Lunar Water Leads Scientists to Question Origin of Moon

Study suggests that the "giant impact" didn't cause the moon to go dry.


The water on Earth came from a big collision with the moon, but that's not why the moon is now dry.

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Water that exists on the moon may have come from the same source that brought water to Earth, raising new questions about the moon's initial creation, according to a new study.

[PHOTOS: Gorgeous Views of the Supermoon From Around the World]

After analyzing volcanic samples collected during the Apollo 15 and 17 missions, researchers at Brown University suggest that the impact that formed the moon also transferred water onto the moon.

The most popular theory for the moon's formation suggests that it was formed when a giant space object collided with the "proto-Earth," causing a chunk of debris to break off. Scientists had long thought that the collision caused all hydrogen to boil off, leaving the moon completely dry. But recent discoveries suggest that the moon has ice at its poles and water under its surface, leaving scientists to wonder if there is another explanation for the moon besides the "proto-Earth" collision theory.


Alberto Saal, a geological scientist at Brown University and lead author of the study published Thursday in Science, says that the "fingerprint" of the water on the moon is very similar to that on Earth, suggesting they came from the same source.

"We concluded that basically, the Earth formed with water. By the time of the giant impact, we don't know what happened, but not all of that water was lost like we had thought before," Saal says. "Some of that water went to the moon."

Previous studies have suggested that solar wind, combined with existing chemicals on the moon, may have led to water's formation there.

Saal and his team analyzed volcanic glass, which is formed when molten material cools extremely quickly. In the glass, he found that lunar water came from the same source as the water on Earth.

[PHOTOS: Constellation, NASA's Moon Program]

That means the moon is likely made up of material from prehistoric Earth, but scientists still aren't sure how hydrogen and other volatile elements could have survived the heat associated with the ancient collision.

Saal's colleague, James Van Orman of Case Western Reserve University, says the team has to "go back to the drawing board to discover more about what giant impacts do."

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