Although a simple, short sentence 'This finding means water is native to the moon,' the sentence is very important to the history of the Moon. This water, for the most part, did not come from impacts with asteroids, comets, and other celestial bodies. It was a part of the Moon when it first formed.
Francis McCubbin, the lead author of the study, stated, 'For over 40 years we thought the moon was dry. In our study we looked at hydroxyl, a compound with an oxygen atom bound with hydrogen, and apatite, a water-bearing mineral in the assemblage of minerals we examined in two Apollo samples and a lunar meteorite."
The study was published in the journal Proceedings of the National Academy of Sciences (PNAS).
Their PNAS article is entitled 'Nominally hydrous magmatism on the Moon.'
They state in the abstract to the paper: 'For the past 40 years, the Moon has been described as nearly devoid of indigenous water; however, evidence for water both on the lunar surface and within the lunar interior have recently emerged, calling into question this long-standing lunar dogma.'
Page two continues.
The crystalline rocks are called KREEP, which is short for potassium (K), Rare Earth Elements (REE), and phosphorus (P).
Specifically, they state, 'In the present study, hydroxyl (as well as fluoride and chloride) was analyzed by secondary ion mass spectrometry in apatite [Ca5(PO4)3(F,Cl,OH)] from three different lunar samples in order to obtain quantitative constraints on the abundance of water in the lunar interior.' [Paper]
They concluded, within their paper, the following
(1) ''¦ the minimum water content ranged from 64 parts per billion to 5 parts per million.'
(2) 'The result is at least two orders of magnitude greater than previous results from lunar samples that estimated water content of the moon to be less than 1 parts per billion.'
The NASA article conjectured on the present theory on the origin of the Moon. It states, 'The origin of the moon is now commonly believed to be the result of a Mars-sized object that impacted the Earth 4.5 billion years ago. This impact put a large amount of material into Earth's orbit that ultimately compacted to form the moon. The lunar magma ocean that is thought to have formed at some point during the compacting process, began to cool. During this cooling, water either escaped or was preserved as hydroxyl molecules in the crystallizing minerals.'
Andrew Steele, from Carnegie and one of the authors of the study, added, "Since water is insoluble in the main silicates that crystallized, we believed that it should have concentrated in those rocks. That's why we selected KREEP to analyze."
Page three concludes.
Besides Steele and McCubbin, the other authors include Erik H. Hauri (Carnegie Institution of Washington), Hanna Nekvasil (Stony Brook University), Shigeru Yamashita (Okayama University), and Russell J. Hemley (Carnegie Institution of Washington).
The researchers conclude in their paper, 'This work confirms that hundreds to thousands of ppm water (of the structural form hydroxyl) is present in apatite from the Moon. Moreover, two of the studied samples likely had water preserved from magmatic processes, which would qualify the water as being indigenous to the Moon.'
'The presence of hydroxyl in apatite from a number of different types of lunar rocks indicates that water may be ubiquitous within the lunar interior, potentially as early as the time of lunar formation. The water contents analyzed for the lunar apatite indicate minimum water contents of their lunar source region to range from 64 ppb [parts per billion] to 5 ppm [parts per million] H2O.'
'This lower limit range of water contents is at least two orders of magnitude greater than the previously reported value for the bulk Moon, and the actual source region water contents could be significantly higher.'