Textural evolution of S-type micrometeorites

Abstract Cosmic dust, the dominant extraterrestrial material entering Earth's atmosphere, undergoes textural transformation during entry. This study investigates the dependence of texture on entry conditions and classifies textures like barred (tabular, platy, and radial) and porphyritic (equant, skeletal, and chain). Texture development hinges on the balance between overheating and undercooling. Particles heated below the liquidus form scoriaceous or equant porphyritic textures. Near-liquidus temperatures yield skeletal morphologies, while exceeding the liquidus by ~ 50 °C produces chain forms. At ~ 100 °C above the liquidus, embryo distortion leads to barred textures, whose type depends on undercooling. Further heating produces cryptocrystalline, glass, and CAT (calcium–aluminium–titanium) spherules. Above 2400 °C, ablation exceeds 90% and hindering spherule formation. Additionally, comparing chondritic olivine liquidus and micrometeoroid residual melt compositions with particle heating temperatures reveals the degree of overheating and identifies entry conditions favouring specific textures. Particles with a size of 400 µm and smaller entering at escape velocity with higher zenith angles (65°–90° for CI and 80°–90° for CV, CM, L, LL, and H precursors) can survive unmelted or form scoriaceous or porphyritic spherules. Barred textures are likely for smaller particles (< 400 µm) entering at escape velocity with moderate zenith angles (50°–70°). Steeper angles, larger sizes, and higher velocities favour glass formation. This work refines our understanding of entry conditions that shape micrometeorite textures.