The Earth is actually two planets - not one

[Thaimon]

The Earth is actually two planets - not one
Posted on Friday, 29 January, 2016 |


The early Earth was involved in a massive planetary collision. Image Credit: NASA/JPL-Caltech
Scientists have determined that the Earth and moon are made up of material from two separate worlds.
Somewhere around 100 million years after the Earth was formed it had a run-in with another planet known as Theia, but while previous studies had suggested that the two worlds had only side-swiped one another, new research has revealed that they were most likely involved in a head-on collision.

The cataclysmic smash was so destructive that Theia was reduced to a cloud of debris which gradually merged together with the Earth to form both the moon and a single, larger planet.

The research was based on a new analysis of rock samples retrieved during the Apollo moon landings which showed an identical ratio of oxygen isotopes to materials collected on the Earth - something that shouldn't be possible if the Earth and Theia had only side-swiped one another.

"Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them," said UCLA geochemist Edward Young.

"This explains why we don’t see a different signature of Theia in the moon versus the Earth."

[Thaimon]

http://www.redorbit.com/news/space/1113412296/head-on-collision-between-earth-theia-likely-created-the-moon-012916/

[Thaimon]

Head-on collision between Earth, Theia likely created the moon
by Chuck Bednar

The collision between Earth and the "planetary embryo" known as Theia that took place roughly 100 million years after our planet formed was most likely responsible for forming the moon, according to new research published Friday in the journal Science.

While the high-velocity impact between Earth and Theia has been well documented by scientists, previous studies had suggested that the two objects simply side-swiped one another. However, in their new paper, Edward Young, a professor of geochemistry and cosmochemistry at UCLA, and his colleagues have found new evidence suggesting that it was a head-on impact.
Young’s team analyzed seven rocks collected from the moon and brought back to Earth by the astronauts of the Apollo 12, 15, and 17 missions, as well as six volcanic rocks from the planet’s mantle, and conducted a chemical analysis and comparison of each set of samples. They found no distinguishable difference between the oxygen isotopes between the Earth and moon rocks.

The findings contradict a 2014 German study that the lunar rocks would have a unique ratio of oxygen isotopes, different from those on Earth. The discovery suggests that a glancing collision between Earth and Theia was unlikely, as such an impact would have caused the moon to have been made primarily of material from Theia that had a non-Earth-like chemical composition.

Oxygen isotopes reveal striking similarities between Earth, moon rocks

During their analysis, Young and his colleagues focused on oxygen atoms, which they noted makes up 50 percent of the weight and 90 percent of the volume of a rock. The overwhelming majority of Earth’s oxygen is referred to as O-16 oxygen, because every atom contains eight protons and eight neutrons, but there are trace amounts of heavier oxygen isotopes.

Those isotopes, O-17 and O-18, have one and two additional neutrons, respectively, the study authors said. Every planet in the solar system has a unique ratio of O-17 to O-16, and by using high-tech equipment to measure the isotope signatures of both the Earth and moon rocks, they found that the ratio of oxygen isotopes in each were nearly identical.

This indicates that the collision between Earth and Theia was no little fender-bender, Young explained. “Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them,” he said, noting that the forming planet did not survive the collision in-tact. “This explains why we don’t see a different signature of Theia in the moon versus the Earth.”

Had Theia survived the impact, it probably would have become a planet similar in size to either Mars or the Earth, the researchers said. Furthermore, they believe that the impact with Theia may have removed any water that might have been found on the young Earth, only for a plethora of small asteroids rich in water to restore the planet’s H2O million of years after the collision.

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Feature Image: Thinkstock

[Thaimon]

[Zalmoxis]

I am not a biologist but I think the idea of a head-on collision of two planets has interesting connotations for the evolution of single-celled life. Life involves lots of carbon, oxygen, and nitrogen as well as essential metal ions. These elements are common in abiotic environments but usually are ``trapped'' in stable minerals (oxygen is especially trapped in silicate rocks) or gasses (CO₂ is quite stable and unusable by life except in photosynthesis). The head-on collision *might* (again, not an expert so take what I am saying with a grain of salt) smash open enough particles to do the job.

[Zalmoxis]

 The Giant Impact theory is a scientific theory in that it's the best explanation of the origin of the Moon which scientists have come up with. That is, it provides the best explanation of the evidence.