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Organic matter and hydrous silicates are intimately mixed in the matrix of chondrites and in-situ determination of their individual D/H ratios is therefore challenging. Nevertheless, the D/H ratio of each pure component in this mixture should yield a comprehensible signature of the origin and evolution of water and organic matter in our solar system. We measured hydrogen isotope ratios of organic and hydrous silicates in the matrices of two carbonaceous chondrites (Orgueil CI1 and Renazzo CR2) and one unequilibrated ordinary chondrite (Semarkona, LL3.0). A novel protocol was adopted, involving NanoSIMS imaging of H isotopes of monoatomatic ($H^-$) and molecular ($OH^-$) secondary ions collected at the same location. This allowed the most enriched component with respect to D to be identified in the mixture. Using this protocol, we found that in carbonaceous chondrites the isotopically homogeneous hydrous silicates are mixed with D-rich organic matter. The opposite was observed in Semarkona. Hydrous silicates in Semarkona display highly heterogeneous D/H ratios, ranging from $150$ to $1800$ ${\times}$ $10^{-6}$ (${\delta}D_{SMOW} = -40$ to $10,600$ permil). Organic matter in Semarkona does not show such large isotopic variations. This suggests limited isotopic exchange between the two phases during aqueous alteration. Our study greatly expands the range of water isotopic values measured so far in solar system objects. This D-rich water reservoir was sampled by the LL ordinary chondrite parent body and an estimate (up to 9 %) of its relative contribution to the D/H ratio of water in Oort cloud family comets is proposed., Comment: 40 pages, 8 figures, 2 tables, one supplement

The insoluble organic matter (IOM) of an unequilibrated enstatite chondrite Sahara (SAH) 97096 has been investigated using a battery of analytical techniques. As the enstatite chondrites are thought to have formed in a reduced environment at higher temperatures than carbonaceous chondrites, they constitute an interesting comparative material to test the heterogeneities of the IOM in the solar system and to constrain the processes that could affect IOM during solar system evolution. The SAH 97096 IOM is found in situ: as submicrometer grains in the network of fine-grained matrix occurring mostly around chondrules and as inclusions in metallic nodules, where the carbonaceous matter appears to be more graphitized. IOM in these two settings has very similar $\delta^{15}N$ and $\delta^{13}C$; this supports the idea that graphitized inclusions in metal could be formed by metal catalytic graphitization of matrix IOM. A detailed comparison between the IOM extracted from a fresh part and a terrestrially weathered part of SAH 97096 shows the similarity between both IOM samples in spite of the high degree of mineral alteration in the latter. The isolated IOM exhibits a heterogeneous polyaromatic macromolecular structure, sometimes highly graphitized, without any detectable free radicals and deuterium-heterogeneity and having mean H- and N-isotopic compositions in the range of values observed for carbonaceous chondrites. It contains some submicrometer-sized areas highly enriched in $^{15}N$ ($\delta^{15}N$ up to 1600 permil). These observations reinforce the idea that the IOM found in carbonaceous chondrites is a common component widespread in the solar system. Most of the features of SAH 97096 IOM could be explained by the thermal modification of this main component.

The Solar System formed about 4.6 billion years ago from a condensation of matter inside a molecular cloud. Trying to reconstruct what happened is the goal of this chapter. For that, we put together our understanding of Galactic objects that will eventually form new suns and planetary systems, with our knowledge on comets, meteorites and small bodies of the Solar System today. Our specific tool is the molecular deuteration, namely the amount of deuterium with respect to hydrogen in molecules. This is the Ariadne's thread that helps us to find the way out from a labyrinth of possible histories of our Solar System. The chapter reviews the observations and theories of the deuterium fractionation in pre-stellar cores, protostars, protoplanetary disks, comets, interplanetary dust particles and meteorites and links them together trying to build up a coherent picture of the history of the Solar System formation. We emphasise the interdisciplinary nature of the chapter, which gathers together researchers from different communities with the common goal of understanding the Solar System history., Comment: Accepted for publication as a chapter in Protostars and Planets VI, University of Arizona Press (2014), eds. H. Beuther, R. Klessen, C. Dullemond, Th. Henning

The D/H ratios of carbonaceous chondrites, believed to reflect that of water in the inner early solar system, are intermediate between the protosolar value and that of most comets. The isotopic composition of cometary water has been accounted for by several models where the isotopic composition of water vapor evolved by isotopic exchange with hydrogen gas in the protoplanetary disk. However, the position and the wide variations of the distribution of D/H ratios in carbonaceous chondrites have yet to be explained. In this paper, we assume that the D/H composition of cometary ice was achieved in the disk building phase and model the further isotopic evolution of water in the inner disk in the classical T Tauri stage. Reaction kinetics compel isotopic exchange between water and hydrogen gas to stop at $\sim$500 K, but equilibrated water can be transported to the snow line (and beyond) via turbulent diffusion and consequently mix with isotopically comet-like water. Under certain simplifying assumptions, we calculate analytically this mixing and the resulting probability distribution function of the D/H ratio of ice accreted in planetesimals and compare it with observational data. The distribution essentially depends on two parameters: the radial Schmidt number Sc$_R$, which ratios the efficiencies of angular momentum transport and turbulent diffusion, and the range of heliocentric distances of accretion sampled by chondrites. The minimum D/H ratio of the distribution corresponds to the composition of water condensed at the snow line, which is primarily set by Sc$_R$. Observations constrain the latter to low values (0.1-0.3), which suggests that turbulence in the planet-forming region was hydrodynamical in nature, as would be expected in a dead zone. Such efficient outward diffusion would also account for the presence of high-temperature minerals in comets., Comment: 13 pages, 7 figures, accepted to Icarus