NASA’s Water-Hunting Tool Will Help Scout Moon’s South Pole 

NASA is joining international partners to search for ice on the Moon to support future human exploration. The agency is providing a water detection instrument, the Neutron Spectrometer System (NSS), to the Lunar Polar Exploration (LUPEX) mission led by JAXA (Japan Aerospace Exploration Agency) and ISRO (Indian Space Research Organization).

The instrument, which detects ice beneath the lunar surface, will be installed on the LUPEX lunar rover, which is expected to arrive at the Moon no earlier than 2028. NASA’s support for LUPEX is part of an ongoing effort to identify and characterize lunar water and other materials that readily evaporate near the Moon’s south pole.

Water is an essential material for NASA’s plans to develop a sustainable presence on the Moon. Instead of relying solely on resources from Earth, astronauts could use water from the Moon to produce breathable air, rocket fuel, and more. The first step is to find deposits of significant amounts of water near the surface to mark potential landing zones for future astronauts. Water on the Moon is found primarily as molecules in lunar regolith, the dusty, rocky material that covers the Moon’s surface, but there may be ice deposits beneath the surface of the lunar South Pole. Once we better understand the quantity and quality of resources available, we can learn how to exploit them for exploration.

“There is currently a gap in our understanding of the distribution of lunar ice at small scales, from 10 centimeters to 10 kilometers,” said Rick Elphic, NSS manager at NASA’s Ames Research Center in California’s Silicon Valley, where the instrument was developed in collaboration with the Lockheed Martin Advanced Technology Center in Palo Alto, California. “The only way to understand where and how much lunar ice is to explore the surface at these scales.”

How neutrons signal water

Scientists can search for water on the Moon without drilling into the surface. Instead, they look for concentrations of hydrogen, the H in H₂O. Previous missions to lunar orbit have found signs of water at the Moon’s poles, but ground missions are needed to establish detailed maps of its location and quantity.

Instruments like NSS can infer the presence of hydrogen by detecting interactions with particles called neutrons. Neutrons are constantly moving in the lunar soil and are about the same size as hydrogen atoms. When these two particles interact, fewer medium-energy neutrons are ejected from the ground. The absence of medium-energy neutrons suggests that more particles are interacting with underground hydrogen, a deficit that can be measured with the right tools.

The NSS instrument uses a “gas proportional counter” to detect neutrons bouncing off the lunar soil. It has two tubes containing a rare gas called helium-3, which is very sensitive to neutrons. When neutrons strike helium-3 atoms, the gas produces electrical pulses that can be counted to infer the presence and amount of hydrogen up to three feet underground.

Water chaser series

The ongoing investigation of the Moon’s water will help determine how astronauts might access it in the future. To this end, NASA researchers in Ames have developed a series of NSS instruments intended to be carried aboard different missions to study sites at the Moon’s South Pole.

The first Moon-bound NSS instrument in the series was carried aboard Astrobotic’s Peregrine lander, Astrobotic Peregrine Mission One, launched in January 2024. That mission ended without landing on the lunar surface, but the onboard NSS powered on and operated for several days during the 10-day mission. These operations successfully captured data on the deep space particle background, which strongly supported NSS operations on future missions.

NASA’s Volatiles Investigating Polar Exploration Rover (VIPER) mission, part of the agency’s Artemis campaign, will carry another NSS. As part of NASA’s continued efforts in commercial lunar payload services, a fourth NSS instrument will board the MoonRanger “micro rover” developed by Carnegie Mellon University in Pittsburgh.

“The next three NSS rover expeditions will tell us what kinds of places on the Moon are most likely to host ice,” Elphic said. “Missions to the lunar surface can then be planned to similar sites where ice can be found.”

The neutron spectrometer system was jointly developed by NASA Ames Research Center and the Lockheed Martin Advanced Technology Center in Palo Alto, California.

For more information on water science on the Moon, visit:

https://science.nasa.gov/moon/moon-water-and-ices

Karen Fox / Molly Wasser
Headquarters, Washington
240-285-5155 / 240-419-1732
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov

Arezu Sarvestani
Ames Research Center, Silicon Valley
650-613-2334
arezu.sarvestani@nasa.gov