PLEASE NOTE:


*

CCNet DABATE, 19 November 1998
------------------------------

(1) THE LEONIDS MISUNDERSTOOD
    Duncan Steel <dis@a011.aone.net.au>

(2) BREAKING NEWS: LEONID IMPACT IN SCOTLAND?
    Graham Richard Pointer <grp1@st-andrews.ac.uk>

=========================
(1) THE LEONIDS MISUNDERSTOOD

From Duncan Steel <dis@a011.aone.net.au>

Dear Benny,

This offered with good intentions and I hope that no-one takes it
amiss. Iwan Williams reported the 'success' of various teams in
predicting the Leonids activity:

>There are two points to be made, one doing science gets it correct
>more often than wild speculation, and two, more seriously perhaps,
>Why did all four models get the rate about correct but the timing
>(ie the longitude of the node) wrong by about half a degree. [sic]

Well, there's a third point to be made, and that is that all four
groups Williams mentioned (plus various other people) GOT IT WRONG.
Suggesting that they/science got it right, because they very vaguely
gave limits on the count rate which were in the right ballpark, is
persiflage.  One might as well say that you got it right when you
predict the score for a Manchester United versus Wrexham FA Cup
Final as being 6-0, but in the event it's Wrexham that wins by that
score.  Tell your story to the bookies.  Science is all in the
details, and here the details were wrong.  Actually, the big picture
was wrong, too.

Is it true that "all four models get [got] the rate about correct"?
Actually, skilled visual meteor observers coordinated by the
International Meteor Organization have reported that the zenithal
hourly rates both at the predicted time of peak activity (witnessed
from Asia), and the earlier period around 12 hours before (witnessed
from Europe), were of the order of a few hundred.  Thus it appears
that the models were incorrect in this aspect also.

Further, one might note that one would expect that accurate
modelling would be much more likely to get the time of occurrence
correct, rather than the actual count rate. The former could/should
be available through quite straightforward dynamical study, if we
have an understanding of the past orbital evolution of the parent
comet and some notion of the vague ejection/relative speeds of the
meteoroids.  On the other hand, predicting (properly, and not
through some chance agreement) the activity rate depends upon a
whole lot of presumed values for parameters, such as production
rates, ejection speeds and directions, ejection epochs, orbital
evolution in space under various forms of perturbation. Thus there
are many fudge factors and 'getting it right' may be more a matter
of chance than skill.  Anyone can win the lottery. How many alien
civilizations are there in the galaxy?  Put a few dozen knowledgeable
people into a room and those who aren't sure that N=0 will mostly
agree that N=10 to 100 even though their individual assumed input

values for the separate parameters in the Drake Equation may differ
by some orders of magnitude.

>All these works are published in refereed scientific journals. The
>conclusions of all are remarkably similar...

Many papers discussing the orbit of Mercury were published in
'refereed scientific journals' prior to the start of this century. 
They generally got 'remarkably similar' results, with the precession
rate of that planet's perihelion position being unexplained.  This
led to suggestions such as that of Le Verrier of an undiscovered
intra-Mercurial planet tugging Mercury around.  An understanding
awaited Einstein and the recognition that Newtonian mechanics is not
a good enough approximation. I doubt that the problem with the
Leonids predictions was as fundamental as this, but you get the
point.  That last part of Williams' statement I quoted just above is
most useful not in the way he perhaps intended it, but rather as
showing that there was a consistency of error in the modelling by
the various groups, hopefully permitting us to move forward from
there and eventually get it right.

One may of course appeal to historical records and use those almost
alone, comparing only the recent path of 55P/Tempel-Tuttle to get
the near-Earth trajectory and thus make a prediction based upon
little science but much interpretive skill (as in Yeomans' admirable
paper in Icarus, 1981), but that's similar to using the results from
all Manchester United versus Wrexham games over the past century (or
more!?) to predict the next result of a meeting between those soccer
clubs. The history helps, but it is not definitive.  With respect
(and I mean that sincerely: all the teams mentioned by Williams are
very skilled and accomplished) what is needed here is scientific
understanding, and the 1998 Leonids showed that we do not have that.

This is not a time to breath a sigh of relief and clap everyone on
the shoulder, but to step back and admit that we are a long way from
knowing what is going on.  The Leonids may or may not be spectacular
in 1999: at this stage my own view would be that since all models
were wrong for 1998, those models are unlikely to have it right for
next year.  On top of that we know that even during recent centuries
there have been meteor outbursts of no known origin/parent.  If
there is 'danger' then that danger is neither passed nor recognized.

Whilst writing, I will briefly mention another matter which others
have mentioned and in many cases misunderstood or misrepresented,
and this pertains to my own suggestion that most of the meteoroidal
(sizes like a millimetre or less) influx to the atmosphere is
actually organic in nature, being composed of moderately volatile
tarry-type components. For the Leonids specifically I discussed this
in the October issue of Astronomy & Geophysics.  Be clear that this
work does NOT pertain to the actual flux or time of occurrence of
the Leonids: my suggestion is limited to saying that conventional
radar and optical meteor observation techniques detect only a small
part of the total influx (I would guess of order 1 to 10 percent) of
such meteoroids, which comprise the majority of the annual mass
influx.  For the Leonids the situation would be especially acute
because (i) They are recently-released on orbits with perihelia near
1 AU, and thus will not have been so grossly devolatilized in space
as would be the 'average' meteoroid; (ii) Their high entry speed
results in extreme ablation heights.  Getting back to the core of
the suggestion, pertaining to the composition of meteoroids in
general, if one wants to differ with my hypothesis then one must do
one of two things: (a) Find some alternative component of meteoroids
which ablates at 120-140 km and maybe higher; or (b) Show that my
MF/HF radar observations, and those preceding, and the VHF heights
of overdense meteors and also head echoes made by many groups, and
the recent UHF radar results of others using the the EISCAT and
Arecibo systems, are all in error, and thus small meteoroids
actually ablate at heights below 110 km and not as indicated by the
many types of study mentioned, thus making stony/metallic
compositions viable.  The Leonids you saw were only those.

Duncan Steel

============
(2) BREAKING NEWS: LEONID IMPACT IN SCOTLAND?

From Graham Richard Pointer <grp1@st-andrews.ac.uk>

From "The Scotsman" 19 November 1998

IT SOUNDS like a case for the X-Files team. But it is a Scottish
fire brigade which is trying to get to the bottom of a mysterious
blaze which may have extraterrestrial origins.

Investigators examining a fire in farm outbuildings near Selkirk say
the damage may have been caused by a meteorite strike.

Preliminary inquiries revealed the fatal spark could have come from
a shooting star crashing into the farm's hay sheds.

A couple who watched the spectacular Leonid meteor storm caused by
the Tempel-Tuttle comet early on Tuesday claimed an object fell from
the sky and hit the ground, where it exploded on impact.

Firefighters thought at first that the blaze at High Sunderland
Farm, near Selkirk, had been started maliciously. But after learning
of the couple's sighting they were forced to reconsider their
reports of the incident.

Tom Munro, of Lothian and Borders Fire Brigade and the station
commander at Galashiels, was one of the first on the scene.

He said: "This was an extremely strange incident and it is one we
are being forced to keep very open minds about.

"When I got there, the barns had been all but destroyed. I searched
the barns looking for bones - to see if it had been started by
someone sleeping rough inside - or other signs of a malicious cause.

"I later learned, via the police, of the reported meteor strike. I
then remembered kicking a football-shaped object with my boot, which
I had disregarded at the time. It had a metallic appearance and had
split in half. Fire investigators later went back but could not find
anything among the mud and other debris."

Professor John Brown, the Astronomer Royal for Scotland, based at
Glasgow  University, said: "This is certainly a fascinating account.
It is perfectly possible the cause of the fire could have been a
meteorite."

Graham Rule, the secretary of the Edinburgh Astronomical Society,
said: "Usually in Leonid showers the debris is no bigger than
grains, but it is entirely feasible that a chunk of something bigger
has come to earth.

"Seconds before impact it was probably glowing red hot, so it is
likely that if it hit something like a hay shed, a fire would have
been the result."

Alastair McBeath, the vice president of the International Meteor
Organisation and the co-ordinator of the meteor section of the
Society for Popular Astronomy, said he had seen several bright
meteors in the skies above the north of England during the Leonid
storm.

He said: "The vital thing is to secure the object and very quick
checks will establish if it is of extra terrestrial origin.

"Leonids do produce a lot of bright meteors and I have never seen so
many in a single night, and many were exceptionally bright.

"However, meteorites tend to be very hot on the outer crust when
they enter the atmosphere but then cool down as they free fall for
the remaining 30 or 40 kilometres."

Copyright 1998, The Scotman


*

CCNet DEBATE, PART II, 19 November 1998
---------------------------------------

(1) SKEPTICISM REGARDING SCOTTISH IMPACT STORY
    Neil Bone <bafb4@central.susx.ac.uk>

(2) MORE DOUBTS ABOUT IMPACT REPORT
    Simon Mansfield <simon@spacer.com>

(3) OUR ESTIMATE WAS CORRECT NEVERTHELESS
    Iwan Williams <I.P.Williams@qmw.ac.uk>

(4) ASTROBIOLOGY: YESTERDAY'S RIDICULE, TODAY'S SCIENCE
    Chandra Wickramasinghe <xdw20@dial.pipex.com>

(5) COMET 'BRINGS EXTRATERRESTRIAL LIFE'
    THE TIMES, 18 November 1998 <http://www.sunday-times.co.uk>

============================
(1) SKEPTICISM REGARDING SCOTTISH IMPACT STORY

From Neil Bone <bafb4@central.susx.ac.uk>

I think someone's got a bit carried away, partly by suggestion from
all the nonesense in the media over the past few days surrounding the
Leonids. There is *no* way a piece of leonid debris could be
responsible, and - given the numbers of people out watching - it seems
unlikely that a progenitor fireball for an object of this nature would
have been missed; it'd have had to be extremely bright. Just shows what
some people will do for a bit of publicity.

Neil Bone
Director, BAA Meteor Section
'The Harepath', Mile End Lane, Apuldram, Chichester, West Sussex,
PO20 7DZ. Tel.  01243 782679.

================
(2) MORE DOUBTS ABOUT IMPACT REPORT

From Simon Mansfield <simon@spacer.com>

Just for grins,

How big a hole (crater) would a piece of rock traveling at 80,000
mph leave if it hit the ground and left a meteorite the size of a
football?

>"I later learned, via the police, of the reported meteor strike. I
> then remembered kicking a football-shaped object with my boot, which
> I had disregarded at the time. It had a metallic appearance and had
> split in half. Fire investigators later went back but could not find
> anything among the mud and other debris," said the Fireman.

Still I sure was watching them fireballs hoping to see one come down.

What have the past 12 hours of pre dawn been like - any further
reports? Sydney has a beautiful clear sky tonight (Thursday) after
three nights of storms. Glad I drove west for the main event, but
the continued reports of heavier that expected fireballs makes me
think another few hours of early morning watching might be worth it.
We also have no city lights to the East just a rising sun.

Simon Mansfield

================
(3) OUR ESTIMATE WAS CORRECT NEVERTHELESS

From Iwan Williams <I.P.Williams@qmw.ac.uk>

Dear Benny,

I do not wish to comment in general about the points Duncan Steel
makes and in particular, my point about the timing of the event was
I thought the same as the one Duncan makes, namely that there is
something wrong in the models. I also do not wish to comment further
on other people's models, let me however state that the "conclusion"
of the paper of Wu and Williams was neither vague nor incorrect
namely "For 1998, the numbers are very similar to 1933 and predict
that the storm will be of a similar level to 1933".

In 1933, the level was 250 per hour. As far as I can tell, that is
still the 'best' estimate for 1998.

best wishes
Iwan Williams

================
(4) ASTROBIOLOGY: YESTERDAY'S RIDICULE, TODAY'S SCIENCE

From Chandra Wickramasinghe <xdw20@dial.pipex.com>

Dear Benny:

If you would like to publish the letter Fred Hoyle and I had in the
Independent of 18/11/98 and the front page news item in the Times of the
same day, you are welcome to do so.  I find your publications most
interesting!

Thanks

Chandra Wickramasinghe

--------------------- 

From Professors Chandra Wickramasinghe and Sir Fred Hoyle

Sir:

MICROORGANISMS FROM THE LEONID METEOR STREAM

Recent comments on the crossing of the Leonid meteor stream have all
overlooked an interesting and potentially important consequence. It
is now widely accepted that comets carry complex organic molecules
including amino acids that might at the very least have been
connected with the beginnings of life on this planet. And there are
also serious discussions in progress in scientific circles of the
even more radical possibility of cometary panspermia of the type we
pioneered in the late 1970's. The importance of the present crossing
of the Leonids is that the source comet Tempel-Tuttle (which has a
period of 33 years) came closest to the sun on the last occasion
only 9 months ago, so the Earth will be in receipt of freshly
evaporated cometary particles over the next few days. Spectacular
meteor shows are caused by the entry of particles of sizes typically
larger than a grain of sand, which burn up as they plough into the
Earth's high atmosphere at a speed of some 70 kilometres per second.

Besides these larger particles the meteor stream will also contain,
perhaps in comparable mass, a population of bacterial sized
particles. We have shown that particles of the sizes of micrococci
or smaller travelling at 70 kilometres per second would be
flash-heated to temperatures upto about 200 degrees Celsius for
brief intervals of the order of seconds, after which they will be
slowed down to reach the stratosphere. (See for instance our book
Diseases from Space (J.M. Dent, 1979).  In several laboratory
experiments it has been demonstrated that bacteria retain viability
under such conditions of flash heating in a near vacuum. Laboratory
experiments have also shown that bacteria that become deactivated
through exposure to ultraviolet light (as might happen after 9
months in orbit) are easily reactivated, through the operation of
enzymes, when the source of radiation is removed. Thus the
possibility of viable microorganisms from Comet Tempel-Tuttle
reaching the Earth cannot be ruled out.

The average daily input of cometary dust to the Earth is estimated
at about 50 tonnes. A ten-thousand fold increase in this quantity

over a couple of days seems likely, leading to a total mass of the
order of a million tonnes. If as little as one part in a thousand of
this is in the form of viable microorganisms the total number of
microbes drifting down to the Earth will be a staggering 10 to the
power 23  ! 

N.C. Wickramasinghe
F. Hoyle
Cardiff University
17 November 1998

------------------
(5) COMET 'BRINGS EXTRATERRESTRIAL LIFE'

From THE TIMES, 18 November 1998
http://www.sunday-times.co.uk

By Nigel Hawkes, Science Editor

THE Earth may have been showered with bacteria as it passed through
the Leonid meteor stream last night, two astronomers believe.
Professor Chandra Wickramasinghe and Sir Fred Hoyle have long
championed the theory that microscopic forms of life may have
originated elsewhere with Earth sweeping them up on its orbit.

Once ridiculed, the theory has gained in plausibility with the
discovery that comets do contain large amounts of organic matter and
carbon-based chemicals which include amino acids, the basic building
blocks of proteins. It achieved respectability last night when Nasa,
the US space agency, launched its first "astrobiology" mission using
aircraft to seek traces of extraterrestrial life in the meteor
stream.

The Leonid shower, expected to peak at about 7pm yesterday, consists
of the trail of the comet Tempel-Tuttle. As the Earth passes through
that trail, thousands of tiny particles of matter burn up in the
atmosphere to create "shooting stars" - brief streaks of light.

Every 33 years or so, the spectacle is enhanced because the comet
has recently passed close to the Sun, boiling off more material from
its surface. This year and next promise such a show, and astronomers
were out last night hoping to see a repeat of the last major Leonid
storm in 1966.

Most people have overlooked the possibility of living bacteria from
Tempel-Tuttle reaching the Earth, said Professor Wickramasinghe.
Because the comet last passed close to the Sun only nine months ago,
cometary particles will be freshly evaporated from its surface.

As well as solid particles the size of a grain of sand, which burn
to create meteors, the stream will contain perhaps an equal mass of
bacterial-sized particles, he believes. As these reach the
stratosphere, they will be flash-heated to 230C (446F) for a few
seconds.

Copyright 1998, The Times

----------------------------------------
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----------------------------------------
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*

CCNet DIGEST, 19 November 1998

THE LION THAT DIDN'T ROAR: STILL CONFLICTING LEONID REPORTS
-----------------------------------------------------------


(1) REPORTS OF A METEOR STORM....
    Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>

(2) ... WERE WRONG
    Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>

(3) UK ASTRONOMERS COUNT TO 2000 IN ONE HOUR
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(4) INTERNATIONAL OBSERVERS CAN ONLY COUNT TO 500 IN ONE HOUR
    Rainer Arlt <rarlt@aip.de>

(5) POOR UNDERSTANDING OF LEONIDS RESPONSIBLE FOR WRONG PREDICTIONS
    ESA Science News <http://sci.esa.int>

(6) LEONID METEOROID STORM & SATELLITE THREAT CONFERENCE
    The Aerospace Corporation
    http://www.aero.org/conferences/leonid/

(7) DRAWING ATTENTION TO IMPACT HAZARD & SPACEGUARD
    Michael Paine <mpaine@tpgi.com.au>

(8) IS THIS A BULLET FROM THE K/T IMPACTOR?
    Andrew Yee <ayee@nova.astro.utoronto.ca>

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

(1) REPORTS OF A METEOR STORM....

From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>

A meteor storm did occur during the 1998 Leonids, though you had to
be at the right place at the right time to observe it.  According to
IAU Cirular 7052, Alan Fitzsimmons in La Palma, Canary Islands,
observed about 1000 Leonids/hour on November 17 at 3:36 UT which
increased to about 2000 Leonids/hour on November 17 at 4:34 UT.  In
other words, he observed the Leonids at a rate of over 1000
meteors/hour over a period of one hour.

Ron Baalke

=====================
(2) ... WERE WRONG

From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>

Apparently the 2000/hour observation from the Canary Islands was a
a group observation. IAU circular reports the max ZHR was around
500/hour, so the 1998 Leonids does not qualify as a meteor storm. 

Ron Baalke

======================
(3) UK ASTRONOMERS COUNT TO 2000 IN ONE HOUR

From Andrew Yee <ayee@nova.astro.utoronto.ca>

Royal Astronomical Society Press Notice

Date: 18 November 1998
Released at 1.00 a.m.

Ref. PN 98/24

Issued by:

Dr Jacqueline Mitton
RAS Public Relations Officer
Office & home phone: Cambridge ((0)1223) 564914
FAX: Cambridge ((0)1223) 572892
E-mail: jmitton@dial.pipex.com

Leonid Meteor Storm Springs Early Surprise

Early reports suggests that the expected Leonid meteor storm did
indeed take place -- but around 16 hours sooner than forecast.
Astronomers working at the UK's Isaac Newton Telescope on the island
of La Palma in the Canary Islands estimated that they were seeing
meteors at a rate of 2000 per hour as dawn broke around 5 a.m. GMT
on Tuesday 17th November, with numbers still going up.

Amateur astronomers and member of the public in the UK and other
western European countries have been reporting large numbers of
meteors -- hundreds per hour -- between about 1..00 and 6.00 a.m. on
the 17th. By noon GMT, the rate seemed to have declined substantially,
according to reports from observers in the US, where it was still
dark. The peak of the storm probably occurred over the Atlantic Ocean
around 6 a.m. GMT.

Astronomer Dr Alan Fitzsimmons of the Queen's University, Belfast, was
one of the lucky observers to witness the storm in the clear dark
skies over the La Palma Observatory. "The number of bright meteors is
astounding" he wrote as the storm grew in intensity at about 5.30
a.m.. "Every couple of minutes you get a bright flash behind you and
you turn around to see the trail fading. The brightest meteors have
bright green trails, and often bright red heads. We are approaching
one meteor per second and the rate still seems to be increasing, but
twilight is now beginning."

The precise timing and strength of an exceptional meteor storm such as
this is extremely difficult to predict. Astronomers bold enough to
make forecasts had suggested the peak was most likely to be seen
around 8 p.m. GMT, and any storm best seen from the Far East. Once the
observations made this year are analysed, it should be easier to
predict whether there could be a repeat performance in 1999.

No information has yet been received on whether any satellites or
spacecraft suffered damage as a result of the meteor storm.

========================
(4) INTERNATIONAL OBSERVERS CAN ONLY COUNT TO 500 IN ONE HOUR

From Rainer Arlt <rarlt@aip.de>

-------------------------------------
I M O   S h o w e r   C i r c u l a r
-------------------------------------


LEONID Activity 1998

No strong, short-lived activity peak of the Leonids was
observed in 1998. An enhancement of activity up to a level
of ZHR=150-200 can be found at solar longitude=235.29
(eq. 2000.0). All reports from Japan, Korea, Mongolia,
Thailand and India indicate this level of activity.

The peak was preceded by a strong background component
being rich in bright meteors and fireballs as bright as
-16 mag. ZHR activity between 200 and 500 was observed
from November 17, 0h UT to 12h UT corresponding to 234.4
to 235.0 degrees in solar longitude. This is much earlier
than the Leonid returns of previous years had suggested.

Reports about rates as high as 1000-2000 meteors per hour
as seen from Switzerland and La Palma cannot be confirmed
by regular observations from Europe made at the same time.

The ZHR profile given below is based on the following
observers:

ARLRA Rainer Arlt             LUKVL Vladimir Lukic
BARRO Rony Barry              LUNRO Robert Lunsford
BETFE Felix Bettonvil         MCCST Stephen McCann
CARAR Arturo Carvajal R.      MCBAL Alastair McBeath
CARTA Tal Carmon              NATSV Sven Nather
CASAN Andrew Casely           OFEER Eran Ofek
COOTI Tim Cooper              OKODR Dragana Okolic
DAVMA Mark Davis              OSAKA Kazuhiro Osada
EENTO Tonis Eenmae            PERAL Alfredo Pereira
ENZFR Frank Enzlein           RENIN Ina Rendtel
GABOF Ofer Gabzo              SHUBR Brian Shulist

GNAOR Orly Gnat               SPAGE George Spalding
GODSH Shelagh Godwin          SPEUL Ulrich Sperberg
GORRO Roberto Gorelli         TAIRI Richard Taibi
JAAHE Helle Jaaniste          TRIJO Josep Trigo
KIDMA Mark Kidger             VITCA Catarina Vitorino
                              WEEAN Anne van Weerden

Date   Period (UT)  ZHR +-
--------------------------
Nov 15  1800-0150   12   8
Nov 16  0813-1028   16   6
Nov 16  1915-2319   64  12
Nov 17  0000-0200  460 180
Nov 17  0200-0330  510 220
Nov 17  0300-0420  360 210
Nov 17  0400-0630  255 124
Nov 17  0700-1000  242  37
Nov 17  1000-1200  256  18
Nov 17  1500-1700  100  16
Nov 17  1700-1840   86  18
Nov 17  1800-1940  102  19
Nov 17  1900-2050  130  35
Nov 17  2000-2100  180  48
Nov 17  2145-0040   62  15
Nov 18  0000-0200   47   5
Nov 18  0130-0240   38  14
Nov 18  0220-0500   33  11
Nov 18  0430-0650   36  22
--------------------------

ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.

---
Rainer Arlt, 1998 November 18, 19h UT.
100114.1361@compuserve.com
Please use this address, since the IMO computer may not be working.

====================
(5) POOR UNDERSTANDING OF LEONIDS RESPONSIBLE FOR WRONG PREDICTIONS

ESA Science News
http://sci.esa.int

18 Nov 1998

Leonids peak earlier than expected

This year's Leonids shower was a wonderful event for those who finally
enjoyed clear skies and stayed up long after midnight on 16 November,
or got up early on the 17th. All indications are now that the peak of
the Leonids shower was well ahead of the predicted time for the
maximum rates (predicted time 19:15 to 20:00 UTC 17 November).
Preliminary results indicate that the Earth passed the maximum about
16 hours earlier.

This is, however, well within the uncertainties. Besides the threat
meteor storms pose to spacecraft, there is also a significant interest
in their scientific study. Meteors provide us with information about
the larger grains (size of a grain of sand to a few centimetres)
emitted from the nucleus of comets and about their dynamics, i.e.
orbits in space. The study of their trails when they burn up in the
upper atmosphere gives us information on the composition of the
grains.

Our poor understanding of how the dust grains are emitted from comets
and of their density and shape -- all factors that influence their
dynamics -- is responsible for the large uncertainties that exist when
predicting the occurrence of storms.

But here Rosetta, ESA's mission to comet Wirtanen, will provide the
crucial information. Besides studying in detail the composition of a
cometary nucleus, the spacecraft will follow the comet along its path
from its most distant point from the Sun through perihelion (about the
Sun).

It will provide detailed information of the dust emission process --
the emission speeds as a function of grain size -- and study if the
emission is continuous or in outburst, (so-called jets).

All this will contribute to a significantly better understanding of
cometary processes and to a more accurate prediction of phenomena like
meteor showers and storm.

G. Schwehm
Rosetta project scientist

USEFUL LINKS FOR THIS STORY

ESA's John Zarnecki speaking on BBC (RealAudio)
http://news.bbc.co.uk/olmedia/215000/audio/_216474_zarnecki.ram

Rosetta project
http://sci.esa.int/rosetta/

BBC news report
http://news.bbc.co.uk/hi/english/special_report/1998/11/98/the_leonids_98/
newsid_216000/216446.stm

Leonids Live
http://www.LeonidsLive.com/

=================
(6) LEONID METEOROID STORM & SATELLITE THREAT CONFERENCE

The Aerospace Corporation's Center for Orbital and Reentry
http://www.aero.org/conferences/leonid/

May 11-13, 1999

Manhattan Beach Marriott Hotel
Manhattan Beach, California

A symposium devoted to all aspects of meteoroids and their effects
on spacecraft.

General Information:

This three-day conference will be devoted to all aspects of
meteoroids and their effects on spacecraft. The goals of the
workshop are to:

Provide feedback on what was learned from the 1998 Leonid storm.

Present and disseminate new results on the meteoroid threat to
spacecraft.

Bring technical and program people together to help assess the
threat.

Acquaint the community with the latest information and analysis
tools.

Develop interagency/organizational cooperation on future data
collects.

Papers are solicited in the following areas:

* The Leonid meteoroids: dynamics, composition, occurrence
* History of meteoroid impacts on spacecraft
* Orbital and meteoroid dynamics: 1997-2000
* Hypervelocity impact phenomenology
* Mitigation strategies
* Anomaly classification
* Civilian/Commercial vs. Military concerns
* UV, Optical, IR and radar observations of the 1998 Leonid storm
* Spacecraft anomalies resulting from 1998 micrometeoroid showers
  and storms
* Analysis tools
* Insurance, legal and business perspectives

Sponsors: The Aerospace Corporation's Center for Orbital and Reentry
Debris Studies (CORDS) and the American Institute of Aeronautics and
Astronautics.

Location: Manhattan Beach Marriott Hotel, Manhattan Beach, CA

Classification: The meeting is unclassified and open to all.

For more information, please contact leonid-conf@aero.org.

===============
(7) DRAWING ATTENTION TO IMPACT HAZARD & SPACEGUARD

From Michael Paine <mpaine@tpgi.com.au>

Dear Benny,

On Tuesday evening I sent a press release to Australian and several
overseas media. It started:

"Astronomers have pointed out that tonight's Leonid Meteor Shower is
a timely reminder that the paths of the Earth and comets do cross
from time to time. The meteor shower should put on a spectatular
display in the early hours of Wednesday morning in Australia. It is
caused by sand-grain sized particles left in the wake of Comet
Tempel-Tuttle. There is no chance of the Earth colliding with the
comet this time but, had the timing been different, then a
catastrophic impact might have occurred." I then raised the issue of
the need for a Spaceguard Survey. I wanted to take advantage of the
graphics appearing on TV showing the comet sweeping around the Sun
and crossing the Earth's path! (Maybe an animation like that
prepared for the Leonids would be useful in promoting the Spaceguard
cause).

I got two responses - one radio interview and one newspaper
reporter. The latter asked me "would Tempel-Tuttle ever collide with
the Earth?". I replied that it was estimated that, over a period of
about 100 million years, about 40% of Near Earth Objects eventually
collide with the Earth. Obviously the use of the words "estimated"
and "million" turned him off because there was no mention of the
conversation in the article.

Regards

Michael Paine
http://www1.tpgi.com.au/users/mpaine/   
See also Spaceguard Australia                      
http://www1.tpgi.com.au/users/tps-seti/spacegd.html

================
(8) IS THIS A BULLET FROM THE K/T IMPACTOR?

From Andrew Yee <ayee@nova.astro.utoronto.ca>

University of California-Los Angeles

Contact: Stuart Wolpert, stuartw@college.ucla.edu, (310) 206-0511

Date: November 18, 1998

UCLA Geochemist's Fossil Meteorite Provides Strong Evidence that
Asteroid Caused Mass Extinctions 65 Million Years Ago

UCLA geochemist Frank T. Kyte has found a fossil meteorite believed
to be from the huge asteroid that crashed to Earth 65 million years
ago -- the probable cause of the extinction of the dinosaurs and
many other species worldwide.

In the cover story of the Nov. 19 issue of the journal Nature, Kyte
presents his analysis of the sample and concludes that the cosmic
impactor, some six miles in diameter, that broadsided Mexico's
Yucatan peninsula was probably an asteroid, and not a comet.

"The fossil meteorite strongly supports the idea that the impactor
was an asteroid and not a comet," Kyte said. "There is a strong
probability that this is a bullet from a smoking gun."

"That was one of the worst days the Earth had in the last billion
years, and it is important to understand what happened."

Kyte's analysis of the sample's texture and chemistry confirmed that
the object is a meteorite. He considers it highly likely that the
sample is from the asteroid that struck 65 million years ago, and if
so, it is the first piece of the asteroid that is large enough to
study and analyze.

What is Kyte's evidence that the meteorite was from an asteroid?
First, comets travel at much higher velocities than asteroids, most
likely vaporizing themselves on collision, Kyte noted. Therefore,
the mere fact that a sample survived the impact is evidence that the
object was not a comet, he said.

Second, Kyte's analysis suggests that the meteorite came from a
typical, rocky carbonaceous chondrite -- a description of objects in
the asteroid belt -- rather than the porous, fluffy type of
interplanetary dust associated with icy comets.

The fossil meteorite was encrusted in mud for 65 million years,
buried beneath more than 50 yards of sediment in the North Pacific
Ocean. It no longer has any of its original minerals, but its
texture and shape remain the same, Kyte said.

Kyte located the piece while studying a sediment layer from the
Cretaceous/ Tertiary boundary -- whose sediments are widely
recognized to contain the record of a large asteroid or comet impact
-- and suspected right away that he found an important clue to the
mystery of what happened 65 million years ago.

"Although the fossil meteorite is only a tenth of an inch in size,
it was 1,000 times bigger than anything else in the sediment, "Kyte
said. "In this dark brown sediment, I saw this small white speck."

In his National Science Foundation-funded research, Kyte analyzed
the piece using UCLA's electron microprobe and neutron activation
laboratories. He found it to be high in iridium -- an element that
is abundant in meteorites.

"That's when I knew I had something special -- a small chunk of the
asteroid," Kyte said.

Asteroids, which originate in the asteroid belt between Mars and
Jupiter, are pieces of largely rocky material remaining from early
in the evolution of the solar system. They did not form into
planets, probably because of their close proximity to Jupiter. A
typical asteroid travels at about 40,000 miles per hour, Kyte noted.
Comets are from beyond Pluto, and travel about twice as fast, he
said. Comets are believed to be composed of about half rocky
material and half icy material.

Some scientists think the destructive meteorite 65 million years ago
is an example of comet showers that bombard the Earth every 25-30
million years, causing mass extinctions. If the impact was from an
asteroid, as Kyte believes, such theories become harder to defend,
he said.

The impact 65 million years ago, at the end of what is known as the
Cretaceous period, is believed to have had devastating effects on
the world's climate, and has been implicated in the extinction of
the dinosaurs and many other forms of life. Prior to the crash, a
few thousand dinosaur species had thrived for 160 million years.

Questions remain about how the asteroid affected the environment,
how long it took for the extinctions to occur, and the exact size of
the massive object.

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