Evidence of Water in Moon’s Interior

A research team from Brown University has found for the first time evidence of water deep within the moon. The researchers believe the water was contained in lunar magmas ejected more than 3 billion years ago. The new discovery strongly suggests that water has been a part of the moon since its early existence, perhaps since it was first created.

The discovery of water evidence from deep within the moon strongly suggests that water has been a part of the moon for a long while; researchers even consider the possibility that the water existed there 4.5 billion years ago, during a cataclysmic collision between the early earth and a Mars-sized object. The study is published in the July 10 issue of the journal Nature and it was written by a team led by Alberto Saal, assistant professor of geological sciences at Brown University

The new study suggests that the water was contained in magma erupted from fire fountains onto the surface of the moon more than 3 billion years ago. About 95 percent of the water vapor from the magma was lost to space during this eruptive “degassing,” but traces of water vapor may have drifted toward the cold poles of the moon, where they may remain as ice in permanently shadowed craters. 

The water clue came from lunar volcanic glasses, pebble-like beads collected and returned to earth by NASA’s Apollo missions in the late 1960s and early 1970s. In the decades since, scientists have a set goal to determine the content and origin of a class of chemical elements known as volatiles in the multicolored glasses. In particular, they searched the glasses for any sign that will indicate to presence of water. However, such evidence had remained elusive, thus proving once again that the moon is dry. 

Now, that evidence has been found. “What is important for me is it’s telling me something about the origin of the moon and the earth and the presence of water at very early times,” said Saal, the paper’s lead author. Three other researchers from the Department of Geological Sciences at Brown – Professors Reid Cooper and Malcolm Rutherford, and graduate student Mauro Lo Cascio – contributed to the research along side Erik Hauri, from the Carnegie Institution for Science, who developed the analytical technique used to identify water and the other volatiles. 

Based on their observations, which support the theory claiming that nearly all the water in the lunar magma was lost to space during the eruptions, the researchers calculated the amount of water in the magma. The results show that the pre-eruption magma may have contained water up to 750 parts per million — similar to the water content of primitive magmas that erupted on the earth’s seafloor at mid-ocean ridges. “This suggests the very intriguing possibility that the moon’s interior might have contained just as much water as the earth’s depleted upper mantle,” Hauri said. He used secondary mass ion spectrometry, a technique that measures the elemental composition of solid materials, to detect the minute amounts of water in the samples. “We developed a way to detect as little as five parts per million of water,” he explains. “We were really surprised to find a whole lot more in these tiny glass beads, up to 46 parts per million.” 

Furthermore, the team has 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,” Saal said. “It has nothing to do with secondary processes, such as contamination or solar wind.” 

Another insight the research might yield regards the amount of time water has been on earth. “It suggests that water was present within the earth before the giant collision that formed the moon,” Saal said. “That points to two possibilities: water either was not completely vaporized in that collision or it was added a short time – less than 100 million years – afterward by volatiles introduced from the outside, such as with meteorites.” 

TFOT has also covered the discovery of evidence of water on the surface of Mars and the resemblance of Mars soil to Antarticas soil. Other related TFOT stories include the Crew Mobility Chassis, which is a new concept truck for lunar transportation under development by NASA, as well as NASA’s testing of an inflatable habitat, designed to be used on the moon. 

More information on the new evidence of water on the moon can be found on Brown University’s website.