CCNet SPECIAL, 21 May 1999



     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

    Mario Carpino <>

    Mark B Boslough <>

    Andrew Glikson <>

    Mark Kidger <>

    Michael Paine <>

    Jon Richfield <>

     Benny J Peiser <>


From Mario Carpino <>

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. (, 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


From Mark B Boslough <>

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

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


From Andrew Glikson <>
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

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


From Mark Kidger <>

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

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.


From Michael Paine <>

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


From Jon Richfield <>

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
   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.




From Benny J Peiser <>

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
<>, 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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From Andrea Milani (05/21/99) <>

CCCMENU CCC for 1999

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