Water ice is expected to be trapped in permanently cold regions near the lunar poles. Other ices (super-volatiles) are trapped at lower temperatures, close to the lowest temperatures measured within the lunar permanently shadowed regions (PSRs). Here, the thermal stability of solid carbon dioxide in the south polar region is determined by analysis of 11 years of temperature measurements by Diviner, a radiometer onboard the Lunar Reconnaissance Orbiter. Sublimation rates averaged over a draconic year are far lower than peak sublimation rates. Small spatially contiguous pockets of CO2 ice stability are found in the craters Amundsen, Haworth, de Gerlache, and others, over a cumulative area of roughly 200 km(2). The LCROSS probe impacted one of those pockets and released CO2, serving as validation of the thermal stability calculations. Future surface missions can utilize this highly localized resource for the production of fuel, steel, and biological materials. Plain Language Summary Carbon-bearing species would be essential for sustained robotic or human presence on the Moon, for use in rocket fuel and biological materials. Various volatiles can be cold-trapped in permanently shadowed craters near the lunar poles. The existence of carbon dioxide cold traps has previously been surmised, but the required temperatures are near the lowest surface temperatures that have been reliably measured. Extensive and improved analysis of 11 years of orbital surface temperature measurements establishes the existence of carbon dioxide cold traps on the Moon, which potentially host high concentrations of solid carbon dioxide. Large CO2 cold traps are rare, however, and the geographic concentration of the resource will have policy implications. Key Points Time-dependent sublimation rates for CO2 are calculated based on 11 years of Diviner temperature measurements Extensive data analysis establishes the existence of carbon dioxide cold traps in the south polar region of the Moon Solid carbon dioxide is expected to be highly localized

Although some of the coldest surface temperatures in the entire Solar System are found near the poles of our own Moon, the thermophysical properties of lunar regolith at these ultracold temperatures (i.e., below similar to 150 K) are not well understood. Standard lunar thermal models generally match the surface temperatures observed by global orbital remote sensing data but are inconsistent with infrared data collected from ultracold polar terrain. We build upon previous theoretical work on the low-temperature physics of lunar regolith to introduce a global thermal conductivity model consistent with the temperature trends observed by the Diviner Lunar Radiometer Experiment (Diviner). This updated thermophysical model primarily affects nighttime surface temperatures, subsurface temperatures at high latitudes, and permanently shadowed regions (PSRs). An additional outcome of this thermophysical model is the ability to accommodate the surface temperature trends observed by Diviner both in warm low latitudes and cold high latitudes. Subsurface temperatures in near-polar craters are similar to 5-10 K warmer than previous thermal models, and cooler nighttime surface temperatures are observed globally. Model results of PSRs reveal larger surface temperature amplitudes (as observed by Diviner) and steeper geothermal gradients. A comprehensive understanding of lunar regolith's low-temperature thermal behavior is an essential step in modeling the potential location and quantity of cold trapped volatiles in the lunar south pole. Here, we hope to provide theoretical support and motivation for more complete low-temperature thermal conductivity laboratory measurements.

The Diviner Lunar Radiometer Experiment on NASA's Lunar Reconnaissance Orbiter will be the first instrument to systematically map the global thermal state of the Moon and its diurnal and seasonal variability. Diviner will measure reflected solar and emitted infrared radiation in nine spectral channels with wavelengths ranging from 0.3 to 400 microns. The resulting measurements will enable characterization of the lunar thermal environment, mapping surface properties such as thermal inertia, rock abundance and silicate mineralogy, and determination of the locations and temperatures of volatile cold traps in the lunar polar regions.