Moon likely ripped from Earth by wayward planet

By Barry Eitel

SAN FRANCISCO

The moon was violently shorn from the earth by a Mars-sized rock roughly 100 million years after the planet’s formation, according to a new report citing strong evidence released by scientists Thursday.

Astronomers had previously theorized about such a catastrophic event but the new research from the studied rocks showcase that the moon and Earth have similar chemical signatures that differentiate them from other heavenly bodies.

The study reveals that about 4.5 billion years ago, earth was hit head-on by a “planetary embryo” named Theia -- the mother of moon goddess Selene in Greek mythology -- by planetary scientists, who believe it had a diameter of 6,000 kilometers (3,700 miles) making it roughly the same size as Mars.

Researchers analyzed seven rocks brought back from the moon on the Apollo 12, 15 and 17 missions as well as five volcanic rocks from Hawaii and another from Arizona.

Cosmic bodies each have a distinctive ratio of oxygen isotopes, which scientists can use as a planetary “fingerprint”.

“We don't see any difference between the Earth's and the moon's oxygen isotopes; they're indistinguishable,” UCLA professor Edward Young, lead author of the new study, said in a statement.

The research was published Wednesday in the journal Science.

Theia would have likely become a planet if weren’t for the destructive meeting with the Earth. It was absorbed into the moon and the Earth, suggesting a full-on collision instead of a glancing blow -- unlike what astronomers thought previously. UCLA scientists claimed they would expect the moon to contain most of Theia and, therefore, have a different chemical footprint than Earth.

“Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them,” Young said. "This explains why we don't see a different signature of Theia in the moon versus the earth.”