Timescales and mechanisms of hydration of primitive amorphous silicates in the early solar system: implications for the evolution of water and the role of organics

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The origin of water and silicates in asteroids, comets and the Earth is a major scientific question of cosmochemistry. Their interaction through aqueous alteration is a widespread phenomenon in primitive solar system bodies such as asteroids or comets. The characteristics of alteration in chondritic meteorites are becoming increasingly well understood, but significant questions regarding the location, timescales and effects of aqueous alteration remain enigmatic. Of particular interest are the amorphous silicates, observed by astrophysicists in accretion disks around young stars as well as in chondrites, where they are submitted to serpentinization. These observations suggest that they are an important component of the early solar system evolution and are related to the history of water in the early solar system. In chondrites, reactions seem to be kinetically controlled and the amorphous nature of these silicates may significantly accelerate their reaction rates. However, almost nothing is known on their kinetic behavior in such conditions. We plan to carry out hydrothermal serpentinization of amorphous silicates at low temperatures (< 200°C) and to compare their reaction rate to those of olivine. Experimental products will be characterized by state of the art nanoscale analytical techniques to characterize the phase relationships and study the diffusion of hydrogen within the materials. We also plan to investigate the role of organic compounds, known to catalyze dissolution rates. By comparing our results to published data on textural relationships in chondrites, we hope to understand the kinetic and reaction mechanisms of amorphous silicate serpentinization, in order to constrain the conditions, location and timescales of the hydration in the early solar system. This work could provide a new perspective on the origin of water on terrestrial planets.