"We see X-rays from these elements directly, independent of assumptions about the mineralogy and other complications," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts.

One theory on the formation of the Moon is that a body the size of Mars collided with Earth 4.5 billion years ago, flinging molten debris out of the Earth's mantle in the impact.

Over tens of millions of years, so the theory goes, the debris formed the Moon.

By measuring the oxygen, magnesium, aluminum and silicon across a wide area of the lunar surface and comparing them with the Earth's mantle, Drake and his colleagues plan to test the hypothesis.

"We have Moon samples from the six widely-spaced Apollo landing sites, but remote sensing with Chandra can cover a much wider area," Drake told a press conference at the "Four Years with Chandra" symposium in Huntsville, Alabama.

Data from Chandra also allowed a glimpse into the mystery of X-rays previously perceived as coming from the far side of the Moon.

"Our results strongly indicate that the so-called dark Moon X-rays do not come from the dark side of the Moon," said Brad Wargelin, also of the CfA.

"The observed X-ray spectrum, the intensity of the X-rays, and the variation of the X-ray intensity with time, can all be explained by emission from Earth's extended outer atmosphere, through which Chandra is moving," Wargelin said.

SPACE.WIRE