The moon's oldest and darkest craters could be hiding the most water ice, hidden in permanently shadowed craters at the lunar south pole. The research suggests that the water probably arrived on the surface gradually rather than in one big event. The discovery comes as NASA's Artemis 2 mission continues to put lunar exploration back on the map. Water on the moon could be used for drinking, split into hydrogen and oxygen atoms for rocket fuel and air to breath. However, the source of the moon's water has been a mystery since it was discovered in 1994 by NASA's Clementine mission. The findings could be significant for future astronauts and suggest that the moon has been accumulating water continuously for up to 3 or 3.5 billion years.