Nov. 13, 2008 -- Etched in the shockwaves of exploding stars, in the gas and dust of fledgling stellar nebulae -- and in Earth's ample oceans, winds and fiery volcanoes -- the multi-billion-year history of minerals appears ageless to us mere mortals.
But an ambitious new study describes how these seemingly static forms have evolved through the ages, just like biological life. From the 12 "primordial" minerals forged inside supernovae to the 4,300 or so mineral species known today, minerals have diversified, grown in complexity, and even been driven into extinction.
"The most basic definition of evolution is change over time," said Robert Hazen of the Carnegie Institution in Washington, D.C., who led a team of researchers in the work, published today in the journal American Minerologist. "And that's dramatically displayed in the stories of minerals."
Before life evolved on Earth, the slow, inexorable grind of plate tectonics created a total of 1,500 mineral species. Now, Hazen said, most minerals require living creatures to spring into existence.
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"That's about as far as we think you can get without life," he said. That means about two-thirds of all known minerals depend on Earth's living creatures to survive.
In life's beginnings, it may have been the other way around.
"Many people believe that life first appeared from some sort of interaction of organic molecules on a mineral surface," said Peter Heaney of Pennsylvania State University.
Soon afterward, the earliest life forms began changing the same chemistry that formed them. About 2.3 billion years ago, photosynthetic organisms started consuming carbon dioxide and sunlight and exhaling oxygen. For the first time, our planet had free oxygen floating around in the atmosphere.
"Before that, if you left a piece of iron or steel on Earth's surface, it wouldn't rust," Hazen said. "But all of a sudden, life produced oxygen, and you start getting get rust -- and oxides of copper, manganese, and cobalt. There are literally thousands of minerals analogous to rust. You wouldn't have these without oxygen."
If all life were suddenly wiped out, the 20-percent-oxygen atmosphere we currently enjoy would vanish in a matter of years. Along with the O2, all those minerals would go extinct.
Minerals containing radioactive elements with short half-lives, such as plutonium, melted into extinction long ago (all plutonium on Earth today is man-made). And Heaney suspects there's a new field of mineral archaeology just waiting to be born.
"No one has ever mapped out mineral extinction in Earth's history," Heaney said. "In a way, [Hazen's] work forces us to think in those terms and look for the mineral equivalent of a fossil record."
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