Scientists using data from NASA’s Lunar Reconnaissance Orbiter, or LRO, have identified bright areas in craters near the moon’s south pole that are cold enough to have frost present on the surface. The icy deposits appear to be patchy and thin, and it’s possible that they are mixed in with the surface layer of soil, dust and small rocks called the regolith. The researchers say they are not seeing expanses of ice similar to a frozen pond or skating rink. Instead, they are seeing signs of surface frost. The frost was found in cold traps close to the moon’s south pole. Cold traps are permanently dark areas — located either on the floor of a deep crater or along a section of crater wall that doesn’t receive direct sunlight — where temperatures remain below minus 260 degrees Fahrenheit (minus 163 degrees Celsius). Under these conditions, water ice can persist for millions or billions of years.
Another tantalizing question is how old the moon’s ice is. If the water was delivered by icy comets or asteroids, it could be as ancient as the solar system and could mark the early delivery of water to Earth and the moon. But if the water was produced by chemical reactions driven by the solar wind, it is much more recent. Or both may be true. There could be eons-old ice deposits buried below ground and newer water at the surface.
Not only could the moon’s ice provide resources for exploration, it also might help us understand the origins of Earth’s water.