Late Heavy Bombardment

Heavily cratered (隕石坑) surfaces on the Moon, Mars, and Mercury show that the terrestrial planets were battered by an intense bombardment during their first billion years or more, but the timing, sources, and dynamical implications of these impacts are controversial. The Late Heavy Bombardment refers to impact events that occurred after stabilization of the planetary lithospheres (地殼) such that they could be preserved as craters and basins.

William, F.B., & Marc, D.N. (2017).The Late Heavy Bombardment. Annual Review of Earth and Planetary Sciences, 45, 619-647. https://doi.org/10.1146/annurev-earth-063016-020131