June 24, 2009

Lunar neutral hydrogen atoms discovered

The U.S. space agency says its Interstellar Boundary Explorer has made the first detection of very fast neutral atoms emanating from the moon.

The discovery came during the spacecraft's commissioning, when scientists turned on the IBEX-Hi instrument, which measures atoms with speeds from about half a million to 2.5 million miles per hour.

Just after we got IBEX-Hi turned on, the moon happened to pass right through its field of view, and there they were, said David McComas, IBEX principal investigator. The instrument lit up with a clear signal of the neutral atoms being detected as they backscattered from the moon.

The discovery, NASA said, comes after decades of speculation and unsuccessful searching for such lunar neutral atoms.

IBEX -- the latest in NASA's series of low-cost, rapidly developed spacecraft -- was built to primarily observe and map the complex interactions occurring at the edge of the solar system, NASA said the spacecraft carries the most sensitive neutral atom detectors ever flown in space, enabling researchers to not only measure particle energy, but also to make precise images of where they are coming from.

The new findings appear in the journal Geophysical Research Letters.