Banner image: Shadows on the moon as seen by NASA's Lunar Reconnaissance Orbiter. (Credit:听NASA/GSFC/Arizona State University)
Hidden pockets of water could be much more common on the surface of the moon than scientists once suspected, according to new research led by CU Boulder. In some cases, these tiny patches of ice might exist in permanent shadows no bigger than a penny.
鈥淚f you can imagine standing on the surface of the moon near one of its poles, you would see shadows all over the place,鈥� said Paul Hayne, assistant professor in the at CU Boulder. 鈥淢any of those tiny shadows could be full of ice.鈥�
In a study , Hayne and his colleagues explored phenomena on the moon called 鈥渃old traps鈥濃�攕hadowy regions of the surface that exist in a state of eternal darkness.听
Many have gone without a single ray of sunlight for potentially billions of years. And these nooks and crannies may be a lot more numerous than previous data suggest. Drawing on detailed data from NASA鈥檚 Lunar Reconnaissance Orbiter, the researchers estimate that the moon could harbor roughly 15,000 square miles of permanent shadows in various shapes and sizes鈥攔eservoirs that, according to theory, might also be capable of preserving water via ice.
Future lunar residents, in other words, may be in luck.听
Top: Sunlight catches the rim of Shackleton Crater near the moon's south pole; bottom: Using computer simulations, Paul Hayne and his colleagues developed a hypothetical temperature map (left) in kelvin of a small stretch of the lunar surface. For comparison is a photo taken by Apollo 14 astronauts (right) of a patch of moon about the same size.听(Credit:听NASA/GSFC/Arizona State University; Paul Hayne,听NASA)
鈥淚f we鈥檙e right, water is going to be more accessible for drinking water, for rocket fuel, everything that NASA needs water for,鈥� said Hayne, also of the Department of Astrophysical and Planetary Sciences.听
Visiting a crater
To understand cold traps, first take a trip to Shackleton Crater near the moon鈥檚 south pole. This humungous impact crater reaches several miles deep and stretches about 13 miles across. Because of the moon鈥檚 position in relation to the sun, much of the crater鈥檚 interior is permanently in shadow鈥攁 complete lack of direct sunlight that causes temperatures inside to hover at around minus 300 degrees Fahrenheit.
鈥淵ou look down into Shackleton Crater or Shoemaker Crater, you鈥檙e looking into this vast, dark inaccessible region,鈥� Hayne said. 鈥淚t鈥檚 very forbidding.鈥�
That forbidding nature, however, may also be key to these craters鈥� importance for planned lunar bases. Scientists have long believed that such cold traps could be ideal environments for hosting ice鈥攁 valuable resource that is scarce on the moon but is occasionally delivered in large quantities when water-rich comets or asteroids crash down.
鈥淭he temperatures are so low in cold traps that ice would behave like a rock,鈥� Hayne said. 鈥淚f water gets in there, it鈥檚 not going anywhere for a billion years.鈥�
In their latest research, however, Hayne and his colleagues wanted to know how common such traps might be. Do they only exist in big craters, or do they spread over the face of the moon?
To find out, the team pulled data from real-life observations of the moon, then used mathematical tools to recreate what its surface might look like at a very small scale. The answer: a bit like a golf ball.听
Based on the team鈥檚 calculations, the moon鈥檚 north and south poles could contain a tremendous number of bumps and knicks capable of hosting permanent shadows鈥攎any of them just a centimeter wide. Previous estimates pegged the area of cold traps on the moon at substantially less than what Hayne and his colleagues have predicted.
Mining for water
Hayne notes that his team can鈥檛 prove that these shadows actually hold pockets of ice鈥攖he only way to do that would be to go there in person or with rovers and dig.听
But the results are promising, and future missions could shed even more light, literally, on the moon鈥檚 water resources. Hayne, for example, is leading a NASA effort called the Lunar Compact Infrared Imaging System (L-CIRiS) that will take heat-sensing panoramic images of the moon鈥檚 surface near its south pole in 2022.听
If his team鈥檚 findings bear out, locating the ingredients for a hot shower on the moon may have just gotten a lot easier.听
鈥淎stronauts may not need to go into these deep, dark shadows,鈥� Hayne said. 鈥淭hey could walk around and find one that鈥檚 a meter wide and that might be just as likely to harbor ice.鈥�
Coauthors on the new study include Oded Aharonson and Norbert Sch枚rghofer of the Weizmann Institute of Science and the Planetary Science Institute.
