Residual mass from atmospheric ablation of small meteoroids

Abstract

Numerical solutions of the equations of meteor ablation in the Earth's atmosphere have been obtained using a variable step size Runge-Kutta technique in order to determine the size of the residual mass resulting from atmospheric flight. The equations used include effects of meteoroid heat capacity and thermal radiation, and a realistic atmospheric density profile. Results were obtained for initial masses in the range 10 −7–10 −2 g, and for initial velocities less than 24 km s −1 (results indicated no appreciable residual mass for meteors with velocities above 24 km s −1 in this mass range). The following function has been obtained to provide the logarithm of the ratio of the residual mass following atmospheric ablation to the original preatmospheric mass log r = 4.7 −0.33v ∞ −0.013v ∞ 2 + 1.2 log m ∞ + 0.08 log 2 m ∞ −0.083v ∞ log m ∞M The pre-atmospheric mass and velocity are represented by m ∞ and v ∞. When the results are expressed in terms of the size of the residual mass following atmospheric ablation as a function of the initial mass and velocity, it is found that the final residual mass is almost independent of the original mass of the meteoroid, but very strongly dependent on the original velocity. For example, the residual mass is very nearly 10 −7 g for a meteoroid with velocity 18 kms −1 for initial masses from 10 −7 to 10 −3 g. On the other hand, a slight change in the initial velocity to 20 km s −1 will shift the residual mass to approx. 10 −8 g. This strong velocity dependence coupled with the weak dependence on the original mass has important consequences for the sampling of ablation product micrometeorites.