Diamonds in the Sky
Did carbonados form in the unimaginably explosive shock waves emitted by dying stars, such as this one shot recently by NASA's Hubble Space Telescope?
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This finding helped lead to a new theory of carbonado formation. In 1985,
Joseph Smith of the University of Chicago and J. Barry Dawson of the University
of Sheffield in England suggested in an article published in the scientific
journal Geology that large meteor impacts in the Precambrian Era
(roughly 570 million years ago back to Earth's beginning some 4.5 billion years
ago) formed the black diamonds we find today. Scientists had long deemed
carbonados quite old, because the streams where they are typically found cut
through geologic strata dated from one to more than two billion years old. In
fact, recent atomic measurements of black diamonds have placed their origins at
nearly four billion years ago, a time when a constant barrage of giant meteors
battered the Earth.
In the 1990s, other scientists showed that Brazilian and African carbonados
bear similar isotopes of carbon and nitrogen, suggesting a common origin, while
still others provided theoretical and physical evidence that black diamonds
could have arisen during the extreme shock and heat of a meteor impact. But
why, some scientists wondered, had no unambiguous evidence ever been shown for
craters associated with carbonados? Geologist Stephen Haggerty of the
University of Massachusetts at Amherst had an idea why, and he shared it with a
dumbfounded audience at a 1996 American Geophysical Union meeting in Baltimore.
Carbonados were born not on Earth, either the way regular diamonds are or by
meteor impact, he said. Rather, they originated in dying stars, when shock
waves from exploding red giants crushed carbon into dense aggregations of black
diamond and sent them hurtling into deep space. Eons later, the Sun's gravity
lured some of this material into our solar system, where blocks of it slammed
into our atmosphere, shattering into the fragments we find strewn over select
areas today, perhaps billions of years after they formed.
Lucid in the sky with diamonds
Uranus (left) and Neptune may be veritable diamond
Even nearby planets may be churning out diamonds. In fact, planetary scientists say
that Uranus and Neptune, the seventh and eighth planets from our Sun,
respectively, may rain diamonds, which then pile up miles-thick at the
Uranus and Neptune are each nearly four times the size of Earth. Scientists
believe that, beneath an outer layer of hydrogen and helium, the gaseous
atmospheres of both planets contain 10 to 15 percent methane, a hydrocarbon.
Deep within the extremely dense atmospheres, above a rocky core, these planets
are also thought to bear temperatures ranging from 3,000 to 12,000°F and pressures varying from 200,000 to six million times the pressure
of our own atmosphere (which is 14 pounds per square inch).
In other words, possibly ideal conditions for producing diamonds.
With this in mind, a team at Lawrence Livermore National Laboratory tested in
the early 1980s what would happen to methane under intense pressure. One of the
team's leaders, Marvin Ross, had calculated that the gas would separate into
hydrogen and carbon at temperatures above 3,000°F and pressures exceeding
200,000 Earth atmospheres. The carbon atoms would be squeezed so tightly
together that they would become diamonds, he theorized. To find out if he was
right, Ross and his team used a gas cannon to severely compress and shock
methane samples. Resulting data, they later reported, indicated the fleeting
formation of diamonds in the instant before the target material evaporated, and
recent experiments at several labs support the predictions.
For the foreseeable future, the greatest benefit we'll see from diamonds
in the sky will be improved scientific understanding.
Reaping the benefits
As for tapping the riches of any diamonds from space, don't hold your breath.
Earth-hitting meteorites that either bear or engender diamonds are few and far
between, and unlike diamonds you're likely used to, their associated diamonds
often cannot be seen, much less admired, with the naked eye. Black diamonds,
for their part, are rare and are primarily used for industrial purposes. And
the challenges of harvesting any diamonds on Uranus and Neptune, which are
roughly 1,700 and 2,720 million miles away from Earth, respectively, are as
clear as the Koh-i-Noor diamond. Alas, scientific understanding is the primary
beneficiary of diamonds from the heavens.
Peter Tyson is Online Producer of NOVA.
Further reading (see also Books under Resources)
"Prospecting for Diamonds in the Outer Planets," by Warren E. Leary, The New
York Times, 10/5/99.
"Giant Black Diamonds Of Mysterious Origin May Hail From Space," by William
Broad, The New York Times, 9/17/96.
Photos: (1,2,5-7) NASA; (3) courtesy of Justin Gould; (4) courtesy of Stephen Haggerty.
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