When an extraterrestrial object penetrates the Earth, it sends molten rock high into the atmosphere. These debris cool and crystallize again and fall back to earth. Tiny glass beads that form are called microtectites, and researchers in Florida have found microtectites in fossilized shells.
This story begins over 10 years ago in a quarry in Sarasota County, Florida. The walls of this quarry are overflowing with fossilized shells from the last millions of years, which is a beautiful geological record for the students they can study. In 2006, students from the University of South Florida worked there, picking up fossilized shells and directing their sediment through fine sieves. They searched for fossilized unicellular organisms, the so-called benthic foraminifera, and for a hugely diverse and important class of life forms.
Roger Portell of the Florida Museum of Natural History led the students in their field work. He urged them to look for the Southern Quahog or Mercenaria campechiensis because they are storage containers for sediments and smaller creatures. "Rain can wash a lot of the finds in the shell section," Portell said. "But if you're trapped in two big shell valves, you catch all the fine stuff."
One student, Mike Meyer, found something else in some shells: tiny translucent glass balls that are smaller than grains of salt.
"You've really excelled," said Meyer, now Assistant Professor of Earth System Sciences at Harrisburg University in Pennsylvania. "Sand grains are lumpy, potato-shaped things. But I found these tiny, perfect bullets again and again. "
Meyer was curious about the tiny bullets and turned to the scientific community for help. But his emails to researchers did not help. Nobody could tell him what they were. Meyer has kept 83 of them in a box for 10 years, until he had the opportunity to re-examine them.
"Only a few years ago I had some free time," he said. "I thought I just started over."
He set to work to analyze the microtectites. First he analyzed their chemical composition and physical properties, then compared them to volcanic rocks and other things like coal ash and other industrial by-products. But these were different, and his analysis pointed to an extraterrestrial origin.
Mind = Blown
"It blew me away," Meyer said.
Petrified fossils themselves are like time capsules. When they die, fine sediments and particles can be trapped in them. Since they are buried in the fossil record over time, they must close. This makes them excellent records of their time.
Roger Portell, co-author of the study and field leader of the 2006 Summer Trench, who released the tiny orbs, said, "In such shells we find whole crabs, sometimes fish skeletons. It is a good way to preserve specimens. "
Finding extraterrestrial microtectites could be more exciting than finding a fish skeleton.
Meyer believes these tiny bullets come from one or more small, previously unknown meteor impacts that may have occurred on or near the Florida platform, the plateau that surrounds the Florida Peninsula.