Researchers studying fossil clams in Florida believe they found the souvenirs of an ancient meteorite.
In the summer of 2006, a University of South Florida student named Mike Meyer was part of a fieldwork project collecting shell fossils from a Sarasota County quarry. Prying open fossil clams and rinsing the inner sediment through fine sieves, they were looking for the shells of tiny organisms called benthic foraminifera. But Meyer discovered something else; dozens of small, translucent glassy balls.
"They really stood out," said Meyer, now an assistant professor of Earth systems science at Harrisburg University in Pennsylvania. "Sand grains are kind of lumpy, potato-shaped things. But I kept finding these tiny, perfect spheres."Replies to his initial queries about the unique find were inconclusive ... and so into a box they went, and stayed for more than a decade. But then, he decided to take another stab at identifying them.
"It wasn't until a couple years ago that I had some free time," he said. "I was like, 'Let me just start from scratch.'"
New analysis of the pretty little pearls suggests they are microtektites, explains the Florida Museum, "particles that form when the explosive impact of an extraterrestrial object sends molten debris hurtling into the atmosphere where it cools and recrystallizes before falling back to Earth."
The museum says that they are the first documented microtektites in Florida; and they may also be the first to be found in fossil shells.
During the analysis, Meyer considered that they might be the product of volcanic rock or byproducts of industrial processes; but in the end, all signs pointed to something extraterrestrial in nature. They were found to contain traces of exotic metals, adding to the evidence that they are microtektites.
"It did blow my mind," he said.
The cosmic pearls were found inside fossil southern quahogs (Mercenaria campechiensis). As the clams died, fine debris seeped inside; as sediment slowly buried the clams, the shells closed and created little geological time capsules, of sorts. It is estimated that Meyer's microtektites are two to three million years old.
Meyer suspects that there are plenty more to be found in Florida and is putting out the word to amateur fossil collectors to be on the lookout for them. Unfortunately, the museum notes, no one will be finding any microtektites from Meyer's quarry any time soon. "It's now part of a housing development."
"Such is the nature of Florida," Meyer said. Maybe in another two million years or so...
You can read more about the wondrous discovery here: A first report of microtektites from the shell beds of southwestern Florida.