Moon’s surface may hide water-rich interior

Parts of the Moon’s mantle – the layer between crust and outer core – could contain as much water as Earth’s interior, says new research that uses light data to measure the mineral makeup of the lunar surface. 

Researchers Ralph E. Milliken and Shuai Li at Brown University, USA have used light data to measure the makeup of volcanic deposits scattered across the lunar surface, and found a surprising amount of water. {%recommended 4389%}

Their study, published this week in Nature Geoscience, contributes to mounting evidence that the Moon’s interior is far more water-rich than previously thought.

Serious discussions of lunar water arose in 2008, when volcanic glass beads brought back to Earth by Apollo missions were found to contain traces of water. Since then, there’s been a question mark over whether this might be a common occurrence, or more of an anomaly.

To investigate this, Milliken and Li measured light reflected off the Moon’s surface across its orbit, using different wavelengths to estimate which compounds are present in a particular area.

They combined this data with existing mapping of large pyroclastic deposits – remnants of magma eruptions from deep within the Moon’s interior – that lie dormant across the surface. 

“By looking at the orbital data, we can examine the large pyroclastic deposits on the Moon that were never sampled by the Apollo or Luna missions,” writes Milliken, lead author of the study.

“The fact that nearly all of them exhibit signatures of water suggests that the Apollo samples are not anomalous, so it may be that the bulk interior of the Moon is wet.”

The far-reaching range of these deposits, Milliken says, is crucial. “They’re spread across the surface, which tells us that the water found in the Apollo samples isn’t a one-off. Lunar pyroclastics seem to be universally water-rich, which suggests the same may be true of the mantle.”

The team says the presence of water on the Moon’s surface could be useful for future explorations, because it could potentially be extracted and used to nourish astronauts.

“Other studies have suggested the presence of water ice in shadowed regions at the lunar poles, but the pyroclastic deposits are at locations that may be easier to access,” explains co-author, Shuai Li. 

“Anything that helps save future lunar explorers from having to bring lots of water from home is a big step forward, and our results suggest a new alternative.”