Carbonaceous meteorites contain a large variety of complex organic molecules, including amino acids, nucleobases, sugar derivatives, amphiphiles, and other compounds of astrobiological interest. Photoprocessing of ices condensed on cold grains with ultraviolet (UV) photons was proposed as an efficient way to form such complex organics in astrophysical environments. This hypothesis was confirmed by laboratory experiments simulating photo-irradiation of ices containing H2O, CH3OH, CO, CO2, CH4, H2CO, NH3, HCN, etc., condensed on cold (~10–80 K) substrates. These experiments resulted in the formation of amino acids, nucleobases, sugar derivatives, amphiphilic compounds, and other organics comparable to those identified in carbonaceous meteorites. This work presents results for the formation of sugars, sugar alcohols, sugar acids, and their deoxy variants from the UV irradiation of ices containing H2O and CH3OH in relative proportions 2:1, and their comparison with meteoritic data. The formation mechanisms of these compounds and the astrobiological implications are also discussed.

Sample return missions offer opportunities to learn things about other objects in our Solar System (and beyond) that cannot be determined by observations using in situ spacecraft. This is largely because the returned samples can be studied in terrestrial laboratories where the analyses are not limited by the constraints - power, mass, time, precision, etc. - imposed by normal spacecraft operations. In addition, the returned samples serve as a scientific resource that is available far into the future; the study of the samples can continue long after the original spacecraft mission is finished. This means the samples can be continually revisited as both our scientific understanding and analytical techniques improve with time.

These advantages come with some additional difficulties, however. In particular, sample return missions must deal with the additional difficulties of proximity operations near the objects they are to sample, and they must be capable of successfully making a round trip between the Earth and the sampled object. Such missions therefore need to take special precautions against unique hazards and be designed to successfully complete relatively extended mission durations.

Despite these difficulties, several recent missions have managed to successfully complete sample returns from a number of Solar System objects. These include the Stardust mission (samples from Comet 81P/Wild 2), the Hayabusa mission (samples from asteroid 25143 Itokawa), and the Genesis mission (samples of solar wind). This paper will review the advantages and difficulties of sample return missions in general and will summarize some key findings of the recent Stardust and Hayabusa missions.

The UV irradiation of interstellar/circumstellar ice analogs is known to lead to the formation of organic compounds such as amino acids and maybe nucleobases. In this work, the mechanisms of formation and distribution of amino acids, chosen as tracers for the organic compounds formed in such experiments, are studied and compared with meteoritic data.

The Stardust Mission collected samples from Comet 81P/Wild 2 on 2 Jan 2004 and returned these samples to Earth on 15 Jan 2006. After recovery, a six month preliminary examination was done on a portion of the samples. Studies of the organics in the samples were made by the Organics Preliminary Examination Team (PET) - a worldwide group of over 55 scientists. This paper provides a brief overview of the findings of the Organics PET. Organics in the samples were studied using a multitude of analytical techniques including spatial determination of C and heteroatom elemental abundances (STXM), functional group identification (micro-FTIR/Raman, C,N,O-XANES), and specific molecular identification of certain classes of organics (HPLC-LIF, L2MS, TOF-SIMS). Analyses were also made of spacecraft components and environmental samples collected near the recovered returned capsule to assess contamination issues. The distribution of organics (abundance, functionality, and relative elemental abundances of C,N,O) is heterogeneous both within and between particles. They are an unequilibrated reservoir that experienced little parent body processing after incorporation into the comet. Some organics look like those seen in IDPs (and to a lesser extent, meteorites), while new aromatic-poor and highly labile organics, not seen in meteoritic materials, are also present. The organics are O,N-rich compared to meteoritic organics. Some of the organics have an interstellar heritage, as evidenced by D and 15N enrichments.

Results of the Stardust mission to sample dust from comet Wild 2 are summarized.

During the past decade interplanetary dust particles (IDPs) have been collected in the earth's stratosphere. Isotopic studies of these particles have demonstrated that many of them are greatly enriched in deuterium and at least some of them carry this enrichment in smaller subcomponents. Deuterium enrichments of a similar magnitude are seen in simple molecules in interstellar clouds. Deuterium enrichment in IDPs can be taken as evidence for the presence of interstellar material. It is not clear at this time whether the carriers of the isotopic anomalies represent true, unaltered interstellar dust grains, or whether they represent an altered component with a molecular ‘memory’ of original interstellar grains. The spectra of different components in the collected dust provide suggestive matches to similar components evident in the astronomical spectra of dust in comets, dense molecular clouds, and emission nebulae. The known extraterrestrial nature of the particles, the possible presence of interstellar material in them, and their spectral similarity to many astronomical objects all argue that the collected IDPs provide useful analogs for the modelling of interstellar dust.