Interesting article at BBC
Tut’s gem hints at space impact
http://news.bbc.co.uk/2/hi/science/nature/5196362.stm
In 1996 in the Egyptian Museum in Cairo, Italian mineralogist
Vincenzo de Michele spotted an unusual yellow-green gem in the
middle of one of Tutankhamun’s necklaces. The jewel was tested
and found to be glass, but intriguingly it is older than the
earliest Egyptian civilisation.
Working with Egyptian geologist Aly Barakat, they traced its
origins to unexplained chunks of glass found scattered in the
sand in a remote region of the Sahara Desert.
But the glass is itself a scientific enigma. How did it get to
be there and who or what made it?
Thursday’s BBC Horizon programme reports an extraordinary new
theory linking Tutankhamun’s gem with a meteor.
Sky of fire
An Austrian astrochemist Christian Koeberl had established
that the glass had been formed at a temperature so hot that
there could be only one known cause: a meteorite impacting
with Earth. And yet there were no signs of an impact crater,
even in satellite images.
American geophysicist John Wasson is another scientist
interested in the origins of the glass. He suggested a
solution that came directly from the forests of Siberia.
“When the thought came to me that it required a hot sky, I
thought immediately of the Tunguska event,” he tells Horizon.
In 1908, a massive explosion flattened 80 million trees in
Tunguska, Siberia.
Although there was no sign of a meteorite impact, scientists
now think an extraterrestrial object of some kind must have
exploded above Tunguska. Wasson wondered if a similar aerial
burst could have produced enough heat to turn the ground to
glass in the Egyptian desert.
Jupiter clue
The first atomic bomb detonation, at the Trinity site in New
Mexico in 1945, created a thin layer of glass on the sand. But
the area of glass in the Egyptian desert is vastly bigger.
Whatever happened in Egypt must have been much more powerful
than an atomic bomb.
natural airburst of that magnitude was unheard of until, in
1994, scientists watched as comet Shoemaker-Levy collided with
Jupiter. It exploded in the Jovian atmosphere, and the Hubble
telescope recorded the largest incandescent fireball ever
witnessed rising over Jupiter’s horizon.
Mark Boslough, who specialises in modelling large impacts on
supercomputers, created a simulation of a similar impact on
Earth.
The simulation revealed that an impactor could indeed generate
a blistering atmospheric fireball, creating surface
temperatures of 1,800C, and leaving behind a field of glass.
“What I want to emphasise is that it is hugely bigger in
energy than the atomic tests,” says Boslough. “Ten thousand
times more powerful.”
Defence lessons
The more fragile the incoming object, the more likely these
airborne explosions are to happen.
In Southeast Asia, John Wasson has unearthed the remains of an
event 800,000 years ago that was even more powerful and
damaging than the one in the Egyptian desert; one which
produced multiple fireballs and left glass over three hundred
thousand square miles, with no sign of a crater.
"Within this region, certainly all of the humans would have
been killed. There would be no hope for anything to survive,"
he says.
According to Boslough and Wasson, events similar to Tunguska
could happen as frequently as every 100 years, and the effect
of even a small airburst would be comparable to many Hiroshima
bombs.
Attempting to blow up an incoming asteroid, Hollywood style,
could well make things worse by increasing the number of
devastating airbursts.
“There are hundreds of times more of these smaller asteroids
than there are the big ones the astronomers track,” says Mark
Boslough. “There will be another impact on the earth. It’s
just a matter of when.”
Horizon: Tutunkhamen’s Fireball, made by TV6 Productions, is
on BBC Two at 2100 BST on Thursday, 20 July
