Historically, all attempts at aging the Moon have revolved around radiometric dating — i.e.
testing the decay of radioactive elements found in lunar samples.
By using a series of 259 computer simulations, the researchers — led by Seth Jacobson, a planetary scientist at the Côte d’Azur Observatory in France — found they could work out how heavy the Earth was before the Theia impact, how heavy it was after, and then how heavy we are now, after 4.5 billion years of further asteroid impacts.
Along the way, they worked out that the Earth-Theia impact must’ve occurred around 4.47 billion years ago, or about 95 million years after the Solar System came into existence.
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We also believe that huge impacts, like the Earth-Theia event, were pretty common back then — but if so, why doesn’t Venus have a moon?Anyway, the theory (which is very well supported by this point) is that Theia’s collision drove almost all of these siderophiles into the Earth’s core.The theory postulates that the crust was so stripped of these rare elements that almost all of the siderophiles that we find today must’ve come from later, smaller impacts (asteroids).In this case, the study highlights that the Earth did not finish forming until around 100 million years after the birth of the Sun — but Mars appears to have taken only a few million years to form completely.Why is there such a huge disparity, and is such a disparity common, or is Earth (or Mars) special?Do you find your Linux desktop background boring but don’t know where to find good-looking wallpapers to download? They automatically find or download beautiful wallpapers for you and change your desktop background at regular intervals.