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Supernova could be responsible for extinction of the mammoth Lawrence Berkeley National Laboratory press release September 24, 2005 BERKELEY, CA A distant supernova that exploded 41,000 years ago may have led to the extinction of the mammoth, according to research that will be presented tomorrow (Sept. 24) by nuclear scientist Richard Firestone of the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab). Now, a supernova may join the lineup. Firestone and West believe that debris from a supernova explosion coalesced into low-density, comet-like objects that wreaked havoc on the solar system long ago. One such comet may have hit North America 13,000 years ago, unleashing a cataclysmic event that killed off the vast majority of mammoths and many other large North American mammals. They found evidence of this impact layer at several archaeological sites throughout North America where Clovis hunting artifacts and human-butchered mammoths have been unearthed. It has long been established that human activity ceased at these sites about 13,000 years ago, which is roughly the same time that mammoths disappeared. They also found evidence of the supernova explosion's initial shockwave: 34,000-year-old mammoth tusks that are peppered with tiny impact craters apparently produced by iron-rich grains traveling at an estimated 10,000 kilometers per second. These grains may have been emitted from a supernova that exploded roughly 7,000 years earlier and about 250 light years from Earth.
In support of the comet impact, Firestone and West found magnetic metal spherules in the sediment of nine 13,000-year-old Clovis sites in Michigan, Canada, Arizona, New Mexico and the Carolinas. Low-density carbon spherules, charcoal, and excess radioactivity were also found at these sites. "Armed with only a magnet and a Geiger counter, we found the magnetic particles in the well-dated Clovis layer all over North America where no one had looked before," says Firestone. Analysis of the magnetic particles by Prompt Gamma Activation Analysis at the Budapest Reactor and by Neutron Activation Analysis at Canada's Becquerel Laboratories revealed that they are rich in titanium, iron, manganese, vanadium, rare earth elements, thorium, and uranium. This composition is very similar to lunar igneous rocks, called KREEP, which were discovered on the moon by the Apollo astronauts, and have also been found in lunar meteorites that fell to Earth in the Middle East an estimated 10,000 years ago. "This suggests that the Earth, moon, and the entire solar system were bombarded by similar materials, which we believe were the remnants of the supernova explosion 41,000 years ago," says Firestone.
"The potassium-40 in the Clovis layer is much more abundant than potassium-40 in the solar system. This isotope is formed in considerable excess in an exploding supernova, and has mostly decayed since the Earth was formed," says Firestone. "We therefore believe that whatever hit the Earth 13,000 years ago originated from a recently exploded supernova." Firestone and West also uncovered evidence of an even earlier event that blasted parts of the Earth with iron-rich grains. Three mammoth tusks found in Alaska and Siberia, which were carbon-dated to be about 34,000 years old, are pitted with slightly radioactive, iron-rich impact sites caused by high-velocity grains. Because tusks are composed of dentine, which is a very hard material, these craters aren't easily formed. In fact, tests with shotgun pellets traveling 1,000 kilometers per hour produced no penetration in the tusks. Much higher energies are needed: x-ray analysis determined that the impact depths are consistent with grains traveling at speeds approaching 10,000 kilometers per second. "This speed is the known rate of expansion of young supernova remnants," says Firestone. The supernova's one-two punch to the Earth is further corroborated by radiocarbon measurements. The timeline of physical evidence discovered at Clovis sites and in the mammoth tusks mirrors radiocarbon peaks found in Icelandic marine sediment samples that are 41,000, 34,000, and 13,000 years old. Firestone contends that these peaks, which represent radiocarbon spikes that are 150 percent, 175 percent, and 40 percent above modern levels, respectively, can only be caused by a cosmic ray-producing event such as a supernova. "The 150 percent increase of radiocarbon found in 41,000-year-old marine sediment is consistent with a supernova exploding 250 light years away, when compared to observations of a radiocarbon increase in tree rings from the time of the nearby historical supernova SN 1006," says Firestone. Firestone adds that it would take 7,000 years for the supernova's iron-rich grains to travel 250 light years to the Earth, which corresponds to the time of the next marine sediment radiocarbon spike and the dating of the 34,000-year-old mammoth tusks. The most recent sediment spike corresponds with the end of the Clovis era and the comet-like bombardment. "It's surprising that it works out so well," says Firestone. Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California. Visit our website at http://www.lbl.gov. This is a modified press release from the Berkeley Lab. Related articles: Last 4 missing Gulfport dolphins rescued following hurricane - 21-September-2005 The NOAA Fisheries Service and the Marine Life Aquarium of Gulfport, Miss., working with a number of other partners, rescued the last four of the eight trained bottlenose dolphins that were swept out of an aquarium tank torn apart by the storm surge of Hurricane Katrina on August 29. Normally held in captivity, the dolphins don't have the necessary skills to survive on their own. They have survived various injuries and predators and have stayed together since the storm. NOAA Missing Gulfport dolphins rescued following Hurricane Katrina - 16-September-2005 Wildlife experts on Thursday began rescuing a group of eight bottlenose dolphins swept from their aquarium home into the Gulf of Mexico by Hurricane Katrina. Reuters New Orleans Aquarium animals shipped to Monterey Bay Aquarium - 12-September-2005 Two sea otters and 19 penguins from the New Orleans Aquarium have been sent to Monterey Bay Aquarium. The aquarium will start providing updates on the animals once they have been stabilized. There are currently no plans to place them on exhibit at Monterey Bay. Monterey Bay Aquarium release Surviving animals from New Orleans aquarium to be sent elsewhere - 9-September-2005 Surviving animals from the New Orleans will find new homes according to aquarium spokeswoman Melissa Lee. Despite escaping Hurricane Katrina with little physical damage, the Aquarium of the Americas in New Orleans suffered significant loss of animal life when the facility's emergency generator failed and made conditions unlivable for most its animals. mongabay.com
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Radiocarbon peaks in Icelandic marine sediment samples, indicated by the black line, coincide with three supernova-caused events that Firestone and Wells believe led to the extinction of the mammoth. Graph courtesy of Berkeley lab.
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