As cosmic real estate goes, few places are less desirable than the moon. Last week, however, the bleak world started to look more hospitable when scientists announced that it is home to a decidedly terrestrial feature: a mammoth field of ice.
For all the visits spacecraft and astronauts have made to the moon, they have limited their explorations to roughly equatorial areas, largely neglecting the polar regions. In 1994 NASA and the Pentagon launched a probe into a vertical lunar orbit that would reach those extreme latitudes.
One of the first things they looked for was water. Though moisture elsewhere on...