Lava flows that formed the maria are only 3–4 billion years old. Compared to the Moon’s formation 4.5 billion years ago, these are relatively recent. Some craters are even younger, less than 100 million years old. Meteor impacts continue shaping the surface. Space weathering gradually darkens and erodes rocks. The Moon is a dynamic, if slow, world.
It matters because surface features reflect ongoing processes. Scientists must date formations to understand lunar history accurately.
It also suggests that the Moon isn’t entirely geologically dead. Late volcanic and impact activity could affect future exploration.
Some lava flows are younger than the oldest known rocks on Earth.
NASA [nasa.gov]