The destruction of tektites by micrometeoroid impact

Damage to tektites caused by collisions with micrometeoroids has been studied by firing small projectiles at high speed against glass spheres. In terms of the projectile kinetic energy per unit mass of the spheres, less than 106 ergs/g produces a crater on the surface of the sphere. Increasing the energy per gram causes progressively larger craters and large spallaticm zones centered about the antipodal point of the impact. A kinetic energy input of approximately 107 ergs/g completely ruptures the sphere into small fragments; this rupture energy can be delivered either by a single impact or by multiple impacts having an equivalent total energy input. These results, combined with estimates for the flux of micrometeoroids at 1 AU, indicate that the mean survival time before the complete destruction of tektites in circular heliocentric orbits is of the order of 103 and 104 years for, respectively, objects 1 to 10 cm in diameter. Partial fragmentation and loss of physical identity as tektites would occur in much shorter periods of time. Thus, any tektites ejected from the moon that initially miss the earth and pass on into interplanetary space do not provide a source of recognizable tektite bodies which the earth could subsequently sweep up over extended time periods.