Above, thickness of the Earth's crust across Antarctica . Thicker crust appears red. The location of the Wilkes Land crater is circled (below right of center). Image courtesy of Ohio State University.
The Permian-Triassic (PT) extinction, also known as "The Great Dying" among paleontologists, wiped out over 90% of terrestrial animals some 250 million years ago, but left no clear evidence of its cause. Now, a piece of evidence bigger than the state of Ohio could shed light on this mystery.
Ralph von Frese, professor of geological sciences at Ohio State University, led a research team that uncovered a crater-like circular ridge buried under more than a mile of Antarctic ice that he believes may be linked to the mass extinction. Von Frese and his team had originally been surveying the area for faults or tectonic plates.
"When we heard that people were talking about impacts in that area we looked at the data for evidence of an impact, and we found it," said von Frese, who presented his findings at an American Geophysical Union meeting in late May.
Advertisement
Von Frese said a added that A 30-mile-wide meteor would have been required to create the 300-mile wide crater that his team discovered. By contrast, the meteorite that struck at Chicxulub (near the modern-day Yucatan peninsula), which is believed by some to have killed the dinosaurs, was only about six miles wide.
Before stumbling onto the crater itself, von Frese discovered a well-known geological structure that typically indicates an area struck by a massive impact--—a "mascon" or mass concentration. The mascon von Frese found is a 200-mile-wide section of the Earth's mantle that had risen up into the Earth's crust. He used NASA's GRACE satellite, which is capable of detecting changes in the Earth's gravitational field, to help locate the geological disturbance.
Impacts of this size are not uncommon in our solar system, said von Frese.
"The moon has at least 20 craters indicative of similarly sized impacts.," said von Frese.
However, the moon provides the geologists an advantage since it's a "dead" world which that lacks dynamic processes like erosion and volcanism. This stability allows the moon's surface to retain a relatively pure record of impacts dating back for eons. The Earth, on the other hand, has a tendency to destroy geological evidence through its myriad physical systems, all of which are constantly reshaping the surface of the world.
Since the PT crater is buried under a mile-thick layer of ice, and the mascon is buried even farther—, under the crust of the Earth—, all of the research team's observations are relatively indirect. The GRACE satellite and ice-penetrating radar were necessities when dealing with such difficult terrain.
"We've put more people on the moon than on this area of the world," von Frese said.
Douglas Erwin, a Smithsonian paleobiologist and author of the book Extinction: How Life on Earth Nearly Ended 250 Million Years Ago, is skeptical of von Frese's findings.
"Most claims of craters this size evaporate under closer inspection," he said.
Von Frese emphasized that the findings are preliminary and must be followed-up with aircraft surveys of the region to provide more concrete data.