September 26th 05, 05:36 PM
http://www.lbl.gov/Science-Articles/Archive/NSD-mammoth-extinction.html
Supernova Explosion May Have Caused Mammoth Extinction
Lawrence Berkeley National Laboratory
September 23, 2005
Contact: Dan Krotz, 510-486-4019,
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).
Firestone, who conducted this research with Arizona geologist Allen
West, will unveil this theory at the 2nd International Conference "The
World of Elephants" in Hot Springs, SD. Their theory joins the list of
possible culprits responsible for the demise of mammoths, which last
roamed North America roughly 13,000 years ago. Scientists have long
eyed
climate change, disease, or intensive hunting by humans as likely
suspects.
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.
"Our research indicates that a 10-kilometer-wide comet, which may have
been composed from the remnants of a supernova explosion, could have
hit
North America 13,000 years ago," says Firestone. "This event was
preceded by an intense blast of iron-rich grains that impacted the
planet roughly 34,000 years ago."
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.
In addition, Berkeley Lab's Al Smith used the Lab's Low-Background
Counting Facility to detect the radioactive isotope potassium-40 in
several Clovis arrowhead fragments. Researchers at Becquerel
Laboratories also found that some Clovis layer sediment samples are
significantly enriched with this isotope.
"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.
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.
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 .
Supernova Explosion May Have Caused Mammoth Extinction
Lawrence Berkeley National Laboratory
September 23, 2005
Contact: Dan Krotz, 510-486-4019,
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).
Firestone, who conducted this research with Arizona geologist Allen
West, will unveil this theory at the 2nd International Conference "The
World of Elephants" in Hot Springs, SD. Their theory joins the list of
possible culprits responsible for the demise of mammoths, which last
roamed North America roughly 13,000 years ago. Scientists have long
eyed
climate change, disease, or intensive hunting by humans as likely
suspects.
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.
"Our research indicates that a 10-kilometer-wide comet, which may have
been composed from the remnants of a supernova explosion, could have
hit
North America 13,000 years ago," says Firestone. "This event was
preceded by an intense blast of iron-rich grains that impacted the
planet roughly 34,000 years ago."
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.
In addition, Berkeley Lab's Al Smith used the Lab's Low-Background
Counting Facility to detect the radioactive isotope potassium-40 in
several Clovis arrowhead fragments. Researchers at Becquerel
Laboratories also found that some Clovis layer sediment samples are
significantly enriched with this isotope.
"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.
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.
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 .