According to a recent analysis from NASA’s Lunar Reconnaissance Orbiter (LRO) mission, the presence of ice in lunar dust and rock (regolith) is much more widespread than previously understood. This ice is a crucial resource for future missions to the Moon. It can serve multiple purposes: providing radiation protection, supporting human explorers, or being separated into hydrogen and oxygen to create rocket fuel, energy, and breathable air.
According to a recent analysis from NASA’s Lunar Reconnaissance Orbiter (LRO) mission, the presence of ice in lunar dust and rock (regolith) is much more widespread than previously understood. This ice is a crucial resource for future missions to the Moon. It can serve multiple purposes: providing radiation protection, supporting human explorers, or being separated into hydrogen and oxygen to create rocket fuel, energy, and breathable air.
Past research identified signs of ice primarily in larger, permanently shadowed regions (PSRs) close to the lunar South Pole, including specific craters like Cabeus, Haworth, Shoemaker, and Faustini. However, the latest findings indicate, “We find that there is widespread evidence of water ice within PSRs outside the South Pole, extending to at least 77 degrees south latitude,” explained Dr. Timothy P. McClanahan from NASA’s Goddard Space Flight Center and lead author of the study published on October 2 in the Planetary Science Journal.
This study is beneficial for those planning lunar missions as it includes maps and identifies surface characteristics that indicate where ice is more or less likely to be found. “Our model and analysis show that the highest concentrations of ice are expected near the coldest parts of the PSRs, which are below 75 Kelvin (-198°C or -325°F), and at the base of the slopes facing the pole,” McClanahan noted.
“While we cannot accurately measure how much ice is present in the PSRs or confirm if it is buried beneath a dry layer of regolith, we estimate that for every surface area of 1.2 square yards (1 square meter) over these deposits, there should be at least five additional quarts (five liters) of ice within the top 3.3 feet (1 meter) of the surface, compared to surrounding areas,” said McClanahan. The study also identified areas with fewer, smaller, or less concentrated ice deposits, mainly located in warmer, periodically sunlit regions.
Ice can become trapped in lunar regolith through impacts from comets and meteors, through vapor released from the Moon’s interior, or from chemical reactions between hydrogen from the solar wind and oxygen in regolith. PSRs are typically found in low-lying areas near the Moon’s poles, where the low angle of sunlight has kept these regions in darkness for billions of years, leading to extremely cold temperatures. Ice molecules can be dislodged from the regolith by meteor impacts, radiation, or sunlight, traveling across the lunar surface until they settle in a PSR and become trapped in the intense cold. The consistently cold surfaces in PSRs can preserve these ice molecules for billions of years, potentially forming deposits that are substantial enough to mine. Ice tends to vanish quickly in areas exposed to direct sunlight, making it challenging to accumulate in those locations.
The research team employed LRO’s Lunar Exploration Neutron Detector (LEND) instrument to identify ice deposits by measuring moderate-energy “epithermal” neutrons. They specifically utilized LEND’s Collimated Sensor for Epithermal Neutrons (CSETN), which operates within a fixed 18.6-mile (30-kilometer) diameter field-of-view. Neutrons are produced by high-energy cosmic rays, originating from astronomical events such as supernovae, which impact the Moon’s surface, fracture regolith atoms, and scatter the subatomic neutrons. These neutrons can be detected by LEND as they travel through the regolith, originating from depths up to about 3.3 feet (1 meter). A collision with hydrogen, which has a similar mass to a neutron, results in a more significant energy loss for the neutron compared to collisions with other common elements in regolith, creating a corresponding drop in the number of detected neutrons where hydrogen is present.
“We proposed that if all PSRs have uniform hydrogen concentrations, then CSETN should proportionately detect these concentrations based on their areas. Therefore, larger PSRs should show more hydrogen,” McClanahan stated.
This model was based on theoretical research that illustrated how hydrogen-enriched PSRs could be detected using CSETNs with a fixed-area field-of-view. A correlation was established using neutron emissions from 502 PSRs, ranging in size from 1.5 square miles (4 km2) to 417 square miles (1079 km2), contrasting with surrounding areas that had less hydrogen. The expected correlation was weak for smaller PSRs but became stronger with larger PSRs.
This research was supported by the LRO project science team, NASA’s Goddard Space Flight Center’s Artificial Intelligence Working Group, and NASA grant number 80GSFC21M0002. It utilized instruments including NASA’s LRO Diviner radiometer and Lunar Orbiter Laser Altimeter. The LEND instrument was developed by Russia’s Roscosmos through its Space Research Institute (IKI) and was integrated into the LRO spacecraft at NASA’s Goddard Space Flight Center, which manages the LRO mission for NASA’s Science Mission Directorate in Washington.
