The Moon, Earth’s only natural satellite, has always been surrounded by an aura of mystery. Theories regarding it, even after landing on it, have been controversial and highly disputed. However, the technological evolution that we see today opens unprecedented paths into discovering the origins of the Moon.

By analyzing samples of volcanic pebble-like glass brought back from the Moon by the Apollo mission decades ago, researchers were able to break the theory according to which our Earth’s natural satellite is perfectly dry. The new technique used permitted them to identify water molecules, which led to the conclusion that water played an important role in the way the Moon was formed.

A study published in the journal Nature adds new facts to the “old” theory according to which the Moon formed as a result of a giant impact of a Mars-sized object with our planet. Scientists suggested in the new study that the samples taken from the Moon were actually formed 3.3 to 3.6 billion years ago, when violent lunar eruptions took place. The water is believed to have been present within the Moon, and ejected along with magma during the eruptions.

There have been several theories on the origins of the Moon: some suggested the Moon is actually a fragment that broke from the Earth’s crust, leaving the Pacific Ocean behind, others believed the Moon could have been captured by Earth’s gravity but formed somewhere else, others adopted the impact theory, but none of them was easy to prove.

The impact theory, which seems to be the most popular among scientists, excluded the presence of water through the fact that the heat produced by the impact should have vaporized all light elements, including hydrogen, which is a base element in forming water. All until now.

The new study revealed that the rocks contained traces of hydrogen, along with chlorine and fluorine, which can easily be found in eruptive rocks. The presence of hydrogen among other elements suggests that the water came from inside the Moon during the volcanic eruptions.

Scientists eliminated the possibility that the solar winds were in fact the source of the hydrogen they found in the samples analyzed. As study lead-author Alberto Saal explained, the different concentrations they found on the surface and in the core were exactly the opposite of what they should have found if the solar winds theory was right.

The similarities between the Moon and Earth’s geological pasts become more obvious now. Scientists calculated that the Moon magma contained 750 parts per million of water, which is very close to the Earth’s primitive magma.

“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,” Erik Hauri, geologist at the Carnegie Institution and co-author of the study said.

Furthermore, new discoveries may well change facts about our own planet, if we follow the general accepted theory of the giant impact. The water in the Moon’s past could be a sign that water was also present within the Earth at the time of the impact.

More evidence should become available once NASA’s robotic probe, the Lunar Reconnaissance Orbiter, reaches the Moon. LRO will be the first of a series of mission to collect critical data on the Moon’s topography, radiation environment, temperatures, and chemical makeup, which will help scientists prepare for future manned missions.