Illumination map of Shackleton crater (circle just to the right of center). The area within the crater that receives no solar light (i.e., lies permanently in shadow) is believed to maintain a temperature of about 40 K (-233 °C or -388 °F). If water vapor has been deposited there, it should remain frozen at or below the surface.
The walls of the Moon’s Shackleton crater are likely the site of small patches of ice.
Thanks to the Mini-RF radar on NASA’s Lunar Reconnaissance Orbiter (LRO), data collected show that small patches of ice could make up at most 5 to 10 percent of material in walls of the crater.
“These terrific results from the Mini-RF team contribute to the evolving story of water on the moon,” says LRO’s deputy project scientist, John Keller of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Several of the instruments on LRO have made unique contributions to this story, but only the radar penetrates beneath the surface to look for signatures of blocky ice deposits,” he said in a press statement.
A team of researchers led by Bradley Thomson at Boston University’s Center for Remote Sensing reported the findings in a paper recently published in the journal Geophysical Research Letters.
According to Mini-RF’s principal investigator, Ben Bussey of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.: “The interior of this crater lies in permanent shadow and is a ‘cold trap’ – a place cold enough to permit ice to accumulate.” The radar results, he added, are consistent with the interior of Shackleton containing a few percent ice mixed into the dry lunar soil.
The radar measurements of Shackleton crater were made during three separate observations between December 2009 and June 2010.
Radar illuminates shadowed regions and can detect deposits of water or ice, which have a distinctive radar polarization signature compared to the surrounding material.
Thanks to the new findings, and other data regarding water on the Moon, Shackleton crater is gathering momentum as a high-priority target for future exploration.
By Leonard David