The interstellar medium (ISM) is a physico-chemical laboratory where extreme conditions are encountered and where particular environmental parameters (e.g., density, reactant nature, radiation, temperature, time scales) define the composition of matter. With present observational possibilities, the fundamental question regarding the possible link between ISM and solar system samples can be addressed by astrophysicists, planetologists, and cosmochemists. This article focuses on observations of diffuse ISM and dust components of molecular clouds, setting constraints on the composition of organic solids and large molecules associated with matter cycling in the Galaxy. This study aims at drawing some commonalities and differences between the materials found in the Solar System and those found in interstellar dust.

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Two homologous series of alkylpyridines (C_nH_2n-5N and C_nH_2n-7N) were identified in the methanol extract of the Murchison meteorite by liquid chromatography/high-resolution mass spectrometry. The wide range of saturated- and unsaturated-alkylated (C₁ to C₂₁) pyridines is more diverse than previously found, and could be produced by reactions of aldehyde condensation and aldehydes with NH₃ by imine formation in Solar or pre-solar environments. This finding implies a high aldehyde activity under alkaline conditions in the presence of ammonia during the chemical evolution of soluble organic matters detected in a CM2-type carbonaceous meteorite.

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Our solar system originated from a protoplanetary disk about 4.6 billion years ago. We simulate the formation of this disk by a three-stage model of the solar nebula (SN) which describes the hydrodynamic and chemical evolution of a cold cloud core consisting of gas and one mass percent dust. Considering the first two stages of this SN-model we have studied the formation and deuteration of water, which is an important precondition of life. During the quasi-stationary stage of the cloud core, corresponding to the first SN stage, water has been formed on the surface of dust grains by the hydrogenation of oxygen. The gas and dust temperatures, which differ at the outer boundary of the core, are nearly 14 K and reach 9 K in its center. Therefore an icy mantle forms on the dust grains in less than 10⁵ years and changes slowly afterwards. Because of the large abundance of hydrogen and a carbon to oxygen (C/O) ratio of 0.44 the major component of this mantle is water ice. We found that the water produced in the gas phase amounts to less than 20 ppm of the water formed on dust grains. In both phases, the deuterium enrichment δD (‰) relative to the Standard Mean Ocean Water varies at 1 AU from 15,050 to 63,100‰ (or a D/H ratio from 2 to 0.5%) and indicates the low formation temperature of water molecules. In the second stage of our SN-model, the collapse of the cold cloud core is simulated using a semi-analytical solution of the magneto-hydrodynamic equations. Due to relatively high temperatures around the center (10^2-3 K), this range is identified with the hot corino observed in regions of low mass star formation in our galaxy. There, the icy mantles of the grains vanish due to desorption of water molecules from their surfaces. As a result the water to hydrogen ratio in the gas phase increases to 10^-5-10^-4. Since this water was formed in a cold region and a collision related destruction of water molecules (occurring at ∼10⁵ K) can be neglected everywhere except for the protostellar source in the core center (<10^-2 AU), the deuterium enrichment in the outer hot corino (1 AU) reaches δD of 2,210‰ (or D/H of 0.1%) at the end of the main collapse phase. Different reasons for this high value are discussed.

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Determination of isotopic composition of extraterrestrial liquid water provides important information regarding the origin of water on Earth and the terrestrial planets. Fluid inclusions in halite of ordinary chondrites are the only direct samples of extraterrestrial liquid water available for laboratory measurements. We determined H and O isotopic compositions of this water by secondary ion mass spectrometry equipped with a cryogenic apparatus for sample cooling. Isotopic compositions of the fluid inclusion fluids (brines) were highly variable among individual inclusions, -400 < δD < +1300‰; -20 < Δ¹⁷O < +30‰, indicating that these aqueous fluids were in isotopic disequilibrium before trapping in halite on asteroids. The isotopic variation of fluids shows that various degrees of water-rock interaction had been underway on the asteroids before trapping between D-rich-¹⁶O-poor aqueous fluid, D-poor-¹⁶O-rich aqueous fluid, and asteroidal rock by delivery of cometary water onto hydrous asteroids. This may be a fundamental mechanism in the evolution of modern planetary water.

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We report Al-Mg isotope systematics in fourteen mineralogically pristine chondrules from six CR2 (Renazzo-type) carbonaceous chondrites measured with secondary ion mass spectrometry. Six chondrules show resolvable excesses of ²⁶Mg that correlate with Al/Mg ratios, indicating in situ decay of ²⁶Al. The inferred initial ²⁶Al/²⁷Al ratios [(²⁶Al/²⁷Al)₀] in these chondrules range from ∼1 × 10^-6 to ∼6 × 10^-6. The other eight chondrules show no detectable ²⁶Mg excesses and have upper limits of (²⁶Al/²⁷Al)₀ ∼(2-3) × 10^-6. Most CR chondrules have (²⁶Al/²⁷Al)₀ significantly lower than those in the other least metamorphosed primitive chondrites, LL3.0, CO3.0, and Acfer 094 (ungrouped). Assuming uniform distribution of ²⁶Al in the protoplanetary disk, these observations suggest that majority of CR chondrules formed >1 Myr later than those in LL3.0, CO3.0, and Acfer 094.

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Hayabusa2 is an asteroid exploration mission to return surface samples of a near-Earth C-type asteroid (162173) 1999 JU₃. Because asteroids are the evolved remnants of planetesimals that were the building blocks of planets, detailed observation by a spacecraft and analysis of the returned samples will provide direct evidence regarding planet formation and the dynamic evolution of the solar system. Moreover, C-type asteroids are expected to preserve the most pristine materials in the solar system, a mixture of minerals, ice, and organic matter that interact with each other. Space missions are the only way to obtain such pristine materials with geologic context and without terrestrial contamination. Hayabusa2 will launch off in 2014, arrive at 1999 JU₃ in mid-2018, and fully investigate and sample the asteroid at three different locations during its 18-month stay. The concept and design of the Hayabusa2 sampler are basically the same as that on-board Hayabusa, and impact sampling with a 5-g Ta bullet will be made at three locations of the asteroid. The sample container has three separate chambers inside to store samples obtained at different locations separately. The spacecraft will return to Earth with samples in December 2020. Returned samples will be investigated by state-of-the-art analytical techniques in 2020 to understand the evolutionary history of the solar system from 4.56 Gyr ago to the present by combining results from laboratory examinations of the returned samples with remote-sensing datasets and comparing all results of observations of meteorites, interplanetary dust particles, and future returned samples.

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