The presence of water ice on the Moon is one of the most significant discoveries in planetary science of the last few decades. It transforms the Moon from a barren rock into a potential cosmic gas station, with water that could be harvested for drinking, breathing oxygen, and—crucially—rocket fuel. However, despite multiple mission confirmations, scientists say the crucial challenge is no longer if water is on the Moon, but establishing exactly where it is, how much is available, and how deep it is buried to be considered a usable resource. The answer, according to researchers, is that we need a more precise map—we need to know where to look.
The Confirmation and The Uncertainty
The initial, definitive proof of substantial water ice came in 2009 when NASA's Lunar Crater Observation and Sensing Satellite (LCROSS) was purposely crashed into a crater at the lunar south pole. The resulting ejecta cloud confirmed the presence of water ice, with measurements indicating around 6% ice content in that specific spot. While this was a monumental finding, it was a "single-shot experiment," and follow-up spectroscopic detections from orbiters have often been described by scientists as "hopelessly incoherent" and leading to many 'maybe' observations.
Further complicating the picture, NASA’s SOFIA (Stratospheric Observatory for Infrared Astronomy) later confirmed water molecules on the sunlit surface of the Moon. This proved water is more globally distributed than previously thought, but the concentration is incredibly low—estimated to be the equivalent of a 12-ounce bottle of water dispersed throughout a cubic meter of soil. This surface water is likely formed by micrometeorite impacts or the solar wind.
What's Missing: The Three Key Knowledge Gaps
To move from scientific confirmation to resource utilization—a critical step for NASA’s Artemis program and international lunar ambitions—scientists have identified three major missing pieces of data:
A Comprehensive Volatiles Survey: There is a lack of robust mapping for water ice, especially in the most promising areas, the Permanently Shadowed Regions (PSRs). In these extremely cold, perpetually dark craters, water ice is stable and preserved. We need definitive measurements of the ice content to turn speculative deposits into known, recoverable resources.
Vertical Distribution Knowledge: Most current data is on surface or near-surface composition. Scientists lack knowledge of how volatiles distribute vertically—how deep the water ice layer is. This is vital for designing the proper drilling and excavation equipment.
In-Situ Sampling and Analysis: Finally, a lack of physical sampling means we don't fully understand the origins of the volatiles or their physical state. Is the water in ice chunks, mixed with regolith (soil), or chemically bound? We need definitive and reproducible evidence from multiple locations.
The Hunt is On: The VIPER Mission
To answer these pressing questions, NASA is relying on the Volatiles Investigating Polar Exploration Rover (VIPER).
VIPER, about the size of a golf cart, is the first-ever resource mapping mission on another celestial body. Its primary goal is to get a close-up view of the location and concentration of water ice near the lunar south pole. The rover is equipped with four science instruments, most notably a 1-meter drill designed to excavate the lunar regolith and a suite of spectrometers to analyze the composition of the retrieved samples.
The rover will venture into the hazardous, pitch-black PSRs, which are among the coldest places in the solar system (some reaching -400°F). It is designed to navigate the challenging terrain and extreme thermal environment for its approximately 100-Earth-day mission. The data VIPER collects is intended to inform the first global water resource maps of the Moon, paving the way for the establishment of a sustainable, long-term human presence as part of the Artemis program.
The Moon holds water, but the difference between having water and having a resource is the ability to locate and access it efficiently. Until VIPER or similar missions provide high-resolution, definitive data on the depth, concentration, and lateral distribution of the ice, the abundance of usable lunar water remains uncertain—stressing the fact that we can find it, but only if we know precisely where to look.