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Earth, Moon Share Water Source

File--The moon seen from the Belarusian capital Minsk, during a partial lunar eclipse, lat April 25, 2013. Scientists believe the Moon and Earth share the same source of water.
The Moon and Earth share the same source of water, according to new research. The latest analysis is based on new data collected by NASA spacecraft as well as the Moon rocks brought back by the Apollo missions. It shows that water inside the Moon’s mantle comes from primitive meteorites, which also supplied most of the water on Earth.

The research raises questions about the formation of the Moon. Prevailing theory holds that the moon was formed about 4.5 billion years ago from a disc of debris left over from a giant object that collided with the early Earth. Such an impact, scientists believed, would have created so much heat that hydrogen and other volatile elements would have burned off, meaning the Moon would have started completely dry.

Now, scientists are starting to believe the water on the Moon has been there all along.

“The simplest explanation for what we found is that there was water on the proto-Earth at the time of the giant impact,” said Alberto Saal, associate professor of Geological Sciences at Brown University and the study’s lead author. “Some of that water survived the impact, and that’s what we see in the Moon.”

While the findings do not necessarily negate the notion that the Moon was formed by a giant impact, scientists still can’t explain how water was able to survive.

“The impact somehow didn’t cause all the water to be lost,” Saal said. “But we don’t know what that process would be.”

Scientists were able to determine the origin of the Moon’s water by measuring the ratio of deuterium to hydrogen in the water molecules trapped inside Moon rocks and comparing that ratio to water molecules from different areas of the solar system.

Objects formed closer to the Sun have less deuterium than objects formed further out in the solar system. Researchers found that the ratio in the Moon rocks matched those on meteorites in the asteroid belt near Jupiter, which are thought to be among the oldest objects in the solar system. This, scientists say, means the source of the water on the Moon is primitive meteorites.

As much as 98 percent of the water on Earth is believed to come from primitive meteorites, according to the study, suggesting a common source of water for the Earth and Moon.

The research was co-authored by Erik Hauri of the Carnegie Institution of Washington, James Van Orman of Case Western Reserve University, and Malcolm Rutherford from Brown and published online in Science Express.