Mass loss due to sputtering and thermal processes in meteoroid ablation

Conventional meteoroid theory assumes that the dominant mode of ablation (which we will refer to as thermal ablation) is by evaporation following intense heating during atmospheric flight. Light production results from excitation of ablated meteoroid atoms following collisions with atmospheric constituents. In this paper, we consider the question of whether sputtering may provide an alternative disintegration process of some importance. For meteoroids in the mass range from 10 - 3 to 10 - 13 kg and covering a meteor velocity range from 11 to 71 km / s , we numerically modeled both thermal ablation and sputtering ablation during atmospheric flight. We considered three meteoroid models believed to be representative of asteroidal ( 3300 kg / m 3 mass density), cometary ( 1000 kg / m 3 ) and porous cometary ( 300 kg / m 3 ) meteoroid structures. Atmospheric profiles which considered the molecular compositions at different heights were use in the sputtering calculations. We find that while in many cases (particularly at low velocities and for relatively large meteoroid masses) sputtering contributes only a small amount of mass loss during atmospheric flight, in some cases sputtering is very important. For example, a 10 - 10 kg porous meteoroid at 40 km / s will lose nearly 51% of its mass by sputtering, while a 10 - 13 kg asteroidal meteoroid at 60 km / s will lose nearly 83% of its mass by sputtering. We argue that sputtering may explain the light production observed at very great heights in some Leonid meteors. We discuss methods to observationally test the predictions of these computations. A search for early gradual tails on meteor light curves prior to the commencement of intense thermal ablation possibly represents the most promising approach. The impact of this work will be most dramatic for very small meteoroids such as those observed with large aperture radars. The heights of ablation and decelerations observed using these systems may provide evidence for the importance of sputtering.