Time sequence of a hypothetical Mercury-forming hit and run collision into Venus (from Asphaug and Reufer 2014). A differentiated chondritic impactor several times the mass of Mercury collides with a Venus-mass planet in an impact that is 30° from head-on, and 3 times the escape velocity. The mantle of proto-Mercury is dispersed and leaves a metallic secondary remnant that matches the mass and composition of Mercury, in this simulation. After thousands of years of orbits around the Sun, most of the dispersed mantle accretes onto Venus, providing a sink for lost silicates. But Mercury has to be lucky to not be accreted itself.