According to a new study published in the Nature Journal by researchers at the University of Bristol, roughly 3.9 billion years ago a gigantic meteor shower of glittering gold and platinum fell on earth. The ancient meteor shower serves as an explanation for why tens of thousands of times more gold exists today on earth’s crust and mantle than was initially thought to have existed.
Prior to this study, however, so many scientists pointed to the meteorite theory, however no substantial evidence was actually there to support the theory; that is, until now.
According to The National Geographic, contemporary scientists have put this hypothesis to the test by analyzing the oldest rocks in the world; those discovered in Greenland in 2008, and afterward comparing them to the makeup of other rocks found elsewhere around the globe.
Matthias Willbold of the University of Bristol study said:
“We hoped that by analyzing these rocks we could get an idea of how the Earth looked before that meteoritic bombardment, so we can estimate how much meteoritic material was added to the Earth…Our work shows that most of the precious metals on which our economies and many key industrial processes are based have been added to our planet by lucky coincidence when the Earth was hit by about 20 billion billion tonnes of asteroidal material…”
So the next time that you put on that charming gold piece of jewelry, just remember to thank your lucky stars. Based on the differing isotopes that were found from those two samples of rocks, researchers finally concluded that an ancient meteor shower had to have occurred.
The study in the journal, Nature:
Many precious, ‘iron-loving’ metals, such as gold, are surprisingly abundant in the accessible parts of the Earth, given the efficiency with which core formation should have removed them to the planet’s deep interior. One explanation of their over-abundance is a ‘late veneer’—a flux of meteorites added to the Earth after core formation as a ‘terminal’ bombardment that culminated in the cratering of the Moon. Some 3.8 billion-year-old rocks from Isua, Greenland, are derived from sources that retain an isotopic memory of events pre-dating this cataclysmic meteorite shower. These Isua samples thus provide a window on the composition of the Earth before such a late veneer and allow a direct test of its importance in modifying the composition of the planet. Using high-precision (less than 6 parts per million, 2 standard deviations) tungsten isotope analyses of these rocks, here we show that they have a isotopic tungsten ratio 182W/184W that is significantly higher (about 13 parts per million) than modern terrestrial samples. This finding is in good agreement with the expected influence of a late veneer. We also show that alternative interpretations, such as partial remixing of a deep-mantle reservoir formed in the Hadean eon (more than four billion years ago) or core–mantle interaction, do not explain the W isotope data well. The decrease in mantle 182W/184W occurs during the Archean eon (about four to three billion years ago), potentially on the same timescale as a notable decrease in 142Nd/144Nd (refs 3 and 6). We speculate that both observations can be explained if late meteorite bombardment triggered the onset of the current style of mantle convection.