Innovative approaches advance search for ice on the moon

Scientists and space explorers have been on the hunt to determine where and how much ice is present on the Moon. Water ice would be an important resource at a future lunar base, as it could be used to support humans or be broken down to hydrogen and oxygen, key components of rocket fuel. University of Hawai‘i at Mānoa researchers are using two innovative approaches to advance the search for ice on the Moon.

ShadowCam scouts for surface ice 

Water ice was previously detected in the permanently shaded regions of the Moon’s north and south poles by Shuai Li, assistant researcher at the Hawai‘i Institute of Geophysics and Planetology (HIGP) in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST).  A new study led by Jordan Ando, planetary sciences graduate student in Li’s laboratory, examined images from a specialized camera, the “ShadowCam,” that was on board the Korea Aerospace Research Institute Korea Lunar Pathfinder Orbiter. 

Craters in the Moon’s polar regions receive no direct sunlight, but sunlight that bounces off of one side of a crater can indirectly illuminate another side. The ShadowCam, designed specifically to look only at the dark, permanently shaded areas on the Moon, is extremely sensitive to the indirect light reflected off the lunar surface.

“Ice is generally brighter, that is, reflects more light, than rocks,” said Ando. “We analyzed high-quality images from this sensitive camera to look really closely into these permanently shaded areas and investigate whether water ice in these regions leads to widespread brightening of the surface.”

While the ice in the shaded regions did not significantly brighten the surface, the team’s analysis of the ShadowCam images helps to refine the estimate of the amount of ice that could be on the lunar surface. Li’s previous method suggested that the lunar surface contains between five and 30 percent water ice. The analysis of Shadow Cam images narrows the range—indicating that water ice makes up less than 20 percent of the lunar surface. 

Cosmic rays help search for buried ice

In addition to these investigations of lunar ice at the surface, another group of UH Mānoa researchers with HIGP and Department of Physics and Astronomy recently published a study in Geophysical Research Letters that outlines an innovative approach to detect buried ice deposits at the Moon’s poles.

“With our recent study, we showed that a new technique for detecting buried water ice on the Moon is possible using naturally-occurring cosmic rays,” said Emily S. Costello, study lead author and postdoctoral researcher at HIGP. “These ultra-high-energy cosmic rays strike the lunar surface and penetrate to the layers below. The rays emit radar waves that bounce off buried ice and rock layers, which we can use to infer what’s below the surface.”

The team used an advanced computer simulation that tests how radar waves travel through the lunar soil and how they encode information about possible buried ice layers.

“This method for searching for water ice on the Moon is brand new and really exciting,” said Christian Tai Udovicic, a co-author on the study who presented the findings at the recent Lunar and Planetary Science Conference in Houston, Texas. “Since it relies on high-energy physics that only a few scientists in the world are experts in, even planetary scientists who are studying ways to find lunar water ice are often surprised when they hear about this technique.”

A team of HIGP and Physics Department researchers are working to assemble a radar instrument specifically tuned to listen for these signals on the Moon and hope to test the full system by early 2026. They will look for opportunities to send it to the Moon to hopefully detect large deposits of buried water ice on the Moon for the first time. 

“More and more, Hawai‘i is becoming a hub for space exploration, and specifically the exploration of the Moon,” said Costello. “These projects, led by UH Mānoa scientists, represent up-and-coming opportunities for students and professionals in Hawai‘i to lead and participate in the budding space industry.”