In March, 1998, NASA announced that an unmanned lunar spacecraft had discovered up to 6 billion tons of ... what? ... on the moon?

This major 1998 announcement came from data gathered by the Lunar Prospector spacecraft. For decades, scientists had theorized that water could exist on the moon, but this was the first strong evidence. The discovery wasn't made with a camera, but with an instrument called a neutron spectrometer. This device detected high concentrations of hydrogen atoms, a key component of water (H2O), mixed in with the soil. The most logical explanation for that much hydrogen in those specific locations was the presence of frozen (Review) water.

The key to its existence is location. The ice was found not on the sunlit surface, but hidden within permanently shadowed craters at the lunar poles. In these incredibly cold, dark regions, temperatures can plummet below -238 degrees Celsius (-397 Fahrenheit). Sunlight has not directly struck the floor of some of these craters for billions of years, allowing ice delivered by comets and asteroids to accumulate and remain perfectly preserved.

This finding was revolutionary because it transformed the moon from a barren, dry rock into a potential resource depot for future human exploration. Access to local water could mean providing drinking water, breathable oxygen (by splitting the water molecules), and even the components for rocket fuel. This dramatically increases the feasibility of establishing a sustainable, long-term human presence on the moon and beyond.