The moon’s south pole has hidden water-ice in its craters, but new research suggests this ice didn’t all arrive at once. Instead, it likely built up over time.
Interestingly, those so-called “permanently” shadowed craters aren’t always in the dark. The moon’s tilt changes over billions of years, shifting which areas receive sunlight. Craters that were once cold and shadowy may be lit now, and some that were sunny are now in shadow.
This revelation comes just as interest in lunar exploration rises, especially with the recent Artemis 2 mission gaining attention.
Back in the 1960s, scientists believed craters at the moon’s poles could hold ice due to their permanent shadows. However, samples from the Apollo missions showed that the moon was dry. Then, in 1994, NASA’s Clementine mission provided evidence of water-ice. This was later confirmed by the Lunar Prospector and the Lunar Reconnaissance Orbiter (LRO).
Having water on the moon could be game-changing for future astronauts. It can be used for drinking, converted into fuel, and even provide air to breathe.
The source of this water remains a puzzle. Did it arrive from a giant comet impact, or did it accumulate slowly? Researchers like Paul Hayne from the University of Colorado and his team found clues suggesting it wasn’t a single event. Instead, they think that multiple smaller impacts or volcanic activity could have brought it to the surface.
One key idea is that the ice found in shadowed craters, like Haworth, has been there for over three billion years. “The oldest craters also have the most ice,” Hayne explained, indicating that water may have been accumulating for billions of years.
What’s fascinating is that even the solar wind—a stream of hydrogen particles from the sun—could contribute to the moon’s water. This hydrogen might react with oxygen from Earth, as some Earth’s atoms and molecules have been drifting over to the moon for eons.
Ultimately, the exact origin of the moon’s water will require more exploration. Hayne is leading the effort to develop the Lunar Compact Infrared Imaging System (L-CIRiS), which aims to gather detailed data on lunar craters. This thermal camera is set to launch to the moon in late 2027.
For more in-depth analysis on the findings, you may refer to the study published in Nature Astronomy.
