Astronomers have finally resolved the riddle of moon’s origin. According to a study published in the prestigious Nature journal, the moon was formed by a collision between baby Earth and a primordial planet called Theia. Scientists said Theia was strikingly similar to the Earth in composition. The study resolves a long-standing puzzle about why Earth and the moon have a similar chemical composition.
Most of the moon’s material came from Theia
Computer simulations showed that a large chunk of material that formed the moon came from Theia. Alessandra Mastrobuono-Battisti of the Israel Institute of Technology in Haifa and the lead author of the study said that Theia, the shattered impactor, likely had a slightly different isotopic makeup than Earth.
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Using advanced computer models, researchers ran multiple simulations of late-stage planet formation. Within a period of 100-200 million years, each simulation gave birth to three or four planets due to the collision of planetary embryos and planetesimals. After analyzing the last moon-forming impact scenarios, astronomers concluded that Earth and Theia had the same chemical composition.
Mastrobuono-Battisti told Discovery News that, in most cases, impactors are more similar to the planets they impact than other planets in the same system. Another study published in the same journal found slight differences in an isotope of tungsten found on Earth and the moon. That could be because Theia had a slightly different isotopic makeup that Earth, said scientists.
The ‘giant impact’ theory of moon’s formation
In 1970s, astronomers had proposed the “giant impact” hypothesis to explain the formation of the moon. It suggested that the moon was formed about 4.5 billion years ago from the debris scattered when a giant Mars-like planet slammed into the Earth. But the similar composition of the Earth and moon had been one of the major challenges to the hypothesis.
The new studies show that the scenario was not so far-fetched. Earth and Theia might have closely resembled each other because of their similar distance from the Sun. It means they would have formed from the same proto-planetary materials.