The amount of water present on the moon may have been overestimated by scientists.
Researchers created a computer model that looked at lunar levels of a mineral called apatite, which is believed to have been created when bodies of magma cooled down in the distant past, a University of California- L.A. news release reported.
The model suggested many of the "hydrogen-rich apatite crystals" did not actually form in water-rich environments as researchers had previously believed.
"The mineral apatite is the most widely used method for estimating the amount of water in lunar rocks, but it cannot be trusted," Jeremy Boyce of the UCLA Department of Earth, Planetary and Space Sciences, said in the news release. "Our new results show that there is not as much water in lunar magma as apatite would have us believe."
Scientists long-believed the moon was completely dry, but the discovery of hydrogen-rich apatite in lunar rocks back in 2010 changed that idea. Scientists believed the mineral could hint at a lunar past of magma or even bodies of water, but this new study suggests apatite may be deceiving.
Boyce and his colleagues believe a glitch is what makes apatite appear to be water-rich.
"Early-forming apatite is so fluorine-rich that it vacuums all the fluorine out of the magma, followed by chlorine," Boyce said. "Apatite that forms later doesn't see any fluorine or chlorine and becomes hydrogen-rich because it has no choice."
Once the fluorine and chlorine become depleted the magma can shift from forming hydrogen-poor to hydrogen-rich apatite, which would not accurately reflect the magma's water content.
Researchers suggest the moon was formed when an ancient impact ripped a chunk out of the Earth; in this case the moon would have been completely molten, causing lighter elements such as hydrogen to bubble to the surface and escape into space. This would have left the moon completely dry.
Most lunar samples are consistent with this idea because they are dry and lacking in these lighter elements, despite the presence of misleading apatite.
"We had 40 years of believing in a dry moon, and now we have some evidence that the old dry model of the moon wasn't perfect," Boyce said. "However, we need to be cautious and look carefully at each piece of evidence before we decide that rocks on the moon are as wet as those on Earth."
Researchers hope to gain more insight into the moon's composition in future studies.
"We're knocking out one of the most important pillars of evidence regarding the conditions of the formation and evolution of the moon," Boyce said. "Next, we plan to determine how badly apatite has distorted our view of the moon and how we can best see past it to get at the moon's origin."
