
AsianScientist (Oct. 19, 2016) – An international research team has demonstrated that the relatively high levels of precious metals such as gold or platinum in the Earth’s mantle likely originated from one large-scale planetary impact prior to the formation of the Earth’s crust. The study was published in Earth and Planetary Science Letters.
The debate surrounding the formation of the planets in our solar system, particularly the terrestrial or ‘rocky’ planets, has been ongoing for many years. A few puzzles still remain, including why Earth has a large amount of iron-loving, or ‘siderophile,’ material in its mantle; metals like gold, platinum and palladium would ordinarily be sequestered in the metallic core. The existing explanation for the latter is that the Earth was pummelled by meteors in its early life, leaving behind the highly siderophile elements (HSE) beneath the crust.
The present study, which includes Drs. Ramon Brasser and Shigeru Ida at the Earth-Life Science Institute at Tokyo Institute of Technology, Japan, have shown that Earth’s HSE budget was most likely the result of a single, large-scale impact from space, rather than the slow accumulation of material from many smaller meteors.
Brasser’s team simulated the evolution of the terrestrial planets up to 300 million years after their first formation, a much longer time-scale than in previous studies. The single, large-scale impact that created Earth’s HSE complement was unique to Earth, and must have occurred before the crust had begun to form around 4.45 billion years ago. Furthermore, this single impact may or may not have been the same one that created the Moon.
The work implies that early Earth was a more benign place than previously thought, with fewer impacts from space.
The article can be found at: Brasser et al. (2016) Late Veneer and Late Accretion to the Terrestrial Planets.
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Source: Tokyo Institute of Technology; Photo: Pixabay.
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