Apollo 15's green glass beads reveal hidden water in the Moon's mantle
Samples of tiny green volcanic glass collected by Apollo 15 astronauts in 1971 were later found to contain water, overturning the long-standing view of a dry lunar interior.
In July 1971, Apollo 15 astronauts David Scott and James Irwin spotted unusual green specks while traversing the lunar surface near the Apennine Mountains and Hadley Rille, collecting them as part of a 170-pound sample haul. These specks were later classified as volcanic glass beads formed from deep-origin magma. Decades after the mission, a Brown University team led by geologist Alberto Saal identified hydrogen within the beads, providing the first clear evidence that water existed inside the Moon when the glass solidified.
The 2008 finding challenged the prevailing belief that the Moon was essentially dry, a view based on earlier Apollo soil analyses. Further work in 2011 revealed water concentrations in the beads similar to those in certain terrestrial basalts, implying that portions of the lunar mantle may hold significant water. This insight has reshaped scientific understanding of lunar volatiles, supporting NASA’s broader recognition of water across both permanently shadowed regions and sun-lit areas of the Moon.
Why it matters
The finding shows the Moon holds water deep inside, altering theories of its formation and future resource use.
In this story
