Cosmic spherules from metalliferous sediments: a long journey to the seafloor

The iron cosmic spherules found in the metalliferous sediments of two spreading centers (Mid-Atlantic Ridge and East Pacific Rise) represent different stages of the four-step model suggested by Bi et al. (1993). The occurrence of one spherule with a conic tail and the detailed study of the whole spherule set allow the development of the “Dong Bi” model. If an interplanetary body (iron or iron-rich stony meteorite) has hypervelocity and enters the Earth’s atmosphere under low incidence angle, the path of its derivates to the Earth’s surface will be long. This will provide possibilities for development of the next, fifth step of the “Dong Bi” model: iron oxide shell reversal and formation of a conic tail. If the flight of the iron oxide spherule continues after the first 4 stages (ablation, oxidation, core protrusion, and core detachment) it reverses with its light hollow part back. The surface layer of the front side of the spherule ablates. The removed liquid droplets, entrained in a trail after the flying spherule, crystallize in the antipodal zone of rarefaction capping the hollow with a conic tail.