[Prev][Next][Index][Thread]
(meteorobs) Dr David Morrison 2/20/98 NEO News Letter
List Members:
I think Dr. Morrison comment on the recent The Associated Press article
"More Fireballs Seen in the West" repeated in USA Today and Florida Today
Space On-line is right on point with our discussion of increased bolides
and what it means.
Victor
----------------------------------------------------------------------------
--
Victor Noto - Kissimmee, Florida USA
vnn2@phoenixat.com
http://www.phoenixat.com/~vnn2/BIGROCK.htm
Website theme quote:
"Life really is a Rock and
the Big Rock giveth and taketh away all life!!"
-------------------------------------------------------------------------
NEO News (2/20/98)
Friends and students of NEOs:
There has been a lot of press interest in bright fireballs during the last
year. It is good that people are aware of the presenrce of bright meteors,
and some of this media coverage has helped to inform the public about NEOs
and the impact hazard. However, some of the press reports have been
sensationalistc and have drawn false parallels between relatively common
meteors and rare events that can cause extensive damage and casualties.
Following is an especially instructive example in which many individually
correct facts are linked (perhaps unintenionally) to form a quite
misleading conclusion. I have made comments (in upper case) within the
text to note how this confusing and perhaps misleading result is achieved.
David Morrison
-------------------------------------------------------
More Fireballs Seen in the West
By MARTHA BELLISLE
.c The Associated Press AP-NY-02-15-98 1202EST
DENVER (AP) - The phone lines to Denver's Museum of Natural History have
been
buzzing since a fireball streaked across the Colorado sky last month.
That flash of light, caught on a homeowner's security camera, was not an
isolated incident; it was followed by at least four more fireball
sightings,
said Jack Murphy of the museum's geology department. He hopes to find
pieces
of the celestial objects for the museum's collection.
VERY FEW BRIGHT METEORS PRODUCE METEORITES. THUS MURPHY MAY HOPE TO FIND
SOME, BUT MOST LIKELY HE WILL NOT.
As new reports of sightings keep coming in, scientists are debating the
meteorites' origin and the meaning of the increased activity. There is more
at stake, they say, than where a piece of rock fell to the ground.
WHAT METEORITES? THE REPORT JUMPED FROM METEORS TO METEORITES AS IF THEY
WERE EQUIVALENT.
``These little things are the little brothers and sisters of the bigger
ones,'' said Doug Revelle, a scientist at Los Alamos National Laboratory.
``The reason for the interest is eventually a big one is going to hit, a
real
big one. And the question is: Can we protect ourselves?''
If a large meteor hit Earth, ``life as we know it would be very
different,''
he said.
REVELLE'S COMMENTS ARE TRUE BUT IRRELEVANT AS INTERPOSED IN THE STORY HERE.
IT IS A LONG LONG WAY FROM A FEW BRIGHT METEORS (OBJECTS A FEW CENTIMETERS
ACROSS) TO A KILOMETER-SIZE IMPACT.
When a fireball fell into the Earth's atmosphere on Jan. 11, a Front Range
resident's home security camera documented the bright light and shadows
along
with the sonic boom caused by the apparent meteorite, Revelle said.
Scientists will use the time between the flash and boom - 132 seconds - to
help determine where the meteorite touched down, assuming it didn't burn
out
before landing.
AGAIN, THIS IS A DUBIOUS ASSUMPTION, SINCE VERY FEW METEORS "TOUCH DOWN" TO
PRODUCE METEORITES.
Then, at about noon on Jan. 27, a commercial airline pilot flying over
Wyoming spotted ``a ball of flame trailing smoke.''
``He reported he did get some turbulence from the object,'' Jim Patton,
operations supervisor for the Federal Aviation Administration's flight
service center in Casper told the Rawlins, Wyo., Daily Times. ``He saw the
debris and felt the shock wave from it.''
ALMOST CERTAINLY A MISINTERPRETATION BY THE AIRLINE PILOT. METEORS ARE
TYPICALLY A HUNDRED KM OR MORE AWAY, AND IT IS ALMOST INCONCEIVABLE THAT
ONE CAME BY WITHIN A FEW HUNDRED METERS OF THE PLANE AND CAUSED TURBULANCE
OR A SHOCK. I DON'T DOUBT THE TURBULENCE, JUST THE ASSOCIATION WITH THE
METEOR. THE UFO LITEATURE IS FULL OF FALSE CAUSE-EFFECT ASSOCIATIONS OF
THIS KIND.
Residents in Breckenridge, Colo., also reported seeing that daytime
fireball.
Murphy said they believe the space rock was heading south to north and
landed
just north of Hanna, Wyo.
WITNESSES OFTEN THINK A METEOR "LANDED" WHEN IN FACT IT WENT BEYOND THE
HORIZON OR BURNED OUT IN THE ATMOSPHERE.
That night, another fireball broke into the Earth's atmosphere.
Scientists believe that meteorite came down in southern Colorado or
northern
New Mexico, Murphy said. People in Breckenridge spotted that fireball, too.
VERY UNLIKELY THAT RESPONSIBLE SCIENTISTS THINK IT "CAME DOWN"; SEE ABOVE.
``That one was seen traveling east to west,'' Murphy said. ``It has been a
long time since we've seen one moving like that.''
WHO IS "WE"? METEORS GO IN PRETTY MUCH RANDOM DIRECTIONS. MAYBE MURPHY
HASN'T SEEN ONE RECENTLY GOING EAST TO WEST, BUT THERE IS NOTHING UNUSUAL
ABOUT THE DIRECTION.
Another meteorite was seen and heard at sunrise in eastern Colorado on Jan.
30. And Murphy is investigating a report that came in earlier this month.
So what's happening?
``I don't know,'' Murphy said. ``We can't attribute it to anything. But it
is
unusual to have so much activity.''
ONE DOESN'T NEED TO ASSUME ANYTHING CAUSED THIS UNUSUAL ACTIVITY. IT IS
PROBABLY JUST A STATISTICAL FLUCTUATION. ONLY IF THE INCREASE WERE
OBSERVED WORLWIDE WOULD THERE BE A STORY HERE.
University of Denver astronomer Robert Stencel suggested that Earth may be
getting pelted with pieces of the Hale-Bopp comet. Early in January the
Earth
passed through the part of space the comet had traveled.
``Comets are like kids with muddy boots,'' Stencel said. ``They leave a
trail
of debris in their wakes.''
THIS ASSOCIATION WITH HALE-BOPP NOT A VERY CREDIBLE IDEA, AS LATER NOTED BY
OTHERS.
Meteorites from asteroids breaking out of the orbital belts between Mars
and
Jupiter are made up of metals, mostly iron. A meteorite from a comet would
have a lighter element composition, Stencel said.
NOT TRUE; PROBABLY THE REPORTER MISUNDERSTOOD. ONLY A SMALL FRACTION OF
ASTEROIDAL METEORS ARE IRON, PROBABLY LESS THAN 2%.
Such space debris is rare and would be of great scientific value, he said.
Scientists will test the composition of the meteorites - if they can get
their hands on them.
VALUABLE YES, BUT RARE, NO.
Revelle said he's excited about the meteorite activity, but he can't
account
for it.
NOR SHOULD THE REPORTER EXPECT HIM TO ACCOUNT FOR IT.
The reports describe a smoke trail following the fireballs - or bolides,
which are exploding meteors.
``The smoke trail is an indication that the object was quite big and
strong,'' Revelle said. ``Over the globe we see objects that are about a
meter across an average of only 12 times a year.''
THIS IS A SUBSTANTIAL UNDERESTIMATE. MORE THAN 100 PER YEAR WOULD BE
CLOSER TO THE CONSENSUS FLUX RATE FOR 1 METER OBJECTS.
Last Oct. 10, a meteorite crashed near West Texas and New Mexico; then on
Dec. 9, a large fireball crashed near Greenland, and on Dec. 13, a
meteorite
was seen across hundreds of miles, from Minnesota and Wisconsin south into
Iowa and northern Missouri.
NOT TRUE. BOTH THE TEXAS AND GREENLAND EVENTS WERE INITIALLY REPORTED AS
CRASHES, BUT THERE IS NO EVIDENCE OF A METEORITE HITTING THE GROUND IN
EITHER CASE. THIS IS A GOOD EXAMPLE OF HOW ONE EXAGERATED PRESS STORY
SPAWNS ANOTHER.
Revelle said history may give us some insight into the meaning of the
increase in fireball activity.
About 60 million years ago, an asteroid crashed into the Earth and kicked
up
enough dust to blot out the sun. Some scientists believe this resulted in
the
death of more than 80 percent of all animals and led to the extinction of
dinosaurs.
"SOME SCIENTISTS BELIEVE" IS AMAZINGLY CONSERVATIVE. BETTER WOULD BE "MOST
SCIENTISTS ARE CONVINCED". IT IS INTERESTING HOW THE REPORTER EXAGERATES
IN DEALING THE WITH METEOR/METEORITE ISSUES BUT BECOMES VERY CONSERVATIVE
WHEN MENTIONING EXTINCTIONS.
``These events seem to occur every 60 million years, give or take 10
million,'' he said. ``We're about three million years short of 60 million.
STARNGE STATEMENT; I DOUBT ANY SCIENTISTS THINK THESE LARGE IMPACTS ARE
STRICTLY PERIODIC. THUS A CLEVER PHASE BECOMES MISLEADING IN THIS CONTEXT.
``In order to defend the Earth from a large meteor, we would need to know
about it while it was months away to deflect it,'' he said. ``If we knew
about it when it was weeks away, it would be too late.''
NOTE THAT USE OF THE TERM "METEOR" FOR A BIG EXTINCTION-CAUSING COMET OR
ASTEROID IMPACT MAKES THE MASS EXTINCTIONS SEEM LIKE A LOGICAL PART OF THE
METEOR STORY.