Collision that formed the moon also brought Earth water, planetary scientists claim

Brooks Hays
Scientists hypothesize that the collision that formed the moon also delivered much of Earth's water. Photo by NASA/JPL/Caltech
Scientists hypothesize that the collision that formed the moon also delivered much of Earth's water. Photo by NASA/JPL/Caltech

May 21 (UPI) -- Without the moon and water, life on Earth wouldn't be possible. New research out of Germany suggests both were delivered by Theia, which collided with Earth 4.4 billion years ago.

Scientists have long puzzled over the origins of Earth's water. Earth was formed in the inner solar system, and the inner solar system was dry. The solar system's wet materials were relegated to the outer solar system.


Water-rich carbonaceous meteorites, for example, hail from the outer solar system. Non-carbonaceous meteorites from the inner solar system are without water.

At some point during Earth's early history, carbonaceous materials delivered large quantities of water. But the details and timing of this delivery process aren't well understood.

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"We have used molybdenum isotopes to answer this question," Gerrit Budde, a researcher at the University of M√ľnster's Institute of Planetology, said in a news release. "The molybdenum isotopes allow us to clearly distinguish carbonaceous and non-carbonaceous material, and as such represent a 'genetic fingerprint' of material from the outer and inner solar system."

Analysis performed by Budde and his colleagues showed some of Earth's molybdenum hails from the outer solar system. Because molybdenum is an iron-loving element, most of it is located in Earth's core -- but not all of it.

"The molybdenum which is accessible today in the Earth's mantle, therefore, originates from the late stages of Earth's formation, while the molybdenum from earlier phases is entirely in the core," said planetary scientist Christoph Burkhardt.

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The new research, published this week in the journal Nature, showed large quantities of water arrived after Earth's building blocks had coalesced. The study's authors suggest much of this water-rich material was delivered by Theia, the Mars-sized planet that scientists theorize struck Earth head on around 4.4 billion years ago, vaporizing much of Earth and triggering the formation of the moon.

"Our data demonstrate that Earth accreted carbonaceous bodies late in its growth history, probably through the Moon-forming impact," scientists wrote. "This late delivery of carbonaceous material probably resulted from an orbital instability of the gas giant planets, and it demonstrates that Earth's habitability is strongly tied to the very late stages of its growth."

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