Some time ago I was thinking about this.
We know that space is almost matter-free, and also is plenty of particles and objects orbiting around all planets and sattellites. If objects orbit around planets then particles can do it too, isn't it? When there are solar explosions, the sun launches tons of particles, and also some comets that crosses our path also leaves a trail of particles.
When the Moon crosses those particles, some particles are destroyed because of collision, but some other particles just pass near it and sure starts an orbit around the Moon. I'm talking about the Moon because does not have atmosphere.
That is, with these assumptions, can we say that the Moon have an orbit of particles almost touching the ground at really high speed? If this is correct, why any astronaut wandering around Moon surface or any Moon lander received an impact of those particles? The Moon has been there for about 4.5 billion years, so that's a lot of chances of having particles orbiting around.
Surely I'm wrong at something, please, give me a bit of knowledge.
Keep in mind that I'm talking about bullet sized particles.