The status of the solid materials and mineralogical and petrological results of the Stardust mission to comet 81P/Wild 2 are presented. This mission became the first successful sample-return mission since the Apollo project. This time the challenges were much less related to the availability of state-of-the-art analytical capabilities. Still, dedicated tools had to be developed to manipulate the samples that were all firmly embedded in the tracks they made when decelerating in the silica aerogel tiles of the collector. The comet particles were loosely bonded aggregates that shed their grains along the entire length of these tracks. It appears that most of the original comet minerals survived but interactions of debris with melted aerogel occurred and new minerals were made, adding to the incredibly, and unanticipated, diversity of the comet minerals, including some that so far were known only in meteorites. The latter alone showed that transport distances in the solar nebula extended all the way out to beyond Pluto into the Kuiper Belt of icy, comet-like, bodies. The full extent of the scientific yield of this mission is still unknown, promising but stressing current models of the formation of solar systems.

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 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.