The Moon's great basins are excavated
Impacts gouge out the dark plains that give the Moon its face.
- When
- Known to
- ± 30 million years
- Era
- Eoarchean, Archean
The Imbrium impact, dated by lunar breccias to about 3.92 billion years, blasts a basin 1,200 kilometres across; Nectaris and several others fall close to the same window. Their clustering was the original evidence for a Late Heavy Bombardment cataclysm, and dating them precisely remains the central problem in lunar chronology. Earth was struck at least as hard, but plate tectonics has destroyed every trace.