A couple of weeks ago, Roy Lewis was in a small storage room filled with meteorites at the Field Museum of Natural History, showing off an exquisite, 2-inch-long glass ampul.
Pooled at its bulbous bottom, less than a quarter-inch across and deep, was a milky, viscous liquid, giving the ampul the look of a pendant from a New Age jewelry collection. In that drop, creating the milky tinge, are more diamonds than any king, pasha or even Elizabeth Taylor ever dared dream of.
“It’s stardust,” Lewis said simply, “the only objects we have that we know come from outside the solar system.”
Lewis, 49, is a cosmochemist at the University of Chicago’s Enrico Fermi Institute. Using chunks of meteorite donated by the Field Museum, he and colleagues at the institute in 1987 announced they had found honest-to-gosh stardust.
Since then, while not exactly churning out mounds of the stuff, Chicago has been the world’s preeminent center for recovering stardust.
Diamonds, Lewis was surprised to discover, are the most common stardust material. He has collected enough to prepare the ampul of diamonds for the first permanent display of stardust at the Smithsonian Institution later this year.
The diamonds are less than 80 billionths of an inch wide, measured in numbers of atoms. They were spewed out of dying stars billions of years ago.
“If I had a penny for every diamond in here,” said Lewis, tapping the ampul, “I would have enough money to retire the national debt.”
Considering the national debt is in the neighborhood of $3.5 trillion, that means there have to be at least 350 trillion diamonds (350,000,000,000,000) in the ampul.
“Yes, easily that many,” said Lewis, a rangy, quizzical sort.
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Lewis and his principal co-discoverers, led by his now-retired Fermi colleague Edward Anders, were investigating noble (inert) gas elements of meteorites when they made their stardust discovery.
Calling it “pre-solar” dust, Lewis and Anders said it could be 6 1/2 billion years old.
Lewis believes the stardust he has found comes from giant red stars that died many billions of years ago, hurtling dust and gas into interstellar space as they expired.
Our own solar system is believed to have been formed from dust and gases from dead stars, material that began to swirl and collapse on itself years ago. The core of the mass became our sun, igniting into a nuclear furnace.
Material left over within the pull of the sun’s gravity began to agglomerate into smaller planetesimals, space rocks that eventually combined to form the planets. The tremendous heat generated in the formation of the sun and the planets altered the material within them, making the material “newer” than stardust.
However, material in one area of the solar system never quite succeeded in forming a single, large planet. It is known as the asteroid belt between Mars and Jupiter, composed of thousands of small planetesimals, called asteroids.
By getting trapped in smaller, cooler planetesimals rather than large planets, some of the original stardust survived unaltered.
The asteroids occasionally collide with one another, sending chunks shooting into space as meteors, some reaching Earth and entering the atmosphere in a fiery display. Few survive that fiery entry, but those that do are called meteorites.
About 40,000 tons of space material rains down on earth annually, but most of that is in the form of tiny grains of matter. Even shooting stars, which streak so brilliantly across the night sky, are only about the size of a grain of sand and burn up before reaching the ground.
Only a few hundred pea-sized or larger meteorites are believed to reach the ground annually, most falling unseen by humans.
Of those that make it, the ones most often discovered are iron meteorites. Though they make up only about 10 percent of all meteorites, they survive well on the ground and are occasionally found by farmers.
Stone meteorites are far more numerous, but once they have hit the ground, they are difficult to recognize and detect.
While the Field Museum’s meteorite collection is one of the world’s largest, the bulk of it is stored in a bedroom-size room in the vast warren of offices and labs in the museum’s upper floors. It has 4,000 meteoritic chunks from 1,500 meteorites, most of them softball size or smaller.
The rarest, most valuable meteorites are called carbonaceous chondrites, water-soluble, clay-like stony meteorites that disintegrate rapidly in Earth’s weather.
Only about 70 carbonaceous chondrites have ever been recovered. Two huge ones that fell to Earth in 1969 have been yielding tantalizing, sometimes stunning scientific discoveries ever since.
The 800-pound Murchison meteorite fell near a town of that name in Australia in September 1969. The one-ton Allende meteorite fell near a village of that name in northern Mexico in February 1969.
Both the Murchison and the Allende are “primitive,” their mineral content less altered by heat generated during the solar system’s formation than most other solar objects.
The Murchison is one of the most primitive meteorites ever recovered. Shortly after it fell, researchers found it carried amino acids, the basic building blocks of life itself.
That discovery electrified the scientific community, suggesting possibilities of how life may have begun on Earth.
It was in chunks of Murchison and Allende, donated by the Field, that Lewis and Anders first found stardust. Almost all stardust material so far recovered is carbon-based, diamonds being the most prevalent but also including silicon carbide (the stuff of sandpaper), graphite and titanium carbide. Aluminum oxide is the one non-carbon exception.
Lewis perfected the brutal, painstaking process used to recover stardust, spending a third of a century, all of his professional life, developing it. It took years to do it the first time, and it still takes about six months to process a chunk of raw meteorite until the actual stardust is recovered.
“Ed Anders liked to say we were searching for needles in a haystack by burning down the haystack,” Lewis said.
Lewis dissolved chunks of the Murchison and Allende meteorites in hydrofluoric acid, reducing them to less than a half of a percent of their original mass. The stardust is found in what is left.
Given the destructiveness of the process, no museum wants to give up much of a meteorite in the name of science. The Field meteorite collection has more than 100 pounds each of the Murchison and Allende meteorites. It has given less than 10 percent of it to Fermi for its work.
Currently the Field’s meteorite curator, hence its keeper of the stardust, is Ignacio Casanova, 32, a Barcelona-born, ex-NASA geologist, who came to the museum two years ago. He is in charge of deciding which and how much of each meteorite should be sacrificed for research.
Until now, the museum simply supplied meteorite material for research done at the Fermi Institute and other research labs. This spring, Casanova, working with Lewis, has begun separating stardust himself, so that the museum can send dust samples off to interested researchers elsewhere.
The first meteorite Casanova began working with is one that, until recently, had been used as a doorstop in a barn since it was found in 1943 near Axtell, Texas. Early in May, Casanova identified the 12-pound Axtell meteorite as a heretofore unexamined carbonaceous chondrite.
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The Field Museum has obtained two pounds of it, and Casanova is now searching for stardust in it by dissolving 4.5 grams of it in hydrofluoric acid.
If he finds it, Casanova will be continuing Lewis’ and Anders’ rewriting of the books of how the stars and the solar system began.
Ultimately, Lewis said, because the universe is made up of the same, basic materials, studying the stardust also forces us to consider some philosophical questions. That means we are made from stardust too.
“That means we are looking at the same kind of material we all came from originally,” Lewis said.