The surface of the moon is covered with lunar regolith, a mixture of fine dust and rocky debris made by meteorite impacts, considered the soil of the moon.[5] Astronauts found few rock samples to pick up on mature regolith surfaces. The rocks had all been broken to fine soil by micrometeorite bombardment over the past billion years. The bulk of lunar regolith is a fine gray soil, breccia and rock fragments of the local bedrock.