For years scientists have believed that our moon was formed when a Mars-sized object collided into the Earth about 4.5 billion years ago. However, this giant impact hypothesis had a problem. If the moon resulted of the collision between Earth and another object, why is the moon a near chemical twin to our planet? Shouldn’t it contain the chemical signature of the other body also? Then why didn’t we find any remnant of the other object that collided?
“In terms of composition, the Earth and moon are almost twins, their compositions differing by at most few parts in a million,” Dr. Alessandra Mastrobuono-Battisti, an astrophysicist at the Israel Institute of Technology in Haifa, told . “This contradiction has cast a long shadow on the giant-impact model.”
Now, an international group of scientists have found why no there is no distinct remnant of the other object (sometimes called the Theia). It might be because Earth and Theia were very similar in composition. Previously, scientists believed that likelihood was only around 1 percent. The new research increases the odds to 20-40 percent.
The scientists created computer simulations of 40 artificial solar systems to examine how often planets are similar to big objects that hit them. The results showed big impacts involved collisions between bodies that formed at similar distances from the sun and so had similar makeup. This makes a good case for Theia being a close neighbor of Earth and of a similar composition and their impact resulted in the formation of a moon with a similar composition.
While these studies make the story of moon’s formation a little clearer, the case is far from being closed. There is still the issue of the abundance of tungsten in the bodies.