Periodic Reporting for period 3 - HYDROMA (Origin and evolution of organic matter in carbonaceous chondrites: influence of hydrothermal processes)
Berichtszeitraum: 2022-09-01 bis 2024-02-29
Carbonaceous chondrites (CC) are believed to be fragments of carbonaceous asteroids from the asteroidal belt. They contain up to 4wt% of organic compounds, showing a huge diversity and extremely variable H and N isotope compositions. Molecular and isotope heterogeneities are visible at all scales: between chondrites, within chondrites and at 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 aqueous alteration on the parent body? Can these molecular and isotopic heterogeneities be useful to understand the formation of the solar system and the first small bodies? Are there molecules more resistant to secondary processes? Can we define a common organic precursor CC?
The HYDROMA project aims at deciphering the influence of hydrothermal events on the H- and N- isotope compositions of organic molecules detected in CC. This will allow disentangling the isotope composition of the organic precursors accreted on the carbonaceous asteroids hence identifying the synthesis environments in the protoplanetary disk or the parent molecular cloud. HYDROMA will also lead to the creation of a new proxy for describing the aqueous alteration on CC parent bodies, based on OM isotope composition. The research proposed in HYDROMA will answer to three major questions:
- How did the hydrothermal events modify the isotope signature of the organic matter in carbonaceous chondrites? Aqueous alteration has been invoked to explain the variations observed in H- and N-isotope compositions. Nevertheless, there are no robust estimations of how large was the isotopic exchange with the fluid that circulated in the CC parent body and its kinetics, although water and OM are far from equilibrium for hydrogen isotopes.
- Is there any record of the primordial signature of organic precursors? HYDROMA will reveal the original D/H and 15N/14N of organic molecules, deciphering the processes that promoted the formation of OM in the solar system with unprecedented confidence.
- Is it possible to use the isotope composition of organic molecules for determining duration and temperature of aqueous alteration on carbonaceous asteroids? The quantification of the kinetics of H- and N-isotope exchanges for several organic molecules and the associated fractionation factors will lead to the development of a new proxy to resolve the temperature and duration of hydrothermal events.
The HYDROMA project aims at deciphering the influence of hydrothermal events on the H- and N- isotope compositions of organic molecules detected in CC. This will allow disentangling the isotope composition of the organic precursors accreted on the carbonaceous asteroids hence identifying the synthesis environments in the protoplanetary disk or the parent molecular cloud. HYDROMA will also lead to the creation of a new proxy for describing the aqueous alteration on CC parent bodies, based on OM isotope composition. The research proposed in HYDROMA will answer to three major questions:
- How did the hydrothermal events modify the isotope signature of the organic matter in carbonaceous chondrites? Aqueous alteration has been invoked to explain the variations observed in H- and N-isotope compositions. Nevertheless, there are no robust estimations of how large was the isotopic exchange with the fluid that circulated in the CC parent body and its kinetics, although water and OM are far from equilibrium for hydrogen isotopes.
- Is there any record of the primordial signature of organic precursors? HYDROMA will reveal the original D/H and 15N/14N of organic molecules, deciphering the processes that promoted the formation of OM in the solar system with unprecedented confidence.
- Is it possible to use the isotope composition of organic molecules for determining duration and temperature of aqueous alteration on carbonaceous asteroids? The quantification of the kinetics of H- and N-isotope exchanges for several organic molecules and the associated fractionation factors will lead to the development of a new proxy to resolve the temperature and duration of hydrothermal events.
The PAH of Kolang, Mukundpura, Tarda and Aguas Zarcas chondrites were extracted and analyzed. Molecular distribution and concentrations were compared to reported data on Murchison and Paris chondrites. C and H isotopes on the most abundant compounds were also measured, to confirm an extraterrestrial origin. In parallel, a series of experiments were conducted to document the molecular evolution of PAHs along with their isotope signatures during aqueous alteration.
The insoluble organic matter of the same chondrites was isolated and characterized by solid state NMR, FTIR, Raman, EPR, LDI-FTICR and XANES. This allowed us to investigate the impact of aqueous alteration on the CM parent body on the molecular properties of the IOM. Its N and H isotope composition was investigated by EA-irMS and NanoSIMS, revealing the influence of fluid circulation on these isotope compositions.
An experiment was conducted on the IOM of the Paris chondrite at 150°C in presence of pure water. The molecular structure and isotope properties of experimental product were compared to those of the starting material, to document the influence of hydrothermal conditions. A similar experiment was performed on intact powder of the Orgueil chondrite to assess the influence of clay minerals on the alteration of organic macromolecules during aqueous alteration.
Experiments were conducted to evaluate the evolution of amino acids and nucleobases under hydrothermal conditions, in presence of absence of minerals. The role of minerals on the evolution of macromolecules was also experimentally investigated. The impact of organic matter on the formation of phyllosilicates under conditions typical of carbonaceous asteroids was also followed in our experimental setup.
The water content of chondrules of the Paris, Mukundpura and Aguas Zarcas CM chondrites was determined using the NanoSIMS and Atom Probe Tomography. The D/H ratio allowed us to investigate the source of this water contained into the emblematic components of chondrites. The same analytical procedure was applied to chondrules of CO chondrites. Indeed, these carbonaceous chondrites are often assumed originating from parent reservoirs as CM chondrites, but they suffered from anhydrous secondary processes instead of aqueous alteration for CM.
The insoluble organic matter of the same chondrites was isolated and characterized by solid state NMR, FTIR, Raman, EPR, LDI-FTICR and XANES. This allowed us to investigate the impact of aqueous alteration on the CM parent body on the molecular properties of the IOM. Its N and H isotope composition was investigated by EA-irMS and NanoSIMS, revealing the influence of fluid circulation on these isotope compositions.
An experiment was conducted on the IOM of the Paris chondrite at 150°C in presence of pure water. The molecular structure and isotope properties of experimental product were compared to those of the starting material, to document the influence of hydrothermal conditions. A similar experiment was performed on intact powder of the Orgueil chondrite to assess the influence of clay minerals on the alteration of organic macromolecules during aqueous alteration.
Experiments were conducted to evaluate the evolution of amino acids and nucleobases under hydrothermal conditions, in presence of absence of minerals. The role of minerals on the evolution of macromolecules was also experimentally investigated. The impact of organic matter on the formation of phyllosilicates under conditions typical of carbonaceous asteroids was also followed in our experimental setup.
The water content of chondrules of the Paris, Mukundpura and Aguas Zarcas CM chondrites was determined using the NanoSIMS and Atom Probe Tomography. The D/H ratio allowed us to investigate the source of this water contained into the emblematic components of chondrites. The same analytical procedure was applied to chondrules of CO chondrites. Indeed, these carbonaceous chondrites are often assumed originating from parent reservoirs as CM chondrites, but they suffered from anhydrous secondary processes instead of aqueous alteration for CM.
Chondrules of CM chondrites appear to contain a significant amount of water. This H-reservoir exhibits a complex D/H signature, showing imprint of pre-accretional and asteroidal processes on the water content of chondrule olivine. Chondrule of CO chondrites indicate that metamorphism and aqueous alteration have opposite effect on water content of nominally anhydrous minerals. A scenario of incorporation of hydrogen in chondrule is proposed in a paper that will be submitted soon.
Experiments confirm that PAHs can be considered as stable molecules under aqueous alteration. In the meantime, their D/H ratio is affected by fluid circulation. This is confirmed by measurements in natural objects. The thermodynamic parameters of the H-isotope evolution will be determined to allow for determination of pre-accretion D/H ratios of these molecules.
The insoluble organic matter also appears to be quite recalcitrant to aqueous alteration. However, LDI-FT-ICR reveals evolution of an organic labile component under to aqueous alteration, as described in a paper by Laurent et al. recently accepted at Geochemical Perspective Letters. Experiments performed on IOM of the Paris CM chondrite indicate that N-isotope signature are preserved despite aqueous alteration on the carbonaceous asteroids. H-isotope composition is marginally modified by this process. Altogether, experimental results are consistent with observations made on several CM chondrites showing various degrees of alteration. Experiments performed in Orgueil bulk powder shows that the presence of minerals has a minor effect on the alteration of IOM. However soluble organic molecules tend to be remobilized by fluid circulation.
Aqueous alteration of minerals is affected by the presence of organic matter. When amorphous silicate is altered in presence of organic analogue of extraterrestrial organic matter, the phyllosilicate minerals formed exhibit smaller silica sheet stacking. On the other hand, the presence of clays or silicate prone to form clays hamper the formation of complex molecules. This confirms previous report from our group. Hence, in contrast of the common belief that phyllosilicates promote the synthesis of organic molecules, they trap simple molecules hence reducing the increase in molecular complexity.
Preliminary experimental results reveal that amino acids are surprisingly resistant under aqueous alteration at 150°C. This indicate that amino acids accreted on carbonaceous chondrite parent bodies may have survive aqueous alteration.
Experiments confirm that PAHs can be considered as stable molecules under aqueous alteration. In the meantime, their D/H ratio is affected by fluid circulation. This is confirmed by measurements in natural objects. The thermodynamic parameters of the H-isotope evolution will be determined to allow for determination of pre-accretion D/H ratios of these molecules.
The insoluble organic matter also appears to be quite recalcitrant to aqueous alteration. However, LDI-FT-ICR reveals evolution of an organic labile component under to aqueous alteration, as described in a paper by Laurent et al. recently accepted at Geochemical Perspective Letters. Experiments performed on IOM of the Paris CM chondrite indicate that N-isotope signature are preserved despite aqueous alteration on the carbonaceous asteroids. H-isotope composition is marginally modified by this process. Altogether, experimental results are consistent with observations made on several CM chondrites showing various degrees of alteration. Experiments performed in Orgueil bulk powder shows that the presence of minerals has a minor effect on the alteration of IOM. However soluble organic molecules tend to be remobilized by fluid circulation.
Aqueous alteration of minerals is affected by the presence of organic matter. When amorphous silicate is altered in presence of organic analogue of extraterrestrial organic matter, the phyllosilicate minerals formed exhibit smaller silica sheet stacking. On the other hand, the presence of clays or silicate prone to form clays hamper the formation of complex molecules. This confirms previous report from our group. Hence, in contrast of the common belief that phyllosilicates promote the synthesis of organic molecules, they trap simple molecules hence reducing the increase in molecular complexity.
Preliminary experimental results reveal that amino acids are surprisingly resistant under aqueous alteration at 150°C. This indicate that amino acids accreted on carbonaceous chondrite parent bodies may have survive aqueous alteration.