PLEASE NOTE:


*

CCNet 99/2001 - 10 September 2001
---------------------------------

 
"I once worked on a newspaper where we had a fretful colleague
nicknamed "Dr Death". He was the environmental correspondent, and the
high point of editorial conference was his sepulchral announcement of
yet another threat to the human race, animal species, soil, rainforests,
oceans, the atmosphere, the planet. His tales of descending asteroids,
killer mosquitoes, plummeting sperm counts and prions lurking in everything
from beefburgers to mother's milk were regularly front-page news.
Whatever else one might conclude about these dire predictions, they kept
readers gripped and Dr Death employed. But were they balanced? Were they
even accurate?"
--John Cornwell, The Sunday Times, 9 September 2001


"The new generation of zealots who want to protect us against every
risk need reminding that living and surviving is a risky business. They
also need reminding that life has somehow gone on for millions of
years on this planet and that to assume that this age, this decade, even
this century is the pinpoint moment of disaster, when the volcanoes finally
explode, the ice caps finally melt, (or the new ice age arrives), the Earth
finally explodes or swallows us all up, is a sort of arrogance we
can do without. Sensible precautions may be in order -- do not live
on the slopes of an active volcano; make buildings reasonably proof
against earthquake tremors; avoid polluting rivers; challenge extremist
views wherever they are found (which lead to ideologies and wars). But to
live in a permanent state of anxiety is not to live at all -- and
leads to officious and often destructive over-reactions."
--Lord David Howell, The Japan Times, 9 September 2001


(1) NASA SPACECRAFT TO FLY NEAR COMET
    AP, 9 September 2001

(2) DISASTER HASN'T STRUCK - YET
    The Japan Times, 9 September 2001

(3) GIANT WAVE HIT ANCIENT SCOTLAND
    Michael Paine <mpaine@tpgi.com.au>

(4) NEW OBSERVATIONS OF SUN ADD TO SPLIT OVER BIRTH OF PLANETS
    The New York Times, 7 September 2001

(5) SOME OLD TALE OF AN ASTEROID: 2001 PM9
    Andrea Milani

(6) FEELINGS OF AN AMATEUR OBSERVER OF NEAS
    Jaime Nomen

(7) HUNGARIANS SAY THEY FOUND TRACES OF LIFE ON MARS
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(8) ASTEROID ALARMS & NEO SOCIOLOGY
    Daniel Fischer <dfischer@astro.uni-bonn.de>

(9) RE: A WORD OF WARNING ABOUT FUTURE ASTEROID SCARES
    Jens Kieffer-Olsen <dstdba@post4.tele.dk>

(10) NEW PREPRINT ON TUNGUSKA
     Luigi Foschini <foschini@tesre.bo.cnr.it>

================
(1) NASA SPACECRAFT TO FLY NEAR COMET

>From AP, 9 September 2001
http://dailynews.yahoo.com/h/ap/20010909/sc/comet_close_up_1.html

By ANDREW BRIDGES, AP Science Writer

PASADENA, Calif. (AP) - A battered NASA (news - web sites) spacecraft will
attempt to fly within 1,240 miles of the heart of a comet this month to give
scientists only their second glimpse of the dark heart of a glowing space
snowball.

The Deep Space 1 spacecraft will swoop past the comet Borrelly on Sept. 22,
snapping up to 32 black-and-white images of its nucleus.

If it succeeds in sending back close-up images of the nucleus during its
approach - and the odds are slim - it will be the first to examine the dark
yet dynamic core of a comet since the Giotto spacecraft flew past Halley in
1986.

``We expect to see an irregularly shaped, black potato spewing fountains of
gas and dust,'' said Donald Yeomans, a comet expert at the National
Aeronautics and Space Administration's Jet Propulsion Laboratory.

The flyby is anything but a sure thing for the spacecraft, which is on its
swan song assignment.

``There is a very real chance none of this is going to work,'' said Marc
Rayman, the mission's project manager at JPL.

``Deep Space 1 is flying on duct tape and good wishes,'' he said.

The probe was launched in October 1998 and completed its main mission of
testing a suite of a dozen innovative technologies a year later.

Shortly thereafter, however, it lost use of its navigational camera.
Engineers fashioned a replacement by reprogramming the probe's science
camera with hastily written software.

But it continues to run into problems, most recently last month when it lost
its orientation in space. And its supply of hydrazine fuel is dwindling,
leaving little for maneuvering.

NASA will turn off the spacecraft in late November, but scientists hope to
use data from the Borrelly flyby to plan for four other NASA missions
scheduled to fly past comets in the next few years.

``The little we know about comets is that they are really individual beasts
and that probably no two comets are alike,'' said Joseph Ververka, a Cornell
University professor of astronomy and principal investigator on the Comet
Nucleus Tour, or CONTOUR, mission to study at least two comets at close
range.

While comets are celebrated for how brilliantly they shine, at their heart
they are thought to be cloaked in a pitch black crust. When they swing close
to the sun, the heat boils off the mix of dust and ice that lies beneath.

When illuminated by the sun, that vaporized material glows brightly, giving
comets their distinctive head, or coma.

In Borrelly's case, the coma is as big as the Earth, dwarfing a nucleus
thought to be just 5 miles long and perhaps half as wide.

That means NASA scientists will have to guess about pointing the
spacecraft's camera and setting its exposure, because they won't know
exactly where or how bright the nucleus will be.

"We make our best estimate and then plunge into the coma," Rayman said.

The closest nucleus images will be taken from about 4,960 miles away, but
other instruments will continue gathering information as the craft nears the
nucleus.

Borrelly may well mean the death of Deep Space 1. Debris will batter the
spacecraft as it flies past the comet at a relative velocity of 36,900 mph.
At that speed, particles no larger than a human hair is thick can damage the
probe or send it spinning.

But NASA officials say the flyby is icing on the cake for the $152 million
Deep Space 1 mission. The flyby cost an additional $12 million.

"That's nothing compared to the cost of building a new spacecraft," said
Paul Hertz, the Deep Space 1 program executive at NASA headquarters.

On the Net:

Deep Space 1: http://nmp.jpl.nasa.gov/ds1/index.html

Copyright 2001 Associated Press

=============
(2) DISASTER HASN'T STRUCK - YET

>From The Japan Times, 9 September 2001
http://www.japantimes.co.jp/cgi-bin/getarticle.pl5?eo20010909dh.htm

By DAVID HOWELL

LONDON -- At the end of the first millennium, it was widely predicted, and
widely believed -- at least in the West -- that the world was about to end.

At the end of the second millennium most people, bar a few cranks, scoffed
at such early medieval superstitions and talked of the better world in reach
in the 21st century and the new age -- providing, of course, that we protect
the environment, save energy, stop wars and control population growth.

But suddenly this confident and modern mood seems to be wavering. It seems,
after all, that catastrophe really is around the corner. The new breed of
doom-laden threats to the world are not just the usual, slightly hysterical
ones about global warming, running out of fuel or food, carbon-dioxide
poisoning and so on.

No, the new prophecies that the end is nigh are the really big ones, and
they come not from green zealots or so-called friends of the Earth but from
hard-headed scientists and geologists.

The latest, and scariest, is that a volcano is about to blow itself to bits
in the Canary Islands slide into the sea and set in motion a tsunami as high
as St. Paul's Cathedral (about 40 meters). This will then race round the
Atlantic Ocean, hitting both America and Britain with tremendous force,
traveling kilometers inland and destroying all before it. It is, apparently,
"bound to happen" sooner or later. [MODERATOR'S NOTE: this particular
volcano/tsunami scare has been criticised as another example of hyped
exaggeration by other tsunami experts, BJP].

But if that is not enough to keep us awake at night, the scientists have now
come up with another global apocalypse. It seems that only sheer luck
prevents our world from being hit by gigantic asteroids and that one is
bound to get through at any moment. Kindly Jupiter has been acting as a sort
of protective umbrella for us, taking big hits for the last few billion
years, but it cannot field them all. When one of these rocky monsters hits
the Earth, it will create a blast of mega-nuclear proportions and bring
eternal winter, probably wiping out the human race at the same time. It must
happen, it's just a question of when.

How are people going to react to all this news of imminent extinction?

Well, we know how one section of our busybody world will react, and are
reacting already. They will say that governments must "do something." There
must be new regulations, new policies, new research, new programs.

Coastal defenses must be raised 40 meters high, everyone moved 16-km inland.
Or the approaching asteroids must be diverted, somehow rocketed off course,
while shelters must meanwhile be built in every garden or backyard just in
case that does not work.

These sorts of reactions can be confidently predicted because they are just
an extension of the present attitudes now held by large numbers of people.
Global disasters can and must be prevented, and the necessary expenditure
must begin now.

Yet more sober reflection ought to tell us to calm down. For most of its
existence, the human race has lived with the prospect of imminent
extinction, if not by fireballs and cosmic assault then by plague, floods,
war and famine.

That is what led people to be thankful to God for each day survived, each
harvest brought in, each new birth and each life lived to its fullness.

The Cold War may be a fading memory, but anybody over 20 has actually lived
half their life under the very imminent threat of instant incineration by
arsenals of nuclear missiles, with Hiroshima and Nagasaki there to remind
everyone that it could really happen.

The new generation of zealots who want to protect us against every risk need
reminding that living and surviving is a risky business. They also need
reminding that life has somehow gone on for millions of years on this planet
and that to assume that this age, this decade, even this century is the
pinpoint moment of disaster, when the volcanoes finally explode, the ice
caps finally melt, (or the new ice age arrives), the Earth finally explodes
or swallows us all up, is a sort of arrogance we can do without.

As the scientists say, it is just a question of when. That "when" may be a
million years hence or it may be tomorrow. Sensible precautions may be in
order -- do not live on the slopes of an active volcano; make buildings
reasonably proof against earthquake tremors; avoid polluting rivers;
challenge extremist views wherever they are found (which lead to ideologies
and wars).

But to live in a permanent state of anxiety is not to live at all -- and
leads to officious and often destructive over-reactions. For example, the
"greens" demand that the countryside be covered with hideous wind pylons
because they believe the oil will run out and nuclear power equals nuclear
disaster. Or governments are urged to tax and penalize every industrial and
wealth-creating process, because it is alleged that we are all about to
suffocate from greenhouse gases, the splintering of the ozone layer, the
rise of sea levels, the turning of green land into deserts and a lot more.
Better, it seems, to starve and freeze in a riskless world than to prosper
in uncertainty.

These are the sort of "over the top" attitudes that blot out clear thinking
and lead to responses which, far from helping the human race, could damage
us all. They promote the dangerous view that every risk, every threat of
catastrophe, can somehow be legislated away or suppressed.

Far healthier, surely, is to thank the higher powers of heaven for each day
lived, knowing that global disaster may hit all of us tomorrow morning, or,
on the other hand, it may be 100,000 years away.

The early medieval mind may have been crowded with superstitions. But it had
a better understanding (sic) of the transient nature of human existence, and
therefore, perhaps, a better harmony with daily life (sic).

David Howell is a former Cabinet minister and former chairman of the Commons
Foreign Affairs Committee. He is now a member of the House of Lords.

Copyright 2001, The Japan Times

============
(3) GIANT WAVE HIT ANCIENT SCOTLAND

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

>From BBC News Online, 7 September 2001
http://news.bbc.co.uk/hi/english/in_depth/sci_tech/2001/glasgow_2001/newsid_1531000/1531049.stm

By BBC News Online's Helen Briggs

A giant wave flooded Scotland about 7,000 years ago, a scientist revealed on
Friday.

The tsunami left a trail of destruction along what is now the eastern coast
of the country.

Scientists believe a landslide on the ocean floor off Storegga, south-west
Norway, triggered the wave.

Speaking at the British Association Festival of Science in Glasgow,
Professor David Smith said a tsunami could strike again in the area but the
probability was extremely unlikely.

Radiocarbon dating of sediments taken from the coastline of eastern Scotland
put the date of the event at about 5,800 BC.

At the time, Britain was joined to mainland Europe by a land bridge.

Settlers at the time would have had little warning of the disaster,
scientists believe. But a scattering of tools found in the sand at a hunting
camp in Inverness yields some clues.

'Very destructive'

"It looks as if those people were happily sitting in their camp when this
wave from the sea hit the camp," Professor Smith of the department of
Geography at Coventry University told BBC News Online.

"We're talking about two, three or four large waves followed by little ones,
that would have been 5-10 metres high.

"These waves do strike with such force that they are very destructive," he
added. "It's like being hit by an express train."

The research provides an opportunity to assess the hazard of tsunamis in
more detail.

They occur frequently in the Pacific Ocean due to underwater earthquakes,
landslides and volcanic explosions.

Long, uncertain history

Scientists hope to find more evidence of similar past tsunamis in eastern
Scotland to predict the frequency of the destructive waves.

Studies of coastal sediments show that it may be possible to develop a
record of past tsunamis extending back several millennia.

Dr Ted Nield, of the Geological Society of London, said: "These events have
a long and uncertain time scale.

"While there is no reason for mass panic, the possibility exists that the
Storegga slide will go again, and it would be imprudent to ignore that
fact."

Copyright 2001, BBC

===============
(4) NEW OBSERVATIONS OF SUN ADD TO SPLIT OVER BIRTH OF PLANETS

>From The New York Times, 7 September 2001
http://www.nytimes.com/2001/09/07/science/space/07CND-SUN.html?ex=1000612800&en=d9e8eb6d956444fd&ei=5040&partner=MOREOVER
By JAMES GLANZ
 
WASHINGTON, Sept. 7 - New observations have revealed that just after the Sun
was born, it was almost certainly much more violent than previously
believed, repeatedly erupting with storms of particles and radiation that
may have influenced the formation of planets and salted the early solar
system with radioactive particles.

The observations, of X-rays streaming from young stars in the constellation
of Orion, have added fuel to a longstanding controversy over exactly how the
solar system and the planets formed. The new results may also help explain
mysterious grains imbedded in meteorites that contain the decay products of
rare radioactive elements. The research was described at a conference here
Thursday by Dr. Eric Feigelson, an astronomer at Pennsylvania State
University who led the work, done with NASA's orbiting Chandra X-ray
Observatory.

Dr. Feigelson said that the observations were of 41 stars in the Orion
nebula "that are about as close as possible to twins of the baby Sun."

The naked eye sees the young stars as a point of light in the sword of
Orion. They each have nearly the same mass as the Sun but are only about a
million years old. Earth's Sun formed about five billion years ago.

The young stars show levels of flaring hundreds of times as strong and as
frequent as the most powerful outbursts seen from the Sun today, Dr.
Feigelson said.

It's as if, he said, "the Sun, which we see as this quiet yellow ball, is
covered with firecrackers."

Dr. Donald Clayton, an astrophysicist at Clemson University who was not
involved in the work, said: "I think they have made a great discovery here.
It has changed the playing field."

The results are likely to have a major impact on a long-running debate over
how the solar system formed. In one view, the blast from a nearby exploding
star, or supernova, swept through a large cloud of gas and triggered its
collapse into a whirling disk from which the sun and planets eventually
coalesced.

Because radioactive elements would have been generated in the tremendous
supernova explosion, they could have been sprinkled into the young solar
system and incorporated into meteors, largely solving the mystery over their
composition.

But some scientists have criticized that theory, saying that there is no
evidence the blast was needed and that the cloud could have collapsed under
its own gravity. The new observations could help those scientists explain
the radioactivity as the product of energetic particles from the flares
bombarding matter in the solar system, a process known as spallation.

Dr. Frank Shu, an astrophysicist at the University of California at
Berkeley, said the results were important, suggesting that the solar system
was not the product of a chance explosion but of processes at work
everywhere in the universe.

The finding, Dr. Shu said, "means that the solar system was highly
radioactive when it first formed."

Heat from such high levels of radioactivity could have melted rocks in the
early solar system, making them more likely to stick together and gradually
form planets, Dr. Shu said.

The problem of the solar system's formation, however, is far from solved,
said Dr. Alastair G. W. Cameron, an astrophysicist who retired from Harvard
University and is working at the University of Arizona.

Dr. Cameron, who is one of the originators of the supernova theory, said
that such explosions were common in star-forming regions and that the flares
could not have produced the entire menu of radioactive elements whose traces
are found in the meteorites.

"To say, O.K., that spallation will make them all is a gross overstatement
and in fact is quite unlikely to be true," Dr. Cameron said.

Dr. Clayton, of Clemson University, said that while such complexities had
yet to be resolved by theorists, the Chandra measurements had shown that the
solar system probably had a hot, violent and highly radioactive birth.

"What this new measurement has done is show it's not some wild, extravagant
idea to think there was strong irradiation in the early solar system," Dr.
Clayton said. "It isn't pulling a rabbit out of a hat."

Copyright 2001, The New York Times

=================
(5) SOME OLD TALE OF AN ASTEROID: 2001 PM9
(or... the worst holiday of my life)

by Andrea Milani *- Copyright Tumbling Stone 2001
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/milani.htm

The story begins on the morning of Saturday 11 August 2001, Central European
Time (CET), but in Arizona it is full night, and the new asteroid observing
station on Mount Palomar is doing its job very efficiently. One of the
discoveries of this night moves faster than allowed for a main belt
asteroid, thus the data are immediately forwarded to the Minor Planet
Center, where it is posted on the Near Earth Objects Confirmation Page.

In the evening (CET) of the same day, 11 August, in the island of Elba, I am
going home on a Suzuki motorbike when the front wheel slips underneath the
bike. Do not ask how it happened, because I am the first one who would like
to know: maybe the road was abnormally slippery, maybe I am too old for
motorbiking. By the time my wife Anna arrives, I am lying flat on the road,
and the ambulance has already been called for: I am in rather bad shape.

The same evening, but later, around midnight (CET), in the Czech Republic,
Jana Ticha, Milos Tichy, and a coworker (J. Jelinek) are at their 57 cm
telescope to recover the Near Earth Asteroid discovered few hours later by
NEAT, and as usual they are successful. Little more than one hour later the
same object is observed from the nearby Ondrejov, and the next day, when the
night sets on the American continent, both NEAT telescopes in Palomar and in
Hawaii are at it again. There are observations from an amateur observatory,
Powell Observatory, Louisburg and in the evening of Sunday, 12 August Ticha
and Tichy observe it again. There are now 22 individual data points, from 5
observatories, over a time span of 2 days. Gareth Williams, of the Minor
Planet Center, decides that this is enough to announce the discovery of a
new Near Earth Asteroid (NEA): only at this point the object receives its
'designation', 2001PM9, by which it will be known from now on (and until it
changes again name, when it is numbered). The Minor Planet Electronic
Circular (MPEC) to announce the discovery, prepared by Williams late in the
evening of Sunday, is disseminated through internet and by the time it is
received the morning of Monday has risen in Europe.
This image shows a piece of sky in the constellation of Pegasus, where 2001
PM9 was spotted during the night of Aug 16. The information provided at the
bottom right corner corresponds to the exact coordinates of the center of
the field. (click on the image for a bigger version)
 

At 10 AM (CET) the NEODyS site at the University of Pisa updates the list of
NEA by processing all the MPEC received in the last 24 hours. In the
process, it computes the Minimum Orbital Intersection Distance (MOID) and
the orbital uncertainty, and as a function of these two quantities it
updates a priority list for impact monitoring: with a MOID of the order of
the distance to the Moon, and a very poor orbit resulting from an
observation arc of 2 days only, 2001 PM9 gets immediately to the top of the
list. At 13:00 another computer program, called CLOMON, following the
indications of the priority list begins to scan for all possible impacts of
2001 PM9 with the Earth between now and the year 2080. At 17:46 CLOMON sends
to all the coworkers of NEODyS the warning message, with:

Subject: POSSIBLE COLLISION DETECTED: 2001PM9
Please see 2001PM9.new
and 2001PM9.risk

You may think this is scary, but we get this kind of messages almost daily.
Most of them are false alarms, that is cases where a close approach within
the distance of the Moon is possible, but upon examination by a human
operator the output file .new turns out to indicate that a collision is not
compatible with the available observations. Only in a few cases another
file, the .risk file, is generated with indication of possible encounters
within 1 Earth radius, which means collisions. Unfortunately, in this case
the 2001PM9.risk file not only exists, but contains the indication of a
possible impact in the year 2003. The probability of such an event, as
estimated on the basis of the knowledge available at that time, is minute,
something like 1 in 10 millions, but the date is so close, and the diameter
of the asteroid can be estimated to be between 500 and 1100 meters, that is
large enough for catastrophic effects.

So far the story appears to contain a positive message: the system has been
working, the problem of this "Virtual Impactor (VI)" (click here to know
more about Virtual impactors (dict.)) is being taken care of, everybody
involved has done his job in a very professional way, why should you worry?
And indeed nobody of the people involved so far, at the observatories, at
the MPC and in the NEODyS team, has even thought of sounding some kind of
alarm, because the problem is very likely to be solved in a routine way: as
new observations come in, the scanning for impacts will be repeated with the
reduced orbital uncertainty, and in most cases the VI just vanish. The devil
is in these three words: "in most cases".

On the morning of Tuesday, 14 August, new observations of 2001 PM9 received
in another MPEC are processed by NEODyS at 10:00. As expected, the
uncertainty decreases significantly, but has the VI vanished? The software
robot CLOMON would rerun 2001 PM9 at 13:00, but in this special case
somebody gets impatient and launches manually the impact scan at 10:38. You
may wonder who did this, since I was still on the Elba island, laying in bed
with ice on my knee. Actually, who are the people behind NEODyS ?

On 14 August, the day in which I should have been back from my motorbike
weekend, Prof. Sansaturio, universally known as Genny, remotely connected
from Valladolid (Spain), is running NEODyS. Under normal circumstances, she
can always consult me if there is something she is not sure about. In
particular, she has never taken care by herself of a Virtual Impactor
crisis: with my continuing absence, on 14 August she is for the first time
fully in charge. At 13:37 the scan of the future close approaches of 2001
PM9 is complete, and unfortunately the worst has happened: the possibility
of impact in 2003 is also compatible with the observations over a 3 days
arc, and the probability has increased to about one in 5 millions. This is
the way it must be: if a different set of observations is used, the
probability, must change; in most cases the probability decreases to zero,
but in rarer cases it first increases, to decrease later (again, in most
cases) when further observations are available. Genny consults Steve
Chesley, who is following the situation from JPL.

A quick computation done by Steve shows that the Torino scale (dict.) of
this possible event is still zero.

Thus the conclusion reached by Genny and Steve on 14 August is the
following: since the case of 2001 PM9 is Torino scale zero, there is no need
to inform the IAU officials and to start a formal IAU technical review
before any announcement. Since the asteroid is still easily observable,
there is no need to notify the observers that they must observe it: they
will do this anyway. On the other hand, it could be extremely harmful to
keep the information on the possibility of impact as a secret: this could be
known later, and rated as cover up. as lack of respect for the right to know
of the public, and could even fuel some of the conspiracy theories which are
so popular among the lunatic fringe. Thus they decide to exhibit the
2001PM9.risk file on the 'risk page' of the NEODyS web site.

Of course Genny knows that, even if she is acting without being able to
consult me, I will stand by her because it is my responsibility anyway.
Still she is quite nervous about it, and she decides she has to do something
more that just stand by and wait for new observations. The opportunity to do
so has to do with another island: Mallorca, where she has met Jaime Nomen,
who is in charge of an amateur observatory near Tarragona, on the Spanish
coast: Ametlla del Mar (obs. code 946). He has only a 40 cm telescope, and
2001 PM9 is fainter than magnitude 19, but when he receives from Genny the
request to observe, and the epehmerides, he is ready to try. Without
repeating their story (see this issue of T.S. "Feelings of an amateur
observer of NEAs" by Jaime Nomen), it is enough to say that the run of
CLOMON concluded on 16 August shows that the observations from Ametlla del
Mar are enough to contradict the possibility of an impact in 2003, but they
leave open the possibility of impacts in either 2005 or 2007. There is also
a possibilty of impact in the year 2042, with a probability of 1 in 1
million.

I am still out of reach, but Genny and Steve have been able to contact
Giovanni Valsecchi, who is on holiday on still another Mediterranean beach.
He supports the idea of exhibiting on the NEODyS risk page the output of the
latest CLOMON run, but when requested of activating the Spaceguard
Foundation Central Node to request more observations he is in difficulty,
because everybody is on holiday. 15 August, or Ferragosto, is the most
sacred holiday in the Italian calendar, really nobody works. Only the next
day, 16 August, Valsecchi is able to get in touch with Andrea Boattini, who
is in San Marcello Pistoiese (obs. code 104) to observe, and indeed will try
to observe 2001 PM9, although he also has only a 40 cm telescope.

The JPL group, which of course was kept informed by Chesley, has also
computed the possible close approaches of 2001 PM9, by using a Monte Carlo,
a method very different from the one of CLOMON. On 16 August, Paul Chodas
confirms that the possibility of impact in either 2003 or 2005 did exist,
but he is uneasy with the new data: "With the Aug. 15 data, the probability
has nearly gone down, but I have not computed a precise new value because
Steve and I are not very happy about the large residuals on the new
observations." Indeed, the observations from the amateur observatories, for
an asteroid at the limit of detectability with such small telescopes, have
quite large residuals, some even have to be discarded. Now this can appear a
very technical point, but let me try to explain. The probabilities of impact
we compute are anyway nothing but the transformation of the probabilities we
attach to observation errors. E.g., if we believe that the astrometric
observations cannot have residuals of more than 2 arcsec, and the orbit
leading to a collision leaves residuals of 3 arcsec, then we can say that
such an orbit is incompatible with the observations. But, if we are unsure
about the quality of the observations, because they have been obtained under
particularly difficult conditions by telescopes too small for the task, how
can we claim that such a lower quality fit is impossible? We would like to
have some professional, comparatively large telescope to provide more
reliable data. This should not be understood as lack of appreciation for the
efforts done by the amateurs, but we need to be sure before proclaiming that
impacts can be excluded, for the very good reason that after such an
announcement less attention would be dedicated to that asteroid, and if the
"all clear" announcement had been premature, we would take the risk of
losing a pontentially dangerous fellow.

On the evening of 16 August I finally limp back to Pisa (by train). As soon
as I am again able to connect to internet from my home computer, I try to
figure out what has happened from the messages and also by phone. The
situation is still fluid, in that we still have Virtual Impactors which have
not been contradicted by the observations, but other observations are coming
in and they have to beprocessed. Normally this is done only once a day, not
only because of the CPU time required for the computations, but because the
MPC supplies observations of NEA only once per day. As an alternative, we
can run NEODyS and CLOMON manually when we receive some observations
directly from the observatories, but this involves more possibility of
mistakes. Thus I take the heroic decision of doing nothing until we can look
at the new computations based upon the data available from the MPC on the
morning of 17 August, in the meantime consulting all the coworkers about
what to do. The problem is always the same: should we try to do something
more visible, to obtain more collaboration, also from professional
observatories with larger telescopes, or should we keep quiet and wait for
the observations to come in 'naturally'?

Maybe I should take this opportunity to reveal one of those 'secrets' which
are not a secret at all for the experts. We can find out exactly who and
when has accessed our risk page (or any other web page in our server) by
consulting the log of the http daemon. Thus we were aware that no one, in
the professional astronomical community, had taken any notice of our
posting, although it had been out for more than 2 days. That is, although we
were not keeping it secret, it was nevertheless not known at all. Is it our
responsibility to wake up the members of the asteroid scientific community?
Or is it their responsibility to follow up a site which is well known to
have sometimes important announcements? I do not know the answer to these
questions.

On 17 August the MPC provides additional observations of 2001 PM9 made on 15
August from Sormano (an amateur, but especially well organized, observatory
in Italy), but the ones from San Marcello are not yet ready (because
Boattini needs to use a tricky procedure, coadding the frames, to detect the
faint target; the new ones from Ametlla del Mar are also not there, because
of the bizarre problem encountered by Jaime (see this issue of T.S.
"Feelings of an amateur observer of NEAs" by Jaime Nomen). When the CLOMON
run ends at 13:42, the results are quite discouraging. The 2042 Virtual
Impactor is gone, but the 2005 and 2007 ones are still there, and of course
their probability has increased, to 1.7 and 1.3 per million, respectively.

I decide to spend a couple of hours analysing the results on the basis of
the 'Palermo' scale (dict.). The results are quite bad: the best estimate of
the impact energy for this asteroid, using 'average' albedo and density, is
11,700 MegaTons (MT). Thus the 'expected energy' for the VI of 2005 and 2007
are 20 KiloTons (KT) and 15 KT, respectively. The expected energy is a
tricky concept, and is obtained by multiplying the energy of the impact, in
case it takes place, by the probability that it indeed occurs. Then we can
compare the specific risk of each Virtual Impactor to the risk for our
planet to be hit by an object with this energy or larger within the time
until the date of possible impact. In this case the conclusion is the
following: the 2005 VI represents 2.5 % of the background risk (until 2005),
while the 2007 one represents 1.3 % of the background risk (until 2007!).
This is rated on the Palermo scale as -1.59 and -1.89 (0 would correspond to
an event fully equivalent to the entire background risk until that time).

These numbers do not look much by themselves, but they are impressive if
they are compared with the previous cases (click here to know more about
XF11 and AN10).

In simple words, 2001 PM9 is a delicate case: the Torino scale 0 lets us
make an announcement without going through the formal IAU procedure, but
this does not allow us to take it lightly.

At this point I formally ask Valsecchi and Boattini to post the announcement
of a new special observation campaign on the SGF web page; this they do in
the same afternoon, by recalling from holidays G. D'Abramo. Then I write a
message to Hans Rickman, General Secretary of the IAU, Dave Morrison, WGNEO
chairman, and Rick Binzel, WGNEO secretary; copy also to Franco Pacini, IAU
President. Beside explaining the 2001 PM9 situation to the IAU officials, I
point out that this is not a formal IAU review procedure, but as a matter of
common sense, if we agree that the proximity of the impact date is relevant
in the perception of risk by the public (and by ourselves), this is a case
of which they should be informed. This does not imply that some special
action is immediately required by the IAU, although IAU support may be
requested later if we do not manage to have enough response from the
observers.

Saturday 18 August. CLOMON is running the new computations, including the
observations by Boattini, Nomen and also from Garradd, and I am at my
computer running a close approach analysis for 2001 PM9 until 2007, by using
another program, this one an interactive, menu driven version which I
normally use for development and verification of the output of the automated
computations. The results are as bad as they can be. Not in the sense that
the new observations have been useless: on the contrary, they have
significantly improved the orbit, and indeed when the CLOMON run is complete
at 12:28 the 2001PM9.risk file has disappeared: that is, our automatic
impact monitoring system cannot find anymore Virtual Impactors.

Unfortunately, a close scrutiny of the output, as well as my interactive
runs, indicate that this is not a reliable result. The problem of the data
quality, of which we were already aware, has caught up with us. In simple
words, we base our statements that some collision has been contradicted by
additional observations on the fact that, to allow the orbit with collision
to be the true solution for a given asteroid, we have to admit values of the
residuals (observations minus prediction) larger than allowed by our
understanding of the observation procedures. To do this we normally set the
limit at a value of the conventional parameter sigma=3 (which sets the
dimension of the region of uncertainty (dict.)). The collision in 2005 can
occur at a value of sigma between 3 and 3.5. That is, residuals only
slightly larger than those we normally allow would be compatible with an
impact. But we do know that the observations of this object are of somewhat
lower quality than usual, because after the first two nights it has been
observed only with telescopes smaller than the ones which should be used for
such a faint target. Thus the data from the amateur observatories are very
useful, but they cannot entirely replace the ones from the observatories
with bigger telescopes, which are still missing. Under these conditions, I
cannot send out an all clear message: I am fully convinced that the
probability of an impact in 2005 has decreased with respect to the
computations of the previous day, but I am not in a position to assign a new
value to the probability. Moreover, for 2007 the output of our automatic
programs contains an error message, indicating that the program has failed
to compute the minimum possible approach distance. This has a completely
different cause, called interrupted resonant return. (click here to know
more about resonance (dict.))

At 13:09 I send to all the people involved in this discussion so far the
following message:

"There is nothing we can do now, apart from 1) making more noise, in
particular asking for professional observers with bigger telescopes to get
more accurate observations [...] 2) developing in a rush a new theory, so
that our monitoring, advertised as providing safety to our planet until
2080, can at least work for 2007. Maybe this kind of adrenalina-driven
development of new theories and software, which was so successful in 1999,
is what we need now. I am working on CLOMON2 this afternoon and tomorrow,
Giovanni Valsecchi is going to be here on Monday. The development of the
theory or resonant deflection maybe can wait until the end of next week."
The last obscure phrase refers to the most pessimistic hypothesis: what if
the worst case happens, that is if we were to end up by concluding that an
impact in either 2005 or 2007 is possible, actually if such a possibility
was confirmed by later observations until it becomes likely? The only way to
protect our planet would be to exploit the 2003 close approach to apply a
deflection impulse to the asteroid; but this requires to develop a suitable
theory of such manoeuvers for a resonant orbit. This gives an idea of how
bad was my mood. For my good luck, I tend to react to these crises in a
positive way, by setting down to work. Maybe the work is made even more
intense by the fact that I can hardly walk, so to sit in front of the
computer all the weekend is the best choice to allow my knee some time to
recover.

On Sunday, 19 August at 16:37 I send another, more optimistic message, for
two reasons. First, new data, arrived with the morning MPEC, have further
restricted the possibilities for close approaches in 2005 and 2007. Second,
I have succeded in applying the unpublished theory of interrupted resonant
returns to the 2007 close approach, and found that there is indeed a minimum
possible distance even in that strange case. This minimum distance, also
thanks to the new data, is quite large, more than 2000 Earth radii. Thus we
can claim the crisis is over, at least for the years until 2008.

This apparent happy ending is, however, not the real end. To be able to
remove the risk page from the NEODyS web site we need to be able to claim
that all the impact possibilities until the year 2080 can now be dismissed.
Although the Virtual Impactors for later years have lower probability, and
of course a much lower rating in the Palermo scale, still they have been
detected and we cannot stop our computations until we are able to dismiss
them too. This requires to run our impact scan programs up to that time:
but, should we run the old CLOMON, which did not work for 2007, or should we
run the new CLOMON2 which is just beginning to work and has not been
properly debugged? And can we draw these conclusions on the basis of the
amateur observations only, knowing as we know that they are of lower
accuracy than usual?

I understand that on this point there have been, and there will be again in
the future, many polemics. But, from my point of view to declare that a
Virtual Impactor crisis is over is a much more delicate step than opening
such a crisis. When we have a non-empty .risk file, there is no question
that we have to post it on the web and take the necessary actions to ensure
that additional observations are obtained. To remove a .risk file from our
web server we need to know that all the possibilities of impact listed in
there have been reliably contradicted by observations. What are we supposed
to do when 'some' of the impact possibilities have been contradicted, but
for others the results are inconclusive, or even not yet available because
our computations are not finished? Should we edit by hand the file and add
some comments to some of the lines of the table? Are we supposed to make
some announcement of the form "the worst possibilities of impact, the ones
for the next 6 years, have been eliminated; for the others we are still
investigating"? Who would feel reassured by this?

After some discussion with my coworkers, I decide to keep the 'old' .risk
file on the web server. The point is that the crisis is not completely over,
observations are still needed, and this is the message which we are sending
by leaving some risk file there; the specific content of the file is not up
to date, but this is stated in the file itself by a clear indication of the
observations used in the scan. The SGF also decides that the special
observation campaign for 2001 PM9 should not be declared closed at this
time. Indeed the first observations of 2001 PM9 from a professional
observatory (after the ones of the discovery and the first two days) have
ben made in the night between Saturday and Sunday (by the Tichy), but they
have not yet been disseminated by the MPC.

The impact scan computer programs, including the new CLOMON2 with its
supposed capability to handle 'interrupted resonant returns', are running
all the night between Sunday and Monday (understandably, the new program has
not been optimized properly and is much less efficient). On Monday, 20
August, G. Valsecchi is with me in Pisa, and we analyse the output of the
old and the new program. Although this is all new, and there are many points
both in the theory and in the software which need to be clarified, in the
afternoon we get to the conclusion that, even taking into account the
incomplete theory of 'interrupted', even allowing some margins to account
for the lower than usual accuracy of the observations, there are no
possibilities of impact until 2080.

Some comments by the author...

In the message sent on 20 August at 17:33, simultaneously with the removal
of the .risk file from the web server, to the IAU offcials to announce that
the crisis is over, I made two comments: First, it is not always the case
that newly discovered asteroids can have impacts only many decades from now:
for 2001PM9, with the data available until Aug. 14, we could not exclude the
possibility of an impact in 2003; later, impacts either in 2005 or in 2007
were still possible. Second, the response from the amateur astronomer
community was prompt and very efficient, while the professional astronomers
have contributed nothing. This is somewhat susprising since the announcement
that new observations were urgently required was posted in web sites (such
as the ones of NEODyS and the SGF) and mailing lists (Minor Planets Mailing
List) well known by the professionals. If you take into account that in some
sense I am myself an amateur, since funding for this specific project has
been refused by the relevant scientific authorites of my country, you can
see that there is a problem of responsibility of the professional
astronomers community for this issue of possible impactors.

Indeed, this is the feeling I have about the 2001 PM9 affair. According to
the Palermo Technical Scale, this was the third largest threat we have had
so far, and the activities needed to ensure a safe handling of this case
have been in the hands of a bunch of amateurs. I do not take offence of
being included in the list of amateurs, rather I have proposed this
qualification myself. Is it acceptable that the proper handling of a serious
environmental protection problem depends upon how slippery are the roads on
the Elba Island? Upon the fact that Genny had just visited Mallorca? Upon
software written on the spot, under the pressure of a crisis, by a single
person closed in his office for the weekend? Should not mankind allocate a
reasonable amount of resources, maybe just a fraction of the ones normally
allocated for research in astronomy, to handle all these problems in a
professional way?
 
Andrea Milani * - Director of NEODyS

Copyright Tumbling Stone 2001

===================
(6) FEELINGS OF AN AMATEUR OBSERVER OF NEAS

by Jaime Nomen* - copyright Tumbling Stone 2001
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/jaime.htm

Dilemma: can you hit the bear with a sling?
Yes, sometimes you can.

There are several factors, such as quality of the sky or focal relation, to
be taken into account when trying to observe an asteroid that requires
excellent measurements to elucidate whether it has some probabilities of
impacting the Earth. But, in general, the limitation in the aperture is the
most decisive one. From the point of view of an amateur observer, two
conflicting feelings then arise: on one hand, the will to collaborate and
provide good measuraments which can be useful and necessary to know the
behaviour of such an asteroid in the future; on the other hand, the
discretion and humbleness to recognize that your own work, even if
meticulous and methodical, due to the lack of a better equipment, can end up
disturbing instead of adjusting and determine a good orbital solution. Jaime
uses a 0.4m f/2.0 Schmidt telescope and a commercial CCD of medium
performance.

by Jaime Nomen* - copyright Tumbling Stone 2001

In what follows, I will report on the really exciting time experienced when
I faced the challenge of following up 2001 PM9and that, I am convinced, many
other observers with medium equipment have lived some time in their lives.

It was a quite clear night and there was an important suggestion to try to
observe the object. Genny Sansaturio had provided me with ephemerides
generated with NEODyS for 2001 PM9 and, after solving my contradictory
feelings, I decided to give it a tryhoping to see it in the images.
The game had started...

After a while, there it was! I saw it jumping on the screen and got very
happy. The equipment was providing an excellent performance and it seemed
everything would go wonderfully. I took more than twelve images to make sure
the astrometry was good enough. But, when I started to reduce them, things
changed suddenly. The initial joy became a drama when the signal produced by
that faint object was not enough to find good centroids in most of the
images. And then, the doubt comes back to your mind: will the measurements
be good enough?... In the MPC Guide to Minor Body Astrometry it is clearly
stated that they do not recommend to check the residuals of the observations
before submitting them but, who is not tempted to do it to see how they look
like?...

Again, the uncertainty increased when I checked the measurements. Due to the
poor signal in the image, they were not giving the usual and desired
consistency, though... they didn't seem to be so off, either. And then I
reach the critical point: the submission is ready and about to be mailed
out, the conflicting feelings fight with intensity; you are sure to have
made a good job, but you also doubt about its quality, the quality that such
an object deserves and for some reason it is not getting... Finally, you
press the "send" button and there is nothing you can do about, but wait and
hope that your observations are good enough, that they are really going to
help to determine a good orbit... and, of course, you eagerly wish to see
your residuals and if they are all under 1 arcsec... and you are afraid of
the corrective "parenthesis" used by the MPC to denote those observations
that are discarded, as well as of the instructive "No" of NEODyS. It's late
(or it is better say, early in the morning) and I went to bed.

The following day I checked the Risk Page of NEODyS: 2001 PM9 goes on being
there, but the impactor table does not contain the possibility of impacting
in 2003!, while those of 2005 and 2007 are still there. Next, I looked at
the residuals of my observations, they are not excellent, but I feel good
knowing that I succeeded to observe it with my medium equipment and that my
observations have contributed to discard one impact solution.

According to the suggestion of keeping on following up the object, the next
night I tried to catch 2001 PM9 again. After the previous night experience,
I knew better the optimum exposure times, so that I was convinced that night
I was to get better images, my astrometry would be better and thus I would
not suffer with the reduction. I start the process, insert the new
ephemerides generated by Genny and wait patiently. There it was 2001 PM9
again! Without doubt, I was getting a better signal than that of the
previous night. I followed it for a big while and took many images. I
reduced them more comfortably than the previous night and checked that the
residuals looked more than acceptable. So, I mailed the observations to Tim
Spahr at the MPC and this time I was not submitting the usual prudent 3
observations, but 7... I was so sure I had done a good job!

But 15 minutes after, I got a mail from Tim saying that they were off by
about 50 arcsec. Impossible. I checked everything, configurations, times and
redid the reduction... but I was getting the same results. I only notice one
discrepancy: the PA giving the direction of motion is 17 degrees off with
respect to that provided by the ephemerides. I was starting to think that
2001 PM9 had changed the trajectory and that I was facing another case of a
WIND satellite... But my common sense tells me to take another look at the
images at the exact point provided by the ephemerides. All of a sudden, I
see the "true" and faint 2001 PM9 jumping at a few arc seconds from the
object I have just measured and that, in reality, is a new "unknown"
asteroid. While doing this, I received a reply from Tim who, from his office
and after revising the astrometry I had sent to him, guesses what was really
happening.

Once again, I reduced the faint signal of 2001 PM9 in the same images...
and, once again, like the previous night, I was suffering to do it... my
doubts, my contradictory feelings: "why do you try to observe such faint
objects?"... I submitted 3 observations and this time I was thinking they
were too many! The other 7 observations were referred to as JNT067, a
supposedly new asteroid with an approximate apparent magnitude 19. Yes, I
know it now, it has received the designation 2001 PO35.

That night, another three amateur observers from Sormano, San Marcello
Pistoiese and Powell Obs. also took some images of 2001 PM9. I checked my
residuals the following day: they were better than those of the first night!
and, more importantly, all our observations together with a few more got in
the next two nights by some other amateur observers (Badlands Obs., Linz,
Starkenburg Sternwarte and Loomberah) have made possible to exclude any
chance of 2001 PM9 impacting the Earth at any time until 2080. All the
suffering, doubts, conflicting feelings have been worth... now I feel I have
done my job and my mind is in peace.

Jaime Nomen (*) - Amateur observer at (946)-Ametlla de Mar and
(620)-Observatorio de Mallorca

Copyright Tumbling Stone 2001

=============
(7) HUNGARIANS SAY THEY FOUND TRACES OF LIFE ON MARS

>From Andrew Yee [mailto: ayee@nova.astro.utoronto.ca ]

[ http://www.reuters.com/news_article.jhtml?type=sciencenews&StoryID=205429 ]

Friday, September 7, 2001, 01:00 PM EDT

Hungarians Say They Found Traces of Life on Mars
By Krisztina Than

BUDAPEST (Reuters) -- Hungarian scientists claimed on Friday to have found
evidence of living organisms on Mars after analyzing 60,000 photographs
taken by the Mars Global Surveyor probe.

The three-man team said the pictures showed evidence of thousands of dark
dune spots, similar to organisms found near Earth's South Pole, in craters
in Mars' snowy southern polar region.

"These spots indicate that on the surface below the ice there are such
organisms which, absorbing solar energy, are able to melt the ice and create
conditions of life for themselves," biologist and team member Tibor Ganti
told Reuters.

During harsh Martian winters, when temperatures plummet to minus 328
Fahrenheit, these so-called Mars Surface Organisms are protected by a thick
blanket of ice which then melts as the planet's early summer temperatures
climb to just above zero.

Large gray dark dune spots -- with a diameter ranging from 30 feet to
several hundred yards -- are left behind.

These, the Hungarians claim, are dried-out organisms which can reactivate
themselves once the colder, icy season sets in again.

"The same mechanisms can be found on Earth in ice covering lakes at the
South Pole. The question is whether harsh Martian conditions allow this
mechanism to work there as well," Ganti said.

Agustin Chicarro, one of the leaders of the European Space Agency's (ESA)
Mars Express program, which plans to launch a Mars probe in 2003, recently
visited Hungary to follow up the team's findings.

"We make proposals (to the ESA) on where and what sort of measurements
should be made and when, how and what should be photographed," Ganti said,
adding that no final ESA decision had been taken yet on Hungarian
participation in the next probe.

Ganti said that if the Hungarian team, also involving biologist Eors
Szathmary and astronomer Andras Horvath, was right, this could be the first
real proof of life on Mars.

"This would be life. These would be living organisms and this would be the
first find of living organisms on another planet," he said.

Copyright 2001 Reuters Limited. All rights reserved.

[NOTE: The MGS image is available at
http://mars.jpl.nasa.gov/mgs/msss/camera/images/dune_defrost_6_2001/index.html ]

============================
* LETTERS TO THE MODERATOR *
============================

(8) ASTEROID ALARMS & NEO SOCIOLOGY

>From Daniel Fischer <dfischer@astro.uni-bonn.de>

Dear Benny,

has it ever occured to you that the policies regarding the announcement of
potentially dangerous NEOs are similar to those adopted for the treatment of
the first contact with alien intelligence? The SETI community thinks so:
During a congressional hearing on July 12, Christopher F. Chyba remarked
that "it is important to avoid making premature - and therefore misleading -
announcements to the public, but it is just as important to provide accurate
information with some assessment of scientific uncertainty. SETI
investigations are in some respects similar to those for Earth-crossing
asteroids. The asteroid observing community has learned over the past decade
the importance of taking extreme care with public announcements to ensure
that misinterpretation and hype did not result when substantial scientific
uncertainty was still present." The SETI institute even employs a
sociologist full time who has to deal with those issues - one wonders
whether there is also a need for a department of NEO sociology sometimes ...
Chyba's full statement is at
http://www.spaceref.com/news/viewpr.html?pid=5494.

Regards, Daniel

==================
(9) RE: A WORD OF WARNING ABOUT FUTURE ASTEROID SCARES

>From Jens Kieffer-Olsen <dstdba@post4.tele.dk>

  Dear Benny Peiser,

> (9) A WORD OF WARNING ABOUT FUTURE ASTEROID SCARES
>
> From Benny J Peiser <b.j.peiser@livjm.ac.uk>
>
> The fact of the matter is that we have ample experience and evidence now
> that, just as 2001 PM9 dropped from the risk page, this will be the case in
> almost all future cases. I believe it is the responsibility of NEODyS and
> SCN to make this point absolutely clear when posting future impact threat
> announcements. Would such a disclaimer/clarification serve as discouragement
> for observers? I don't think so. But it would provide some helpful
> counterbalance to the often 'sensationalist' impact probabilities.

  Transience is a key characteristic of any rating on the Torino scale, and maybe
  we should see it as the scale's strength rather than its weakness! Emphasizing
  the transient nature of asteroid threats underpins the expectation that they are
  all false alarms, whose brevity reflects the determination of astronomers to
  eliminate them as fast as possible.        
  
[snip]
 
> To come back to Alain's worries, it should be stressed that even if the
> impact probability should remain nonzero for a prolonged period of time or,
> worse still, if the virtual impactor is no longer observable for a certain
> period of time, the chances are still extremely high that we won't have a
> problem, particularly if we're talking about something as low as one in a
> million.

Working backwards so to speak, what is the chance that a non-zero impact
probability will linger on for a prolonged time sometime over the next
decade? Whereas an impact requires a hit less than one Earth radius off the
planet center, a sustained threat may result from a grazer coming within,
say, 10 Earth radii from the center. Multiplying the impact threat by a
factor 100 yields a mean time of about 20 years between grazing visits by
200m objects. 
    
> However, the real problem we may be facing in the future is another one of
> our own making. Alan has already point out that it is fairly probable that
> the NEO community might "start a real asteroid scare" if only a virtual
> impactor would "have a long lasting spot on the so far immaculate Torino
> Scale."

Fortunately a scare from an Earth grazer rather than from an impactor is the
more likely scenario, and also what the public expects  -  astronomers would
be a mean bunch would they not, if they didn't provide us with a happy end
:-)

Yours sincerely
Jens Kieffer-Olsen, M.Sc.(Elec.Eng.)
Slagelse, Denmark 

===========
(10) NEW PREPRINT ON TUNGUSKA

>From Luigi Foschini <foschini@tesre.bo.cnr.it>

Dear Friends and Colleagues,

at the web page of Tunguska at the University of Bologna
(http://www-th.bo.infn.it/tunguska/), you can find now two more preprint to
download freely. They refer to the proceedings of the meetings CELMEC III
(Roma, Italy, June 2001) and METEOROIDS 2001 (Kiruna, Sweden, August
2001).

Greetings,

Luigi
 
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