Misleading mineral overestimates water.

• Position: The Moon

The amount of water present in the moon may have been overestimated by scientists studying the mineral apatite, says a team of researchers led by Jeremy Boyce of the UCLA Department of Earth, Planetary, and Space Sciences.

Boyce and his colleagues created a computer model to predict how apatite would have crystallized from cooling bodies of lunar magma early in the moon's history. Their simulations revealed that the unusually hydrogen-rich apatite crystals observed in many lunar rock samples may not have formed within a water-rich environment, as originally thought. This discovery has overturned the long-held assumption that the hydrogen in apatite is a good indicator of overall lunar water content.

"The mineral apatite is the most widely used method for estimating the amount of water in lunar rocks, but it cannot be trusted," explains Boyce, adjunct assistant professor in the College of Letters and Science. "Our new results show that there is not as much water in lunar magma as apatite would have us believe."

For decades, scientists thought the moon almost entirely was devoid of water. However, the discovery of hydrogen-rich apatite within lunar rocks in 2010 seemed to hint at a more watery past. Researchers originally assumed that information obtained from a small sample of apatite could predict the original water content of a large body of magma.

Boyce believes the high water content within lunar apatite results from a quirk in the crystallization process rather...