Peering Inside Fossils
A scanning device most commonly seen in hospitals is reshaping the science of paleontology by allowing researchers to peer inside irreplaceable fossils without damaging them. They are seeing things in these chunks of stone that they've never seen before -- things like hearts and brains and embryos.
As NPR's John Nielsen reports, paleontologist Tim Rowe is one the scientists driving this emerging science of "paleoradiology." For the last six years, Rowe has run the full-time fossil-scanning lab at the University of Texas at Austin. When he's not digging fossils out of the ground, Rowe creates stunningly accurate three-dimensional computer images of the petrified organs and tissues inside of them.
Fossils used to give these secrets up only rarely, and only if they were destroyed. Diamond-tipped grinding machines took thin slices off of fossil bones and teeth so that scientists could put them under microscopes.
Rowe doesn't do it that way. He cuts fossils into digital slices by running them through a supercharged computed tomography device, or CT scanner, that resembles a medical CAT scanner.
" We can get somewhere on the order of 400 slices through the head of a pin," Rowe says. "They make some very precise grinding machines, but in six hours we can scan an entire specimen. It's faster and it's much more efficient, and then it's digital. And once the image is digital, we can measure it and we can do things that you can't do with your analog slice."
There are other places to get fossils scanned, but Rowe's lab sets the standard, says NPR's Nielsen. Since 1997 Rowe's team has scanned about 150 rare and important items, including a Martian meteorite, the fossilized egg of an elephant bird and the 147-million-year-old skull of a feathered dinosaur known as Archaeopteryx.
The CT scanner, which sits inside a 30,000-pound lead box, is much more powerful than a medical scanner, says Rich Ketchem, the lab's manager. It blasts fossils with lethal amounts of radiation for hours at a time.
"The problem with medical CAT scanners is that they're specifically engineered not to kill anybody," Ketchem says. "That's something you don't have to worry about when you're doing inanimate objects like fossils and things like that. As a result, we can use higher energy x-rays and image for a much longer time. We don't have to worry about them moving around or having beating hearts or breathing."
Ketchem says paleontologists began experimenting with CT scanners many years ago, but they were slow to embrace this new technology.
"Some of the older paleontologists are worried that their prize specimen is going to be a pile of dust in five years because we did this thing to them," Ketchem explains. "We're using high-energy x-rays, but we're not damaging anything -- there's no evidence that there's any damage to anything that comes from it."
So far, the only damage CT scanning has dealt fossils has come in the way of revealing fakes. Two years ago, one of Rowe's scans invalidated a "missing link" fossil he himself had just helped unveil at a press conference on the steps of the National Geographic Society in Washington, D.C. The memory of that fiasco still eats at him.
Rowe says fakes should be expected in a world where fossils sometimes sell for millions. He's found three in the last six years. But that's not what keeps him at his job. By allowing scientists to peer inside relics of the past once considered too fragile for such perusal, he says CT scanning is quickly reshaping a science that has long been ruled by a hunt for fossils that look good in museums.
"It's revitalized a field that's 300 years old, one of the great classical fields," Rowe says.
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