[meteorite-list] Very good newspaper article on the Duluth fireball

From: Michael Groetz <mpg4444_at_meteoritecentral.com>
Date: Thu, 4 Mar 2010 19:23:14 -0500
Message-ID: <ad733151003041623q5935be2cuab449377c0e4d17f_at_mail.gmail.com>

http://www.duluthnewstribune.com/event/article/id/162010/group/home/

Fireball over Duluth!

Were you one of the lucky ones to see the brilliant, flaming object
plunge over the region about 7:15 p.m. last night? People all the way
from Cook County along Lake Superior's North Shore to Duluth to the
Spooner area in northern Wisconsin all reported seeing what appears to
be the same object. Audrey Monicken, who lives on Park Point, said she
was watching TV when she caught the sight.

"I saw a flaming thing come down out of the sky," she said, and
described the object as about the size of a mattress with red flames.
>From her vantage point, Monicken said the object seemed to disappear
in the middle of the bay.

Then we have this description from Wendy Hamm:

"My daughter and I were driving across the Bong Bridge (heading to
Superior) when we saw the object in the sky which was on its way down
(large, green with red on the bottom and the size of an average round
dinner table). It appeared to land in the water/ice in between the
Bong Bridge and railroad bridge or possibly where the old Arrowhead
Bridge was located. Someone might want to check that area out. And I
thought objects from space always landed in the ocean!!"

Brad Wick with the Duluth Police Department checked with the Duluth
International Airport in case the object was a plane in distress, but
no planes were in the area at the time. So what was it? The most
likely explanation is a brilliant meteor called a fireball. In a
lifetime you might see a half dozen of these spectacular sights, but
they occur somewhere over Earth every day and night.

Every meteor or "shooting star" you see is a fragment of a comet or
asteroid. The small ones might only be the size of grain of sand, but
the larger ones like last night's can range from pebble-sized to many
meters. While still in outer space, fragments destined to become a
meteors are called meteoroids. When they enter Earth's atmosphere at
speeds from 25,000 to 160,000 mph, they vaporize in a bright flash,
creating a brilliant trail we see as a meteor. Because they're so
bright and with no ready clues to their true distance, we're usually
tricked into thinking meteors are very close by. If one happens to
fade out over your downtown you might think it fell on Main Street. In
reality meteors burn up some 70 miles over our heads -- and that's if
you see one straight up at the top of the sky. If you're watching a
fireball off in one direction or another, you have to add in the
horizontal distance between you and the object. A more typical
distance between you and a bright meteor would be closer to a hundred
miles or more.

If a meteor is large enough to survive the friction and pressure of
atmospheric entry and lands in pieces on the ground it's called a
meteorite. A meteor destined to become a meteorite usually fades out
about 30 miles above the ground and continues in "dark fall" until it
strikes the ground. The larger the object falling, the more likely it
will create a sonic boom or rumblings like cannon fire on its way
down. Did anyone out there hear anything at the time? Could fragments
have reached the ground? Unless someone actually sees and hears the
objects falling nearby, chances are that this meteor -- if it did
produce meteorites -- will be extremely difficult to find. Most
fireballs produce a great show but vaporize to dust. Given the vast
surface area of the Earth, meteorites land with regularity, but actual
 witnessed meteorite falls are uncommon. On average meteorites from
falls are recovered only about five to ten times a year.

Let's assume for a moment that last night's fireball made it all the
way down. How would we go about finding it? We'd have to gather many
eyewitness reports of brightness, time and direction of travel and
then triangulate a possible fall location. Meteorite hunters would
then "work" the area with their eyes and metal detectors to look for
fresh, black, rounded and fragmented rocks. The black coating on a
fresh meteorite is called fusion crust and the result of frictional
heating during its plummit through the atmosphere. Fusion crust is
only a couple millimeters thick; the inside of the meteorite still
holds onto the chill of outer space. Most meteorites contain
iron-nickel metal which a properly tuned metal detector can detect.
Another more recent technique is using Doppler weather radar to pick
up the dust and debris trail from a falling meteor. Precise data like
that is invaluable in helping to pinpoint the fall location.

Doppler was used to help find last year's well-publicized Ash Creek
fall last February near West, Texas. Needless to say, it's a lot
easier to find meteorite fragments if you're searching farm fields and
open prairie than a region covered by forests and lakes!

All this time I've been talking meteor fragments but there's also the
small possibility the flaming object was a piece of manmade space
junk. I haven't seen any postings on a listserv on the subject but a
small piece coming down could easily mimic a meteor.

If you have any additional information about the object that fell,
please click on the Comments link below and share your story with us.
And if you have a photo, we're crazy to see it. Thanks!



(Material from the Duluth News Tribune was used in this article.)



Posted by: rking at duluthnews.com on 3/4/2010 at 11:48 AM | Comments (0)
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Tags: daily updates, cook county, fusion crust, astro bob, life, news,
fireball, meteor, meteorite, duluth
Received on Thu 04 Mar 2010 07:23:14 PM PST