Nanometer-sized smoke particles produced during ablation of incoming micrometeorites influence the ion chemistry in the 80--120 km region and are believed to play an important role in the nucleation of mesospheric ice particles. We present a new model of cosmic dust ablation and smoke production in the Earth's atmosphere using realistic size and velocity distributions of the incoming dust particles. We show that, while the seasonal changes in our atmosphere can be safely neglected, the shape of micro-meteoroids strongly affects their ablation. ¿ 2000 American Geophysical Union