According to the prevailing theory, the moon was formed from debris ejected into space when the Earth collided and merged with another celestial body of the Mars size. But now European researchers estimate that the body that crashed on our planet was even bigger and managed to “survive” after the accident.
Although now it is almost certain that the moon was formed more than 4 billion years ago, the details of its formation still remain unclear.
“Birth” from fragments of the collision
Previous studies have shown that the concentration of iron on the moon is different than that on the Earth, indicating that our satellite was formed from different building materials. This observation, coupled with other analyzes, suggests the prevailing theory, according to which the moon is mainly composed of fragments of the body that collided with Earth at relatively low speeds.
There are also studies that do not agree with this scenario: for example, the ratios of different isotopes of oxygen and titanium are nearly identical on the Earth and on the Moon, indicating their possible common origin.
The new study, which has been accepted for publication in the prestigious journal Icarus, offers a different picture of the “violent birth” of the moon. The research was based on computer models showing that the moon could have been formed from debris ejected into space after the Earth was abandoned by the crashing celestial body.
Object larger than Mars
Specifically, the models show that a body larger than Mars struck the Earth at high speed and then continued its course, having lost only a fraction of its mass.
This collision would form a disk of warm debris which eventually became a building material for the moon. But simulations show that most of the debris came from the Earth, rather than from the passing body, which seems to explain the similar isotope ratios.
However, the research leader Andreas Reufer of the Center for Space and Habitability in Bern, Switzerland, says that the new theory better explains the results of the observations, but should be confirmed by further simulations and analysis of the Moon samples brought by the Apollo missions in the 1960’s.