I have decided to circulate the following 'addendum' from Clark
Chapman’s up-dated “Statement about the 1997 XF11 Affair” because it
might have far-reaching consequences for the future of international
co-operation in matters of NEO research if ever implemented. I have
also added my request for clarification in the hope that Clark will be
happy to address these important issues openly..

Benny J Peiser

The following statement by Clark Chapmane can be found on the internet

ADDENDUM, 6 April 1998

I have been accused of trying to unseat Marsden from his MPC position.
Nothing could be further from the truth. I have known Brian for a long
time and regard him as a friend. As I look around the world, I see
nobody who is more expert, dedicated, and deserving of continuing in
his capacity. I am sure that he has acted with the best intentions
throughout. My concern is that Brian acknowledge (or otherwise
convincingly refute) (1) that correct analysis of the data he had on
March 11th, on which basis he issued his announcement, in fact yields
the conclusion that XF11 is NOT hazardous (compared with the very low
background probability of an unknown asteroid impacting); (2) that he
should consult with other colleagues before going public with a
worriesome prediction; and (3) that he should make the international
data immediately available to other researchers so that they can
independently assess potentially threatening objects. I think that the
international astronomical community MUST require this of him. And I
think, and hope, that Brian will agree. Indeed, he did seem to agree to
(2) and (3) at a mid-March meeting, but his later comments in the
Boston Globe seem to be a backsliding.

I am adamant on one point that seems lost on several astronomers who
have advocated, in Internet chat, that the MPC should continue
"business as usual." It is NOT OK to dominate the world's headlines on
the excuse that "this is the way we've always done it." Children were
scared. Politicians and the press have grown a step more cynical about
impact predictions...and it may be important one day that we are taken
seriously. It is not trivial to raise issues about the ethics of
scientists interacting with the media, the public, and governmental
institutions. An ivory-tower view that only the media are responsible
is irresponsible.

International colleagues are jutifiably concerned about NASA being the
final arbiter in these matters. Since the IAU withdrew funding support
of the MPC, and NASA stepped in, the MPC will have to live with NASA's
requirements. It certainly would be far superior to have international
contributions (and much more total funding) to the MPC, and to have its
operation overseen by representatives from many nations.

A final point: Several people have "rejected" my analysis without
saying a word about what they found wrong. I doubt that they read my
Case Study. I have spent a great deal of time listening to dozens of
colleagues, and I believe my latest revision to be balanced, fair, and
accurate. No doubt, errors remain and some will dispute the conclusions
I reach. I would appreciate hearing from anyone about where I am wrong
before they send "flames" to dozens of others.


Clark R. Chapman (, Institute Scientist,
Space Studies Department, Southwest Research Institute, Boulder,


From: Benny J Peiser <>

Dear Clark

I would like to ask you to clarify some of the points you have raised
in your statement:

1) On the basis of the observational data available on March 11th,
Brian Marsden calculated that “the object will pass only 0.00031 AU
from the earth on 2028 Oct. 23.73 UT!” On the basis of the same data,
four independent NEO researchers confirmed Brian Marsden’s prediction
that the asteroid would pass within 0.002 AU. D.K. Yeomans & P. Chodas
calculated a miss distance of 0.00058 AU, K. Muinonen found the miss
distance to be around 0.00033 AU and E. Bowell derived a miss distance
of 0.00023 AU (see IAUC 6839, 12 March 1998).

Let’s presume that all we had on March 11th were the orbital arc after
88 days of observation and the above calculations by five of the
world’s leading NEO researchers, (i.e. without the addtional data
provided by Eleanor Helin’s films from the 1990 observations). Do
you believe that on the basis of this knowledge any responsible NEO
expert would have publicly declared that “XF11 is NOT hazardous”?

2) Let us further assume that Brian Marsden had received the above
quoted calculations by his outside colleagues PRIOR to the release of
IAUC 6839. Do you believe that he should have informed the public about
these calculations of passage (ranging between 0.00023 and 0.00058 AU)
which, due to their confirmation of an extremly close approach, would
have necessarily included “a worriesome prediction”?

3) Brian Marsden has suggested to “make available, generally on a daily
basis, all new observations of unnumbered NEOs.” Could you clarify what
other data you wish to be made public and why?

4) Let us finally assume we could turn back the clock to March 11th.
All we have to our disposal is the data after 88 days of observation of
1997 XF11. According to the calculations of one team of experts (say
IAU), the future approach of the asteroid is so uncomfortably close
that a collision in 30 years cannot be ruled out entirely. However,
another group of  experts (say JPL/NASA) believes that their
calculations are more reliable and thus believe that they can rule out
collision in 30 years time. What is worse, even after another six
months, the two groups cannot agree about their conflicting
calculations. Should such a case ever occur in the future, do you
believe that the first group of scientists should be allowed to
release their “worriesome prediction” or should they be prevented
from going public by an agency of the American Government?

(5) You state that "MPC will have to live with NASA's requirements."
and that NASA will be "the final arbiter in these matters." Does this
mean that the international astronomical community in general and NEO
researchers in particular will be under the control and dictate of
a governmental agency (i.e. NASA) which is accountable to and
controlled only by the US Government? If the answer to this
question is Yes, do you seriously believe that professional and amateur
astronomers from Russia, China and other independent nations will
continue to provide their scientific information to an agency of the
American Government?

I am sure your clarifications will be much appreciated by all list

Benny J Peiser
7 April 1998



    David L. Chandler <>

(2) THE SIZE OF 1997 XF11
    Alan Harris <> (DLR Berlin!)

    Michael Martin-Smith <>

    Dave Tholen <tholen@hale.IFA.Hawaii.Edu>


From: David L. Chandler <>

I'd like to direct your attention (and that of Cambridge Conference
subscribers) to my article today [6 April 1998] in the Boston Globe.
Feel free to reproduce it on the list itself (with copyright line
attached). The article is at:
David L. Chandler
science writer
The Boston Globe
Boston, MA 02107
FAX: 617-929-2019


By David L. Chandler

The next time the Earth finds itself possibly in the crosshairs of a
cosmic cannonball, how will the world find out?

Many astronomers are feeling traumatized by the public reaction, and a
few especially stinging attacks in print, that resulted from the
announcement on March 12 - and the retraction a day later - that the
Earth might suffer a cataclysmic impact on Oct. 26, 2028. The episode
set off a furious debate about how, or if, these things could be handled
differently the next time such a discovery is made - as it inevitably
will be.

But at the same time, boosted by all the public attention generated by
the affair - and perhaps by the imminent arrival of two Hollywood
blockbusters about asteroid impacts - the National Aeronautics and
Space Administration decided last week to double its spending this year
on efforts to track down most of the rocks hurtling through space that
might have Earth's name on them.

While the planet is now certain to be spared from an impact by asteroid
1997 XF11 in the year 2028, Brian Marsden, the astronomer whose
announcement triggered the furor, is now the target of harsh criticism
by some of his colleagues. Even though the initial announcement clearly
stated that a hit was extremely unlikely, some worry that their
profession has been tainted by a public perception that they ''cried
wolf.'' They also complain that the warnings of possible calamity gave
the impression that astronomers had simply botched the math.

''Of course, that really isn't what happened,'' said Carl Pilcher, the
NASA official who manages the agency's office that supports efforts to
track asteroids. Rather, he said, it was the normal scientific process
of consultation and review that ultimately resulted in the discovery of
earlier pictures of the asteroid, taken in 1990 by astronomer Eleanor
Helin. Those allowed the asteroid's orbit to be calculated much more
accurately - and showed Earth was safe after all.

But because of the way the episode played out, Pilcher said, NASA last
week drafted preliminary guidelines for any future reports of
potentially threatening asteroids. The plan, drafted after a long and
heated meeting among the specialists last month in Houston, in essence
calls for private consultation among the groups involved before any
public announcement is made.

''I think the obligation we have as a community is to provide the best
possible information about whatever is out there, in the shortest
possible time,'' said Pilcher, NASA's acting science director for solar
system exploration. With 1997 XF11, that ''best information'' was
compiled the day after the initial announcement.

But others in the field worry that any attempts to keep a lid on the
information - even for a day or two -would just arouse public suspicion
and provide ammunition for conspiracy theorists. It would be doomed to
failure anyway, they add, because so many people would inevitably have
access to the information and could leak the news.

Duncan Steel, an Australian astronomer who has been tracking asteroids
for years and recently wrote the book ''Rogue Asteroids and Doomsday
Comets,'' says ''there are amateurs both in the USA and elsewhere who
are now capable of making the required calculations to predict
near-misses...If anyone thinks it will be possible to keep all those
people quiet, it is likely that they also believe that Elvis Presley
killed JFK [or vice versa].''

Astronomers estimate that there are 2,000 asteroids big enough to do
global damage that are on paths that could conceivably put them on a
collision course with Earth, and fewer than one-tenth of them have been
discovered. Because the majority are unknown, as astronomer David
Morrison of NASA's Ames Research Center puts it, the most likely first
warning people would get is ''when they feel the ground begin to shake
and see the bright light on the horizon.''

But as efforts to track down objects traveling through space gear up,
astronomers will find more and more that, initially at least, might
seem to have the potential to slam into Earth. The initial analysis of
the path of these tiny, distant points of light is always highly
uncertain - and in the first few days or weeks after discovery, their
potential to strike Earth is often among the uncertainties.

It is only after many observations and intricate calculations - so
specialized that only a handful of people know how to do them well -
that an asteroid's orbit can be nailed down precisely enough to say
that there's no risk for the foreseeable future. (Over a period of
hundreds of millions of years, however, astronomers figure that most
asteroids whose orbits cross that of the Earth will, in fact, end up
hitting us).

So for astronomers, the debate boils down to this: How can they inform
the public about newly discovered objects before their potential to
crash into Earth has been ruled out, without causing undue alarm?

Some astronomers, including Tom Gehrels of the University of Arizona,
who directs a program called SpaceWatch that seeks out potentially
threatending asteroids, see the handling of that announcement as a
strong reassurance to those who fear that governments might try to
suppress such news. (It was a SpaceWatch observer, James Scotti, who
first spotted the now infamous 1997 XF11 asteroid.)

Countering colleagues who have suggested that Marsden should have
withheld his announcement until others had confirmed his calculations,
Gehrels said last week that ''it's easy to criticize hardworking
people. But what this proved - we get so many questions over the years
about `would you keep it secret?' - and obviously that was not the

Gehrels said he is ''fairly happy'' with the present tracking efforts,
which include about a half-dozen groups worldwide, and that even with
increased funding, the problem will be finding the right people
''willing to do the hard work'' of scanning the skies for asteroids.

Pilcher said NASA will double its funding for searches this year, from
$1.5 million to $3 million. But that is still far short of the $50
million annually that NASA's own 1992 SpaceGuard study concluded would
be required to find 90 percent of the possibly threatening objects
within a decade or two.

More recent analyses have questioned the need for that much money,
Pilcher said, and NASA is studying the question.

''We have the goal in our strategic plan to identify all the objects
greater than 1 kilometer in diameter'' - those large enough to be
capable of producing global damage if they were to strike Earth - ''and
do that in a decade. That is our objective.''

But that will require a significant increase over the present efforts,
which are finding ''potentially hazardous asteroids'' at a rate of about
one a month.

''It's clear that NASA intends to expand the search, but it's not clear
how much,'' said Morrison. ''There's a much stronger sense of interest
and commitment at NASA than before.''

Even a modest increase might achieve dramatic results, he said. At
present, for example, one search, directed by Helin, uses an Air Force
missile-tracking telescope for six nights a month. Some astronomers
have proposed expanding that search to 15 nights a month - the maximum
possible, because the moon's glow renders the other 15 nights useless.
They would also add a similar effort at two other Air Force telescopes.

''That might not be enough by itself, but it would be a good step,''
Morrison said.

Marsden added that besides funding additional efforts to scan the
skies, NASA should consider paying a few people to study old pictures
of the sky - the tactic that found the key 1990 pictures that clarified
the orbit of 1997 XF11. If there was enough funding to provide manpower
for scanning such old plates routinely, the warnings about 1997 XF11
might have been avoided: the earlier images might have been found even
before the initial announcement of the possible close approach in 2028.

''It shouldn't really have happened as a last-minute thing,'' Marsden
said. ''We've known since January'' that this asteroid might come close
to Earth in 2028; the question was how close? And that, it turns out,
could have been answered with a search through old pictures.''

Overall, Morrison said he is gratified that all the attention paid to 1997
XF11 ''has raised the level of public awareness'' of the threat Earth
faces from above. But, he added, ''it also was a sort of warning shot
that we'd better not come out with too many predictions that are later
retracted. We can't go through this very often and still retain our

Copyright 1998 Globe Newspaper Company.

(2) THE SIZE OF 1997 XF11

From: Alan Harris <> (DLR Berlin!)

With reference to    (2) LOTS OF WORDS, FEW OBSERVATIONS

                     From: Rob McNaught <RMN@AAOCBN3.AAO.GOV.AU>

                     CAMBRIDGE-CONFERENCE DEBATE, 3 April 1998

Rob McNaught writes:

>"I am interested in how big 1997 XF11 really is. The "1 mile" estimate
> based on a default albedo has been converted in the metric press to
> 1.6 km with no quoted uncertainty! The range 1 to 4 km is more
> appropriate. I would hope that whilst the arguments rage back and
> forward, someone has actually gone out and tried to determine the
> colour/albedo/size of the object."

I was also upset by the way the "1 mile" estimate was taken by the press as
being an accurately determined size. A reliable estimate of size requires
(near-) simultaneous optical and thermal infrared photometry (see, for example,
Harris, 1998, Icarus 131, p. 291 and references therein). Unfortunately,
1997 XF11 is much too faint at present for this to be feasible and we'll have
to wait for subsequent returns. If we take the range of possible optical
albedos as 0.05 - 0.6, and H = 17.0 +/- 0.5, then the diameter could be
anywhere in the range 0.5 - 3 km. OK, so even 0.5 km would be a nasty bang, but
how can anyone seriously predict the consequences of an impact given that
degree of uncertainty? I think this underlines the vital importance of
follow-up observations of PHAs, wherever feasible, especially thermal infared


Alan Harris (DLR, Berlin)


From: Michael Martin-Smith <>

As a reasonably informed amateur, who makes his living as a family
doctor, can I make a few "observations from the street" on the subject
of NEOs & impacts.

In medicine it is a good principle that you set up screening/preventive
medicine programmes against a dreaded illness, on three main premises;
firstly, that it is a genuine danger; secondly, that it can be
accurately detected/predicted by a reputable test process; and thirdly,
that, having found it, you can take remedial/preventative action - else
why raise anxieties and spend the money?

How does the impact threat measure up to health prevention principles?
In the case of impact hazards, in their broadest sense - asteroids of
Atren, Apollo, or Amor classes, and new comets - the danger is now
becoming recgnisd quite widely. Since 1989, we have had two passes by
300 metre objects at lunar distance with discovery (1989, and May 1996)
only 5-14 days from closest passage. We have also found a number of
Aten objects in that time span.

Two new comets, Hyakutake 3 kms nucleus 15 million kms closest passage,
and Hale-Bopp, 25 kms nucleus, 100 million kms close passage were
discovered 2 and 21 months beforehand; impact from either of these four
objects would have been disastrous - amounting to perhaps trillions of
dollars and millions of lives lost. Geology and, according to Clube and
Napier, history attests to the reality of the threat - criterion one is
clearly met.

Detection; It is accepted that some 2,000 major(1km or bigger) unknown
potential impactors await discovery, and that they could be found by a
dedicated programme of 6 x2metre telescopes over a decade or so, at a
reasonable cost; however, Atens, since they often approach us from a
sunwards direction, and new comets, are likely only to be detectable
with comparatively short lead times, years rather than decades. Large
space based detectors may add to the inventory, or detect at an earlier

Countermeasures; It is here that the problem arises, since, for
detection to be attractive, convincing countermeasures must be
devisable - and these aree difficult to set up without a valid and
imminent threat( catch-22)

Measures range from 100 megaton nuclear problems of trust, nuclear
treaties, and test bans - would we trust the fate of civilization to an
untested system? Considerable lead times are needed cf atens and new
comets). Also, to avoid the risk of mirving the tragets, we would need
compositional data - extensive probes/drillings etc. Lunar based
lasers - can achieve rapid transit to the target, be placed accurately
by line of sight, and could induce local rocket effects to deflect
objects - might be especially suitable to the new comets, mass drivers
emplanted on the asteroids by astronayuts, with the same goal of
gradual gentle deflection.

It will be noted that ALL these solutions require an extended presence
in space or augmented space capability - to various degrees. However,
they could all let us down, in the event of a large fast new comet, or
a major body defelcted our way by collision in space. In this case,
only a civilization which was ALREADY dispersed into the Solar system
for other reasons could expect to survive such an impact. Lunar base,
Mars colonies and O'Neill colonies are thus the only absolute insurance
of the survival of Civilization and its further development; In so
doing they can also generate new industries and energy for earth
itself - clean energy, tourism learning etc. Consumption of the same
asteroids and comets which threaten us provides the feedstock of such
Diaspora, and in time, depletes the threat in the most positive way

I thus propose a new law of survival "The probability of the longterm
survival of a civilization is inversely proportional to the cost of
Space Travel!" As a member of the public, can I ask that this become
our longterm and openly stated aim?

Michael Martin-Smith


From: Dave Tholen <tholen@hale.IFA.Hawaii.Edu>

Just a quick correction to Jim Benson's item about the Benson Prize:

Prize winner Roy Tucker lives in Tucson, Arizona, not Texas.


CCCMENU CCC for 1998