Carbon dioxide cold traps offer potential lunar resource
"After water, carbon is probably the most important resource on the Moon. It can be used for the production of rocket fuel, but also for biomaterials and steel. If we have to bring carbon or fuel from earth, it drives up the cost of sustained presence. It's part of 'living off the land,' or in-situ resource utilization," said Schorghofer, lead author of "Carbon Dioxide Cold Traps on the Moon" which appears in Geophysical Research Letters. PSI's Matthew A. Siegler is a co-author on the paper.
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 by the Diviner Lunar Radiometer Experiment on board NASA's Lunar Reconnaissance Orbiter establishes the existence of carbon dioxide cold traps on the Moon, which potentially host high concentrations of solid carbon dioxide, Schorghofer said. "Our work has established the existence of CO2 cold traps, where theory predicts solid CO2 should have accumulated. Our work does not show that there actually is CO2 in these areas, but it is a reasonable expectation, especially since CO2 was detected in the LCROSS (NASA's Lunar Crater Observation and Sensing Satellite) impact plume in 2009."
In the new study, many terabytes of Diviner data were processed to capture the full time dependence of surface temperatures. The Moon actually has seasons; the lunar year is about 347 Earth days long, a period known as the "Draconic year." These seasons are not noticeable on most of the lunar surface, but they are important within the permanently shadow areas where H2O and CO2 cold traps lie. Carbon dioxide ice is lost to space only during a short period in summer.
The total area of CO2 cold traps in the south polar region of the Moon is about 200 square kilometers. For comparison, water ice cold traps cover nearly 14,000 square kilometers. Concentrated CO2 is an extremely scarce resource, only found at a few places, and a large portion of its cold trap area resides on the floor of Amundsen Crater, which is relatively accessible, so it may be a promising exploration target. In this area, temperatures never exceed negative 350 degrees Fahrenheit, so it will definitely be a technological challenge to explore these extremely cold and permanently dark places.
Norbert Schorghofer et al, Carbon Dioxide Cold Traps on the Moon, Geophysical Research Letters (2021). DOI: 10.1029/2021GL095533
Provided by Planetary Science Institute