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Published December 2013 | public
Journal Article

Complementary and Emerging Techniques for Astrophysical Ices Processed in the Laboratory

Abstract

Inter- and circumstellar ices comprise different molecules accreted on cold dust particles. These icy dust grains provide a molecule reservoir where particles can interact and react. As the grain acts as a third body, capable of absorbing energy, icy surfaces in space have a catalytic effect. Chemical reactions are triggered by a number of possible processes; (i) irradiation by light, typically UV photons from the interstellar radiation field and Ly-α radiation emitted by excited hydrogen, but also X-rays, (ii) bombardment by particles, free atoms (most noticeably hydrogen, but also N, C, O and D-atoms), electrons, low energy ions and cosmic rays, and (iii) thermal processing. All these effects cause ices to (photo)desorb, induce fragmentation or ionization in the ice, and eventual recombination will make molecules to react and to form more and more complex species. The effects of this solid state astrochemistry are observed by astronomers; nearly 180 different molecules (not including isotopologues) have been unambiguously identified in the inter- and circumstellar medium, and the abundances of a substantial part of these species cannot be explained by gas phase reaction schemes only and must involve solid state chemistry. Icy dust grains in space experience different chemical stages. In the diffuse medium grains are barely covered by molecules, but upon gravitational collapse and darkening of the cloud, temperatures drop and dust grains start acting as micrometer sized cryopumps. More and more species accrete, until even the most volatile species are frozen. In parallel (non)energetic processing can take place, particularly during planet and star formation when radiation and particle fluxes are intense. The physical and chemical properties of ice clearly provide a snapshotroot to characterize the cosmological chemical evolution. In order to fully interpret the astronomical observations, therefore, dedicated laboratory experiments are needed that simulate dust grain formation and processing as well as ice mantle chemistry under astronomical conditions and in full control of the relevant parameters; ice morphology (i.e., structure), composition, temperature, UV and particle fluxes, etc., yielding parameters that can be used for astrochemical modeling and for comparison with the observations. This is the topic of the present manuscript. Laboratory experiments simulating the conditions in space are conducted for decades all over the world, but particularly in recent years new techniques have made it possible to study reactions involving inter- and circumstellar dust and ice analogues at an unprecedented level of detail. Whereas in the past "top-down scenarios" allowed to conclude on the importance of the solid state for the chemical enrichment of space, presently "bottom-up approaches" make it possible to fully quantify the involved reactions, and to provide information on processes at the molecular level. The recent progress in the field of "solid state laboratory astrophysics" is a consequence of the use of ultra high vacuum systems, of new radiation sources, such as synchrotrons and laser systems that allow extensions to wavelength domains that long have not been accessible, including the THz domain, and the use of highly sensitive gas phase detection techniques, explicitly applied to characterize the solid state such as fluorescence, luminescence, cavity ring-down spectroscopy and sophisticated mass spectrometric techniques. This paper presents an overview of the techniques being used in astrochemical laboratories worldwide, but it is incomplete in the sense that it summarizes the outcome of a 3-day workshop of the authors in November 2012 (at the Observatoire de Meudon in France), with several laboratories represented, but not all. The paper references earlier work, but it is incomplete with regard to latest developments of techniques used in laboratories not represented at the workshop.

Additional Information

© 2013 Springer Science+Business Media Dordrecht. Received: 2 January 2013. Accepted: 26 August 2013. Published online: 26 September 2013. Authors acknowledge several grants and persons as follows: H. Linnartz: Grants within NWO, NOVA and Marie Curie programs. The setups and conclusions presented here have been the outcome of dedicated work by several PhD students, postdocs, and scientific collaborators. Special thanks go to Karin Oberg, Jordy Bouwman, Edith Fayolle, Steven Cuylle, Lou Allamandola, Jean-Hugues Fillion and Mathieu Bertin. S. Ioppolo: NASA SARA and Exobiology/Astrobiology programs, Niels Stensen Foundation (NSS) through a bursary and a Marie Curie Fellowship (FP7-PEOPLE-2011-IOF-300957). G.A. Blake: NASA SARA and Exobiology/Astrobiology programs. M. A. Allodi: Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program. G. Strazzulla: European COST Action CM 0805: The Chemical Cosmos: Understanding Chemistry in Astronomical Environments. Z. Kaňuchová: VEGA—The Slovak Agency for Science, grant no. 2/0022/10 and the European COST Action CM 0805: The Chemical Cosmos: Understanding Chemistry in Astronomical Environments. M. Gudipati and A. Lignell: NASA Astrobiology Institute (NAI) through Icy Worlds (JPL) and Early Habitable Environments (NASA Ames) nodes, NASA Spitzer Science Center (Cycle 5), NASA funding through Rosetta US Science Team. Research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. R.A. Baragiola, U. Raut and D. Fulvio: NASA program: Origins of the Solar System and Outer Planet Research, and programs NSF. F. Salama: The Astrophysics Research and Analysis program (APRA) of NASA SMD, The technical support provided at NASA-Ames by R. Walker is gratefully acknowledged. C. Contreras and E. Sciamma-O'Brien: NASA Postdoctoral Program (NPP). Ph. Boduch and H. Rothard: CAPES-COFECUB French-Brazilian exchange program; European COST Action CM 0805: The Chemical Cosmos: Understanding Chemistry in Astronomical Environments; T. Langlinay and H. Hijazi, and Region "Basse Normandie".

Additional details

Created:
August 22, 2023
Modified:
October 25, 2023