Pretty wild theory

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.

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.?

[Supernova Explosion May Have Caused Mammoth Extinction 1]

Image: 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

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.

Source: Berkeley Lab




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