Micro cold traps on the Moon

Water ice is thought to be trapped in large permanently shadowed regions in the Moon's polar regions, due to their extremely low temperatures. Here, we show that many unmapped cold traps exist on small spatial scales, substantially augmenting the areas where ice may accumulate. Using theoretical models and data from the Lunar Reconnaissance Orbiter, we estimate the contribution of shadows on scales from 1 km to 1 cm, the smallest distance over which we find cold-trapping to be effective for water ice. Approximately 10-20% of the permanent cold-trap area for water is found to be contained in these micro cold traps, which are the most numerous cold traps on the Moon. Consideration of all spatial scales therefore substantially increases the number of cold traps over previous estimates, for a total area of similar to 40,000 km(2), about 60% of which is in the south. A majority of cold traps for water ice is found at latitudes > 80 degrees because permanent shadows equatorward of 80 degrees are typically too warm to support ice accumulation. Our results suggest that water trapped at the lunar poles may be more widely distributed and accessible as a resource for future missions than previously thought.

Automated summary

Water ice is believed to be trapped in large permanently shadowed regions in the lunar polar regions, but recent studies have revealed the presence of numerous small-scale cold traps, significantly expanding the areas where ice may accumulate. The majority of cold traps for water ice are found at latitudes greater than 80 degrees, with permanent shadows equatorward of 80 degrees typically too warm for ice accumulation to occur. This suggests that water resources at the lunar poles may be more widespread and accessible than previously thought.