[meteorite-list] Vancouver Meteorite Boom Friday

From: JoshuaTreeMuseum <joshuatreemuseum_at_meteoritecentral.com>
Date: Tue, 21 Apr 2009 13:33:36 -0400
Message-ID: <F52E8BC4832947C69185859014EA35CC_at_ET>

I have two problems with this story:

1.) Wouldn't it have to be a really really bright bolide to see the flash
while inside a vehicle under a thick sleeping blanket with your eyes closed?

2.) The 1908 Siberian guy: From 60 Kilometers away, would your shirt really
catch on fire? If it did would it burn before the concussion blast? If your
shirt caught fire, wouldn't all flammables nearby also catch fire resulting
in a general conflagration? Wouldn't this have been mentioned in the story?



A mysterious "boom" that resounded across Vancouver early Friday may have
been an extraterrestrial wake-up call, theorizes a geophysicist with the
U.S. Geological Survey in Vancouver.

"I can't think of any other explanation, other than a fairly substantial
gravel quarry explosion," said Jeff Wynn, research geophysicist with the
Cascades Volcano Observatory.

Local gravel quarries reported no activity, especially at 6 a.m.

Several online readers last week offered theories about the noise, which
some reported rattling windows and spooking animals. But, in a story on
Saturday, experts ruled out some of the obvious theories. It wasn't a
thunderclap. It wasn't a volcanic eruption. As far as emergency managers
know, nothing exploded on the ground.

Wynn said Monday he's reasonably confident that it was a relatively large
meteorite known as a bolide blowing apart in the atmosphere miles above
Vancouver. He said these arrivals are surprisingly common, though normally
not in such a densely populated urban area where it's experienced by so many
people.

People generally reported the noise in an area of no more than about 10
miles, from west Vancouver to Hazel Dell and Orchards.

"A relatively small object could do that," Wynn said. The object was
probably "on the order of maybe a foot when it hit the upper atmosphere. It
was probably pretty close to vertical" to be heard in such a confined area.

If it was any bigger?

"Portland wouldn't be here," he said.

Wynn personally studied the landscape impacted by an iron-nickel object that
crashed down in a remote area of Saudi Arabia in 1863. It had "all the
effects of a Hiroshima-scale atom bomb except one: no radiation," he wrote
in an e-mail.

The objects enter our atmosphere at mind-bending speed - 7 to 25 kilometers
a second, Wynn said - which causes air to stack up in front and a vacuum
behind. When the bolide breaks apart, its now-exponentially larger surface
area creates a blindingly bright flash and a sonic boom.

Wynn recalled witnessing one by happenstance while in the midst of a fierce
sandstorm on the Arabian Peninsula in 1994.

He had bundled up against the storm inside his Land Cruiser, pulled a thick
sleeping bag over his head and had his eyes shut. The flash penetrated the
total darkness.

Depending on the size, composition and angle of entry, space rocks can do
worse than create a loud noise or an interesting flash.

A bolide that detonated over the Siberian Taiga on June 30, 1908, leveled a
forest the size of Rhode Island, Wynn said. Sixty kilometers south of the
detonation point, a man in a remote trading post was assembling barrels with
his back to the action.

"The first thing he knew, the back of his homespun wool shirt caught on
fire," Wynn said. "As he pulled the shirt off, the concussion blast hit him
and knocked him end over tea kettle."

Wynn said the man's wife, spotting her husband laying half-naked and
unconscious at the base of a tree, lugged him inside their cabin and nursed
him back to health.

In the case of the Vancouver boom, he said, the object had to be much
smaller and composed of stony material rather than dense iron.

"If people find pieces of this thing on the ground, it will have a burned
and pitted look," he said.

Wynn downplayed the chance that it was a sonic boom from an early-morning
military operation, both because a spokesman for the Oregon Air National
Guard discounted it and because the area affected was more confined than
what Wynn would expect from a sonic boom from an aircraft.

"The idea that it would be a sonic boom from a military aircraft is pretty
darn small now," he said. "It's a huge waste of energy, and you'd only do
that if you're trying to chase someone down and shoot them."
Received on Tue 21 Apr 2009 01:33:36 PM PDT