Lucky strikes

To understand the worth of gold in society, one only needs to consider that the precious metal is the traditional anniversary gift to mark 50 years of marriage. In economics, the “gold standard” refers to the value of currency as backed by some amount of gold. Gloomy economic forecasts from around the world have thus been the reason the price of gold exceeded $1,900 an ounce more than once in recent weeks.

A report from British researchers suggests that the importance of this metal may have been influenced by the Earth’s encounter with visitors from outer space. “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 [metric] tons of asteroidal material,” said the study’s first author Matthias Willbold from the University of Bristol in a statement.

In the Sept. 8 issue of the journal Nature, Willbold and his colleagues use a metal that isn’t as illuminating these days as it once was and rocks up to nearly four billion years in age to explain why gold is fairly easy to mine even though it isn’t supposed to be so accessible.

Surprisingly abundant

Gold, wrote the researchers, likes iron, so it should be located deeper underground and closer to the Earth’s core, which lies roughly 3,000 kilometers below the Earth’s surface. Instead, they said, these metals “are surprisingly abundant in the accessible parts of the Earth,” including the mantle, which is just 100 km underground.

Willbold and his team considered the theory that meteorites struck the Earth several times billions of years ago, causing what’s called a “late veneer” of precious metals on the planet. They analyzed the makeup of rocks from Greenland that rose up from the mantle after the meteorite shower laid down the veneer of precious metals. Though the rocks were younger than the meteorites, the properties of the elements found in the samples still contained information about previous events.

The researchers’ analysis focused specifically on isotopes of tungsten, a metal used in the filaments for incandescent light bulbs. They found a difference between the levels of tungsten isotopes in the older rock samples that date back to just 500 million years after the meteorite shower, and samples from younger rocks.

Making precious metals

The results suggested that while the meteorite veneer did play a role in making precious metals such as gold more accessible to humans, the event may have had other, lasting influences. In particular, Woodland and his colleagues noted that the meteorites’ impact may have also influenced the way the tectonic plates move underground to push heat from the Earth’s core up and rearranging the planet’s surface.

The single most important reason people are so fascinated with gold, however, is probably the fact that despite millenniums of finding, shaping and keeping gold, humans still haven’t found very much of the precious metal. In one episode of his hit TV series tackling the science of outer space, British particle physicist Brian Cox, who worked at CERN’s Large Hadron Collider before taking on hosting duties, mentioned that the total amount of gold discovered thus far would fill no more than three Olympic-sized swimming pools, each of which can hold 2.5-million liters of water.

In comparison, Energy Secretary Jose Rene D. Almendras once noted that in the Philippines, 50 million liters of diesel are consumed on a daily basis.

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