Scientists have confirmed that water ice on the Moon has been accumulating steadily for at least 1.5 billion years, with some of the oldest craters holding ice that may be as old as 3 to 3.5 billion years. This finding, published in Nature Astronomy, resolves a long-standing mystery about why ice is unevenly distributed across the lunar poles and provides a clearer roadmap for future human missions aiming to leverage lunar ice as a resource.
The research, based on data from NASA’s Lunar Reconnaissance Orbiter and its Lyman-Alpha Mapping Project instrument, shows a direct correlation between the age of a permanently shadowed region and the amount of water ice it contains. Younger shadowed areas, formed around 100 million years ago, have a higher proportion of exposed ice on the surface — about 3.4% in some cases — while older regions, which have remained in darkness for billions of years, harbor ice buried beneath layers of regolith.
This pattern emerged as the Moon’s axial tilt gradually decreased over time, causing permanently shadowed regions to expand and trap water molecules delivered by comets, asteroids, and solar wind. As modern cold traps formed, they began accumulating ice, while older traps experienced cycles of burial and preservation. The result is a layered history of ice accumulation, where exposure to sunlight in some craters caused ice to sublime and migrate to colder, more stable locations.
One striking example is the Haworth crater near the Moon’s south pole, which has remained in continuous shadow for more than three billion years and shows some of the strongest signals of water ice detected to date. Researchers note that this supports the idea that the Moon has been accumulating water more or less continuously for billions of years, rather than receiving it in a single catastrophic event like a major comet impact.
The findings have direct implications for NASA’s Artemis program and other planned lunar missions. By identifying which craters are most likely to contain accessible, ancient ice reserves, mission planners can prioritize landing sites for in-situ resource utilization — extracting water for drinking, oxygen production, or rocket fuel. The study suggests that the oldest, most stable shadowed regions offer the most reliable long-term resources.
Paul Hayne, a lead researcher on the study, emphasized that the patchy distribution of ice is not random but a direct consequence of the Moon’s evolving orientation and surface conditions over geological timescales. “It’s not concentrated in the same quantities in every crater,” he told Space.com. “And there was no great explanation for that — until now.”
How did scientists determine the age of ice in lunar craters?
By analyzing ultraviolet data from the Lyman-Alpha Mapping Project on the Lunar Reconnaissance Orbiter, researchers linked the visibility and depth of ice deposits to how long a region has remained in permanent shadow, using the Moon’s changing axial tilt as a timeline.
Why is some ice buried while other ice is exposed on the surface?
>Older permanently shadowed regions, which have existed for hundreds of millions to billions of years, have accumulated ice that has been gradually covered by regolith over time, while younger traps, formed around 100 million years ago, still show a higher proportion of exposed ice due to more recent accumulation.
Could this ice be used to support human missions on the Moon?
Yes, the study indicates that the oldest, most stable shadowed regions — such as Haworth crater — contain significant, accessible ice reserves that could be processed for drinking water, oxygen, or rocket fuel, supporting long-term lunar exploration under NASA’s Artemis program.