“Lunar volcanic glasses were generated by melting different compositional reservoirs within the interior of the Moon,” geologist Alberto Saal, who recently published a study in Science Advances, told SYFY WIRE. “The different sulfur isotopes of those reservoirs give clues about processes that were responsible for the generation of those different reservoirs within the Moon.” Billions of years ago, volcanoes were throwing heated tantrums on the Moon, which explains the volcanic rock and glass found in lunar regolith samples. When a volcano vomits lava, the lava undergoes the process of degassing, which releases sulfur and other volatile elements (which evaporate easily). The micro-globs, or melt inclusions, found in fragments of olivine—also a common volcanic rock on Earth—were captured before degassing could occur. Any sulfur and other volatiles that could tell us more about the ancient composition of the Moon’s innards were also preserved with them.