This artist’s rendering shows the collision of two planetary bodies. A collision like this is believed to have formed the moon within the first 150 million years after our solar system formed. Credit: NASA/JPL-Caltech Within the first 150 million years after our solar system formed, a giant body roughly the size of Mars struck and merged with Earth, blasting a huge cloud of rock and debris into space. This cloud would eventually coalesce and form the moon. For almost 30 years, planetary scientists have been quite happy with this explanation–with one major exception. Although this scenario makes sense when you look at the size of the moon and the physics of its orbit around Earth, things start to break down a little when you compare their isotopic compositions–the geological equivalent of a DNA “fingerprint.” Specifically, Earth and the moon are too much alike. The expectation has long been that the moon should carry the isotopic “fingerprint” of the foreign body, which ...
Its about Earth Science & Universe.

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