PLEASE NOTE:
*
AN OPEN LETTER TO THE PLANETARY SOCIETY
From: Benny J Peiser <b.j.peiser@livjm.ac.uk>
To: Louis Friedman <tps.ldf@mars.planetary.org>
Liverpool, 22 December 1998
Dear Lou Friedman,
Exactly one year has passed since the announcement, on 23
December
1997, of Jim Scotti's discovery of asteroid 1997 XF11. Thanks to
this
mile-wide object and the headlines it made last March (in
addition to
the two impact related Hollywood blockbusters), 1998 brought home
to
many the potential dangers from space. For many people involved
in NEO
research, however, this year will also be remembered for the
displeasing XF11 affair.
While it was apparent at the time of the initial announcement
that XF11
could come exceptionally close to Earth, little attention was
paid to
the object until the report on 11 March 1998 that it would in
fact do
so in 2028. Since then, the experts have been deeply split about
this asteroid, and no unanimity was reached with regards to the
future
risk this object might pose to Earth. After three months of
observations, astronomers involved in orbit calculations were
divided
into two groups: those who believed that any risk of impact in
the next
century could be ruled out altogether, and those who maintained
that
the limited data available at that time did not allow for such
unequivocal conclusions.
With the benefit of hindsight it would have been wiser, I
suppose, if
b o t h of these conflicting views could have been
presented from the
start. But even if the announcement had been made in this way, it
would
not have prevented the interested public from becoming aware of
the
existence of a small degree of uncertainty regarding the future
of
asteroid 1997 XF11.
Nine months later and this controversy still remains unresolved.
Indeed, there has been a conspicuous reluctance to evaluate data
and
calculations which show that, prior to the unearthing of the 1990
images of the object, an impact of 1997 XF11 with Earth in the
year
2040 was a potentiality. This crucial information has been known
for
half a year. While a number of astronomers have confirmed Brian
Marsden's calculations, none of his critics, as far as I am
aware, have
invalidated his findings. Instead of thorough analysis and
impartial
reporting, the Planetary Society has disseminated misleading
information which is unlikely to bring about a constructive
resolution
of this conflict.
I very much regret that Clark Chapman has recently re-opened the
campaign against the Minor Planet Centre (see his article below).
I find it particularly saddening that a widely respected
organisation
such as the Planetary Society have given free publicity to
unjustified
and incorrect assertions in its Planetary Report. After all,
anyone who
has followed the events surrounding XF11 knows that, contrary to
Chapman's claim, the MPC did not make a "mistaken forecast
last March
of an impact impending in 2028." In reality, the information
released
by the MPC stated correctly that this object would make an
exceptionally close approach to Earth on 26th October 2028. It
goes
without saying that these calculations had been corroborated by
other
groups of astronomers before the information was made public.
Clark Chapman would have every right to criticise the wording of
IAU Circular 6837. But instead, he resorts to the distortion of
facts.
And why does he limit his discussion to the 2028 calculations in
spite
of his knowledge of the hypothetical post-2028 impact scenario?
The
XF11 dilemma, I believe, has not resulted from an alleged 'lack
of
institutionalised experience.' It is the inescapable consequence
of a
very real scientific predicament. As Brian Marsden has pointed
out
repeatedly, without the discovery of the observational data from
1990,
we would currently be uncertain as to whether or not XF11 might
pose a
serious threat to Earth some 40 years from now. Since nobody knew
how
close the asteroid would approach the Earth in 2028, its future
orbit
could not be determined with any certainty. As a result, reliable
impact probability evaluations were not possible either.
Marsden's calculations have been known for half a year. They have
been
confirmed by others. Why is it then that his critics have failed
to
take his claim into consideration? As long as this is true, it
would
appear that the criticism of IAUC 6837 is a red herring, a
diversionary
tactic to shift attention from the very real scientific
difficulties
regarding this exceptional asteroid.
Sometimes, scientific problems such as these cannot be resolved
unanimously. Even an "impact prediction evaluation
council" (if
established as a scientific rather than political committee),
would be unable to force conformity upon scientists. If, in a
similar
future case, agreement cannot be reached among the world's
leading NEO authorities, the public has the right to be informed
of
the conflicting evaluations and the reasons for the disagreement.
The suggestion, on the other hand, that a NASA council should
censor "mistaken professionals", borders on the absurd.
Even if
such a body had an international basis, it is hard to see how, in
cases
of actual disagreement, "mistaken professionals" would
be recognised or
silenced.
Clark Chapman has been concerned with public relations for quite
a
while. No doubt, it is important to address the problem of how to
handle truthfully and responsibly the issue of the impact hazard
in public. But how, I wonder, can the interested public have
confidence in his statements if he cannot even present the basic
facts and scientific problems accurately? Given Clark's
legitimate
concern for the credibility of NEO research, his ungentlemanly
attack,
I regret to say, is neither politically helpful nor
scientifically
correct. I hope that the Planetary Society will rectify the
errors in
his report and will ensure that future publications on the impact
hazard are factually accurate.
Yours sincerely
Benny J Peiser
==============================
ISSUES ON RISK ASSESSEMENT AND NEO IMPACT PREDICTION
NEWS & REVIEWS, by Clark R. Chapman, for the Nov./Dec. 1998
issue of THE PLANETARY REPORT. [As circulated by David Morrison
<dmorrison@mail.arc.nasa.gov>]
I've just attended a workshop on public policy implications of
predictions about natural hazards (like earthquakes, hurricanes)
and
about environmental degradation (global warming, nuclear waste
storage) ["Workshop on Prediction in the Earth Sciences: Use
and
Misuse in Policy Making," organized by the Geological
Society of
America and the National Center for Atmospheric Research.] The
participants included philosophers, ex-staffers of the
congressional
House Science Committee, the operations director of Fargo who
dealt
with the 1997 floods, an ex-Emergency Management Director for Los
Angeles, economists, structural engineers, social scientists, a
Nebraska rancher (who relies on climate forecasts), a public
utility
official, a science journalist, a National Science Foundation
official, a reinsurance analyst, and experts in the predictive
earth
and environmental sciences.
Prediction Councils
I attended the workshop to present a case study of the
asteroid/comet
impact hazard. I felt a bit out of place. Most of the other nine
case
studies dealt with hazards for which institutions and protocols
have long
existed. For example, the problematic selection of Yucca Mountain
(Nevada)
as the permanent repository for nuclear wastes during the next
10,000
years was the outgrowth of an elaborate, two-decade-long
governmental
process. Forecasts about whether the mountain will or won't
contain
the wastes successfully emanate from an official deliberative
body,
the Nuclear Waste Technical Review Board. When and if California
seismologists dare again to make any short-term earthquake
predictions (like the failed Parkfield prediction of 1985), they
will
be endorsed by the governor of California only after being vetted
within the California Earthquake Prediction Evaluation Council
(CEPEC).
Space scientists, on the other hand, are woefully unprepared to
deal
with the social impacts of their science. The heavens normally
play
little role in earthly affairs, despite the quackery of
astrologers.
Solar flares were the unique exception until the recent
recognition
of the impact hazard. Eight years after a congressional mandate
to
evaluate the hazard, NASA has only begun to augment the limited
funding of telescopic searches for hazardous objects. I am
hard-pressed to think of any research project on the nature and
consequences of the modern-day impact hazard that has been funded
by
NASA. Among well-funded earthquake, hurricane, and climate-change
researchers at the workshop, I felt alone in relying on my
employer's
overhead to pay for my participation.
Lack of institutionalized experience led, no doubt, to the
mistaken
forecast last March of an impact impending in 2028. A South
Carolina
banker at the workshop recalled his anger upon hearing the
retraction
two days after the apocalyptic headlines. We now know, as
reported at
the October meeting of the American Astronomical Society/Division
for
Planetary Sciences in Madison, Wisconsin, that the positions of
asteroid 1997 XF11 observed just two weeks after its
early-December
discovery were already sufficient to rule out an impact in 2028.
Those data, given normal celestial mechanics, imply a chance of
impact less than the chances of a poker player in an honest game
being dealt seven royal flushes in a row. This reassuring
information
would have been available, had anyone been adequately funded to
use
existing software to evaluate the probabilities.
Calculations and Protocols
Obvious lessons from this fiasco are that (1) NASA should fund
experts to make valid impact probability calculations and (2)
formal
protocols should be established for evaluating impact predictions
before entities like the American Astronomical Society publicly
endorse them. The widely promulgated, face-saving story that the
unearthing of pre-discovery (1990) images of 1997 XF11 saved the
day
might lead NASA to conclude that all it needs to do is fund more
observations (benefiting observers and those who archive
observations) when in fact we really need better early
calculations.
Case studies presented at the Prediction Workshop document that
economic and institutional biases often strongly influence
predictions
as well as conclusions drawn from them.
As for protocols, much discussion on the Internet has chided NASA
for
proposing to "censor" impact predictions. But consider
this: NASA's
establishment of an impact prediction evaluation council would no
more censor the predictions of quacks (or of mistaken
professionals)
than CEPEC has censored amateur earthquake predictions (including
one
based on prophecies of Nostradamus), but it would provide a forum
for
evaluating predictions to which responsible news media would
(hopefully) turn before printing scary headlines.
Predictive Space Science
It is odd that space scientists should be so unfamiliar with risk
assessment and prediction. After all, astronomers are renowned
for
accurately predicting eclipses, and NASA engineers routinely
predict
the arrival of spacecraft at targets years in the future. The
occasionally less successful predictions of comets and meteor
storms
"of-the-century" at least have no social consequences,
other than
causing would-be watchers to lose a few hours of sleep. Yet there
*are* real social and economic costs in the use and misuse of
predictions in the space sciences that extend beyond impact
prediction. The *Challenger* astronauts were lost in part because
of
NASA's failure to heed a cold-weather forecast. The successes or
failures of expensive spacecraft depend not only on
space-qualified
engineering but also on predictions from scientific models about
planetary radiation belts, micrometeoroid fluxes, and planetary
surface environments. Space scientists should catch up with other
scientific disciplines and learn about risk assessment and the
pitfalls of predictive science.