Moon's largest crater may be rich in ice: Study

The interiors of polar craters on the moon are in nearly perpetual darkness, making them cold traps that researchers have long suspected might be home to vast amounts of frozen water and thus key candidates for human exploration.

However, previous orbital and Earth-based observations of lunar craters have yielded conflicting interpretations over whether ice is there.

Now scientists who have mapped Shackleton Crater, which is more than 19 km wide and 3km deep (as deep as Earth's oceans),

With unprecedented detail have found evidence of ice inside the crater.

NASA's Lunar Reconnaissance Orbiter essentially illuminated the crater's interior with infrared laser light, measuring how reflective it was.

The crater's floor is more reflective than that of other nearby craters, suggesting it had ice.

"Water ice in amounts of up to 20 per cent is a viable possibility," study lead author Maria Zuber, a geophysicist at the Massachusetts Institute of Technology, told SPACE.Com.

Don't get your hopes up, though.

The amount of ice in Shackleton Crater "can also be much less, conceivably as little as zero," Zuber cautioned.

This uncertainty is due in part to what the researchers saw in the rest of the crater.

Bizarrely, while the crater's floor was relatively bright, Zuber and her colleagues observed that its walls were even more reflective, the researchers reported in the journal Nature.

Scientists had thought that if highly reflective ice were anywhere in a crater, it would be on the floor, which live in nearly permanent darkness.

In comparison, the walls of Shackleton Crater occasionally see daylight, which should evaporate any ice that accumulates.

The researchers think the reflectance of the crater's walls is due not to ice, but to quakes. (MORE)