Earth is regularly hit by space rocks we have never found. A large amount of space material hitting Earth comes from unknown, primitive asteroids that do not have representation in our meteorits collection. Micrometerites could be the missing link.
The Moon has no atmosphere, yet it faces an invisible bombardment more relentless than any terrestrial storm, a constant rain of micrometeoroids, tiny fragments of rock and metal traveling at speeds up to 70 kilometers per second.
