Our Earth and its Moon Have a Common Water Source

The Moon's water did not come from comets but was already present on Earth 4.5 billion years ago, when a giant collision sent material from Earth to form the Moon, new research shows. 

Credit: NASA/JPL

Researchers used a multicollector ion microprobe to study hydrogen-deuterium ratios in lunar rock and on Earth.

Their conclusion: The Moon's water did not come from comets but was already present on Earth 4.5 billion years ago, when a giant collision sent material from Earth to form the Moon.

Water inside the Moon's mantle came from primitive meteorites, new research finds, the same source thought to have supplied most of the water on Earth. The findings raise new questions about the process that formed the Moon.

By showing that water on the Moon and on Earth came from the same source, this new study offers yet more evidence that the Moon's water has been there all along.

Alberto Saal

"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."

Erik Hauri

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.

Journal Reference:

1. Alberto E. Saal, Erik H. Hauri, James A. Van Orman, and Malcolm J. Rutherford. Hydrogen Isotopes in Lunar Volcanic Glasses and Melt Inclusions Reveal a Carbonaceous Chondrite Heritage. Science, 9 May 2013 DOI: 10.1126/science.1235142