RAHIIA
(ANR-16-CE29-0015)

Scientific context

Comets and meteorites contain organic material formed very early in the Solar System history. The organic matter found in interplanetary objects may be related to interstellar icy grains present before the Solar System formation or during its formation, in the so-called proto-planetary disk. Organic matter then accretes on planetesimals and comet cores and may undergo hydrothermal alteration and reactions with minerals once water ice starts to melt. The effects of aqueous alteration of organic matter on interplanetary object remain poorly understood, blurring our current understanding of the nature of the accreted organic matter. This organic matter has been delivered on the surface of planets and could constitute a source of precursors for the emergence of life on the primitive Earth.

The RAHIIA project, thanks to a Laboratory Astrophysics approach developed in the interdisciplinary field of astrochemistry/astrobiology/cosmochemistry, addresses the origin and subsequent chemical evolution of the extraterrestrial organic matter: (1) during the Solar nebula epoch in ices, when subjected to irradiation and thermal alterations, (2) during the Solar System epoch in interplanetary objects, when submitted to hydrothermal or space weathering alterations.

Our project relies on the multi-scale and multi-technique analyses of organic residues synthesized in the laboratory in conditions mimicking astrophysical environments. These analogues will be compared to the organic matter of interplanetary objects (comets, asteroids, meteorites, TNO). The comparison will constrain the physical and chemical evolution of interplanetary objects and thus, we will refine the scenario of the formation of their organic matter.

A key aspect of this project is interdisciplinary collaborations. This project will offer a unique opportunity to build a French consortium implying research groups with worldwide expertise in either experimental simulations or characterization of extraterrestrial organics. Our consortium encompasses a wide range of analytical techniques on organic matter synthesised in laboratory in strong connection with extraterrestrial organics in natural objects. It will shed light on new chemical, structural and isotopic information about reaction pathways involved in the evolution of organics from the interstellar medium to interplanetary objects, parent bodies of objects found on Earth (meteorites, micrometeorites) or directly collected by space probes and returned to Earth.

Scientific objectives

Tracking the evolution of organic matter from interstellar grains to interplanetary objects

We seek the relationship of interstellar icy grains present in the solar nebula or proto-planetary disk with the organic matter found in interplanetary objects. Our research starts with the production of analogues of interstellar grains (ices and silicates) as they are observed by infrared space telescope. The analogues are then submitted to physical and chemical processes that may occur during the solar nebula formation, such as alteration by VUV photons, electrons and ions or by thermal processing. All these primary processes will provide an overall view of the primary organic matter that has been accreted in interplanetary bodies such as comets and asteroids. The organic matter has then undergone various levels of secondary processes such as space weathering, hydrothermal alteration and reactions with minerals. The secondary processes will be also experimentally simulate, since natural processes remain poorly understood. Our simulations will thus give information on the primary matter and its secondary evolution.

Link between experimental simulations and interplanetary objects

The main goal of this project is the development of relevant experimental simulations to understand the chemical evolution of Solar System organic matter. This implies a back and forth approach in which high quality characterization of experimental organic residues will be compared to information on organic material from interplanetary objects in order to feed-back the experimental conditions for synthesizing analogues as close as possible to the natural objects. The constant feedback between analogues synthesis and observations on natural objects with the same analytical methods constitutes an original methodology, allowing to tweak the experimental conditions to obtain relevant analogues. Ultimately, we will be able to provide consistent conditions and mechanisms to explain the origin and evolution of organic matter detected in interplanetary objects. This original approach will improve our understanding of the processes that controlled the formation of organics in the solar system. The choice of the analytical techniques and therefore the partners has been dictated by the techniques already used for the analyses of the interplanetary samples.

Link with space exploration

Other important outcomes of our project are: (i) the connection to the current space missions and (ii) the development of future analytical instruments for space exploration. All results obtained along this project will be useful for data treatment and interpretation of past or current space missions, especially for the Rosetta mission, since numerous analytical techniques, such as GC-MS or MS, are used in common (partner 5 co-I of COSAC and partner 3 Associate Scientist of COSIMA). Furthermore, our developments on astrophysical analogues will be available to the community to test future space instruments and to evaluate their ability to handle complex and representative organic samples.