Meteorite storm showered planet in gold

FOUR billion years ago, the newly formed Earth took a walloping. A storm of meteorites slammed into it, delivering gold and other new metals to the planet.

Earth's crust and mantle should not contain metals like gold, because while the planet was molten they would have sunk into the core. As a result, many geologists think they were supplied by one final meteor bombardment after the planet solidified. "We now have the opportunity to show that this terminal bombardment happened," says Matthias Willbold at the University of Bristol, UK.

Willbold and his colleagues looked at samples from Isua, a rock formation in Greenland. Although these rocks erupted to the surface around 3.8 billion years ago - after the posited meteor storm - the mantle reservoir that they sprang from formed 4.3 billion years ago - before the storm.

Willbold found that Isua rocks carry a different ratio of tungsten isotopes to both modern terrestrial rocks and meteorites (Nature, DOI: 10.1038/nature10399). He says something must have changed this ratio, and that the only explanation is a meteorite bombardment that mixed new metals into the Earth.

A sticking point remains, though: if the storm gave Earth its precious metals, then sedimentary rocks laid down at the time should contain plenty of those metals, but they don't, says Balz Kamber of Trinity College Dublin in Ireland. There is little doubt of the bombardment, he says, but it may have brought in other substances, like water, not precious metals.

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

Have your say

Only subscribers may leave comments on this article. Please log in.

Only personal subscribers may leave comments on this article

Subscribe now to comment.

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

If you are having a technical problem posting a comment, please contact technical support.

Source: http://feeds.newscientist.com/c/749/f/10897/s/18125768/l/0L0Snewscientist0N0Carticle0Cmg211282940B20A0A0Emeteorite0Estorm0Eshowered0Eplanet0Ein0Egold0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

mozart vegan the bachelor black hole quarantine quarantine frederick douglass