Imbrian

The Imbrian is a time period in the history of the Moon. It is divided into two smaller parts, called epochs: the Early Imbrian and the Late Imbrian. This period is important for understanding how the Moon changed over time, especially after big events like impacts from space rocks. Scientists study this time to learn more about the Moon's surface and what happened there long ago.

Early Imbrian

The Early Imbrian was a time long ago when the Moon changed a lot. It started about 3,850 million years ago and ended about 3,800 million years ago. This was when a big crash made the huge Mare Imbrium area on the Moon. Other big areas like Mare Crisium, Mare Tranquillitatis, Mare Serenitatis, and Mare Fecunditatis also formed during this time. These places later filled with a kind of rock called basalt.

This time was after the Nectarian period and before the Late Imbrian. It also happened at the end of a time when many things hit the Inner Solar System.

Late Imbrian

In the Lunar geologic timescale, the Late Imbrian epoch happened from 3,800 million years ago to about 3,200 million years ago. During this time, the layer below the moon's surface partly melted and filled in the moon's basins with a type of rock called basalt. Scientists believe this melting happened because big impacts during an earlier time made the surface thinner. This allowed hotter material from deeper down to come closer to the surface. Most of the moon rocks brought to Earth for study are from this period.