Water may be present in the Moon's interior

Impacting asteroids and comets may have delivered water to early Moon before it fully cooled.
By Laurel Kornfeld | Jul 25, 2017
An analysis of satellite data collected by the Moon Mineralogy Mapper on India's Chandrayaan-1 probe reveals evidence ofwater trapped in layers of rock located deep in the Moon's interior.

Researchers at Brown University studied the Chandrayaan-1 data, which measured sunlight reflected from the lunar surface in both visible and infrared wavelengths.

To focus on interior deposits likely created by ancient volcanic eruptions, they had to separate heat produced by reflected sunlight from that produced by thermal deposits on the lunar surface.

Known as pyroclastic deposits, these ancient layers of rock were likely ejected from deep within the Moon's interior to its surface during long-ago volcanic eruptions. Magma produced in these eruptions likely carried water from the Moon's mantle to its surface while Earth's satellite was still cooling from the giant impact that formed it, according to team leader Ralph Milliken of Brown University.

Traces of water previously detected in shadowed areas of the Moon's poles likely have a different origin. Water at the poles probably came from hydrogen in the solar wind, the researchers believe.

Evidence of water in lunar surface deposits indicates there could still be a significant amount of water in the Moon's mantle.

"We observe the water in deposits that are at the surface today, but these deposits are the result of magma that originally comes from deep within the lunar interior," Milliken explained. "Therefore, because the products of the magma have water, the deep interior of the Moon must also contain water."

The researchers specifically focused on images taken in wavelengths where both water (H2O) and hydroxide (OH) absorb light.

"We found that there were larger absorptions, or less reflected sunlight, at these wavelengths for pyroclastic deposits, which indicates they contain OH or H2O," he said.

Because the early Moon was too hot to retain liquid water, some scientists theorize the water in its mantle was brought by colliding asteroids and comets after the giant impact that created it but before it fully cooled.

If these deposits could be mined for water, they could be a game-changer in terms of establishing a permanent Moon base. Mining them for water would be easier than extracting water from ice at the poles.

Future robotic missions could produce detailed maps of the deposits, which could be collected and returned to Earth for study.

Findings of the study were published in the journal Nature Geoscience.

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