Pulse heating experiments on magnesium-rich olivine and pyroxene, two silicates often found in micrometeorites collected in the stratosphere, show that iron ion tracks remain detectable in the transmission electron microscope for temperature maxima up to ~600 ¿C. Assuming thermal emissivities near unity, this implies that micrometeorites with surface densities above 1 mg/cm2 are likely to have their track record erased, and that tracks in reentrant or low-density micrometeorites smaller than 7 μm in size are likely to survive atmospheric entry.