The massive impact that left a puzzling crater near the northern border of Greenland’s ice sheet occurred around 58 million years ago, according to a study published on March 9 in Science Advances. The crater was caused by a meteorite striking the ice sheet.
That chronology, which two different dating techniques have validated, indicates that the asteroid, comet, or meteorite that cut the depression did so long before the Younger Dryas cold snap, which occurred around 13,000 years ago. According to some scholars, the mean period may have been brought on by such an event.
The crater was discovered in 2015 during a scan conducted by NASA’s Operation IceBridge, which utilized airborne radar to estimate the ice sheet’s thickness in the Antarctic. It was discovered from these and other data that the crater, known as Hiawatha, is a circular depression that spans 31 kilometers and is buried under one-hundred-kilometer-thick glacial ice.
The next stage was to figure out how ancient the Hiawatha crater may be, which took some time. Even though the depression itself is inaccessible, meltwater at the ice’s base had ported out pebbles and other sediments that bore telltale signs of being altered by an impact, including sand from partially melted rocks and stones containing intensely deformed zircon crystals, which were referred to as “shocked.”
These modifications were discovered by geochemist Gavin Kenny of the Swedish Museum of Natural History in Stockholm and colleagues. They used two techniques based on the radioactive decay of isotopes, or various versions of the same element, to determine their age. The scientists measured the decay of uranium to lead in the zircons and then compared the abundances of radioactive argon isotopes in the sand with the lots of stable argon isotopes in the sand. By these approaches, the impact happened around 57.99 million years ago.
As a result, the crater is much too ancient to constitute the smoking gun that proponents of the disputed Younger Dryas impact idea have been searching for decades.
Another problem with linking it to the Paleocene-Eocene Thermal Maximum is that the chronology isn’t quite correct. That epoch started approximately 56 million years ago and was characterized by extreme warmth. For the time being, according to the experts, it is unclear what effect this cosmic punch may have had on the Earth’s global climate.