The Organics experiment is integrated into the multi-user facility Expose mounted on the International Space Station ISS, that contains 9 experiment dedicated to Astrobiology. In this experiment organic samples of astronomical interest will be exposed for a long duration and will at least remain one year on-board the International Space Station before they are returned to Earth. The radiation dose that is collected by the samples during flight, exceeds the limits of simulations in the laboratory and the results will greatly enhance our knowledge on the evolution of large molecules in space environments. Due to changes in the ISS external payload program, the mounting site of the Expose experiment on the ISS is currently not defined.
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| The complete Expose package with the location of the Organics experiment depicted. |
Samples are deposited in thin (~ 1 µm) films by spin coating on MgF2 windows inside the sample cell. Dark samples are shielded from the UV photons and enable us to discriminate between the effects of exposure to photons and cosmic rays. Additional filters will allow us to select specific spectral regions for samples. The 1 mm thick MgF2 windows that hold the sample films are transparent, well into the UV. We will test the effects of solar UV field and space conditions on specific polycyclic aromatic hydrocarbons (PAHs), fullerene compounds and different types of macromolecular networks.
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| The layout of the Organics experiment. Each cell contains a thin layer of one type of PAH (see text). The upper and lower sample carrier are separated with a thin aluminium foil, allowing us to distinguish between UV ("exposed" cells) and cosmic ray photoproducts ("dark" cells). |
PAHs are a highly abundant and ubiquitous compounds in the interstellar medium, and kerogens represent analogues to organic extracts from carbonaceous meteorites. The spontaneous formation and stability of fullerene compounds have suggested their existence in relation to carbon dust. Our group has recently detected fingerprints of interstellar fullerenes in astronomical spectra, indicating that fullerenes may play an important role in interstellar chemistry. The samples will be analyzed before and after exposure to space environment with various chemical and physical techniques: UV, visible, infrared and fluorescence spectroscopy, gas chromatography/mass-spectrometry (GC/MS) and Secondary-Ion-Mass-Spectrometry (SIMS). The Organics experiment will monitor the chemical evolution, survival, destruction and chemical modification of PAHs, fullerenes and macromolecules in space environment. From the results we shall determine constraints on the photochemistry of these compounds in the interstellar medium. Since PAHs, fullerenes and macromolecules are also present in meteorites, the obtained data are most relevant for the reconstruction of events in the early Solar System.
It was foreseen that the Organics experiment was to be tested in a simpler form (smaller PAH molecules) and a short duration in Earth's orbit (2 weeks) on the Biopan 4 facility (2002). Unfortunately, the Russian Foton-M1 rocket with Biopan on-board exploded 27 seconds after launch on October 15, utterly destroying Richard Ruiterkamp's experiment. The next flight opportunity for Biopan 5 is scheduled for 2006.
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| Important men posing behind the Biopan: Bernard Foing (ESA), Zan Peeters, Christiaan Penn (engineer, Leiden University) and Richard Ruiterkamp (P.I.). |
In preparation for both the Biopan/Foton 2002 orbit flight and the Expose experiment on the International Space Station, Richard Ruiterkamp has measured for the first time the spectroscopic properties of polycyclic aromatic hydrocarbons (PAHs) with sizes up to 600 amu, including 5-ring species and PAHs containing heteroatoms. The spectra of the neutral species and the associated cations and anions, measured in this work are published (Ruiterkamp et al. 2002).
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| The inside of Biopan 4. The Organics experiment is the gold-coloured metal box in the upper right corner of the picture. The samples are hidden behind a dust cover labeled "Remove before flight". The other experiments in Biopan 4 are listed here. Click picture for large image. |
More information on the Biopan and the Expose experiments can be found on the ESA home page on Biopan and Expose. More about the explosion of the Foton-M1 rocket with the Biopan 4 experiment can be found here (in Dutch).