For years, scientists have wondered whether there might be water ice on the Moon’s surface. The question is of more than academic interest, because ice could be used by a future Moon base to produce oxygen to breathe and hydrogen to fuel spacecraft.
Since almost all of the Moon is exposed to sunlight, ice could exist only in the few areas that are in permanent shadow — the inside walls and floors of certain craters near the poles. One candidate is Shackleton crater, which is about 13 miles in diameter and 2.5 miles deep.
But images taken by a Japanese spacecraft throw hot water on the idea that Shackleton might have surface ice. Since parts of the crater are in permanent shadow, the images relied for illumination on sunlight glancing off the walls on the opposite side.
In an analysis of the images published in Science, Junichi Haruyama of the Japan Aerospace Exploration Agency and colleagues report that the area is certainly cold enough to harbor ice, but that the reflectance indicates there is only soil on the surface. If ice does exist there, they say, it is probably mixed in small concentrations with the soil.