Bright Carbonate Veins on Asteroid (101955) Bennu: Implications for Aqueous Alteration History

Carbonaceous asteroids formed early in Solar System history and experienced varying degrees of aqueous (water-rock) and thermal alteration. Most models of the evolution of these asteroids suggest that aqueous alteration was driven by hydrothermal convection. However, it is debated whether this alteration occurred in a chemically closed or open system. The bulk chemical compositions of the carbonaceous chondrite meteorites imply that the system was closed. Models predict that large-scale fluid flow in an open system took place on at least some asteroids. In this scenario, fluids would have flowed through fractures from the interior, and minerals would have precipitated into these fractures, forming veins.