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Institut de minéralogie, de physique des matériaux et de cosmochimie
UMR 7590 - Sorbonne Université/CNRS/MNHN/IRD

Research Topics

Evolution of organic molecules under hydrothermal conditions typical of carbonaceous chondrites

 

Organic matter occurs in carbonaceous chondrites shows an impressive molecular diversity: more than 14,000 different soluble organic molecules were identified in a methanol extract of the Murchison meteorite. The organic content of CC can be divided into insoluble and soluble organic material, the former one being the most abundant (more than 50 wt%). The soluble fraction comprises various classes of molecules; among them were reported: carboxylic acids, amino acids, hydrocarbons, sugar derivatives, alcohol, ketones and nucleobases. It must be noted that significant variations can be observed from one meteorite to another, in both abundance and distribution.

The question of the origin of these molecules remains debated: were they formed on the parent body? Were they accreted as constituents of dust or ice? Are they solar or interstellar products?

 

Building of organic matter / mineral associations during hydrothermal alteration on the carbonaceous asteroids

 

Although carbonaceous chondrites still contain primordial solar system constituents, like chondrules and CAIs, in addition to presolar grains, they exhibit signs of secondary processes. Due to the decay of short-lived radionucleides, including 60Fe and 26Al, temperature of the parent body increased and induced reprocessing of the accreted components. If ice was present, a local fluid circulation has altered the matrix, resulting into a fine scale association of hydrated silicates, oxides, hydrated sulfides and OM. This aqueous alteration occurred a few million years after the formation of the solar system, but the exact duration of the hydrothermal events remains undisclosed.

Interestingly, the most hydrated CC (petrologic types 1 and 2, type 3.0 being the least modified by secondary parent body processes) are also the richest in OM. Matrix texture and petrology are related to the hydrothermal process intensity. The organo-mineral association points to a co-evolution of organic matter and minerals in the matrix of CC. These observations are consistent with the accretion of OM associated with water ice and inorganic dust to form the first solids in the protoplanetary disk, which evolved due to hydrothermal events. But how did the mineral influence the evolution of organic molecules? How the presence of organic molecule could influence the stability of minerals in the matrix?

 

Preservation and evolution of isotope signatures of organic molecules on carbonaceous asteroids

 

Stable isotope compositions constitute valuable tools to investigate the origin and evolution of organic molecules in geological systems; in particular, H and N isotopes are relevant to determine the origin of OM in carbonaceous chondrites and in comets. Organic matter is heterogeneous in isotope composition distribution. This heterogeneity is visible at all scales: between chondrites, within chondrites and the molecular scale. Is this heterogeneity a heritage of pre-accretion processes (in the protoplanetary disk or the parent molecular cloud)? How is this heterogeneity affected by hydrothermal events on the parent body? Can this heterogeneity constitute a new proxy to understand the formation of the solar system and the first small bodies?

 

Global hydrogen budget of carbonaceous chondrites

Two main reservoirs of hydrogen occur in carbonaceous chondrites hydrated minerals and organic matter, which are intimately mixed at the nm scale. Besides, hydrated CC have experienced fluid circulation that may have redistributed H-isotopes, hence blurring the original isotopic signature of both components. The origin of hydrogen and water in CC hence remains questioned: are they inherited from nebula molecular gas? Are they related to ice that condensed in the solar system, beyond the snow line? How was water reprocessed in the gaz phase?

Answering this question requires to assess the extent of H-isotope redistribution that occurred during hydrothermal events between organic matter and water, in addition to the determination of the content and isotope signature of H contained in chondrules, the largest mineral component of chondrules.

Cécile Duflot - 19/09/19

Traductions :

    Egalement dans la rubrique

    Zoom Science - Septembre 2015 - Les effets du sel sur la symétrisation de la glace planétaire
    Illustration de la transition entre la glace salée (en bleu le chlore, en orange le lithium, en rouge l’oxygène et en blanc l’hydrogène) en phase moléculaire VII (en haut) et en phase symétrique X (en bas) sous l’effet de pressions supérieures à un million d’atmosphères, typiques de croûtes de glaces à l’intérieur de planètes comme Neptune (à droite).

    Des physiciens de l’Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC - CNRS/UPMC/IRD/MNHN), et du Earth and Planetary Science Laboratory de l’EPFL à Lausanne, ont montré que la présence de sels dans la glace empêche la transition sous pression de la phase moléculaire VII...

    » Lire la suite

    Contact

    Guillaume Fiquet (Guillaume.Fiquet @ upmc.fr)

    Directeur de l'institut

    33 +1 44 27 52 17

     

    Nalini Loret (Nalini.Loret @ upmc.fr)

    Attachée de direction

    33 +1 44 27 52 17

     

    Jérôme Normand (jerome.normand @ upmc.fr)

    Gestion du personnel

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    33 +1 44 27 74 99

     

    Antonella Initili (Antonella.Intili @ upmc.fr)

    Accueil et logistique

    Réservation des salles

    33 +1 44 27 25 61

     

    Danielle Raddas (cecile.duflot @ impmc.upmc.fr)

    Gestion financière

    33 +1 44 27 56 82

     

    Cécile Duflot (cecile.duflot @ upmc.fr)

    Communication

    33 +1 44 27 46 86

     

    Contact unique pour l'expertise de météorites

     

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    Stages d'observation pour les 3e et les Seconde : feriel.skouri-panet@upmc.fr (feriel.skouri-panet @ upmc.fr)

     

    Adresse postale

    Institut de minéralogie, de physique des matériaux et de cosmochimie - UMR 7590

    Sorbonne Université - 4, place Jussieu - BC 115 - 75252 Paris Cedex 5

     

    Adresse physique

    Institut de minéralogie, de physique des matériaux et de cosmochimie - UMR 7590 - Sorbonne Université - 4, place Jussieu - Tour 23 - Barre 22-23, 4e étage - 75252 Paris Cedex 5

     

    Adresse de livraison

    Accès : 7 quai Saint Bernard - 75005 Paris, Tour 22.

    Contact : Antonella Intili : Barre 22-23, 4e étage, pièce 420, 33 +1 44 27 25 61

     

     

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    L'IMPMC en chiffres

    L'IMPMC compte environ 195 personnes dont :

     

    • 40 chercheurs CNRS
    • 46 enseignants-chercheurs
    • 19 ITA CNRS
    • 15 ITA non CNRS
    • 50 doctorants
    • 13 post-doctorants
    • 12 bénévoles

     

     Chiffres : janvier 2016