For a long time, scientists believed that water on the Moon was brought by asteroids and comets during the Late Heavy Bombardment period, approximately 4.1 to 3.8 billion years ago, when planet surfaces were frequently bombarded. This event could have occurred even hundreds of millions of years earlier, shortly after the planet's formation. However, the geological activity on Earth, characterized by constant tectonic plate movement, erases traces of ancient impacts, complicating the direct verification of this hypothesis.

In contrast, the Moon's lack of air and liquid water, alongside billions of years without geological activity, preserves a record of early impacts, allowing scientists to study these traces. By analyzing a large collection of Moon samples brought back by the Apollo missions using a new method, researchers have concluded that impacts from asteroids and comets during the solar system's youth contributed only a tiny fraction of Earth's water. This finding reshapes our understanding of the origins of water on both celestial bodies and questions prior theories attributing the lunar water primarily to external impacts.

The research suggests a need for further exploration into alternative sources or mechanisms that could explain the presence of water on the Moon, which is crucial for future lunar exploration and potential colonization. Establishing a more comprehensive understanding of the Moon's water origin can help scientists learn more about both the early solar system environment and the resources available for human endeavors on the Moon in the future.