Weizmann-led study finds ice has built up at the Moon's poles for over a billion years

A study led by planetary scientist Oded Aharonson of the Weizmann Institute of Science, published in Nature Astronomy and announced on 7 April 2026, offers a new explanation for how water ice collected at the Moon's poles. Working with Paul Hayne of the University of Colorado Boulder and Norbert Schörghofer of the Planetary Science Institute, the team found that ice has been accumulating steadily for at least 1.5 billion years, and probably far longer.

Craters near the lunar poles that never see sunlight can become extremely cold, around minus 160 degrees Celsius, cold enough to hold ice for very long periods. But not every shadowed crater qualifies, because the sunlit walls around some of them radiate warmth into the floor. The researchers used geometric models and temperature data from NASA's Lunar Reconnaissance Orbiter to identify which shadowed regions are true cold traps, and to work out when in lunar history each one became cold. That history is tied to the Moon's slowly changing tilt, which has gradually put more polar terrain into permanent shadow.

They then compared those ages with ultraviolet observations from the orbiter's LAMP instrument, which can detect ice because it reflects certain ultraviolet wavelengths differently from bare rock. The pattern was clear: the earlier a region became a cold trap, the larger the share of its area that holds ice. That suggests a nearly continuous supply of water, from sources such as comets, asteroids, the solar wind or volcanic gases, rather than a single large delivery. Hayne told The Debrief that the data imply accumulation over as much as three billion years or more, though the study itself does not settle where the water came from.

The work also names specific targets. Very old cold traps such as Haworth crater near the south pole are highlighted as places likely to hold the richest, oldest deposits, of interest both to scientists and to space agencies planning crewed missions.