CCNet DIGEST 14 April 1999

    The Boston Globe, 14 April 1999

    Jonathan Shanklin <>

    NASA Science News <>

    Ron Baalke <> wrote:



From The Boston Globe, 14 April 1999

By David L. Chandler, Globe Staff, 04/14/99

In a discovery eerily reminiscent of one made just a year ago,
astronomers have found an asteroid that will come quite close to Earth
in a few decades, and that even has a real but minuscule possibility of
an impact.

Last year, astronomers made a similar discovery of an asteroid that
they said had a slight possibility of hitting Earth in about 40 years.
In that case, it was quickly determined that the Earth was safe after
all, and astronomers have been arguing ever since about the way the
original report was disseminated.

The latest asteroid, called 1999 AN10, was described in a detailed
scientific paper posted on a Web site by three astronomers. But unlike
last year's case, no information has been sent directly to the public
and the press.

The asteroid is thought to be about a mile in diameter - similar to the
one last year - and could possibly come very close to Earth in 2039.
There is about a one-in-a-billion chance that it could strike the Earth
that year, with devastating consequences.

That is less than the risk that an unknown asteroid or comet might hit
Earth on any given day, and therefore is not anything to be too
concerned about. What might be more worrisome, scientists said, is its
long-term potential.

For the next 600 years, according to astronomers Andrea Milani, Steven
Chesley, and Giovanni Valsecchi, the asteroid could remain very close
to Earth, and if it comes close enough to be affected by Earth's
gravity its orbit could become chaotic and impossible to predict for
more than a decade or two ahead. In that case, the asteroid would
require constant, careful monitoring for centuries to guard against a
possible impact.

This is only the second time in history - or perhaps the first time,
depending on whose analysis of last year's discovery you believe - that
an asteroid has been discovered that has a small but non-zero
possibility of striking the Earth within a few decades. Even though the
likelihood is quite small, that makes it an interesting find. Some
people have questioned the wisdom of the changes in the way such
information is disseminated as a result of what many astronomers
considered a serious public embarrassment last year.

British anthropologist Benny Peiser, who has written extensively about
the effects of past impacts on the Earth, yesterday circulated an
e-mail message questioning why this discovery, unlike last year's, has
not been announced publicly or shared with news organizations. While
acknowledging that the risk of the asteroid hitting the Earth is tiny
and not something that anyone should lose any sleep over, Peiser said
that he found the lack of public notice disturbing, suggesting that it
reflects an overreaction to astronomers' embarrassment about last
year's announcement followed by a swift reversal.

But astronomers contacted yesterday said that they see this latest case
as a perfect example of how such information should be handled. The
astronomers who made the calculations of impact probabilities have
circulated their unpublished paper to several colleagues around the
world who specialize in such calculations, in order to make sure their
conclusions are correct. Some astronomers contacted yesterday said that
all the comments so far from such specialists have been positive.

"I commend them for the process of being careful," said Richard 
Binzel, an astronomer at Massachusetts Institute of Technology who
specializes in asteroids. Many astronomers felt that last year's press
release about an asteroid called XF11 was premature and alarmist.

Binzel stressed the very low odds of an impact cited by Milani and his
colleagues. Binzel has suggested the use of a hazard scale that would
allow such discoveries to be given a simple classification, similar to
the Richter scale for earthquakes, to allow people to judge their
seriousness. "On a scale of zero to 5," he said, "this thing is a zero."

Astronomer David Morrison of the NASA Ames Research Center said there
was no reason for this finding to be disseminated publicly. Last year,
the asteroid in question was still visible in the sky for a few more
weeks and it was important to alert astronomers around the world to
make every possible observation of it to pin down the orbit. But in
this case, he said, the asteroid is already in a part of the sky where
it cannot be observed for months, so there is no such urgency.

"There's nothing to do, even if we thought it was dangerous," he said.

This story ran on page A03 of the Boston Globe on 04/14/99.
Copyright 1999 Globe Newspaper Company.


From the BBC Online Network

Wednesday, April 14, 1999

By BBC News Online Science Editor Dr David Whitehouse

Astronomers have discovered a mile-wide asteroid that could collide
with the Earth in 40 years time.

If it did, the devastation would be continent-wide, with massive global
effects for decades. Hundreds of millions of people would die and many
animal species would be wiped out.

The object is called asteroid 1999 AN10 and it was discovered on 13
January. It was picked up by the Linear telescopic survey that scans
the sky for so-called Neo's - Near Earth Objects.

1999 AN10 circles the Sun every 643 days and twice each year the Earth
comes close to the giant rock.

From almost a hundred observations made of it since its discovery,
astronomers have determined its orbit. Close approaches to Earth occur
in 2027, but no impacts are possible then according to Andrea Milani
and Steven Chesley of the University of Pisa. But 2039 is a different

Close monitoring

In calculating the orbit for 1999 AN10, the Italian astronomers say
that for August 2039 "a collision solution actually exists."

It is important to note that this is different from a definite
prediction of a collision.

In fact, from what is known at the moment, the probability of 1999 AN10
striking the Earth must be less than the probability of being hit by an
undiscovered asteroid on a given day.

Nonetheless, now that the asteroid has been found, its orbit is
attracting attention. The Italian astronomers say it will have to be
monitored closely.

They add that it is conceivable that at some time in the future a
decision could be made to deflect or destroy it just like in the movie

Website publication

Where has this announcement of major importance been made? Not in a
press release but without much fuss on the astronomers' own Website.

Dr Benny Peiser of Liverpool's John Moores University, an expert in
Near Earth Objects, has expressed concern that the news of 1999 AN10
was released on a Website without going through normal review

"There is no reason whatsoever why the findings about 1999 AN10 should
not be available to the general public - unless they have not been
checked."  He adds that, if they have not been verified, they should
not have been posted on the web in the first place.

The reason why the Italian astronomers have released their worrying
findings this way may be a reaction to stringent Nasa rules regarding
the reporting of potential asteroid impacts.

Asteroid scare

Following a scare last year, when it was thought that asteroid 1997
XF11 may strike us, a claim retracted 24 hours later, Nasa has clamped
down on what it calls the premature release of sensitive data.

1997 XF11 was a false alarm. It is unlikely that 1999 AN10 will hit us
- but it cannot be ruled out completely at this stage.

Calculations suggest that this asteroid will remain "dangerously close"
to Earth for the next 600 years.

According to Benny Peiser, what is worrying is not the chances of 1999
AN10 striking the Earth but the "unnecessary and detrimental secrecy
that surrounds this object."

Copyright 1999, BBC


From Jonathan Shanklin <>

Dear Benny,

Could you post the following to CCNet, I think the workshop should be
of general interest.


Jon Shanklin
British Antarctic Survey, Cambridge, England

The British Astronomical Association Comet Section is very pleased to
be hosting the second International Workshop on Cometary Astronomy. 
This will be held at New Hall Cambridge from August 14 to 16.  The
meeting aims to bring together professional and amateur observers and
as many comet discoverers as possible.

The first IWCA was held at Selvino, Italy in February 1994. Four
previous American Workshops on Cometary Astronomy had been held in the
U.S.A., but had not attracted much attention in Europe.

The 1994 meeting marked the 15th anniversary of the International Comet
Quarterly and attracted a good attendance of active observers. 
Presentations on the work of various national observing groups were
given, along with talks by individuals on their own particular
programs.  Of greater importance were sessions which focussed on
observing methodologies and these lead to significant improvements in
the quality of observations.

Since then we have had two very bright comets which presented new
problems in observation. There has been a huge growth in the Internet,
enabling rapid dissemination of observations and the suspicion that
this may bias observers. Planetarium programs using the Guide Star
Catalogue now give observers precise finder charts enabling them to
observe much fainter comets than in the past.

These new problems need new solutions and hopefully discussion at the
meeting will lead to some conclusions that further improve our
observing standards. However, observers generally have very fixed views
so expect some heated arguments!

Although many amateurs observe comets for their own satisfaction, it
can add enjoyment if you know that your observations are contributing
to the scientific understanding of comets. To this end a number of
leading professionals will be at the meeting, explaining how our
observations are used and what additional observations would help with
their research.

Bearing all this in mind the meeting has three main goals: 1) improving
the acquisition of cometary information. 2) increasing understanding as
to what science can be gained through observing comets by both
amateurs and professionals. 3) providing a forum in which cometary
astronomers can meet others from distant geographical locations and
discuss various issues.

The format of the meeting will be to have selected invited talks, open
panel discussions, contributed talks and poster sessions.  Speakers
scheduled to appear include Doug Biesecker (SOHO comets), Nicolas Biver
(visual magnitudes and CO outgassing beyond 3 AU), Stephane Garro
(French archival observations), Dan Green (comet photometry), Eleanor
Helin (comet searching/discovery at Palomar and with NEAT), Gary Kronk
(on his forthcoming Cometography), Brian Marsden (amateur
contributions), Herman Mikuz (CCD photometry), Charles Morris (possibly
on web issues), Mahendra Singh (comet spectroscopy).

The college bar will be open in the evenings for informal discussion. 
If it is clear there will be opportunity to use the two historic
refractors at the University Observatory.

Cambridge has many sites of astronomical interest and there will be
free time for participants to explore at their leisure.  Many famous
scientists with comet connections studied at Cambridge including
Newton, Herschel, Challis and more recently Lyttleton.

To conclude the meeting I have arranged a trip to Stonehenge on the
Monday evening, when we will be allowed in to the inner circle to view
the stones close up. There have been some suggestions that Stonehenge
was first constructed as either a comet or meteor observatory!  Numbers
for this visit have to be restricted and those attending the meeting
will have priority.

Further details about the meeting are available on the Section web page


From NASA Science News <>

NASA Space Science News for Apr 14, 1999

A Wild Ride in Search of Meteors: On April 11, NASA scientists
successfully launched a weather balloon designed to capture meteoroids
in the stratosphere. The primary payload, a xerogel micrometeoroid
collector, has been recovered and returned to the Marshall Space Flight
Center for analysis. This story features video highlights from the
flight including the sunset as seen from 80,000 ft. and eerie gurgling
sounds caused by high altitude winds. 


From the BBC Online Network
Tuesday, April 13

By BBC News Online Science Reporter Damian Carrington

Icebergs crashing against the sea floor could be the most devastating
natural disaster that any living community on Earth experiences.

Scientists from the British Antarctic Survey have discovered that over
99.5% of all visible sea-bed dwellers are massacred when the bergs
collide with the ocean bottom.

Floods, earthquakes and even meteorite impacts cannot claim such total
destruction. The project leader, Professor Lloyd Peck, told BBC News
Online: "In biological terms it is outrageous - it's almost a sterile

Up to 20% of the world's oceans are prone to catastrophic ice berg
impacts. Even ocean floor as deep as 500m is at risk.


Copyright 1999, BBC


From Ron Baalke <> wrote:

Survey finds nearly 800 debris impacts on Hubble
Posted: April 12, 1999

During the second servicing mission of the Hubble Space Telescope (HST)
by the STS-82 mission in February, 1997, an extensive imagery survey
was performed covering approximately 97% of the HST surface. The
results of a dedicated study to identify and to characterize apparent
micrometoeoroid and orbital debris (M/OD) impacts have been recently
documented in a new NASA JSC report, "Survey of the Hubble Space
Telescope Micrometeoroid and Orbital Debris Impacts from Service
Mission 2 Imagery," by G.J. Byrne, D.R. Bretz, M.H. Holly, M.T. Gaunce,
and C.A. Sapp.

Employing video, photography, and electronic still imagery (a total of
2500 still frames and 17 hours of video), the analysis team was able to
identify 788 potential impacts on the HST aft shroud, equipment
section, aft bulkhead, grapple fixtures, aperture door, and solar
arrays. The analysis process involved first screening and categorizing
the images, then imagery review and M/OD impact identification,
followed by mapping and measurements of the impact features.

Over 500 of the impacts were found on the aft shroud and equipment
section where highly reflective surfaces facilitated detection of
impact features. Approximately 80% of the impact zones measured less
than 0.8 cm, although the largest was 4.7 cm in diameter.

A plot of the number of impacts of a given outer diameter size range
illustrates the expected exponential increase down to a size of 0.4 -
0.5 cm, where sensitivity limits of the imagery apparently lead to a
reduced count. The distribution of impacts around the aft shroud
suggest a real difference in the number of particle impacts on the +V3
and the -V3 sides.

An attempt was also made to compare the number of impacts seen on the
first servicing mission in December 1993 (after 44 months exposure in
LEO) and the second servicing mission (after an additional 38 months
exposure in LEO). A limited comparison of the +V3 quadrant showed an
increase in the density of observed strikes from approximately 5
impacts per square meter to approximately 20 impacts per square meter.
While some of this increase is undoubtedly due to the superior quality
of the imagery obtained during the second servicing mission, a change
in the environment may also be indicated.


W. Pych: Short period oscillations in the light curve of the asteroid
1689 Floris-Jan. ASTRONOMY AND ASTROPHYSICS, 1999, Vol.343, No.2,


We present CCD photometry of the long period asteroid 1689 Floris-Jan.
On the light curve from nights 1997.02.10/11 and 1997.02.11/12 we
detected coherent sine-like oscillations with a period P=4.98 +/- 0.01
minutes and full range amplitude of about 0.11 mag. The observations
from night 1997.03.07/08 show no light variations with this period.
Copyright 1999, Institute for Scientific Information Inc.

The CCNet is a scholarly electronic network. To subscribe/unsubscribe,
please contact the moderator Benny J Peiser <>.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied or
reproduced for any other purposes without prior permission of the
copyright holders. The fully indexed archive of the CCNet, from
February 1997 on, can be found at



    Richard P. Binzel <>

    Andrea Carusi <>

    Clark Chapman <>

    Bill Dillon <>

    Lew Gramer <>

    Gerhard Hahn <>

(7) MY TWO CENTS ON 1999 AN10
    Heidi B. Hammel <>

    Jim Himer <James.Himer@Canada.Sun.COM>

    Brian Marsden <>

     Jonathan TATE <>


From Richard P. Binzel <>

Dear Benny,

The "1999 AN10 Affair" is nothing more than the scientific peer review
process at work. The authors have asked scientific colleagues to
examine and verify their results prior to issuing any IAU Circular or
Press Information Sheet. Better still, the authors intend to publish
their results in the refereed literature. The authors are to be
applauded for doing it right, that is, they are making sure their
results are correct before making any public announcment and they will
provide their full analysis for scrutiny within the professional

The timescales involved require no immediate action, hence the weeks
(or even months) required for the scientific review process to proceed
is of no consequence. Furthermore, there is no reason why this object
should merit any extraordinary public attention as the probability
falls below that for "undiscovered" objects out there.

Richard P. Binzel
Professor of Planetary Science
Massachusetts Institute of Technology


From Andrea Carusi <>

Dear Benny,

Life is really funny! Misunderstandings are always along the way. I
will try to answer your questions, but let me first comment on the note
by Britt that you have just posted. Giovanni Valsecchi, who works at
one door of distance from me, showed me the e-mail by Britt asking
questions: this message was sent out a few minutes after your first
posting. We knew that there are skilled journalists hunting for scoops,
but I think that this is a real record! Giovanni asked me what to
answer, and I suggested to take some time, also because it is
impossible to reach A. Milani at this time (Milani still doesn't know
of your posting). It is surprising the arrogance of a newspaperman
pretending to be answered in a matter of minutes! It would be difficult
for anybody, expert in the field, to provide an understandable
explanation of the case in a lecture of one hour, after days of
preparation, and it is not fair to pretend that "the authors have not
answered" to Britt: there was no time to do it.

Coming to your question: why have Milani et al. posted the paper, the
answer is very simple. 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. Moreover, the authors
requested to the peers a fast review, or they would have made the case
public anyway. Probably no one imagined that there were people
monitoring Milani's home page?

A last point: the story of the NASA embargo to NEO news is rubbish.
Certainly the authors are convinced of the importance of making such
news public and none of them, for the matter, would care of NASA. But
your mention to a possible NASA involvement has triggered Britt to
propose a similar scenario. It is wrong and misleading, and you should
better correct this point as soon as possible.

Milani et al. have not tried to hide an important information: there is
no story about AN10 (10^-9 is a ridiculous probability). The case is of
extreme importance from a scientific point of view, but there is
nothing that may seriously interest the general public.


Andrea Carusi
IAS, Area Ricerca CNR Tor Vergata
Via Fosso del Cavaliere 100
00133 Roma, Italy
Phone: +39-06-49934447 Fax: +39-06-20660188


From Clark Chapman <>

Dear Benny,

I regret the misleading wording you have chosen to use (both in your
heading and in your text) in announcing the Milani study of 1999 AN10
to CCNet subscribers.  You have written that "the chance of an actual
collision is small, but one is not entirely out of the question." In
the context of the impact hazard, those were the words used 13 months
ago to describe a very different situation.  When used about 1997 XF11
in an official IAU statement, they implied -- to both the writer, who
had a mistaken concept of the distribution of errors (see IAU Circular
6879), and to scientifically literate readers (see Stuart Goldman's
sidebar on pg. 33, June 1998 SKY & TELESCOPE) -- a probability of
impact of order 1 in 1000.

Milani estimates that the chance of impact by 1999 AN10 is of order 1
in a billion (1 in a thousand million), a factor of a million smaller
than the mistaken estimate of 1997 XF11's impact probability.  He
estimates the impact probability as 10,000 times less than the chance
that the Earth will be struck by some as-yet-undiscovered kilometer
sized object NEXT YEAR! That makes 1999 AN10 a matter of scientific
interest, but of no practical interest and hardly meriting the
"official press release" you call for. (Unless, of course, you are the
sort of person who worries about being killed by snakes while you drive
around town chain-smoking and not wearing a seat-belt.)

Use of the same wording to describe probabilities that differ by a
factor of a million can only serve to confuse a literate, rational
understanding of risk. You obviously used this wording in an ironic,
argumentative way, rather than as an attempt to confuse.  But the point
needs to be made, if society is to address risks in a rational way,
that the quantitative difference of a factor of a million makes for an
*enormous* qualitative difference. That is why the XF11 announcement
would have *deserved* the world-wide headlines, had it been true, while
the AN10 matter has no relevance to the "man-on-the-street" whatsoever.

Andrea Milani has been very responsible in having other experts check
his work before posting his results on his public web site. There is no
rational reason, however, for Milani to have called a press conference,
or offered his results to CCNet, and risked an unwarranted sensation
(like you seem to be trying to provoke) from a misunderstanding of his
result, which is irrelevant in the larger scheme of things. Such an
announcement would attach undue importance to an arcane result. People
like yourself, who are interested in the impact hazard, have long been
aware of Milani's website, so his work was hardly "hidden" away.

NASA is holding no gun to the head of a researcher at an Italian
university, so your remarks about NASA intimidation seem to be off-
track. There is room, of course, for legitimate debate about how to
handle matters of potential practical interest in a responsible way, so
that the public isn't misled by faulty, premature results but yet *is*
told about potentially important matters in a timely fashion.  This is
a dilemma long-faced by emergency preparedness officials in communities
and nations around the world who have tried to establish responsible
protocols, but there are no easy answers. Your apparent belief, Benny,
that every infinitesimal threat needs to be announced in a press release
seems to me to be a step in the wrong direction.

Clark R. Chapman
Southwest Research Institute


From Bill Dillon <>


Thanks for bringing this interesting paper to our attention.

> Of course, one reason why the authors may have decided to hide their
> data could be due to the current NASA guidelines on the reporting of
> impact probabilities by individual NEOs.

Perhaps another reason is all the flak that Dr. Marsden took over XF11.

> There is no reason whatsoever why the findings about 1999 AN10 should
> not be made available to the general public - unless the findings
> haven't been checked for general accuracy by other NEO researchers.

Perhaps they were checking, and you might have checked with them first,
as some of them are on the CCNet mailing list. I know you would like
to keep the discussion focused on how to report impact calculations
and uncertainties, but once the media gets hold of the story....


--Bill Dillon


From Lew Gramer <>

I have a question: What exactly do we believe is incorrect in the
behavior of this paper's authors? (Note I say in their BEHAVIOR:
obviously there are a variety of external factors which might exculpate
the authors themselves even if their approach to disseminating this
information was questionable.)

But again I'm forced to ask - what exactly should they have done
instead, in this view? Should they ADVERTISE an astronomically
unlikely, and still quite scientifically and mathematically uncertain
result? Surely we aren't holding up the publicizing behavior of certain
parties vis 1997 XF11 as praiseworthy?

Who on our entire planet would truly benefit from a very broad,
necessarily uncontrolled and almost certainly poorly-understood Grand
Announcement of such results? Who that is, other than those directly
dependent on publicly distributed grant monies for the study of NEOs
and their orbital dynamics? And in the end, even if the linkage of
interests between researchers and the public may be argued, how long
would such questionable benefits last?

In the end, I agree that a broad public debate should be opened as to
the precise phases which such research-and-announcement-and-reresearch
cycles should go through. Specific criteria for scientific review of
gradually increasing intensity and breadth, as well as the gradual
broadening of public announcements and recommended wording for them at
each phase, is the agenda for such a debate. However until this debate
is joined, it seems recklessly premature to dictate the dissemination
of such results.

Clear skies and clear debates all,

Lew Gramer - a questioning amateur on the side lines


From Gerhard Hahn <>

Dear Benny,

I have just read your CCNet Special, and I am very surprised to put it
mildly about the conclusions you are drawing, on the fact that you, as
you put it "by pure coincidence", you came across that preprint paper.

I also made the effort to download the original paper from the webpage
of Andrea Milani (by the way the webaddress above is in error!) and
took the time to read the whole article, which is rather technical and
contains a lot of references to additional papers. Already in the
abstract it is clearly stated

"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."

I am not unfamiliar with the field of NEO dynamics and orbital
integrations and the very difficult problem of deriving meaningful
estimates of encounter probabilities and predictions of future close
approaches. Nevertheless it would require me substantially more
time and effort to read and follow that paper in detail. - What I want
to say is that it is rather premature or even quite counterproductive
to jump at such a technical paper and use this preprint to spark off
yet another 1997 XF11 "scandal".

I assume that the authors have submitted or are about to submit the
paper to a peer reviewed journal (as far as I know Andrea Milani, he is
normally doing so - but I suspect he, or some of his co-authors will
reply to your publication rather soon - I hope so). It is rather normal
that preprint versions of papers are put on one's webpage nowadays, and
of course they then also can, and should be discussed - within the
scientific community and the general public.

Now, you straightforwardly revive the 1997 XF11 affair debate by
attacking both the authors for not publishing their results, prior to a
publication in a peer reviewed journal, and at the same time suggest
that this might be a consequence of the guidelines suggested
by NASA, which should prevent publication of unchecked findings. I feel
you are misjudging both the authors and NASA. - Just because they want
to make sure that the results are made available to a wider circle
within the scientific community they prepare this preprint, they do
not want to withold their findings. And the NASA guidelines were just
applicable to NASA funded researchers, and if anything just guidelines.
To my knowledge the authors are not financially dependent on NASA.

It can be asked whether it is wise to make preprints available to a
wider public before the paper in question has been published properly.
Your action as the moderator of the contents of the CCNet has to be
viewed critically, since, as I see it, the authors did not send you a
message with their approval to put the paper on the CCNet. In any case
it would be good editorial practice as I understand it, to get in touch
with the authors prior to spark off such a rather vicious debate, no
matter how good your intentions have been to promote the case of NEOs.

With kind regards

Gerhard Hahn
Institute of Space Sensors and Planetary Exploration
DLR Berlin-Adlershof

(7) MY TWO CENTS ON 1999 AN10

From Heidi B. Hammel" <>

All the grandiloquent language about "secrecy" with respect to the 1999
AN10 abstract is off the mark. The authors summed up their results
succinctly and made them available in a public venue: "the probability
of an impact by 1999 AN10 in 2039 is less than the probability of being
hit by an unknown asteroid within the next few hours."  Any reputable
journalist who reads *that* is not going to bother taking this issue
any further. End of story.

Heidi Hammel


From Jim Himer <James.Himer@Canada.Sun.COM>

And why would AN10 be any more dangerous or invite more public scrutiny
than the many dozens of PAHs that will approach even closer than AN10
or earlier than AN10?

Believe me, all these news feeds have their resident science guys that
know who, how, and where to get additional info.

So, how do we inform the public?  The XF11 Affair, as you put it, did
more initially to confuse the public than it helped to inform (hence
the procedural checks/balances that future announcements now require).
Initially the XF11 error box was going to come uncomfortably close;
then others said not to worry; then more earlier/later data supported
the clean-miss. To the public, it appeared for a time that the
scientists couldn't even agree among themselves.

How do we do announce, so we don't invite proclamations of impending
Rapture, mass suicide (per the Hale-Bopp event), or incite panic?  We
said Kohoutek would be great ... it fizzled, we said the last Leonids
would destroy satellites ... it didn't touch any as far as I know.  We
announced Hale-Bopp and everything about it, every magazine and
newspaper spread accurate information about it ... yet it still led to
a mass-suicide. By the third U.S. Apollo mission the world became passe
to moon landings. By the third NEO that didn't do anything, do you
think the public will have become passe (that crying wolf thing)?

So we want to inform the public ... when? I mean this 'event' won't
happen for another three decades. Do we do an initial blurb with a
caveat that data is premature and as more info comes in we'll update
it? Do we have updates on the Weather Channel for falling rocks?  I
mean, many people don't even heed hurricane and tornado warnings. And
what about the other many dozens that will come closer than the (Aug 8,
2027) 0.03 A.U. of AN10?

So we inform the public ... then what? Do we have the technology to
deal with this? Do we have the political will to deal with this, when
apparently few countries have the will to even conduct the search for
them in the first place? And which country is to save us all ... and
then not hold it pompously as a reminder over our all our heads, or if
they try and fail we blame them for our demise?

Clear skies -- JTH

James T. Himer


From Brian Marsden <>

Dear Benny,

In fairness to Andrea, I point out that he did in fact submit his 1999
AN10 manuscript to "peer review", asking several orbit computers to
confirm his general conclusions, if not the specific details.  I did
spend a fair bit of time making computations on 1999 AN10 (both before
and after I knew of this work), and I certainly agree with his general
conclusion that it is potentially dangerous for some considerable time
to come. At least two other orbit computers also agree in general
terms, although as far as I am aware, nobody has reproduced the 2039
impact. Since this was such a contrived circumstance, with the prior
need for approaches to roughly lunar distance in both 2027 and 2034,
this failure is not surprising. It also means that the chance that 1999
AN10 would "know" to follow such a dangerous course must indeed be
extremely remote.

As Andrea points out, there is some similarity to the post-2028
situation involving 1997 XF11, but there are also important
differences. In the case of 1997 XF11, there was essentially a
100-percent of an approach within the earth's sphere of influence in
2028, and when we had at our disposal only the 88-day arc of
observations in 1997-1998, the uncertainty in the miss distance was
such that we could not say whether a resonant situation would arise or
not. To have a subsequent collision would of course also require that
the minimum distance between the orbits of the asteroid and the earth
would have to be within an earth radius, and it was clear that this
could happen only during a decade or so around 2040. So if no collision
occurred during this time period (and, as you know, I found quite
easily a beautiful impact possibility in 2040), we should be completely
safe from 1997 XF11 for some millennia to come.  The 1999 AN10
situation is complicated by the fact that the corresponding danger
period lasts (mainly because the orbital inclination is as high as 40
degrees) for several centuries, not a decade or so (given that the
inclination of 1997 XF11 is only 4 degrees). It is also not 100-percent
assured that 1999 AN10 will come within the earth's sphere of influence
(about 1 million miles) in 2027 (or any other year, for that matter);
it might not come within 20 million miles, so the chance is certainly
no more than 5 percent.  So even the first boost on the route to the
2039 impact is quite unlikely to occur, let alone the necessary second
one in 2034.  This is geometry and dynamics. To speak in terms of
probabilities is much more difficult, but we can guess that the 2040
impact probability for 1997 XF11 was at least 10,000 times greater than
the 2039 impact probability is for 1999 AN10. Perhaps there are more
direct trajectories that could lead to earth impact at a later date
from just a single initial encounter (or, conceivably, from a
combination of smaller perturbations), but given that we are talking
about a danger period of centuries, as well as the possibility of very
close approaches at both of the orbital nodes, a detailed and complete
analysis of all the possibilities would be a rather intractable
problem. As with 1997 XF11, the solution for 1999 AN10 lies in the hope
of obtaining further observations. For 1997 XF11, we were lucky that
films from 1990 existed and revealed images, for otherwise we should
have had to wait until early in the year 2000 to solve the problem.
For 1999 AN10, there do not seem to be any past images (again largely
because of the 40-degree orbital inclination), but we shall be able to
solve (i.e., almost surely dismiss) the specific 2027-2034-2039
scenario (and probably somewhat beyond) with the help of observations
only two to four months from now.

That 1999 AN10 is a potential "problem" would actually have been quite
evident to anyone who looked at our web page
on Feb. 16. There, right at the top of the list of predicted close
approaches for the next century, was 1999 AN10, shown not only with a
minimum distance of only 0.0035 AU on 2066 Feb. 3, but also with one of
0.0049 AU on 2073 Feb. 3. This was the nominal solution from the
observations then available. As further observations came in the next
day, the new nominal solution was completely changed from this. That
was only to be expected--although this example by chance nicely shows
the rather persistent effect of the 7/4 resonance, as during the
seven-year stretch 2027-2034 discussed above.

Given that peer review did occur, at least partially (and it is still
in fact going on), was it right and proper that Andrea place his MS in
the WWW anyway? That is indeed a good question. For one thing, you and
others "not in the know" were not aware that the review was taking
place. Certainly, Andrea was also quite intent on submitting his MS to
an astronomical journal. What would have happened if the opinion of the
reviewers differed from that of Andrea, and we had found the
possibility of a "direct" hit by 1999 AN10 in 2034 (rather than a miss
then by possibly only 6000 miles from the earth's surface)? That would
certainly have increased the impact probability for this (presumably)
kilometer-sized object! Would the peers then have maintained their
secrecy? Would Andrea have been strongly advised not to put his MS in
the WWW?  In any case, to rely on publication in a journal would mean
that the paper would not be published for at least six months or so.
So how would observers then know that the problem could be solved by
making observations during June-August? By October the object will be a
lot fainter. And the object does not become brighter than magnitude
21.5 again (at observable solar elongations) until late 2004. So it
would be necessary to alert observers on an IAU Circular, say, anyway!

As Andrea acknowledges, the existence of resonant solutions, such as he
has found for 1999 AN10 and I previously pointed out for 1997 XF11 (yet
none of the "peers" who were so quick to speak up when that object was
in the news in March 1998 seems to have foreseen that!), plays a key
role in the examination of impact possibilities.  Now that the
community is aware of this, we can be pretty sure that future cases
will be examined carefully, even as LINEAR and other programs increase
the rate at which PHAs are recognized. I feel completely exonerated!
Just as PHAs (now 168 in number, up from 104 when 1997 XF11 was
discovered) were introduced as a special category to separate possible
dangers from the general category of NEAs (of which there are now 697),
so we should now introduce a category of, say, EDAs--"especially
dangerous asteroids" that cannot be dismissed as threats during the
next couple of centuries.  Since there is really no argument about the
general correctness of the computations (something that was also quite
true of 1997 XF11), there is in fact little need for peer review of the
type envisaged by NASA, for the computations would be quite routine.
There would simply be a list of agreed-upon troublesome objects,
growing from the really rather small number at present, and observers
would know to observe them.  The dilemma of 1997 XF11 was that during
the weeks after its discovery a troublesome object was being virtually

Anyway, you have guaranteed that all observers who can will now be
eager to put 1999 AN10 on their observing lists!  Here is an ephemeris:

1999 AN10                a,e,i = 1.46, 0.56, 40          Elements MPC 34039
Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase     V
1999 06 11    00 50.42   +12 13.8    1.114    1.124    63.5    54.0    20.4
1999 06 21    00 56.03   +18 46.5    1.115    1.217    69.5    51.4    20.5
1999 07 01    00 59.72   +25 10.0    1.108    1.307    75.8    48.9    20.5
1999 07 11    01 00.53   +31 25.2    1.096    1.393    82.4    46.4    20.6
1999 07 21    00 57.18   +37 29.1    1.082    1.474    89.2    43.6    20.6
1999 07 31    00 48.08   +43 13.3    1.070    1.551    96.1    40.6    20.6
1999 08 10    00 31.43   +48 22.5    1.064    1.624   102.8    37.5    20.6
1999 08 20    00 05.81   +52 31.8    1.066    1.692   109.0    34.4    20.6
1999 08 30    23 31.96   +55 12.6    1.080    1.756   114.3    31.6    20.6
1999 09 09    22 54.16   +56 04.6    1.107    1.816   118.3    29.2    20.7
1999 09 19    22 19.24   +55 10.2    1.150    1.872   120.5    27.5    20.8
1999 09 29    21 52.48   +52 57.2    1.208    1.924   120.8    26.6    20.9
1999 10 09    21 35.34   +50 01.5    1.280    1.972   119.3    26.2    21.1
1999 10 19    21 26.83   +46 53.6    1.366    2.016   116.3    26.3    21.3
1999 10 29    21 25.12   +43 54.4    1.462    2.057   112.4    26.5    21.5

Brian G. Marsden


From Jonathan TATE <>

Dear Benny,

I was a little surprised by the tone of your posting entitled "ASTEROID

Having seen the paper as well, I have to say that my response is
slightly different. I am very glad that Andrea Milani, Steven R.
Chesley and Giovanni B. Valsecchi have not yet rushed to inform the
media of their findings, at least not without extensive explanations
attached. The key finding in their paper is that, while an impact in
2039 is not out of the question, the probability is orders of magnitude
less than the likelihood of an impact by an as yet undiscovered
asteroid (10e-9 as opposed to 10e-5). That should be the message passed
to the mass media.

The similarity between 1999 AN10 and 1997 XF11 is not that impacts
cannot be ruled out, but that the uncertainty levels are too high to
ignite the fuse of public excitement.

I quite agree with you when you say that there is no reason why the
findings, once they have been rigorously verified, should not be
released to the public. But my dilemma is just what is the most
appropriate way of doing this?

As we have discussed at length in the past, the NASA guidelines are
quite unsupportable, and I am sure that the IAU WGNEO will reject them
out of common sense. However, that is not to say that caution should
not be applied before bursting into print. One of the main effects of
the XF11 affair was the plummet in public confidence in the
astronomical (specifically the NEO) community due to the apparent
"crying wolf" involved. No matter what the real situation was, the
public image of Spaceguard world-wide was damaged. Uncontrolled and
uninformed release of the 1999 AN10 data could easily cause the same
effect, though I think that the media and public would be rather bored
by this one. We could be in severe danger of becoming regarded as
alarmist, rather boring and wrong!

I agree whole-heartedly with Mark Bailey when he points out that, with
the increased detection rates that we are beginning to see, incidents
like this one are going to become more and more common in the future.
We must avoid being seen as alarmist, but, at the same time we must not
actively conceal data. I am hoping that the IAU WGNEO will soon publish
guidelines on the release of information. I am certainly interested in
developing protocols for the Spaceguard Foundation as we speak.  You
know that I abhor secrecy in these matters, but information release
must be tempered with common sense and careful explanation. The key
phrase in the paper in question is:

"The possibility of such an impact could be frightening, but if we
assume that the probability of an impact by an undiscovered 1 km
asteroid is of the order of 10e-5 per year, the probability of an
impact by 1999AN10 in 2039 is less than the probability of being hit by
an unknown asteroid within the next few hours."

The really scary bit concerns the yet to be discovered threat, and
until we have firm impact predictions we should concentrate on that,
while quietly getting on with contingency planning for the worst case.

Jay Tate
Spaceguard UK

CCNet-LETTERS is the discussion forum of the Cambridge-Conference
Network. Contributions to the on-going debate about near-Earth objects,
the cosmic environment of our planet and how to deal with it are
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Second Edition

    Steve Chesley <>

    Oliver Morton <>

    Mark Kidger <>

    Alan Fitzsimmons <A.Fitzsimmons@Queens-Belfast.AC.UK>


From Steve Chesley <>


by the authors:

Andrea Milani,
Steven R. Chesley,
Giovanni B. Valsecchi,

Dear Benny,

We strenuously object to your characterization of our actions
regarding this paper, and to your attempts to sensationalize our
work. This whole thing could have been explained easily if you had
contacted one of us, but that apparently does not suit your
purposes. Instead you released a uninformed report filled with
speculation and innuendo.

We have submitted the paper in question to a journal, so it is
undergoing the usual peer review process even now. It is customary for
researchers to make available, through a variety of means, papers
which are at all stages of the publication and review process, even
work still in preparation. This fosters discussion among the
scientific community, and is an essential component of the modern
scientific method. In addition to submitting to a journal we have
voluntarily sent the paper to more than a dozen international experts
and officials for comment and criticism before we made the article
available on the Internet. This review has been going on for more than
two weeks now, and in fact some technical issues that we raise are
still under discussion, but, fundamentally, the content of our report
has been well received. (We posted the information to the Internet on
April 6, about one week after selectively releasing the paper.) This
additional level of review was done voluntarily on our part as we did
not want to make available erroneous or misleading information, which
many perceive was done in the 1997 XF11 scare. We also wanted to be in
a position to issue a controlled release to the public after all
issues have been confirmed by our independently convened panel of
experts, should that be deemed necessary. In the end a consensus among
the experts was quickly reached that this object does not fit any
realistic criteria of imminent danger, so we decided to follow normal
channels with the paper. This entails submitting the article to a
journal and posting to the Internet as a preprint.

More than likely, you stumbled upon the paper via Andrea's preprint
page (hardly an "obscure web page"):

You should note that some of the other papers listed there are also
currently under review for publication by scientific journals. Indeed
the paper in question is specified as "submitted." It is not our
custom to contact the media every time we write a paper, nor is it
customary to treat papers undergoing the peer review process as

> Imagine a newly discovered asteroid, some one mile in diameter, is on a
> potential collision course with Earth in just 40 years - and no one is
> telling you about it. This is exactly what is happening with asteroid
> 1999 AN10.

Your opening paragraph clearly indicates that you are trying to spark
fear and controversy where none is warranted. You later call our
results potentially explosive, but then go on to say that the risk of
collision is small enough to be considered negligible.

So which is it? This is the fundamental flaw in your claim that we
had some obligation to broadcast this work as widely as possible to
the general public. Either it is of urgent concern, or it is not. Your
claim that "unnecessary and detrimental secrecy" surrounds this object
is based on an assumption that this paper presents time critical
information which morally obligates us to notify the public, the
press, the United Nations, and the commander of the Enterprise. This
is clearly not the case here, and so your argument is invalid, even
paradoxical. If the important thing is the lack of a press release
rather than the risk of collision, as you stated, then there was
nothing to release outside of normal scientific channels.

You make the point that this case has been handled differently from
the XF11 affair, and you are right. In the XF11 scare, a possibility
of collision in 2028 was announced, when such possibility did not
exist, even based on the then available information. 1999 AN10 is
qualitatively similar except that in the cases where there is a
non-negligible chance of a very deep encounter (2027 and 2034), we
have explicitly stated that collision is not possible. The risk in
2039 is, of course, negligible.

Your speculation that we have decided to hide this report for fear of
losing our NASA funding is demonstrably false for two reasons. First
we have no financial support from NASA, and second, if we were hiding
our results you certainly would not have found them published on the
Internet. Furthermore, to our knowledge, this proposal was only a
proposal, and it was never implemented.

We have scrupulously followed normal conventions for the release of
scientific data. Aware that this report could be sensationalized, we
submitted it to review by the panel of experts. This was done
voluntarily, but we also hope to set a precedent with this action. As a
result of this case the IAU is moving rapidly to formally establish
voluntary guidelines and procedures to be followed in future
cases. Their plans are closely modeled on our approach. Under this
policy, researchers would submit their results to an ad hoc committee
of experts for comment and criticism before going public. How long
this delay should last is unclear, but probably would depend on the
urgency of the situation, anywhere from 2-5 days. After that period
the author could release the information in any manner deemed
appropriate, and the officials and agencies first confronted by the
press will be able to respond with an informed discussion of the
threat. This responsibility to seek confirmation before going public
becomes even more critical for more threatening situations.

You may object to this policy, but we expect that in the future
virtually all researchers in the Earth hazard community will be
following it. We are sorry to report that the reason these voluntary
guidelines are necessary is to thwart those in the press who would
seek to sensationalize reports of potential impact, no matter how
carefully we word them. In that sense you are part of the problem,
Benny, and a careful and deliberate release of information is only a
response to irresponsible actions such as yours.

1999 AN10 itself holds very little relevance to the general public. If
our research does have any relevance for the public at large, it is
because we have developed a general theory that can rule out impact
for some finite period of time, yet it also shows that we can say very
little about the possibility of collision for times beyond that point,
because each encounter predicted by our theory can spawn more close
encounters, creating a cascade too complex to be analyzed. The good
news is that the further down the cascade we go, the lower the
probability of impact should a collision solution exist. The essential
point is that we feel that this paper should not be used to confuse
the general public, and we strenuously object to your accusations that
the information was handled irresponsibly. You will have a very hard
time to find a scientist who will accuse us of a lack of openness in
our research.

An important point: We want to avoid the perception of crying wolf
when we say in April that a collision is possible, while in July, after
more observations become available, we will almost certainly report
that a collision is no longer possible. We have verified that the
object cannot hit the Earth in the next 40 years, far longer than any
threat mitigation would require. And in a few months, when there is
less uncertainty in the orbit, the picture will be very different from
the one we have now.

Andrea Milani
Steve Chesley
Giovanni Valsecchi


From Oliver Morton <>


Brian suggests a new category, and that might be a good idea. It would
provide shorthand to tell us all what's what, and it would temper the
debate by transferring yet more of it from the context of "is it
dangerous?" to the less emotive "what category does it fit in?". But
EDA doesn't seem well chosen -- too strong. How about SHA, with the SH
standing for significantly hazardous by analaogy to the potentially
hazardous in PHA, and defining "significance" as a probability of
impact higher than the background risk from undiscovered objects in a
given year. Thus when explaining things people could say things like
"it's a PHA and we're looking into the possibility that it's an SHA".
Those in the know would then be filled in; those not in the know,
including some of my fellow hard-working seekers after truth in the
media, would ask what an SHA was and in the very act of explanation
would get the crucial point that the standard of comparison is the real
background risk.

As many have now pointed out, AN10 is insignificant from this point of



From Mark Kidger <>


We need to have free and untrammeled discussion about possible impact
threats. One thing is having sensible rules on announcement to avoid
silly panics (like the March 1998 Icarus impact stories) caused by
irresponsible publicity, it is another to stiffle legitimate public
discussion of a possible future threat, even if it is not a
high-probability scenario. One good thing that came out of the 1997
XF11 incident is that the possible threat did receive a lot of
attention from experienced groups who could assess the true danger as
additionl information came available. It can only be healthy
scientifically when a group can  announce openly to the community that
it has detected a possible impact threat, as that will allow careful
detailed peer review far more rapidly than is possible from any
committee or referred publication.

I think that putting firm and rigid rules on announcement is a bad
idea. It looks like people are being asked to conceal their data from
the public. There must be certain limits (eg: it is not acceptable to
release research of this kind to the press before the scientific
community, but it will reach the press's hands some time and it is
better to be seen to be open than to be "hiding" data.


Mark Kidger


From Alan Fitzsimmons <A.Fitzsimmons@Queens-Belfast.AC.UK>

Dear Benny,

It was appreciated and useful that you drew peoples attention to the
paper by Andrea Milani and colleagues on the orbital evolution of 1999
AN10. However I cannot understand your criticism towards their lack of
publicity. Andrea and his fellow co-workers are simply following the
proper proceedure for publication of a scientific study, and having
read the on-line version, I can see no reason why they should be
telling the press about it because

(a) This paper still has to undergo peer-review. Until that process is
complete theses results must necessarily be regarded as preliminary.

(b) As you acknowledge, the actual probability of impact they calculate
is tiny. They themselves show that an impact of AN10 is less likely
than an impact happening today by an undiscovered NEA.

I am sure that if the probability was > 10E3 (or some such number) then
they would indeed have widley publisised this result. In conclusion,
your claim that they have been secretive about this is unjustified. In
fact, by placing on-line the paper before it has been accepted for
publication, I think that they have been actually quite forward in
releasing the results of their work.

Best Wishes

CCCMENU CCC for 1999