fact that these samples - represented principally by chondritic meteorites, but also by IDPs and by samples from Comet Wild 2 collected by the Stardust mission - all come from parent bodies of different kinds. As a result, even the most primitive of these materials has been processed, both physically and chemically, to different degrees. The processes that affected Solar System dust may have occurred in different environments such as the solar nebula (e.g. evaporation/condensation, annealing) and asteroidal parent bodies (aqueous alteration and/or thermal processing, mild compaction to extensive lithihcation). A major challenge is to understand the effects of this secondary processing. 

The process of condensation of minerals in the early solar nebula has long been invoked to explain the chemistry and mineralogy of primitive chondritic meteorites (e.g. Cameron 1963). Their observed bulk compositions show volatile-element depletions that are clearly smooth functions of calculated condensation temperature in a gas of solar composition (Davis 2006). Despite this success in explaining the bulk composition of chondrites, the diverse mineralogy of these bodies is not reproduced well in the condensation sequence calculations. To date, there is no incontrovertible evidence for direct condensation of rocky meteoritic material in the... 

Cameron, A. G. W. Physical conditions in the primitive solar nebula. In Meteorite Research, (ed. P. M. Millman). Reidel Dordrecht 1969. 

O-MIF is present in many atmospheric molecules and aeolian sediments, and is nearly always a result of interactions with atmospheric ozone [6]. It is believed that MIF in O3 results from the non-statistical randomization of energy in vibra-tionally excited O3 during the O3 formation reaction, O -F O2 O3, in a manner that depends on the symmetry of the O3 isotopomer [7]. The source of O-MIF in primitive meteorites is unknown but has been attributed to self-shielding during photodissociation of CO in the solar nebula [3,8-10], and also to ozone-like non-statistical reactions on mineral grain surfaces [11], a hypothesis not yet verified in the laboratory. 

Cl chondrites contain 6% of their cosmic complement of carbon, mainly in the form of organic matter. The intense controversy that once surrounded the origin of this organic matter has subsided. Most authors now agree that this material represents primitive prebiotic matter, not vestiges of extraterrestrial life. The principal questions remaining are what abiotic processes formed the organic matter, and to what extent these processes took place in locales other than the solar nebula interstellar clouds or meteorite parent bodies. 

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