Long ago a Cosmic Collision took place. What do you get when two planet collide? How about Earth with a moon tossed in? You read that right, Earth is actually the result of two planets, not one. The early solar system was a chaotic place. Almost everything we see today, from Mercury to our moon, was the product of a series of collisions that happened at the right place and the right time. Perhaps one of the more violent collisions came when a planet roughly the size of Mars smashed into Earth, leaving only two bodies in its course: the Earth and fragmentary pieces of the two planets that eventually transformed into the Moon.
For some time, scientists believe that Theia side-swiped the Earth at approximately a 45-degree angle. Now, new evidence suggests that the collision between the early planets was a violent head-on collision that left the Earth scarred with fragments of Theia and the Moon with similar ratios of material.
“The collision was so vigorous, so powerful, so rich in energy that it probably mixed the whole system very thoroughly,” Edward Donald Young, lead author of the study commented.
This week, Science published the results of an analysis of material taken from the Apollo 12, 15, and 17 missions. Evidence in the oxygen isotopes gave important answers into a question scientists have been asking for some time: what did this collision really look like. The results showed the same ratios of oxygen isotopes on the Earth and the Moon—meaning they are essentially made of the same materials.
Analysis of salt-heavy lunar rocks and soil taken from Hawaii and Arizona are virtually the same.
“I think this will motivate impact modeling in [the head on collision] direction, so people will be forced to abandon the glancing blow model,” Young added. “People will keep looking with better and better analytic precision.”
The next step in the story is figuring out how the collision led to the Earth-Moon system we see today. How did the Earth and Moon establish their present rotations and orbits? What made the Earth survive and Theia disappear? If it weren’t for the collision, Theia would likely have become a planet.