By Laurence Tognetti, MSc
March 28, 2025
Can the cosmic rays bombarding the lunar surface be used to identify subsurface water ice deposits? This is what a recent study and iposter presented at the 56th Lunar and Planetary Science Conference (LPSC) hopes to address as a team of researchers developed a novel method called the Cosmic Ray Lunar Sounder (CoRaLS) capable of detecting subsurface lunar water ice deposits that are elusive to current radar systems. This study has the potential to help expand the human presence on the Moon since water ice deposits are currently being focused on the permanently shadowed regions (PSRs) of the Moon for the upcoming Artemis missions.
Here, Universe Today discusses this incredible research with Dr. Christian Tai Udovicic, who is a research associate at the Hawai’i Institute of Geophysics and Planetology, regarding the motivation behind the study, the capabilities of CoRaLS based on depth and detections, next steps for the development of CoRaLS, and how CoRaLS could contribute to the upcoming Artemis missions. Therefore, what was the motivation behind the study?
“The main motivation behind CoRaLS is to search for elusive water ice at the lunar poles,” Dr. Tai Udovicic tells Universe Today. “We know that some ice exists in ultra-cold permanently shadowed craters on the Moon, but thus far we don’t see strong evidence for ice layers at the surface or in the upper few meters. Unlike traditional radar techniques that need a high powered antenna to emit radio waves that then only penetrate up to a few meters deep, CoRaLS will listen for radio waves from ultra-high-energy cosmic rays that penetrate several meters deep before emitting a radio pulse. These signals could reveal ice at depths of 5-10 meters for the first time.”
While the Earth has its protective magnetic field and ozone layer to shield the surface from harmful solar and cosmic radiation, the Moon completely lacks any type of atmosphere. As a result, deadly radiation constantly bombards the surface, making it difficult for future astronauts to live and work there without proper shielding. While traditional radar instruments obtain images and data by measuring the amount of reflected energy bounced back from the lunar surface, the depth it can reach is limited.
However, CoRaLS takes advantage of a phenomenon known as the Askaryan effect, which are radio pulses produced by the cosmic radiation interacting with the lunar regolith and can be detected as deep as several dozen meters beneath the lunar surface. Using a series of computer models, the researchers simulated a 2-year mission with CoRaLS in lunar orbit to ascertain the number of water ice detections it could make with the PSRs. In the end, the researchers determined CoRaLS could potentially make more than 100 detections of subsurface water ice in PSRs with a 1-meter-thick buried ice layer. But could the number of detections change based on the depth of the buried ice and/or the thickness of the buried ice?
“Since we don’t yet know how thick or deep buried lunar ice layers are, our team is working on a suite of simulations to plan for all possibilities and determine the number of detections in different cases,” Dr. Tai Udovicic tells Universe Today. “In our most optimistic scenarios, we should exceed 100 detections every 2 years. However, if the ice layers are less distinct, or are deeper and more rare than previously thought, we would detect fewer. Regardless, CoRaLS would yield key insights into where, how deep, and how pure the ice at the lunar poles is – even in the unlikely case that it detects no ice layers at all.”
While CoRaLS is still being developed, it has made some admirably progress towards becoming a real spaceflight mission through NASA’s Technology Readiness Level (TRL) system, which is designed to gauge the maturity level of a developing technology. TRL is rated 1 to 9, with each TRL encompassing their own steps and to advance to the next TRL. TRL 1 consists of basic discussions of the technology and what it could potentially do, but no hardware has been assembled yet.
According to the study, the subsystems for CoRaLS is slated to reach TRL 3 to 5 sometime in 2025, meaning a technology has to achieve proof-of-concept, functional components in a laboratory environment, and functional components in a relevant environment, respectively. Additionally, all CoRaLS systems are slated to reach TRL 6 by 2026, meaning it can demonstrate a successful prototype on the ground or in space. But what will be the next steps once CoRaLS completes this?
“In general, the minimum level required to be selected for spaceflight is TRL 6, ‘Demonstration in a relevant environment’,” Dr. Tai Udovicic tells Universe Today. “To achieve TRL 6, we will assemble all components of the instrument (including individual electronics, the deployment system, and software needed to collect data) into a fully functional instrument that can detect a simulated cosmic ray signal. We will also need to show that the instrument can survive in a simulated space environment. From there, we will have an instrument that is ready to compete for a ride to the Moon on a future orbital mission.”
As noted, scientists are currently focused on finding buried water ice in the lunar PSRs due to the lack of sunlight since they exist at or near the lunar poles, and with the Moon’s 5-degree axial tilt, sunlight never reaches the depths of some of the PSR craters. This is why NASA’s Artemis program is focusing its efforts on landing astronauts near these PSRs with the goal of extracting the buried water ice and using it for drinking, oxygen, or fuel. Through this, future missions will greatly reduce the amount of water that has to be shipped from Earth in a practice known as in situ resource utilization (ISRU), commonly referred to as “living off the land”. Therefore, if CoRaLS becomes a reality, how could it potentially contribute to the upcoming Artemis missions, or perhaps Mars?
Dr. Tai Udovicic tells Universe Today, “CoRaLS would be a boon to the Artemis program’s core goal to characterize useful resources at the lunar south pole by indicating where to look for large buried ice deposits. Water ice could be an extremely valuable lunar resource, primarily since it can be used to produce rocket fuel and would facilitate NASA’s Moon to Mars strategy.”
As CoRaLS continues to be developed, Dr. Tai Udovicic and his team continue full steam ahead while conducting groundbreaking science with the goal of identifying buried lunar ice in previously unexplored regions of the Moon. This includes a very recent study expanding upon their LPSC study where the team’s simulations revealed their technique could identify water ice layers only 10 centimeters thick and buried as deep as 9 meters.
How will CoRaLS help identify buried lunar water ice in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!