Helium detected in Moon's thin atmosphere

An instrument aboard a NASA orbiter has detected helium in the moon's tenuous atmosphere, the space agency said. These remote-sensing observations by the Lunar Reconnaissance Orbiter confirm measurements taken in 1972 by an experiment deployed on the moon's surface by Apollo 17, a NASA release reported Wednesday. The instrument aboard the LRO examined ultraviolet emissions in the tenuous atmosphere above the lunar surface, detecting helium in measurements spanning more than 50 orbits. "The question now becomes, does the helium originate from inside the moon, for example, due to radioactive decay in rocks, or from an exterior source, such as the solar wind?" said Alan Stern of the Space Science and Engineering Division at Southwest Research Institute, Boulder, Colo. "If we find the solar wind is responsible, that will teach us a lot about how the same process works in other airless bodies," Stern said. If additional observations rule out the solar wind, then radioactive decay or other internal lunar processes could be producing helium that diffuses from the moon's interior or is released during lunar quakes, scientists said. "These ground-breaking measurements were enabled by our flexible operations of LRO as a Science Mission, so that we can now understand the moon in ways that were not expected when LRO was launched in 2009," Richard Vondrak, LRO project scientist at NASA's Goddard Space Flight Center, Greenbelt, Md., said.