PLEASE NOTE:
*
CCNet SPECIAL, 20 April 1999: RE-ASSESSING THE 1999 AN10
DEBATE
---------------------------------------------------------------
(1) 'NOW IT'S TOO LATE TO DENY THE EXISTENCE OF THE PAPER'
ON THE CLUMSY RELEASE OF THE LATEST
'IMPACT-THREAT' DATA
Benny J Peiser <b.j.peiser@livjm.ac.uk>
(2) THE CASE OF NEO 1999 AN10
David Morrison <dmorrison@arc.nasa.gov>
(3) FLACK, COURTESY & SIR ARTHUR
John Richfield <jonr@iafrica.com>
(4) RELATIVE RISKS & THE PROVISIONAL NATURE OF TRUTH IN
SCIENCE
Michael Martin-Smith <martin@miff.demon.co.uk>
(5) MORE THOUGHTS ON DEALING WITH THE IMPACT HAZARD
Michael Paine <mpaine@tpgi.com.au>
================
(1) 'NOW IT WOULD BE TOO LATE TO DENY THE EXISTENCE OF THE PAPER'
ON THE CLUMSY RELEASE OF THE LATEST
'IMPACT-THREAT' DATA
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
You don’t have to be an expert on orbit calculations to
guess that the
awkward release of the 1999 AN10 'impact threat' data on the www
would
be contentious. Not surprisingly, the altercation about asteroid
1999 AN10, its potential menace, and the mode in which such
sensitive
information was made 'public' has raised a number of topical
questions:
How should impact threats be handled? What is a proper peer
review?
Should the public be informed, and when? etc.
It is a feature of scientific exploration and progression that
issues
such as these have to be experienced as actual problems first
before
they can be adequately addressed - and subsequently overcome. At
least
in this respect, the 1999 AN10 incident matches pretty much last
year’s
controversy. While the 1997 XF11 affair primarily highlighted the
issue
of 'peer review' prior to the release of nonzero impact
possibilities,
the 1999 AN10 debate hinges on the complexity of exactly how,
when and
where to make potentially alarming information public once some
preliminary form of self-selected 'peer review' has taken place.
These predicaments are certainly not restricted to the scientific
community. After all, the general public has a considerable and
legitimate interest in potentially hazardous asteroids given that
they
might pose a risk to the health of any nation. Joe Public, of
course,
has every right to know if a significantly large chunk of space
debris
is hurtling towards earth on a potential collision course –
no matter
how small the odds.
For two years, the Cambridge Conference Network has provided an
open
forum for NEO experts, impact researchers, science journalists
and
other interested parties. Similar concerns and complexities have
been
addressed here in a sincere and matter-of-fact manner. During
this
relatively short period of time, many of us, whether academics or
amateurs, professionals or interested observers, have learned to
understand a great deal of some of these intricate quandaries.
Electronic communication has forever altered the traditional ways
of
handling, assessing and distributing the flow of new research and
novel
information.
I believe that this deliberate transparency of the CCNet has
provided
the most effective response and remedy to any form of
sensationalism
and scare-mongering. Indeed, the latest debate was initiated
precisely
because I was concerned that the 1999 AN10 data was handled in an
unduly discreet and pernicious way. Imagine the consequences if a
tabloid newspaper rather than a member of the scientific
community
would have brought the controversial issue to light. Primarily
motivated by a desire to highlight a real and still unresolved
dilemma,
I also made mistakes in the process.
In light of last week’s disclosures and debate, I have tried
to reflect
on the main problems and dissension in an attempt to re-assess
the
events - in the hope that some lessons can be learned for similar
cases
in the future.
Foremost, and first of all, I wish to make it clear in no
uncertain
terms that I do not question the integrity and good intentions of
the
authors of the 'impact threat' paper in question. It goes without
saying that I commend the submitting of their findings to
independent
cross-checking before making it public on the www. If I have one
criticism – and one criticism only -, it is that they
appeared to be
somewhat naïve and clumsy in handling the release of their
preliminary
findings.
Probably the strongest criticism to my initial comments regarding
the
1999 AN10 data focused on my perception that the paper had
appeared to
be discreetly placed on the www, out of sight, so to speak, and
on an
obscure web page. In my editorial I had wondered "why such
relevant
information (was) put into the public domain in such a weird and
secretive way."
In response to this comment, a number of list members pointed out
that
there is nothing 'secretive' about placing preprints on one's web
site
since this is normal practice nowadays. The authors themselves
assumed
that I must have "stumbled upon the paper via Andrea's
preprint page,
(hardly an 'obscure web page')."
But this is not the case. The paper I found was posted as a
distinctly
separate file – listed below and unconnected to Andrea's
preprints. It
appeared to me to be in the same format as Andrea's 'Belgrade'
web
paper to which he had directed me about two weeks earlier. These
were
the circumstances that led me to believe that the impact-threat
information was placed on a rather 'obscure' web page. I was
certainly
stunned to read such sensitive data on a publicly accessible web
page
that lacked *any* background information about its status, its
relevance or its context. Had I known that the paper was a
submitted
preprint, I would have reacted differently. Yet the unusual
format in
which it was released in the public domain gave *no* indication
of
this.
I understand that there is a technical explanation as to why the
paper
was accessible on a file separate to Andrea's preprints. I
confess that
I regret not having queried the authors about the confusing
peculiarity
of Andrea's web site. Yet it was this odd (and presumably
accidental)
feature of their web paper which inevitably fostered
misinterpretation
and prompted my initial reaction.
While the confusion about the different web accesses to the 1999
AN10
paper appears to have a technical explanation, the question as to
*why*
the paper was made available on the web still awaits a plausible
answer. As far as I can see, there seem to be at least two
different
explanations.
In a letter to the self-selected reviewers who were asked to
check
their paper for general accuracy (as quoted in David Morrison's
comment
below), the authors simply informed the reviewers that, whilst
they "do
not want the content of this paper to reach the non-scientific
media
until it has been carefully reviewed [...] we intend to make the
paper
available on our web server on April 6 unless some of you can
point out
to some reason not to."
This raises the obvious question: why the need (and the rush, for
that
matter) to place it on the web when the stated object was to keep
it
out of the mass media's 'reach'?
When asked about this apparent inconsistency, Andrea Carusi, a
close
colleague of the authors and President of the Spaceguard
Foundation,
explained that the web paper was actually meant for some of the
selected reviewers who hadn't read it yet:
"Some of the people that had been contacted had no
opportunity to
read it, and the authors have decided to put it on Milani's web
site to make it accessible." (CCNet, 14 April 1999)
To emphasise the author's stated intention that the paper was
never
considered for the general public, Andrea Carusi underlined that,
"Probably no one imagined that there were people monitoring
Milani's
home page" (CCNet, 14 April).
Could it be that the well-meaning authors were perhaps a little
bit too
naïve to believe that their paper could be posted on the web for
a
*selected* number of peers and reviewers - yet that it wouldn't
be
discovered (and disclosed) by others sooner or later?
I have this odd feeling that this might also explain another
conspicuous circumstance of this affair. After all, if the real
reason for making the 1999 AN10 paper available on the web was,
as
the authors later claimed, to "foster discussion among the
scientific
community," it appears at odds with the fact that the NEO
research
community, to my knowledge, was never told about the existence of
the paper. Hence, a proper "discussion among the scientific
cummunity"
was simply impossible.
But was it ever intended? There is at least one indication that
no such
"scientific discussion" was intended (after all, such
an open debate
would have made the 'impact threat' paper immediately public!).
The
evidence comes from an eminent official of the astronomical
community.
In a message to me shortly after I had posted the CCNet Special
on 13
April, the official tried to explain why the authors hadn't
wanted the
paper to become known to the public.
"It would be useless and confusing to diffuse the news
through the
media before an accurate scientific evaluation be
completed."
But, he continued, "Now, that you have spread the news
publicly [...]
it would be too late to deny the existence of the paper that
anybody
can consult."
Whatever may lie behind this curious formulation, I do feel it
might have
been wiser had I contact the authors prior to the CCNet Special
of
April 13. Perhaps the authors would have realised that their
naive and
inconsistent 'release' of their data was bound to cause trouble.
They
might have decided that it would be wiser to make an official
announcement, thus preventing any misinterpretation or suspicion.
Possibly they could have concluded to wait with the publication
of
their 'impact threat' announcement until their findings were
confirmed
by a proper and appropriate peer review. After all, nobody else,
so
far, seems to have reproduced the hypothetical impact scenario
for the
year 2039. So why this discreet rush onto the www?
With hindsight, I am glad that no harm has been done. Contrary to
some critics, the media reports about asteroid 1999 AN10 have not
been sensationalist but fairly accurate and mostly
matter-of-fact. One
of the reasons for this dispassionate, even-handed coverage
is that
many science journalists are CCNet subscribers and therefore
up-to-date
on current NEO issues and debates. I find this very healthy. The
1999 AN10 incident might even help IAU, NASA and SPACEGUARD
officials
to come up with viable, effective and, most of all, transparent
procedures
of how to handle, assess and finally release information about
potential impact threats to the public.
Let us hope that the forthcoming NEO meeting in Turin will
address these
problems and can produce satisfactory procedures for similar
cases in
the future. If so, something good will have come out of the
latest
debate - and we could again focus our attention to our main
research
interests.
Benny J Peiser
==================
(2) THE CASE OF NEO 1999 AN10
[Modertor's note: attached below are two items from David
Morrison's
1999 AN10 file which he circulated yesterday on his 'NEO News'. I
have
not attached most other documents on his file (items 3-9) since
they
were posted on the CCNet last week. Please also note the rather
selective
choice of criticism which, regrettfully, does not reflect the
wide-ranging
reactions by CCNet subscribers.]
THE CASE OF NEO 1999 AN10
From David Morrison <dmorrison@arc.nasa.gov>
[Excerpts from NEO News 4/19/99]
Following is a file of information on the near-Earth asteroid
called
1999 AN10, discovered by the MIT-USAF LINEAR telescope on 13
January
1999. Dynamicists Andrea Milani, Steven Chesley, and Giovanni
Valsecchi
carried out an analysis of its orbit, which involves resonances
with
the Earth and permits close encounters with the Earth over the
next
several hundred years. This research is of general interest
because
there is a very small chance of a collision of this asteroid with
the
Earth.
On 26 March 1999, these authors requested several colleagues to
look at
their manuscript and check the general validity of their
calculations
of the orbit of this asteroid. They wrote, in part: "The
subject of
this paper is such that we consider essential that its content be
reviewed by the most qualified experts before it is made public.
This
paper has been submitted to a scientific journal. We do not want
the
content of this paper to reach the non-scientific media until it
has
been carefully reviewed. . . . Note that it would be unwise to
hurry
with a public announcement for three good reasons. First, we have
established that there is no risk of impact until 2039, and even
then
the probability of impact is well below the background level.
Second,
the asteroid is now almost impossible to observe, and even if it
were
observed new astrometric positions taken now would not contribute
significantly to the improvement of the orbit. Third, the issues
raised
by this case are indeed very complex. . . Please note that
we had no
obligation to submit our paper to this highly unusual refereeing
procedure: we felt this as a moral obligation. We are asking you
to
carefully examine our paper looking for every possible fault in
our
arguments, but with respect for our work and for our scientific
priority. . . . We intend to make the paper available on our web
server
on April 6 unless some of you can point out to some reason not
to. Thus
you should send us your comments, criticisms, and whatever
queries you
have, as soon as possible. In particular if there is some
fundamental
flaw in our arguments we would like to know before making any
information publicly available."
Several of the colleagues they addressed responded with detailed
technical commentary, but none disagreed with the basic
conclusion that
this asteroid poses no significant threat of Earth impact for at
least
the next 40 years. Thus, Milani and his co-authors posted the
manuscript on their website early on 6 April, as they had
indicated
they would do. About a week later the manuscript was circulated
to a
larger group of experts at the request of the International
Astronomical Union. These informal technical referees also agreed
with
the conclusions concerning the exceedingly low probability of an
impact
with Earth.
Subsequently to this Web posting, the case of asteroid 1999 AN10
became
widely known and has stimulated considerable discussion on the
Internet
and in the international press. The remainder of this message
reproduces some of the commentary related to this asteroid and
the mode
of release of information. Everything that appears here has
already
been made public on other websites. The material is drawn
together here
as a reference on a subject of general public interest dealing
with the
probability of asteroid impact and of the best way such
information
should be made available to the public.
David Morrison
---------------------------------
1) ABSTRACT OF THE TECHNICAL PAPER
CLOSE EARTH APPROACHES OF ASTEROID 1999 AN10: RESONANT AND
NON-RESONANT RETURNS
Andrea Milani, Steven R. Chesley
Dipartimento di Matematica, Universitý di Pisa
Via Buonarroti 2
56127 PISA, ITALY
Giovanni B. Valsecchi
IAS-Planetologia
Area di ricerca CNR
Via Fosso del Cavaliere
00133 ROMA, ITALY
March 26, 1999
Abstract:
The Earth passes very close to the orbit of the asteroid 1999
AN10 twice
per year, but whether or not this asteroid can have a close
approach
depends upon the timing of its passage across the ecliptic plane.
The
uncertainty of this timing grows with time: by 2027 it is +/- 12
days.
Among the possible orbital solutions there are some that undergo
a close
approach in August 2027, but no impact is possible. However, the
period of
the asteroid may be perturbed in such a way that it returns to an
approach
to the Earth at either of the possible encounter points. We have
developed
a theory which successfully predicts the 25 possible such returns
up to
2040. We have also identified 6 more close approaches resulting
from the
cascade of successive returns. None of these encounters can
result in an
impact, except one in August 2039: the probability that the true
asteroid
actually follows a collision course for that date is less than
the
probability of being hit by an undiscovered asteroid within any
given day.
Because of this extremely chaotic behaviour there is no way to
predict all
possible approaches for more than a few decades after any close
encounter,
but the orbit will remain dangerously close to the orbit of the
Earth for
about 600 years.
-------------------------------------------
(2) OFFICIAL COMMENTS FROM THE INTERNATIONAL ASTRONOMICAL UNION
From the IAU website
The International Astronomical Union Working Group on Near Earth
Objects (WG NEO) provides, as a service to the international
astronomical community, voluntary expert review of reports that
might
have implications for possible future Earth impacts. The review
process
was first used in April 1999 in the case of newly discovered
mile-wide
asteroid 1999 AN10. NEOs with orbits that permit close encounters
or
even collisions with the Earth are of considerable interest to
scientists who compute asteroid orbits. As a consequence of their
frequent close encounters with the Earth or other planets, it is
difficult to predict their orbits with high precision for more
than a
century or so into the future. One such object is 1999 AN10,
discovered
by the MIT-USAF LINEAR search program on 13 January 1999.
A detailed analysis of the orbit of 1999 AN10 was completed by
researchers Andrea Milani, Steven R. Chesley and Giovanni B.
Valsecchi
in March 1999. Their paper, which has been submitted for
publication in
a technical journal, includes an examination of the potential
risk of
1999 AN10 hitting the Earth in the next several decades. They
conclude
that, while there is some uncertainty in the exact orbit of this
NEO
following its next close planetary encounter in August 2027, the
chances of its actually hitting the Earth in the next 40 years
are
minuscule -- the authors estimate that the chance of impact is of
order
1 in a billion (1 in a thousand million), which they indicate is
10,000
times less than the chance that the Earth will be struck by some
as-yet-undiscovered similar-sized NEO in any one year.
The IAU's Working Group on Near-Earth Objects has formed an ad
hoc
committee, with widely international expert membership, whose
members
are available to review predictions of impact hazards if so
requested.
This committee functions similarly to the referees of most
technical
journal articles in reviewing the predictions, and it also keeps
the
appropriate IAU officials completely informed about any such
predictions.
The technical paper by Milani and colleagues has been subject to
such
informal review during the first two weeks of April 1999, and it
is the
consensus of the reviewers that the work is accurate and of the
highest
scientific quality. The IAU reviewers also note that the chances
of
impact by NEO 1999 AN10 during the time-span considered in this
paper
are negligible compared to the risks we run continuously of being
struck by one of man similar size NEOs that have not yet been
discovered. Like asteroid 1997 XF11, which was widely discussed
in the
press in March 1998, this asteroid does not pose any significant
danger
to the Earth on the time scale of the next several decades.
Astronomers will continue to search for new NEOs and to track the
orbits of those already discovered, especially when, like 1999
AN10,
their orbits bring them close to the Earth. But this object, as
demonstrated in the technical paper by Milani and his colleagues,
should not evoke any particular public concern. Thus, the
reviewers
from the WG NEO agree with the authors in ruling out any danger
to
Earth from 1999 AN10 in the next forty years. The object will be
followed closely over the next several years in order to define
the
longer-term properties of its orbit more accurately, as will be
the
case with numerous other, similar objects that will be continue
to be
discovered over the next several years as NEO searches intensify
and
orbital computation methods improve.
----------------------------------------------------
3) COMMENTS FROM BENNY PEISER TO THE CCNET NEWSGROUP (13 APRIL)
ASTEROID 1999 AN10 ON POTENTIAL COLLISION COURSE
WITH EARTH IN 2039
AND NOBODY SEEMS WILLING TO INFORM THE PUBLIC
-------------------------------------------------------------------------
4) THE AUTHORS RESPOND TO THE CCNET (14 APRIL)
Andrea Milani, Steven R. Chesley, Giovanni B.
Valsecchi
------------------------------------------------------
5) COMMENT TO CCNET FROM RICHARD BINZEL (14 APRIL)
THE TIMESCALE INVOLVED REQUIRED NO IMMEDIATE ACTION
----------------------------------------------------
6) COMMENT TO CCNET FROM CLARK CHAPMAN (14 APRIL)
NASA IS HOLDING NO GUN TO THE HEAD OF ITALIAN
RESEARCHERS
----------------------------------------
7) COMMENT TO CCNET FROM THOMAS (sic!) PAINE (15 APRIL)
MANAGING THE KNOWLEGE OF HAZARDOUS ASTEROIDS
----------------------------------------------------------------------
8) NEWSPAPER COVERAGE IN THE BOSTON GLOBE (14 APRIL)
SCIENTISTS SAY ASTEROID MAY TANGO WITH EARTH
By David L. Chandler, Globe Staff, 04/14/99
=========================
(3) FLACK, COURTESY & SIR ARTHUR
From John Richfield <jonr@iafrica.com>
Benny,
I am in agreement with Sir Arthur on this one. You may have made
a bit
of a booboo, but anyone in your position might do so; the trouble
is,
as you can easily see from a survey of the mail you have
circulated,
that in a matter of such potentially cataclysmic significance, no
matter which way you jump, *someone* will scream for your
crucifixion.
But really, no matter how you do it, it is important that this
sort of
thing gets done. I was pleased to see that the affair has
highlighted
the importance of guidelines for responsible public discussion or
reporting of hazardous objects. With any luck some of this will
rub off
onto other fields, such as genetic engineering and
epidemiology.
Two things:
* Your (as far as I can tell) complete, or at least
representative,
unedited publishing of all the flack you got, as well as
supportive
notes, was most praiseworthy in any case, and greatly increased
the
value of the material to the subscribers.
*The material in those critical communications, though they
counted as
pretty white-hot in this forum, were in themselves by and large
thoughtful, well-informed, informative and courteous. (Yes,
I know! I
read them too! But I stand by what I said in context.) Debate of
this quality is so rare in comparison to the normal vacous,
adversarial
juvenile spit-fights that are self-aggrandisingly called
flamefests and
the like, that I cannot but praise all participants.
Finally, if your digest is not the right medium to publish this,
I
should take it kindly if you could forward this note to Arthur C.
Clarke. I wish to thank him for over forty years of indebtedness.
He
played an important role in my education and has afforded me and
my
family a great deal of pleasure. His writings, particularly the
essays,
were among those seminal not only to my interest in space, but
also my
interest in science in general. I cannot thank him enough and I
procrastinated so long in the case of Isaac Asimov that I never
did
thank him; something for which I have felt uselessly guilty for
years.
Cheers, and my thanks to you too for this digest.
Jon Richfield
=========
(4) RELATIVE RISKS & THE PROVISIONAL NATURE OF TRUTH IN
SCIENCE
From Michael Martin-Smith <martin@miff.demon.co.uk>
Dear Benny,
I do not think we can oppose the inevitable; public interest and
involvement in our areas of interest. Nor should we. The issues
touch
on the profoundest and most universal areas of concern. To put it
simply, a potentially lethal threat to our descendants is now
widely
recognised, to which, in essence we can respond by inaction or
action.
The former spells ruin, the latter carries great opportunities
for us,
and could, one day, entail establishment of industry and
populations
off the Earth with ultimate evolutionary consequences far beyond
our
small blue planet, and this coming millennium.
These issues go to the heart of what Humanity means, and are
legitimate
subjects for our whole culture - it would be a poor reflection
indeed
if they were not!
On a more practical note, understanding and certainly responses
to the
impact threat will need money and organization over a
longer time
frame than most people entertain. The resources (personnel,
equipment,
training, industries etc) involved will come from society
at large,
and so we have to take them along with us, and be ready to
involve
them. If, en route, we can convey to the wider population the
ideas of
relative risks, sound astronomical ideas, and the provisional
nature
of truth in science (ideas evolving with the acquistion of
evidence
etc) only good can result. The idea of a longterm purposeful role
for
Humanity in the Universe at large would IMHO be the greatest
prize of
all! "Nothing is to be Feared - it is to be
Understood!"-- Marie Curie
Michael Martin-Smith
=====================
(5) MORE THOUGHTS ON DEALING WITH THE IMPACT HAZARD
From Michael Paine <mpaine@tpgi.com.au>
Dear Benny
I have given some thought to the chance of the (proposed)
Spaceguard
program actually detecting an object that will impact the Earth
in the
next fifty years.
I have used 50 years because this seems to be an upper limit to
the
ability to predict an orbit (recent events suggest this might be
highly
optimistic). I know that many of the following numbers are
subject to
debate but let's just consider them a ballpark estimate. The
table
shows the estimated chance of an impact by a NEO of given
diameter over
the next 50 years. The smaller NEOs have a much higher impact
frequency
than the larger NEOs but they are also much more difficult to
detect. I
have used a graph from the Spaceguard report which shows
"fraction
completeness after 10 years (of observing)". The following
values for
50m and 100m objects are, however, a guess. (I apologise if the
tabs do
not work for some Web Browsers)
Chance of detecting a NEO that will impact in the next 50
years
Diameter Av.Impact Chance in Completeness Chance of
detected
(m) Interval (yr) 50 yrs after 10yrs object impacting
in 50yrs
1 in... 1 in...
50 100 2 0.5% 400
100 1,000 20 2% 1,000
200 5,000 100 20% 500
500 40,000 800 50% 1,600
1,000 100,000 2,000 90% 2,222
All 152
This is for a full Spaceguard Survey, designed to detect 90% of
NEOs 1km
diameter or greater over a 10 years observing program. The chance
of
this Survey detecting a 1km+ NEO that will impact the Earth in
the next
50 years is about 1 in 2,222.
Although the detection rates (completeness) are lower for
smaller objects their shear numbers mean that the chances of
detecting
an Earth-impactor are actually higher than for 1km+ NEOs.
Combining the
probabilities suggests that the Survey has about 1 chance in 150
of
detecting an object that will impact in the next 50 years.
Applying this
to some of the 1999AN10 parameters:
Chance of a detected object hitting within
6 months: 1 in 15,000
4 years: 1 in 1,875
20 years: 1 in 375
This is with a full Spaceguard Survey. The chances with current
search
efforts are about 10 times less (that is, 1 in 1,500 for an
impact by
any detected NEO within 50 years).
This rough analysis tends to confirm the view that there is no
need to
have an urgent mechanism for assessing the threat from newly
discovered
NEOs and notifying the public - we are much more likely to have
decades
of warning rather than a few months. Also note that a great many
smaller NEOs will "slip through the net" and there is a
high risk of
another Tunguska event occurring without warning over the next 50
years
- this risk should be clearly expressed to the public in any
"selling"
of the Spaceguard proposal because an undetected impact could be
even
more detrimental to the program than a "false alarm".
Cheers
Michael Paine
----------------------------------------
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