Melting of cosmic spherules

Cosmic spherules are dust particles of extraterrestrial origin that are melted during entry into Earth’s atmosphere. The flux of such particles to Earth is approximately 40,000 tons per year [1]. Cosmic spherules have either glassy or quench textures. The process of melting depends on the initial characteristics of the dust particle, e.g., the initial velocity and angle of entry, and also on the precursor composition of the dust particle [e.g., 2]. When a dust particle is melted, the silicates are partially homogenized, while metals and metal sulfides are separated into a distinct core within the spherule [3]. If a spherule remains molten for a long enough period of time, the metal core will migrate to the edge of the spherule and eventually escape the spherule [3]. We report the analysis of cosmic spherules that exhibit various stages of melting and the imaging of the spherules by computer-assisted X-ray nanotomography (CT).