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In the complex tree of the chemical evolution of the Universe, starting from the heart of stars to our planetary biosphere, our project focus on the small link of the transformation of atoms into molecules, such like complex organic molecules (named COMs by astronomers).
This is a long journey which started in the 80s with the discovery of complex organic molecules (COMs) in star forming regions (see, e.g., the reviews from Herbst & van Dishoeck 2009 and Caselli & Ceccarelli 2012) and that is presently exploding, thanks to the advent of the powerful millimeter telescopes IRAM-NOEMA and ALMA. France has always been at the front-end of this new field of research, and not only because of the partnership with IRAM. Indeed, highly specialized French teams have carried out laboratory experiments simulating the space conditions for years (e.g. Theulé et al 2011, Dulieu et al 2010;Duvernay et al 2017, Dulieu et al 2019).
There are two non-excluding pathways to explain the observed molecular complexity in the interstellar medium (ISM): either COMs are formed on the gas or they are synthesized on the grain surfaces (e.g. Garrod & Herbst 2006; Balucani et al. 2015). Very likely, both mechanisms are important even though in different stages and for different molecules, and the permanent exchange between solid and gas is also central (Dulieu et al. 2013). The dust grains have very cold surfaces where gaseous species can accrete, diffuse and react, and have some specific catalytic properties (e.g. Bron et al 2014). However, the release of species from the solid to the gas phase is the key of many observations like in cometary environements or star forming regions. Our project focuses on the solid-state chemistry, and its exchanges with the gas-phase, where molecules are more easily observed. At the gas-surface interface new chemical branches may arise starting from molecules released from the solid phase.
Here we propose to join the forces between two groups with complementary laboratory expertise (LERMA (Cergy) and PIIM (Marseille)) and one with astrophysical, observations and modeling, expertise (IPAG, Grenoble).
Our specific goal is to understand how molecules diffuse, meet and mate on grains in order to assess what COMs are formed on them and how. In this project, we focus on the grain surface chemistry and, specifically, on the role of radicals in the formation of some test COMs. This is a crucial first step to assert the degree of molecular complexity achievable in the de Duve’s cosmic bricks.
We have now the instruments to tackle this problem and to understand how the blocks of life form, where and when in our Galaxy. In a few words, we can now determine how molecular complexity grows up in space, at its first stages.
In addition to its own interest, understanding molecular complexity in space helps to understand the link between the primitive nebula, the young Solar System and its small bodies, in which today we detect complex molecules and even amino acids (as in comets and meteorites), as well as the unexpected molecular oxygen unveiled by the in situ measurements of the Rosetta mission (Bieler et al. 2015).
Where these molecules come from? How and where did they form? What do they tell us about the stars and planets formation processes? And at last, but not the least, atoms and molecules are the remote thermometers and barometers, as their observed line spectra can and are used to extract a mine of precious and often unique information.
In the 50's, the Miller and Urey experiment demonstrated that it was possible to build many amino- acids and others large molecules by provoking an electric discharge in a gas mixture mimicking some atmospheric conditions. This is an approach from the top, in the sense that the complexity is directly observed, but not understood. We propose here an opposite approach: a bottom-up approach or mechanistic approach where we want to start from simple atoms and build up the tree of chemical complexity, exploring each possible path and mechanism, to determine which are the main chemical routes toward complexity. This represents a slow and careful exploration of the paths of the minimum energy.
Work in Cergy
Produce experimental data on radicals to confront the myth
Work in Marseille
EPR : new technology in astrochemistry directly capable of
to study radicals
Work in Grenoble
Implement a new astrophysical model whose core is capable of describe experiments
Outreach and diffusion
