For the first time, NANOCOSMOS has attempted to reproduce the complex molecular chemistry and stardust formation in circumstellar envelopes (CSEs) of asymptotic giant branch (AGB) stars and interstellar environments under accurate and realistic laboratory conditions. These conditions differ from previous studies and techniques to produce stardust analogs, mostly based on laser ablation and pyrolysis, flames, and other far related conditions from those in the CSEs of AGB stars.
Hence, we have used our innovative setups at CSIC and CNRS, e.g. Stardust, AROMA, PIRENEA 2 and cold plasma reactors, to study the processes that lead to carbon dust formation including polycyclic aromatic hydrocarbons (PAHs) and fullerenes. We have studied the chemistry of atomic silicon and the formation of silicate dust grains. We have also investigated the aromatic content of two different meteorites, Murchison and Almahata Sitta.
In summary, our synergetic results provide significant and surprising breakthroughs in our current understanding of the chemical processes at play in CSEs and meteoritic samples. These new and open theoretical grounds have also important implications in current chemical models. These NANOCOSMOS breakthroughs are the following:
Aliphatic nature of carbonaceous cosmic dust analogs. Our realistic laboratory conditions do not lead to the efficient formation of aromatic molecules (PAHs and fullerenes) in the gas phase, contrary to all previous studies (Stardust, AROMA).
Efficient mechanism for the formation of silane and disilane in the gas phase from Si, H, and H2 in the innermost regions of the CSEs around AGB stars (Stardust).
Further evidence for the role of metal (iron) seeds to increase not only the formation of metal clusters but also catalyzed hydrocarbon growth in the CSEs of AGB stars (Cold plasma reactors, AROMA, PIRENEA 2 and ESPOIRS).
First firm detection of fullerenes in meteorites (Almahata Sitta) and co-existence of carbon clusters along with PAHs in this meteorite (AROMA).
AROMA (Astrochemistry Research of Organics with Molecular Analyzer) is a new analytical experimental set-up developed at IRAP/LCAR (Toulouse, France). The main purpose of AROMA is the study and identification, with micro-scale resolution, of the molecular content of cosmic dust analogues, including stardust analogues produced in the Stardust machine and meteoritic samples. AROMA combines laser desorption/ionization (LDI) techniques with a linear ion trap coupled to an orthogonal time of flight mass spectrometer (LQIT-oTOF).
The Stardust machine is a beyond the state-of-the-art equipment that combines various techniques to achieve original studies on individual nanoparticles. These studies include their processing to produce complex molecules, the chemical evolution of their precursors and their reactivity with abundant molecules of astrophysical interest. The simulation chambers are equipped with state-of-the-art in situ and ex situ diagnostics.
Outstanding publications on our innovative development
The Stardust machine has been designed and assembled at the Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC). The elapsed time has been from October 2014 to the end of 2015. Throughout 2016, we entered into the commissioning phase with several ongoing verification experiments and processes. From mid-2017, we are dealing with the first astrophysical experiments, the so-called exploitation phase.
Stardust is basically a forefront facility to produce and analyze in-situ highly-controlled analogs of the dust grains in a versatile ultra-high-vacuum (UHV) experiment, up to pressures of 10-11 mbar. The ultimate goal is to reproduce the physical conditions that prevail in the photospheres of AGB stars. In this environment, we mimick the nucleation of the aggregates and their possible interaction with the circumstellar gases. Stardust characterizes microscopic processes (interaction with photons and gas) through surface science techniques. It encompasses 5 independent vacuum chambers, with their own instrumentation, pumping systems, gas-dosed systems in a highly-controlled UHV environment:
MICS (Multiple Ion Cluster Source) chamber. The MICS is a new optimized route for cluster growth of a standard technique based on a sputtering gas. It allows the formation of nanoparticles of controlled elemental composition by atomic aggregation. A special port has been adapted to perform optical spectroscopy.
NEON (NEutral to iON) chamber that separates neutral from ionized nanoparticles as well as a mass selection. It also accelerates, simulating the radiation pressure, and anneals the formed clusters.
INTERACTION chamber. Interaction and chemical reactions are induced between the generated nanoparticles and molecules in the gas phase (H2, CH4, C2H2, etc).
INFRA-ICE chamber. In-flight analysis is performed through UV, visible, near-mid and far-infrared spectroscopy. We have successfully integrated a cryostat and a sample manipulator to study ice interstellar analogs. Microwave spectroscopy will be performed with the new NANOCOSMOS mm broad band receivers to study second/minute time-dependent changes in the gas composition.
ANA chamber, the analysis chamber. This allows us to collect the nanoparticles and perform X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and Ultraviolet photoelectron spectroscopy (UPS) in-situ. Also some in-situ processing can be performed here. The collected samples are duly transported and delivered to the AROMA setup for ulterior analysis.