New Data Suggests Moon Formed Approximately 50 Million Years After Solar System Formation

Artist’s concept of a giant impact which is assumed to have formed the moon. Image credit: NASA/JPL-Caltech

Artist’s concept of a giant impact which is assumed to have formed the moon. Image credit: NASA/JPL-Caltech

The commonly accepted theory of the Moon’s origin is that a Mars-sized body collided with the proto-Earth, and the resulting debris accumulated to form our satellite. However, there is no consensus as to when this giant impact event happened —  estimates range from very early (30-100 million years after solar system formation) to relatively late (up to 200 million years after solar system formation). A new study by Thiemens et al. (2019) uses tungsten-hafnium isotope systematics to narrow down the time of moon formation. Their measurements show a higher tungsten/hafnium ratio for the silicate moon as compared to that of the silicate Earth and interpret the higher amount of tungsten to be a result of the decay of a now-extinct hafnium isotope (182Hf). This isotope only existed for the first 60 million years after the formation of our solar system. If the excess tungsten is indeed a decay product of extinct hafnium, the Moon would have formed early, approximately 50 million years after solar system formation. READ MORE

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