A new study of lunar volcanic glasses that were collected by Apollo missions in the late 1960s and early 1970s unveiled that the Moon's interior did hold water. This suggests that water has been a part of the Moon since its early existence and challenges some elements of the theory of how the Moon formed.
The team then confirmed through a series of tests that hydrogen had been present all along, and the samples had not been infused by hydrogen-rich solar winds or tainted by other volatiles.
"This confirms that water comes from deep within the mantle of the Moon," said lead author Alberto Saal, assistant professor of geological sciences at Brown University.
"It has nothing to do with secondary processes, such as contamination or solar wind."
The researchers believe the water was contained in magma which erupted via "fire fountains" on to the lunar surface more than three billion years ago.
About 95% of this water vapour was lost during the volcanic activity.
"Since the Moon was thought to be perfectly dehydrated, this is a giant leap from previous estimates," said co-author Erik Hauri, from the Carnegie Institution.
"It suggests the intriguing possibility that the Moon's interior might have had as much water as the Earth's upper mantle. But even more intriguing: If the Moon's volcanoes released 95% of their water, where did all that water go?"
Since the Moon's gravity is too feeble to retain an atmosphere, the researchers speculate that some of the water vapour from the eruptions was probably forced into space.