PLEASE NOTE:


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Date sent: Fri, 20 Feb 1998 12:01:25 -0500 (EST)
From: Benny J Peiser B.J.PEISER@livjm.ac.uk
Subject: CC DIGEST 20/02/98
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL

CAMBRIDGE-CONFERENCE DIGEST, 20 February 1998
---------------------------------------------

INCREASED FIREBALL ACTIVITY OR INCREASED FIREBALL OBSERVATIONS?

During the last couple of months, a number of fireball reports have
made the news headlines around the world. Throughout human history,
in times of increased meteoric and cometary activity, people have
worried about (or preached) the imminent "end of the world". In view
of this deeply-rooted apocalyptic tradition - and due to our new
awareness of the reality of past impacts catastrophes-, it is not
surprising that many people are once again concerned with these
eschatological questions. However, it is far from certain whether
the recent fireball observations during the critical months of
December and January evidence an actual increase of
meteoric/cometary activity or whether there are simply more
astronomers (equipped with better technology) scanning more areas of
the sky when the earth intersects known meteor streams.

I have attached some reactions to Victor Noto's rather apocalyptic
question: "Could all these [recent] fireballs be the precursors to
the big rock? Is an extinction period beating at our door in the
form of mounting numbers of bolides?"

===========================================

(1) SPACE BLAST IN NORTHERN IRELAND?
NEW SCIENTIST, 14 February 1998

(2) NO HARD EVIDENCE FOR METEORITE HYPOTHESIS
Mark Bailey meb@star.arm.ac.uk

(3) MEDIA BLAMED FOR INCREASING APOCALYPTIC FEARS
Bolide Chaser bolidechaser@tripod.net

(4) METEOR INCREASE WORRIES SCIENTISTS
http://www.usatoday.com/life/science/space/lss213.htm

(5) BRIAN MARSDEN'S ASSESSMENT
Victor D. Noto vnn2@phoenixat.com

(6) FIREBALL ACTIVITY HAS DECLINED OVER LAST 40 YEARS
Phil Bagnall http://www.ticetboo.demon.co.uk/

===========================
(1) SPACE BLAST IN NORTHERN IRELAND?

From: NEW SCIENTIST, 14 February 1998, p. 5

An explosion in Northern Ireland that had been blamed on terrorists
was in fact caused by a meteorite. A loud blast wakened the people
of Belleek at 5 am on 13 December 1997. On 6 January, a
1.2-metre-wide crater and the remains of an aluminum water trough
and milk churn were discovered. The churn had a glassy rock fragment
embedded in it. Tom Mason of the Armagh Planetarium believes a
20-centimetre fragment of the comet Phaeton was responsible.

================================
(2) NO HARD EVIDENCE FOR METEORITE HYPOTHESIS

From: Mark Bailey meb@star.arm.ac.uk

Dear Benny,

Short note on the Irish `meteorite' for the CC forum:

The difficulty with the meteorite hypothesis is that in view of the
diameter of the crater (1.7m) any cosmic body should have been of
substantial size when it hit the ground, making the Belleek event
quite exceptional. No meteoritic fragments have been found.

Best wishes, Mark

==============================
(3) MEDIA BLAMED FOR INCREASING APOCALYPTIC FEARS

From: Bolide Chaser bolidechaser@tripod.net

http://www.usatoday.com/life/science/space/lss213.htm

If the attached web page is any indication, it's easy to see how the
media is adding to the general publics misconception of an "increase
in fireball activity!" No amount of media interviews with "meteor
experts" will dissuade the public opinion, not after the recent
comets, and certainly not after the summer block buster (yes, the
Leonid Shower, too, but before that, the movie "Asteroids").

Even though I'm in the "no upswing" camp, I have to admit to
personally seeing more bolides and brighter meteors than in the
past. For now, I'm writing it off to increased awareness and "space
junk". I know that the Air Force tracks this debris but I'm not
confident that they're interested in reporting when it reenters the
atmosphere. I hope the data will be more accessible when NASA
implements the Orbital Debris Radar.

By the way, if a bolide travels from east to west, can we rule out
that it was "space junk"?

As usual, just wondering,
Bolide Chaser

=========================
(4) METEOR INCREASE WORRIES SCIENTISTS

From: http://www.usatoday.com/life/science/space/lss213.htm

Meteor increase worries scientists

DENVER - 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.

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.

"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.

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.

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."

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.

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.

"That one was seen traveling east to west," Murphy said. "It has been a long
time since we've seen one moving like that."

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."

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."

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.

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.

Revelle said he's excited about the meteorite activity, but he can't
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."

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.

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% of all animals and led to the
extinction of dinosaurs.

"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.

"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."
Copyright 1998, Associated Press

======================
(5) BRIAN MARSDEN'S ASSESSMENT

From: Victor D. Noto vnn2@phoenixat.com

Thought the List may be interested in a recent correspondence of
Brian Marsden of cfa Harvard on the subject of his concerns - PHA's
(Potentially Hazardous Asteroid).

----------------------------------------------------------------------------
From: brian%cfaps1.span@vms.noao.edu To: vnn2@phoenixat.com Subject: RE-
Much Bolide activity being reported? Date: Wednesday, February 18, 1998
11:12 AM

I don't go for short-term statistics. I also don't want to have to
contend with an impending large impact with only months (let alone
weeks) notice. The whole point about 1997 BR and the 107 objects on
the PHA list generally is that we need to boost searches to the
extent that it just won't happen that one could appear and be on a
collision course without notice amounting to at least decades, and
preferably centuries and more. Then there really would be time to
"attend to the matter" in a sensibly intelligent manner, rather than
be forced into a potential disaster, perhaps involving nuclear
weapons deployed with disastrous consequences unrelated to any real
asteroid hazard. Actually, we are fortunate that most of the
potential danger, in both human and economic terms, is from objects
in the PHA class with short-period orbits. This is a tremenous
advantage! Not only are these therefore bright enough to be found
easily when they are NOT right on top of the earth, but they don't
go all that far from the sun, so in principle we can observe,
even discover them all the way around their orbits! The astronomical
part of the problem can actually be essentially solved, with the
appropriate expenditure of time and money (like 30 years at $10
million worldwide, say).

Yes, there are smaller objects too, and they hit more often, and
they could, like Tunguska in 1908, do tremendous local damage: but
the financial impact is a lot less, and they don't threaten the very
survival of our species. And there are also objects in larger
orbits, where we do not have the possibility of discovering them
whole revolutions before they may hit. These are somewhat of a
worry, and we need to be aware of that, but, object for object,
long-period objects are at most 2 percent the threat of short-period
objects (and even this is probably an overestimate) over any given
interval of time; actually, the most troublesome objects may in
fact be objects in orbits of intermediate period, say, a century or
so, like comet 109P/Swift-Tuttle, where a 30-year search is not
going to yield them. At some level, therefore, one is going to have
to continue the search indefinitely, even after the 30-year search
has produced most of the PHAs.

I hope this helps put things into perspective for you.
Brian G. Marsden

===============================
(6) FIREBALL ACTIVITY HAS DECLINED OVER LAST 40 YEARS

From: Phil Bagnall http://www.ticetboo.demon.co.uk/

Victor Noto asks:
"Could all these [recent] fireballs be the precursors to the big
rock? Is an extinction period beating at our door in the form of
mounting numbers of bolides?"

The short answer would seem to be no. In fact, fireball activity has
declined slightly over the past 40 years.
Phil Bagnall

Hi, Phil, now I have to ask you the same question! :) What published
results have you read that indicate such a decline in fireball activity? Lew
Gramer

There have been various papers published by organizations like the
BAA and IMO. Comparing reports since the War clearly shows a slight
fall in fireball activity, despite the fact that there are more
observers now than at any time in the past. This lead the BAA Meteor
Section Director to conclude that Taurid fireballs do not exist(!)
even though evidence for Taurid fireballs goes back to at least the
11th Century and there are numerous photographs.

Phil Bagnall
http://www.ticetboo.demon.co.uk/

--------------------------------
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