Two-step nucleation process of silicate interplanetary dust particles at the vicinity of silicate melt

Abstract

Abstract The condensation processes of interplanetary dust particles (IDPs) around a high temperature silicate melt droplet were investigated in situ by a newly developed flash heating technique under microgravity using a drop tube facility. Two-step nucleation process was captured in the vicinity of the MgSiO 3 melt by a CCD camera. The first nucleation was observed at a distance of 7 mm from the vapor source at 0.3 s and the second nucleation was observed 1.4 s after the MgSiO 3 melt evaporated. The first nucleated particles were irregularly shaped amorphous silica with a diameter of 100–500 nm. The amorphous enstatite particles with a diameter of 70 nm nucleated 1.1 s later. The observed condensation sequence was silica and then enstatite . The difference of these condensations sequence with the chemical equilibrium was showed through the present experiment. The present in situ observation under microgravity was found to be a very useful technique to judge the nucleation sequence of various phases in very short duration within 3.0 s.