PLEASE NOTE:
*
CCNet SPECIAL, 21 May 1999
ASTEROID 1999 AN10 & REACTIONS
-----------------------------------
POEM OF THE DAY
The wounded Earth
Some people thought that Barringer was
crazy -
what, that big hole in Arizona, made by
something from the sky?
Press sensationalism! Just like 'Comet
Threatens Earth'
when Halley came in nineteen ten.
On the Moon, seen since man first
looked,
dark markings of mysterious nature,
black circles
among the lighter highlands. Now
we know -
they're lava flows, upwellings from
below,
the younger Moon's response to giant
impacts.
Bigger than mountains, the missiles of
that late bombardment
hammered every planet, left dark bruises
on our satellite,
longer-lasting than the marks we saw on
Jupiter's clouds
when Shoemaker-Levy Nine's bright
fragments fell in line.
Now what about the Deccan Traps, the
huge flows in Siberia?
It's not unreasonable to suppose the
wounded Earth
bled dark andesite and tholeiite flows
like water from a dam
that burst. This possibility, that
cosmic impacts
don't just make craters but shake the
Earth until it bleeds
might peel away another layer of
ignorance
and bring us that much nearer to the
nature of a planet's growth.
Malcolm Miller
stellar2@actonline.com.au
21.5.99
(1) PRECOVERY OPPORTUNITIES FOR 1999 AN10
Mario Carpino <carpino@brera.mi.astro.it>
(2) ASTEROID 1999 AN10 IS A LEGITIMATE STORY
Mark B Boslough <mbboslo@sandia.gov>
(3) 1999 AN10 RISK: A SENSE OF PERSPECTIVE
Andrew Glikson <geospectral@spirit.com.au>
(4) ASTEROID 1999 AN10 & HOW TO DEAL WITH IT
Mark Kidger <mrk@ll..iac.es>
(5) 1999 AN10 GOES OVER THE TOP DOWN UNDER
Michael Paine <mpaine@tpgi.com.au>
(6) CCNet CONSIDERED HARMFUL
Jon Richfield <jonr@iafrica.com>
(7) 1999 AN10 AND PLANETARY DEFENSE
Benny J Peiser <b.j.peiser@livjm.ac.uk>
=====================
(1) PRECOVERY OPPORTUNITIES FOR 1999 AN10
From Mario Carpino <carpino@brera.mi.astro.it>
Dear Benny,
Francesco Manca and Piero Sicoli (Sormano Observatory) point out
(and I
confirm their results) that 1999 AN10 has undergone two close
approaches
with the Earth on Jan 31, 1992 (0.087 AU) and Aug 8, 1990 (0.025
AU).
Although the uncertainty in the position on the sky in these
occasions is
of the order of the degree and the apparent angular velocity
quite high,
these could be interesting possibilities for getting precovery
observations from archive images and improving the orbit.
The two close approaches are listed in the NEODyS database by
Milani et
al. (http://newton.dm.unipi.it/neodys/),
where people interested could
also generate ephemerides and plots of sky plane confidence
regions for
any given date.
Best regards
Mario Carpino
Osservatorio Astronomico di Brera
==============
(2) ASTEROID 1999 AN10 IS A LEGITIMATE STORY
From Mark B Boslough <mbboslo@sandia.gov>
I think this time asteroid 1999 AN10 is a legitimate story, but
overhyped as usual by the press which tends to quote only the
minimum
possible miss distance (which is actually more like 31,000 km,
because
a miss by < 6,000 km is not a miss). Much is made of the
possibility
that it will be perturbed into an Earth-impacting trajectory, but
(as
Clark and others point out) the probability of that is minuscule
and
does not add anything significant to the existing threat from
everything we haven't found. I don't buy the idea that the public
will
get bored and discount a *real* alarm; something doesn't have to
be a
threat to be newsworthy.
In my opinion, the significance of AN10 is the uncommon closeness
of
its most likely 2027 encounter. The probability of an Earth
impact by a
1 km diameter asteroid is roughly 1 in 300,000 per year according
to
Shoemaker's 1983 cumulative frequency curve. The nominal miss
distance
is about 10 times Earth's radius, so the impact probability can
be
multiplied by 10*10 to get a simple-minded probability estimate
of such
a close miss: about 1 in 3,000 per year, or a miss by that
distance
every 3,000 years over the long run.
We have discovered something like 20% of Earth-crossing asteroids
of
this size, so the probability a member of the sub-population we
know
about passes this close only once every 15,000 years in the long
run
(excluding sampling bias). Even if the astronomers are way off on
their
size estimate (which would require that this object has an
unusually
high albedo), it is a very infrequent encounter distance on human
time
scales.
I hate to bring this up, but 1999 AN10 is also a threat of the
class
that Sagan and Ostro warned us about. It could in principle be
diverted
into an Earth-impacting trajectory. If we are going to worry
about
minuscule probabilities, that one is also (unfortunately)
nonzero.
Mark Boslough
==============
(3) 1999 AN10 RISK: A SENSE OF PERSPECTIVE
From Andrew Glikson <geospectral@spirit.com.au>
Dear Benny,
1999 AN10 is certainly an object of scientific interest - no more
and no
less than the thousands of observed and unobserved asteroids and
comets
that come near Earth. However, when this interest is translated
into
the ringing the alarm bells - a unique sense of unreality appears
to
emerge.
Even a cursory look at the vast literature which exists on future
risks, including conferences (from 'Man and his Future', CIBA
Foundation, 1963, to the multidisciplinary studies by the 'Club
of
Rome') and books by people such as Bertrand Russell, Paul
Ehrlich,
Jonathan Schell, and Carl Sagan - leave little doubt as to where
future
threats lie. The risks of nuclear war, overpopulation, infectious
diseases, ozone depletion, deforestation, pollution and
salination are
already here. Should present trends continue, these threats are a
CERTAINTY - posing a risk factors of 1:1!
Most of these risks are man-made and therefore in principle
avoidable.
Which should alleviate concerns regarding 1999 AN10 - with a risk
factor currently estimated at 1:1 000 000.
A sense of perspective is likewise required vis-a-vis potential
asteroid
diversion using N-charges. Over a period of 100 years or so, the
lateral and/or vertical proliferation of these devices pose
threats
orders of magnitude greater than extraterrestrial impact.
The cure may
be worse than the disease...
Andrew Glikson
21.5.1999
geospectral@spirit.com.au
==============
(4) ASTEROID 1999 AN10 & HOW TO DEAL WITH IT
From Mark Kidger <mrk@ll.iac.es>
As has been remarked, this case bears some strong parallels to
the debate
over 1997 XF11. In that case a similar (and very tiny) miss
distance was
estimated, and then revised up. In the case of 1999 AN10 it has
gone the
other way, with a "safe" miss distance suddenly being
enormously reduced.
Of course, there is every possibility that further observations
will
revise the number up again, but it is worth keeping our eyes on
this
object because new observations may, this time, confirm the
predictions.
What is patently obvious in this case is that for 600 years 1999
AN10
is going to be flying around the inner solar system like a hand
grenade
with a dodgy pin. Even if some of our colleagues are unhappy
about
directing too much attention to this object, I personally would
like to
know more about its intentions even if it is only for the sake of
my
great great great grandchildren (should I ever have some). My
guess is
that a lot of other people will feel the same way, even if they
do not
actually feel threatened by this object. A 1km rock would make
one heck
of a mess if it did have the bad taste not to understand
correctly the
error bars on its orbit.
I abhore the idea of "surpressing" information.
Certainly, in both this
case and 1997 XF11 sharing the information led to more
observations
(remember that 1997 XF11 was so poorly observed initially that it
was
close to being lost). If the public gets the impression that
astronomers are hiding information it will lead to distrust and
some
anger. It will also lend succour to those on the lunatic fringe
who
have said for years that astronomers ARE hiding information from
the
public!
It is pretty difficult to argue that the announcement of 1999
AN10 has
been sensational - the press has hardly picked it up, so far -
and most
of the debate has been pretty responsible.
As for CCNet being dangerous, it's an interesting suggestion.
Were
CCNet not to discuss these issues they would be discussed
elsewhere,
and probably in a less open and democratic way. Benny has
published
some pretty stinging rebukes about material which he has offered
to us,
as well as some of the compliments that he has received. Both
sides in
a debate get the chance to be heard. Do we want these issues to
be
discussed in an more hysterical way on other mailing lists? I
guess
that most of us would say "no" to that. It is much
better to give
reasoned information. CCNet is healthy because it tries to
forment
responsible debate, even if some readers are unhappy about some
of the
topics discussed. That is the nature of a democracy - you do not
always
get your own way. Somehow I suspect that not all readers will
agree
with my views and may well say so. If they were not allowed to do
so
THEN it would be right to say that CCNet is dangerous.
==============
(5) 1999 AN10 GOES OVER THE TOP DOWN UNDER
From Michael Paine <mpaine@tpgi.com.au>
I wasn't me!
It is not often that a "science writer" makes it to
page one so I guess
there is the temptation to sensationalise these issues. At least
it
will help keep the NEO issue simmering at a political level in
Australia. :)
Michael Paine
============
(6) CCNet CONSIDERED HARMFUL
From Jon Richfield <jonr@iafrica.com>
Hi Benny,
I will regretfully not be attending the plenary session of the
forthcoming IMPACT workshop (Torino, June 1-4) and I neither
think that
everyone there will share opinions on communication between
experts,
the press and the public or the civil authorities, nor that if
they
were to agree, the correct view, mine, would necessarily prevail.
However, my ha'porth is as ready as any, if less persuasive than
some,
and in case it influences someone, here it is:
1) Deliberate communication is in general an act with the same
burden
of consequence and responsibility as any other. To assume
automatically that one should unthinkingly (because on principle)
release information, as Jim Benson seems to suggest, is exactly
as
morally suspect as to sit on it on principle, which seems to be
nearer
the views of Vincenzo Zappala', Alberto Cellino, Patrick Michel.
(No, I
am not being accusatory, nor ascribing views; this is just an
exercise
in extremes in the interests of illustration.)
We are thinking beings, if only rudimentarily, and every
defensible
moral philosophy that I have seen assumes that the responsible
agent is
aware of his moral imperatives and demands that he select his
course of
action according to those imperatives plus his information about
the
reigning situation.
Insofar as this is meaningful, it means that to tell or not to
tell is
a moral decision and is only automatic if the imperatives leave
no
scope for thought. In our case the theatre fire is a convenient
(and
popular) model. Do we:
a) Scream fire every now and then so that after a
few have been
trampled, people are desensitised
and will not stampede if there
really is a fire? Or will
not escape the fire?
b) Scream fire if there is a fire, to give everyone
an equal chance
to charge the entrance and get
crushed and burned or escape?
c) Whisper repeatedly only to those near the door so
that they at
least can get out, at least until
flames or panic grip the
remainder?
d) Mount the stage and deliver a lecture on
combustion and the things
to be done in case of fires (i-
before the fire starts or ii-
After you notice a fire?)
e) Reflect that all these options have their
drawbacks, and so
relax in your seat to burn with
the rest?
OK, so I'm fussy, but given my druthers, I don't really like any
of
those. I might get trapped into one of course, and as long as I
gave it
proper thought and selected a course of action in good faith and
reasonable competence, I need not feel too guilty. But if I
worked on
a universal unthinking assumption that communication is good or
bad,
and accordingly blurted or sulked unconditionally, I would bear
the
responsibility of not thinking.
2) In practice we are seldom in such an extreme situation, but
rather
are like someone who sees signs of smouldering and is trying to
get the
theatre audience to wake up and invest their resources sensibly
in
systematically dealing with the potential disaster before it gets
out of
control, or at least to rescue as many as possible in case a full
scale
fire develops. But this theatre is crowded and noisy. You keep
getting
shouted down or alerting bunches of people who panic and run in
the
wrong direction or otherwise do silly things and at the very
least annoy
the others.
3) We know that the rest of the audience includes a worrying
proportion
of fools and clowns and screamers, but the best we can do is to
tell
the ones who are best in a position to make sense of the
situation. We
are in serious danger of criminal negligence if we restrict the
information, because it is unrealistically arrogant (ordinary
arrogance
is merely the virtue of hubris; unrealistic arrogance is a sin)
to
think that any of us is in a position to ration the data to all
and
only those that can make sense of it. We don't have to scream at
the
screamers (gutter media), but we can compromise by telling each
other.
The media will after a while get bored with the subject unless
the
projectile is immediately imminent, and in that case the entire
matter
is moot anyway.
4) Some people will panic. At least one nut suicided when (was it
Skylab?) was due to fall. But heck, morbidity rates of the order
of
1e-9 are among the lowest that one can get and frankly, to me it
sounds
like natural selection in action (very slow action!)
5) Shouting wolf does not apply. It might put off the press, and
some
politicians will be typically wrong-headed, but that comes with
the
profession. Just make sure that we have the facts straight,
refuse to
give the media anything but the facts and then only if they come
and
get it themselves, and when we have something that the
politicians must
act on, THEN tell them. No one, after all, asked for
anti-asteroid
launches this time, did they? We would then be in a position when
it
really got necessary, to go to the powers ad say: "Have we
ever lied to
you? THIS time we had better look to our launchings!" And
they will
listen! Slowly, confusedly, but they will!
Bottom line: Benny & co are doing fine. Check the facts and
tell it
like it is internally. Correct the panic mongers as patiently as
may
be. Don't go to the bosses till we have facts and
recommendations.
Cheers,
Jon
===============
(7) 1999 AN10 AND PLANETARY DEFENSE
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
Regarding Jon Richfield's re-assurance that "No one, after
all, asked
for anti-asteroid launches this time, did they?"
I should point out that Andrea Milani, Steve Chesley and Giovanni
Valsecchi do, in fact, suggest that such a cosmic intervention
might
actually be required in the forseeable future. In their web paper
on
the threat from 1999 AN10
<http://copernico.dm.unipi.it/~milani/resret>,
the authors come to the
following conclusion:
"It is conceivable that at some time in
the future a decision could
be made to deflect and/or destroy it. However,
a deflection
decreasing the depth of some specific close
approach could increase
the impact risk at a later date."
To my knowledge, this is the first time that scientists have
considered
the possibility that planetary defense against a specific
asteroid
might be necessary in the near future. *Why* this scenario has
been
suggested given the minuscule impact probability remains unclear.
But
the fact that it is considered at all in this context seems to
suggest
that the web paper on 1999 AN10 might still be sending out rather
mixed
messages. Let's hope that the uncertainty which is the obvious
cause of
this ambiguity might be overcome soon by finding some archived
precovery observational data of this PHA.
Benny J Peiser
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THE DINOSAURS' BEQUEST
From Andrea Milani (05/21/99) <milani@dm.unipi.it>