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

小行星、彗星和地球中水和硅酸盐的起源是宇宙化学的一个重大科学问题。它们通过水蚀变的相互作用是原始太阳系天体（如小行星或彗星）中的一种普遍现象。陨石中蚀变的特征越来越被人们所了解，但关于水蚀变的位置、时间尺度和影响的重要问题仍然是个谜。 特别令人感兴趣的是无定形硅酸盐，天体物理学家在年轻恒星周围的吸积盘中观察到，以及在陨石中，它们被提交给蛇纹石化。这些观测结果表明，它们是早期太阳系演化的重要组成部分，与早期太阳系中的水历史有关。在碳酸盐中，反应似乎是动力学控制的，这些硅酸盐的无定形性质可能会显着加速其反应速率。然而，几乎没有什么是已知的，在这种条件下的动力学行为。 我们计划在低温（< 200°C）下对无定形硅酸盐进行热液蛇纹石化，并将其反应速率与橄榄石的反应速率进行比较。实验产品将通过最先进的纳米级分析技术来表征相关系并研究氢在材料中的扩散。我们还计划研究已知催化溶解速率的有机化合物的作用。通过将我们的结果与已发表的关于陨石结构关系的数据进行比较，我们希望了解无定形硅酸盐蛇纹石化的动力学和反应机制，以限制早期太阳系中水合作用的条件，位置和时间尺度。这项工作可以为类地行星上水的起源提供新的视角。

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.