The Lunar Reconnaissance Orbiter (LRO), launched in June to survey the moon with an eye toward a human return there, is already hard at work. At a news conference from the Goddard Space Flight Center in Greenbelt, Md., NASA presented preliminary results from the spacecraft's instruments, which have just finished a transition from the commissioning to operational phases.

In its one-year primary mission, LRO will seek to map the moon in great detail, measure the radiation that human tissue would be subjected to during a lengthy lunar stay, and search for traces of water ice on the lunar surface. Water would be an invaluable resource for future lunar explorers—astronauts could save enormous amounts of launch weight if they did not have to carry their own water supply.

If the moon harbors ice, it would likely be sequestered in polar craters that remain shadowed from the sun year-round. Although LRO has yet to uncover any blockbuster evidence, the preliminary data from the orbiter at least bode well for the water-ice hunt.

Richard Vondrak, project scientist for the LRO mission, said that the spacecraft's Diviner instrument, which maps the temperature of the lunar surface, showed that the craters are indeed cold enough to trap volatiles such as water. In fact, he said, those permanently shadowed craters may be the coldest places in the solar system.

The Lunar Exploration Neutron Detector (LEND), a Russian-developed instrument that looks for low-energy neutrons to infer the presence of hydrogen, which might mark the location of water ice, confirmed that the lunar poles harbor hydrogen. What is more, Vondrak said, that hydrogen signature is not confined to the shadowy craters. It is worth noting, however, that a neutron detector on board NASA's Lunar Prospector found what was initially hailed as evidence of water ice in 1998, but that finding has since been cast into doubt.

Yet another LRO instrument, the Lyman-Alpha Mapping Project (LAMP), also looks for indications of hydrogen by tracking the lunar surface's absorption of ultraviolet light. At least one such crater showed a possible hydrogen signature, Vondrak said, but the early LAMP results could also be explained by texturing in the crater's interior.

Next month will bring another early test of LRO's instrumentation. The Lunar Crater Observation and Sensing Satellite (LCROSS), launched along with LRO, will perform a two-part bombardment of a south polar crater known as Cabeus A to see what billows up from within. LRO will pass overhead minutes later, Vondrak said, to provide lunar scientists with their closest look at the LCROSS debris plume.

Daytime temperature map of the moon from the Diviner instrument (purple corresponds to a temperature of roughly –400 degrees Fahrenheit; red is roughly 200 degrees F): NASA/GSFC/UCLA