The mystery of the appearance of water on the Moon has been revealed

Water on the Moon did not appear overnight — it accumulated over billions of years. This unexpected conclusion was reached by an international team of researchers, overturning previous ideas about the origin of lunar ice.

As reported by TUT.AZ, the results of the study have been published in the journal Nature Astronomy.

Lunar ice has long intrigued scientists: traces of it have been found in craters near the south pole, yet where it came from remained a mystery.

The new study provides an answer: water accumulated not all at once, but gradually — over the course of 3 to 3.5 billion years. "It appears that the oldest craters contain the most ice. This means the process was nearly continuous," emphasized study co-author Paul Hayne.

The hypothesis that water was "delivered" to the Moon by a single giant comet proved untenable. Instead, scientists point to several sources at once: ancient volcanism, which could have pushed water from the Moon's interior, impacts from comets and asteroids, as well as solar wind — when hydrogen interacts with lunar soil, water molecules are formed. All this ice has been preserved in so-called "cold traps" — craters plunged in perpetual shadow, where sunlight has not penetrated for billions of years.

Drawing on data from NASA missions and computer modeling, the researchers established that the older a crater is and the longer it has remained in shadow, the more ice it contains. For example, the Haworth crater near the Moon's south pole, hidden from the Sun for more than 3 billion years, may turn out to be one of the largest water "reservoirs." At the same time, the distribution of ice is extremely uneven — which is precisely why it is found in abundance in some craters while being virtually absent in others.

As lead author Oded Aharonson noted, understanding where lunar water came from has significance far beyond fundamental science. Ice could become a strategic resource for future lunar missions — a source of drinking water and even rocket fuel when separated into hydrogen and oxygen.

Only direct investigations — analysis of samples on the Moon's surface or their delivery to Earth — will be able to put a definitive end to this question.