PLEASE NOTE:


*

CCNet 22/2003 -  25 February 2003
---------------------------------

"A number of authors have suggested that oceanic waves (tsunami)
created by the impact of relatively small asteroids into the Earth's
oceans might cause widespread devastation to coastal cities. If correct,
this suggests that asteroids > 100 m in diameter may pose a serious
hazard to humanity and could require a substantial expansion of the current
efforts to identify earth-crossing asteroids > 1 km in diameter. The
debate on this hazard was recently altered by the release of a
document previously inaccessible to the scientific community. Careful
reading of the report suggests that previous work on impact-generated
tsunami has exaggerated the hazard posed by such waves."
--Jay Melosh, Lunar and Planetary Lab, University of Arizona
 

"The Spaceguard Survey goal is now within reach. Not unexpectedly,
interested stakeholders are attempting to build a consensus for
expanding NEO surveys to ever-smaller objects. Others are arguing for
investment in mitigation (in the sense of experiments to deflect a
small body). Major astronomy programs (e.g. the Large-aperture Synoptic
Survey Telescope) are adopting NEO survey requirements "ad hoc". The
key policy question is whether such expansion of investment is socially
desirable. More generally stated, "what (if anything) should be done
next?"
--Geoffrey Sommer, RAND Corp.


(1) ASTEROIDS AND SECRECY: IF END IS NIGH, DO YOU WANT TO KNOW?
    Space.com, 24 February 2003

(2) NEO NEWS: AAAS & SECRECY
    David Morrison <dmorrison@arc.nasa.gov>

(3) IMPACT-GENERATED TSUNAMIS: AN OVER-RATED HAZARD
    Michael Paine <mpaine@tpg.com.au>

(4) SUPPORT
    Alain Maury <amaury@obs-azur.fr>

(5) ARE WE BARKING UP THE WRONG TREE?
    Michael Paine <mpaine@tpg.com.au>

(6) RE: THE GREAT IMPACT DEBATE
    James Marusek <tunga@custom.net>

(7) SURVIVAL INSTINCTS
    Linda Sloan <lksloan@informationuniverse.com>


============
(1) ASTEROIDS AND SECRECY: IF END IS NIGH, DO YOU WANT TO KNOW?

>From Space.com, 24 February 2003
http://www.space.com/scienceastronomy/asteroid_secrecy_030224.html

By Robert Roy Britt
Senior Science Writer

Suppose a giant asteroid is heading toward Earth right now. Impact is
certain. The consequences are expected to be globally devastating, with the
human race among the casualties. The chances of doing anything about it are
zero, the government decides.

Would you want to know?

Or would you prefer the Feds keep the information secret and spare you and
your neighbors a bunch of pointless worrying?

In essence, the question concerns whether you'd prefer to die in ignorant
bliss, or if you'd like some options. The alternatives might include dying
in a panic, calmly making peace with your Maker, finally taking the kids to
Disneyland or -- who knows? -- making a last-ditch effort to fight odds your
elected leaders say are wholly against you. 
 
For several reasons that will become apparent as you read on, the question
is largely moot.

But that didn't stop it from coming up at a major science gathering earlier
this month and generating a global round of conspiracy headlines. According
to some articles, the U.S. Government has been advised to withhold
information of a catastrophic impact, were one ever found to be imminent.
The Times of London put this headline above its story: "Don't Tell Public of
Doomsday Asteroid."

The media accounts centered around the words of one graduate student (the
press variously and erroneously called him a scientist, a researcher and a
government adviser). Geoffrey Sommer spoke as part of a seven-person panel
Feb. 13 at an impact hazard symposium during a meeting of the prestigious
American Association for the Advancement of Science (AAAS), held in Denver.

Controversial words

Here are the widely quoted words, from an AAAS press release, attributed to
Sommer (much to his surprise, he said later):

"When a problem arises with high uncertainty, there is an opportunity to
spin the problem to avoid global panic. If you can't do anything about a
warning, then there is no point in issuing a warning at all. If an
extinction-type impact is inevitable, then ignorance for the populace is
bliss."

Those words were taken "severely out of context" and "inaccurately described
my position," according to Sommer, who says he was not advocating a position
but rather discussing choices involving information disclosure that
policymakers would face. Yet the press release was sent out with,
effectively, an AAAS stamp of approval, and for several days, all Sommer
could do was watch as the comments generated ire among readers and some
frustration on the part of scientists.

However misconstrued, the quote seemed to stem logically enough from a case
study that was part of Sommer's doctoral dissertation at the RAND Graduate
School, operated by the RAND Corporation (the media inaccurately placed him
as an employee of the RAND Corporation working for the government). The
dissertation's topic: Low-probability, high-consequence threats and how
policymakers might evaluate them.

Whatever the circumstances, Sommer received some vitriolic responses to his
words, which many saw as downright wrongheaded and arrogant at worst,
pessimistic at best. Here are reactions from three separate people, based on
e-mails supplied by Sommer himself:

"It's rather arrogant of you to presume that not a single human would
survive after a large impact. Perhaps no one would. If people don't try, the
odds are certainly worse."

"One doesn't have to be a RAND 'expert' to realize that the world would
rather go down fighting, than to be lulled into a false sense of security."

"You are not God, Mr. Sommer ... I suppose if you were diagnosed with a
rapidly progressing terminal illness, you would prefer to be told, 'All your
tests came back OK, Mr. Sommer. There's nothing wrong with you at all.'"

The last note came from James Cass, who also told Sommer, "Your arrogance is
pathetic." Upon reflection, Cass told SPACE.com: "I realize that some of my
words were a bit acidic, but after I read Mr. Sommer's comments I was
livid."

'Inconceivable'

Late last week, Sommer explained his true stance to SPACE.com. More on that
shortly. First, the reaction of scientists -- most of whom were somewhat
confused about what Sommer was actually trying to say -- shows how
passionately they detest secrecy.

Across the board, experts in asteroid search efforts and death-by-space-rock
risk assessment, collectively known as the Near Earth Object (NEO)
community, contest whether secrecy could ever be warranted, let alone
possible.

"It is inconceivable to me that anyone involved in NEO surveys and orbital
predictions would want to keep the results a secret," David Morrison, who
spoke at the same AAAS symposium, said in an e-mail interview. "It is also
inconceivable that astronomers could keep such a secret even if they wanted
to. A real impact prediction, even at low probability, would be known all
over the world in a matter of hours."

That is true. In fact, dozens of amateur astronomers -- employed by no
government or institution in their backyard endeavors -- help with the
follow-up observations needed to pin down a newly discovered rock's actual
trajectory. They work from data stored at two publicly available Web sites,
one in the United States and one in Italy.

Journalists have frequently accessed these databases to fuel doomsday
stories about asteroids that had long odds of ever coming in. In each case,
the odds have dropped from highly improbable to zero in a matter of days or
weeks.

The scare stories leave raw scars on the NEO community and its sense of
credibility, perhaps making the researchers particularly sensitive to this
latest round of doomsday headlines laced with suggestions of official
cover-up.

Morrison, senior scientist with the NASA Astrobiology Institute at the Ames
Research Center, called the whole affair a tempest in a teapot. He said
there are no asteroids big enough to cause mass extinction currently in
Earth-crossing orbits. Even a threatening comet, which by nature would start
farther out in the solar system and might wander inward for the first time
after centuries of deep space oblivion, would be spotted by amateur
telescopes months before it hit, he said.

Real threat

Over time, orbits change, however. Asteroids that aren't threatening now
might become so in a few centuries or millennia. All leading experts,
Morrison included, agree that Earth will eventually get pummeled again by a
1-kilometer-wide (0.62-mile) object or bigger. Civilization might teeter.
Odds are very slim, however, that it will happen in any given year or
century.

It could come next year, or not for a million years.

(Scientists estimate there are 1,100 1-kilometer and larger NEOs; about 640
of them have been found. Hundreds of thousands of smaller objects roam the
same region of space as Earth, so the impact odds for smaller, regionally
destructive asteroids are greater in any given time frame. But the bulk of
asteroid search funding and political discussion to date has focused on
rocks above the 1-kilometer threshold.)

Sommer said that prior to his symposium talk, he had only two minutes to
review the press release containing his comments, and it had already been
distributed to reporters. At the meeting and in remarks since, he has worked
to put it all into context.

"I don't advocate 'silence and secrecy' as absolutely as the AAAS press
release indicated," Sommer wrote Feb. 15, two days after the symposium, in
an electronic newsletter called CCNet, which monitors the science and
politics of the NEO search and threat.

In the CCNet writings, however, Sommer did not appear to back down entirely
from the idea that hiding information might be an option under certain
circumstances in order to avoid social panic and the tremendous costs that
might be associated with it (think looting, profiteering, and economic
collapse, he says).

One point Sommer stressed is that the governments of this Earth need to get
together and come up with a mitigation strategy -- what to do if an asteroid
is found bearing down our pale blue dot.

Absent a plan to deflect or destroy an incoming asteroid, or to survive the
hit, Sommer said policy makers might question the value of telling the
public it is doomed.

CCNet is run by Benny Peiser, a social anthropologist who contemplates
"neocatastrophism" in various forms. Peiser, of Liverpool John Moores
University in England, responded: "Even with little time left for
mitigation, many activities could be taken by the world community to attempt
human survival of such a global disaster."

Peiser agrees with Morrison and others that in the case of a huge impacting
object -- a planet destroyer -- there would be a lot of time to prepare and
no possibility for secrecy. Sommer made it clear late last week that he
agrees with these points, too.

Peiser also said science has not even reached a point where it can state
with certainty whether an impact would doom humanity. Further, if a
gargantuan incoming object is detected, it would be weeks, months or years
before a firm determination was made that it was going to hit Earth, or not.


For the record

After the CCNet exchange, we asked Sommer to clarify his position.

"I absolutely do not advocate government keeping secret news of any
impending disaster that would wipe out the world's population," Sommer said.

"I take no stand on what the policymakers should do," he said. "I most
certainly never advocated that information be withheld from the public. In
the purely hypothetical scenario at issue, my point is simply that
policymakers should weigh the plusses and minuses of telling people they
were about to die and that there was nothing that could be done to save
them. It is a value judgment for the policymaker to make."

Sommer said the whole example is peripheral to his main point, which is that
warning the public of an impending disaster "is a social function, not just
a technical function, and that the costs of warning (including false
positives) must be considered in the calculus of resource allocation and
program design."

Meanwhile, researchers are concerned over how media coverage surrounding the
affair might tarnish the public view of NEO science.

Clark Chapman, of the Southwest Research Institute and another of the
symposium speakers, worries about the collective damage to scientific
credibility from coverage of the Sommer controversy combined with hype
surrounding previous asteroid scares. Chapman said individual flames of
controversy tend to be small, but they get fanned "by those who prefer to
see conflict rather than convergence and consensus."

Like other NEO researchers, Chapman is concerned that the public will come
to distrust serious asteroid science and the need to search for, catalogue
and understand space rocks, as well as to begin looking into mitigation
strategies.

Importantly, as Sommer points out, there is no strategy, in the United
States or elsewhere, for what to do in the face of a natural threat from
space. And that, several other experts contend, is a legitimate concern.

At issue is how and whether to deflect or destroy an incoming rock,
something no one knows how to do. Similarly important is the need to develop
plans for moving coastal residents to higher ground. Because our planet is
two-thirds water, any impact is likely to be an ocean splashdown, whose
greatest immediate effect might be tsunami waves that could destroy coastal
regions on two continents within hours.

The panic myth

At the heart of Sommer's case is how people would respond to the knowledge
of looming cataclysm.

Lee Clarke, who advocates asteroid-mitigation planning, spoke at the AAAS
asteroid symposium, too. The Rutgers University sociologist studies big-time
catastrophes and the supposed public panic that comes with them. He says the
whole concept that everyone freaks out is largely a myth.

"We have five decades of research on all kinds of disasters -- earthquakes,
tornadoes, airplane crashes, etc. -- and people rarely lose control," Clarke
said. "Policy-makers have yet to accept this. People are quite capable of
following plans, even in the face of extreme calamities, but such plans must
be there."

A scheme for survival would require good international communication and
ought to be discussed in the United Nations, so that poorer countries are
not left out of any world blueprint for notification and mobilization,
Clarke said. "Earth's history is filled with unanticipated catastrophes and
their disastrous consequences. With appropriate planning, the human toll
could be lessened."

Clarke figures the worst thing governments could do is lose public trust by
withholding information. But he points out that secrecy might appeal to some
public officials.

"Keeping secret something potentially very dangerous is an idea that would
resonate very well with the current administration in Washington," Clarke
said. "It would probably resonate with most high-level decision makers."

In that light, "Geoffrey Sommer did the debate a great service by proposing
a scenario that needs to be talked about," Clarke said, adding that the
discussion was and should continue to be an intellectual one, regardless of
whether scientists disagree on various points.

"The issue is big," Clarke said, "but the individuals are not."

Copyright 2003, Space.com

============
(2) NEO NEWS: AAAS & SECRECY

>From David Morrison <dmorrison@arc.nasa.gov>

NEO News (02/24/03) AAAS & Secrecy

Dear Friends and Students of NEOs:

This edition deals with two related issues about NEAs.

(1) First is the report from an AAAS impact hazard symposium in Denver that
noted the tenth anniversary of the Spaceguard Report and explored several
issues related to communications and societal interactions.

(2) The second part of this report deals with a media flap that began when
AAAS participant Geoffrey Sommer suggested that the government might wish to
keep the news of an impending impact secret. Understandably, this issue was
picked up by many news media, some of which ignored the context (such as
that the other speakers at the AAAS symposium all asserted that such secrecy
was neither desirable nor possible). We present both sides, and let you
reach your own conclusions.

This is undoubtedly more than most of you will want to read about these
topics. There is not much here that is new, but perhaps this will be
interesting especially for those concerned about the media and communication
aspects of the NEO impact hazard. It is ironic that a symposium dedicated
primarily to better communications became itself an occasion for a media
flap.

If you want just a general overview of the issue, go to the final item, a
story by Rob Britt published today in Space.com.

David Morrison

===================================
PART I: THE AAAS SYMPOSIUM

PRESS REPORTS AND COMMENTS FROM PARTICIPANTS
--------------------------------------------------------

AAAS Symposium on "The Asteroid/Comet Impact Hazard: A Decade of Growing
Awareness" American Association for the Advancement of Science: Denver,
February 14, 2003

Co-Chairs: Alan Harris (Space Science Institute) and Richard Binzel (MIT)

* David Morrison (NASA Astrobiology Institute, dmorrison@arc.nasa.gov).
"Overview of the Impact Hazard: Risk and Mitigation." Introductory comments
on the general nature of the hazard from impacts of asteroids and comets,
with emphasis on current mitigation efforts, especially the Spaceguard
Survey of Near Earth Objects.

* Lee Clarke (Dept. of Sociology, Rutgers Univ., lee@leeclarke.com).
"Responding to Panic in a Global Impact Catastrophe." Possible psychological
and sociological responses of the general public to impact disasters: a
vital, but until-now-overlooked, issue in discussions of the impact hazard.

* Geoffrey Sommer (Rand Corp., sommer@rand.org).  "Policy Frameworks for
Impact Mitigation."  Reasons why traditional policy analysis tools are
inapplicable to this low-probability, high-consequence hazard; sensitivities
to uncertainty in social response variables; identification of stakeholders
and valuations; issues involving secrecy, communication, and public
warnings; meta-benefits and meta-hazards of political and societal
responses.

* David Ropeik (Harvard University; dropeik@hsph.harvard.edu). The Impact
Hazard in Its Societal Context: Risk and Risk Perception." Perspectives of a
former reporter who is today professionally involved in the evaluation and
communication of risk.

* Clark R. Chapman (Southwest Research Inst., Boulder,
cchapman@boulder.swri.edu). "Perspectives on the Impact Hazard in a
Dangerous World." Evaluation of relative environmental significance of
impacts of various sizes compared with the very largest natural hazards,
such as earthquakes, floods, and tsunamis; issues in communication with the
public; considerations of the impact hazard in the context of current public
and governmental responses to terrorism.

------------------------------------------
MORRISON SUMMARY: OVERVIEW OF THE IMPACT HAZARD

Today it is commonplace to realize that the Earth is bombarded by rocks from
space, and that a strike by a big one could end civilization. This was not
true ten years ago when the NASA Spaceguard Survey Report was released,
providing a quantitative estimate of the impact hazard and concluding that
we are as much at risk from impacts as from other better-know hazards such
as earthquakes and severe storms. Some in the media treated this original
report with derision. The situation was made worse when parts of the nuclear
and missile defense communities began to promote defenses against asteroids
with suspicious similarities to proposed "Star Wars" anti-missile systems.
At the minimum, there was a "giggle factor" associated with claims that "the
sky is falling".

A decade later the impact hazard is well understood among the science
community and is increasingly accepted by the public at large. Yet it is
still a difficult concept, because the danger from impacts is packaged in
ways that are different from anything in our experience. People are not
killed individually, or by the hundreds or even the thousands, by impacts.
Rather, the primary risk is from a global environmental catastrophe that
might happen only once in a million years, yet could wipe out a substantial
fraction of the Earth's population. Impacts are the extreme example of a
hazard of very low probability but very great consequences. Nobody has ever
been killed in a major impact event, yet we can -- and must -- recognize
this possibility as a serous issue for individuals and the government to
deal with.

The best news after a decade is not that the hazard is better understood,
but that we are actually doing something about it. Unlike any other natural
hazard, impacts can be (1) predicted with high precision, and (2) prevented
(at least in principle) by the application of space technology to defect or
destroy a potential impactor.

The first step in any effort to mitigate the impact danger is to find out
whether we are -- or are not -- the target for such a collision within our
lifetimes, or that of our grandchildren. Sometimes we talk as if this were a
statistical question. In fact, talk of probabilities can be a way of
covering our ignorance. We know enough about probabilities to say that any
impact in our lifetimes, whether it is from an auditorium-sized
"Tunguska-class" asteroid or a larger "extinction level event", is quite
unlikely. You could win a bet by wagering that it will not happen.
Nevertheless, we want to know whether, against the odds, our generation will
need to prepare to defend the planet from this threat. Scientists have
therefore shifted from an emphasis on understanding the probabilities to a
straightforward program to find the potentially threatening asteroids and
compute their orbits, one at a time, to see if any will hit us. That is what
people and governments need to know -- not "what are the odds?" but "will we
be hit?"

The program to search for potentially hazardous asteroids is called the
Spaceguard Survey, and it is funded by NASA and the US Air Force. The
Spaceguard Goal is to find 90% of the near Earth asteroids larger than 1 km
in diameter (thought to be the lower limit for a global catastrophe) by
2008, which is ten years from the beginning of the survey. We are already
more than half way to our goal, with nearly 700 found out of an estimated
total of 1100 such asteroids.  The good news is that while many of these
asteroids will hit the Earth eventually, none is on a collision course
today. By finding and eliminating these asteroids, we are lowering the risk
that we will be hit unawares by a global impact catastrophe. When we
eventually have all the asteroids bigger than 1 km, we will probably find
that none is about to hit us -- and we will thereby have removed, for our
generation, concern about this particular threat to the survival of
civilization. Of course, if we do find one on a collision course, we will
have a very different challenge -- to mount a mitigation campaign that will
divert the asteroid. Given several decades of warning and a high incentive I
am confident that such an effort would succeed.

As we see our way clear to meeting the Spaceguard Goal later in this decade,
we must face the issue of whether to extend the survey to smaller asteroids.
The small ones hit more frequently, but even in sum they pose a much smaller
risk than the objects larger than a kilometer that constitute our first
priority. Fortunately, the asteroids that pose the largest danger are also
the easiest to find. The next step will require a greater expenditure of
money and search effort in order to mitigate a smaller danger. How will
science and society make these trade-offs? How do we deal with this abstract
risk in a rational way? What are the processes by which this sort of issue
will be debated in the science media or on the stage of public policy? These
are all issues that will be discussed in this symposium marking the first
decade in which we have recognized the challenge of protecting our planet
from the ultimate environmental catastrophes.

--------------------------
CLARKE SUMMARY: RESPONDING TO PANIC IN A GLOBAL IMPACT CATSTROPHE

A common fear among high level decision makers is that people react badly to
bad news ("we don't want to  cry wolf") and that they will panic if a
catastrophe happens. Scientists who think and write about global
catastrophes also worry that the public will panic. But our leaders are
wrong, because panic in disasters, at least in the United States, is quite
rare. And our scientists are often unscientific, because they're neglecting
the empirical evidence on how people behave in dire circumstances.

Fifty years of social science research on disasters and extreme situations
shows that panic is rare even when people feel excessive fear. Panic,
according to the Oxford English Dictionary, is an "excessive feeling of
alarm or fear leading to extravagant or injudicious efforts" to secure
personal safety. Panic usually refers to desperate acts of self-preservation
that have the contrary effect of harming self and/or others. People escaping
from the destruction of the World Trade Center didn't act like that; nor did
they disregard the needs of others around them. Instead, they behaved
civilly and cooperatively. We now know that almost everyone survived if they
were below the floors where the airplanes struck the buildings. That is in
large measure because people did not become hysterical but instead
facilitated a successful evacuation.

Hollywood's disaster movies-Armageddon and Deep Impact are obvious examples,
but any "disaster movie" will do-show people running wildly from
catastrophe, knocking over their own grandmothers to save themselves. That's
dead wrong. Not only will they save their grandmothers, they'll save
complete strangers, before saving themselves. This is surprising if one
assumes that people are naturally self-interested. But looking at the
evidence leads to the inescapable conclusion that people are naturally
social.

A major reason that the panic myth persists is that it provides authorities
(i.e., decision-makers, politicians, and administrators) with an easy
explanation for complex events. Even when panic does happen-say at soccer
matches-focusing on it usually detracts attention from more important
factors such as official misconduct or police over-reaction. In addition, by
using pacifying speech (e.g., "Everything is under control") to allay public
fear and hiding information from the public, spokespersons cultivate
distrust at a time when nothing could be more important to public safety
than trust of the information that authorities disseminate.

The truth is that disasters are normal. Disasters are special situations but
they are still social ones, and people generally follow community
expectations when things go awry just like in less tumultuous times.
Furthermore, people don't usually lose their sense of community, even when
every building has been destroyed. The more consistent pattern in disasters
is that people connect in the aftermath and work to rebuild their physical
and cultural environments.

The lion's share of thinking and research concerning near earth objects has
gone into detection and deflection. It's a mistake to neglect the social,
political, and organizational aspects of the problem. Our concern is, after
all, with people: saving them, helping them, educating them, working with
them.

This presentation will consider these issues, and try to specify the
utility, and limitations, of extant social science research for trying to
predict and management the public response to a global impact catastrophe.
Some of the presentation will be built on a paper, "Panic: myth or reality,"
which appeared in the Fall 2002 issue of Contexts, the American Sociological
Association's general-interest journal.

On the question of why governments fear public panic, my hunch is that it's
just common sense, which is sometimes more common than sense. But it's very
real among high level decision makers. Even professional emergency managers
often believe it. One quick example: a fellow who works for the NYC mayor
was speaking at a conference for emergency managers last October. He made a
big deal about how one of the lessons of Guiliani's handling of risk
communication after 9.11 was that he asserted a single, strong voice; had he
not, this fellow claimed, New Yorker's would have panicked. Sadly, he
totally dismissed me, even though I offered real evidence to the contrary.

My claim in Denver won't be that panic never happens, or that it isn't an
issue regarding NEOs. It will be more measured than that. I will point to
the research on disasters, all of which suggests panic, at least the usual
conception of it, probably wouldn't happen. But there are big limits to the
validity of the extrapolations we can confidently make from present
knowledge to NEO-related issues. We can predict confidently, I believe, that
if policy makers act as if people can't handle bad news then they can help
produce the very irrationalities they fear. The problem of risk
communication in this venue hasn't been discussed enough.

---------------------------------
SOMMER SUMMARY:  POLICY FRAMEWORKS FOR IMPACT MITIGATION

The Spaceguard Survey goal is now within reach. Not unexpectedly, interested
stakeholders are attempting to build a consensus for expanding NEO surveys
to ever-smaller objects. Others are arguing for investment in mitigation (in
the sense of experiments to deflect a small body).  Major astronomy programs
(e.g. the Large-aperture Synoptic Survey Telescope) are adopting NEO survey
requirements "ad hoc". The key policy question is whether such expansion of
investment is socially desirable. More generally stated, "what (if anything)
should be done next?"

This is a more difficult question than one might think. There is no general
policy framework for assessing the social benefit of impact hazard response
programs. This is a typical state of affairs for "low probability, high
consequence" problems. The familiar tools of policy analysis (such as
cost-benefit) fall short, although that does not prevent their
misapplication (with potentially specious results).

This work attempts to establish a system approach to the NEO hazard,
considering the interactions between a passive physical threat and a
multitude of coupled social systems. It identifies stakeholders, their
likely valuations and sources of valuation, and operating constraints.  Only
then is it possible to set a social goal (as opposed to technical goal) for
any NEO program.

The social costs of false positives are particularly interesting.  Due to
the technical characteristics of the process of NEO orbit determination, the
usual course of events for any NEO is that a warning is issued, only to be
dropped (not retracted) as the orbit is refined and the uncertainty ellipse
shrinks to exclude the Earth. A high warning rate is thus endemic to the
business of NEO surveying. The NEO community has attempted to regulate the
effects of this process by means such as the "Torino" hazard scale, with
mixed results. Media interlocutors have an institutional incentive to set
their own "thresholds of alarm".  It is doubtful whether asteroid scares can
ever be avoided, and false warning rates will in all likelihood surge upward
with future expanded surveys.   

Social costs associated with warnings will be addressed here.  Although
difficult to quantify, they are not intangible, as our collective experience
with post-9/11 terror warnings amply demonstrates.

On the subject of mitigation (interception), a key point to be made is that
costs associated with actual impacts are a function of impact rate less
interception rate.  In contrast, warning costs are a function of warning
rate less perception of interception capability.  The role of mitigation
systems in reducing social costs, notwithstanding their putative mission
effectiveness, is familiar in the military sphere but has not been advanced
as an argument by proponents of NEO mitigation. 

Finally, the concept of meta-effects (meta-benefits and meta-hazards, when
value laden) will be discussed.  These are defined here as social or
technical shifts that may be catalyzed either consciously or serendipitously
by the NEO hazard itself, with the potential to dwarf direct costs or
benefits. Examples include militarization of space, nuclear proliferation,
the "deflection dilemma", and asteroidal resource exploitation.  In this
context, any analysis treating the NEO hazard in isolation is likely to be
irrelevant to the policymaker.

In summary, the near-realization of the Spaceguard Survey presents an
opportunity to reexamine the NEO impact hazard in a wider social context.
Consideration of society's response to warnings (notwithstanding the
scientific community's attempts to influence that response) may well
determine the preferred scope of future NEO survey and/or mitigation
efforts. Consideration should also be given to the potential catalytic
(future-shaping) effect of what are, for almost any reasonable NEO program,
very small investments from the public purse.

-----------------------------------
CHAPMAN SUMMARY: PERSPECTIVES ON THE IMPACT HAZARD IN A DANGEROUS WORLD

The catastrophic impact of an asteroid or comet with our planet is a hazard
that has become an often humorous, if horrific, touchstone for widespread
public concerns about what feels like an increasingly dangerous world.  Such
an impact -- for example, of a body hundreds of meters or kilometers across
striking the Earth at a velocity 100 times that of a jet airliner -- has
never been witnessed during recorded human history.  Yet such an event could
happen during our lifetimes (although the chances are small) and would be
devastating beyond any natural or manmade catastrophe in recorded history.
Even greater cosmic impacts are known to have caused the mass extinction
that rendered dinosaurs extinct, enabling mammals to thrive, and may be
responsible for most of the upheavals in evolution of life on our planet.

The September 11th attacks have dramatically illustrated that public
reactions to disasters vary enormously compared with the "objective"
destruction, as measured by loss-of-life and property.  America and the
world are still reeling from attacks that killed only 3000 people, compared
with the estimated 20,000 victims earlier in 2001 from an earthquake in
India, which barely registered in western news media after the first day.
Media coverage of anthrax attacks, which killed half-a-dozen people later in
the autumn of 2001, overwhelmed efforts by the Centers for Disease Control
to prevent (by publicizing vaccination programs for the susceptible) many of
the over 30,000 deaths that would occur from the flu during the ensuing
winter.

According to research in risk perception, a similar exaggerated response may
be expected from the public if even a small asteroid were to strike in the
near future. To the degree that media interest in potential asteroid
catastrophes reflects public concern, headlines during 2002 suggest that
this cosmic hazard is alarming for many people far beyond the objective
unlikelihood that such a catastrophe will actually happen any time soon.
Unfortunately, communication between asteroid scientists and the public --
as mediated through science journalists -- has not been good.  Consider
three examples from the past year:

*  In mid-March, CNN headlined: "Whew! Stealth Asteroid nearly Blindsides
Earth."  Similar stories ran in news media throughout the world about a
newly discovered Near Earth Asteroid (NEA) numbered 2002 EM7.  The
strategies controlling the telescopic asteroid surveys necessarily find
asteroids retreating from the Earth about as often as coming toward the
Earth.  Moreover, the danger from NEAs (and what we could do about one)
almost never concerns a body bearing down onus "now"; rather it is much more
likely that a newly discovered NEA willstrike decades, or millennia, from
now, if indeed it will ever impact Earth.  The implied failure of the search
strategy to see 2002 EM7 as it came from the direction of the Sun is
poppycock.  Such reports serve to augment public anxiety about asteroids.

*  During the summer, news media worldwide (but especially in Britain)
worried about another newly found NEA, numbered 2002 NT7. The BBC reported,
falsely, that it "is on an impact course with Earth." Once again,
scientists' understanding of the impact probabilities simply doesn't get
through to the public. (Many newly discovered NEAs will be calculated to
have non-zero -- but extremely tiny -- chances of striking the Earth until
subsequent observations permit refined determination of their orbits; almost
always the Earth will be found to be safe from impact.)  Such failures are
presumably due to a combination of the inarticulateness of researchers, the
poor science and math education of the public, and inappropriate hyping and
sloppy journalism by news media.

*  In late November, the media coverage took an unusual turn when headlines
worldwide declared that new research showed that the danger from asteroids
was less than had been thought. Even this reassuring news was wrong, since
the research in question dealt with impacts by bodies only 1 to 10 meters in
size, which burn up harmlessly (although spectacularly) high in the Earth's
atmosphere. The bodies that statistically account for ~80% of the impact
hazard (asteroids 1 to several kilometers across) are actually somewhat more
numerous than had been estimated a couple of years ago, according to several
more recent estimates. (Long-period comets and sub-kilometer-sized NEAs each
count for about 10% of the hazard.)

Against such a cacophony of misinformation, how important *is* the impact
hazard?  Philosophically speaking, it is very important: not only would we
not be here if the dinosaurs hadn't been destroyed but impacts may be nearly
unique (perhaps along with all-out nuclear war) in threatening the future of
our civilization and even our species. But the chances are extremely tiny
(less than 1 in 100,000) that such a cosmic holocaust will happen this century.

At the other end of the scale, some people worry about the much more
frequent, smaller impacts, like the ~10 megaton-equivalent blast in 1908
over Tunguska, Siberia, that downed hundreds of square kilometers of forest.
And others worry about a several-hundred-meter asteroid crashing into the
ocean and producing a tsunami (and resulting flooding) exceeding all
historical examples. These are real threats, indeed, and the probabilities
are not so tiny as to be considered negligible. There is perhaps a 10%
chance that another Tunguska will happen this century, and
several-tenths-of-a-percent chance of a giant tsunami-making impact. But for
every such small-asteroid impact catastrophe, which might kill tens or
hundreds of thousands of people, there are hundreds of more mundane but
equally lethal natural disasters, like earthquakes, typhoons, and floods. So
impacts, like volcanoes, constitute a tiny fraction (less
than 1%) of the likely major natural disasters society will have to deal
with during the next few decades.

In our anxious times, we need to educate people to be more realistic in
assessing the threats in their lives. It could be reassuring for many to
learn that most of the seemingly frightening hazards are unlikely to kill
them (this list includes sharks, terrorists, airline crashes, and
asteroids). By turning more attention to lifestyle and political choices
concerning eating and health, war, automobile safety, and so on, people
could more effectively control their destiny.  I don't mean to say that we
shouldn't be prudent in dealing with the lesser hazards in our world: we
should give proportional attention to reducing small threats even further.
For instance, it is reasonable to think about how we might divert an
asteroid away from striking the Earth, if the Spaceguard Survey actually
finds one headed our way. And we should keep searching the skies.  But we
really can and should sleep easily at night.

-------------------------------------------------------
PRESS REPORT FROM AAAS:  ASTEROID IMPACT: WHEN, NOT IF
>From Rocky Mountain News, 14 February 2003

On your long list of Things To Fret About, bump "catastrophic impact from
asteroid" down a couple notches. Don't scratch if off, though. The threat
lives on. But in the past 10 years, the people scanning space for killer
rocks have hunted down more than half of the large objects hurtling through
Earth's neighborhood and haven't found any that threaten to finish us off.
-- Yet.

This was the uneasy message delivered by a panel of experts on the topic of
"Asteroids, Earth and Impact Hazards" at the American Association for the
Advancement of Science convention Thursday. "This is not a low-probability,
high-consequence event - it's a certain event," said Lee Clarke, a Rutgers
University sociologist and author of the paper Responding to Panic in a
Global Impact Catastrophe.

It's probably not an event we'll see tomorrow, however. And probably not in
the next few hundred years. After all, asteroids and comets have been
bombarding Earth since the planet's formation more than 4 billion years ago.
Many scientists believe an impact event wiped out the dinosaurs 65 million
years ago.

Astronomers started seriously raising the concern in the 1980s, and NASA has
since embarked on a project called the Spaceguard Survey to track 90 percent
of so called Near Earth Objects (NEOs) larger than 1 kilometer by 2008. NEOs
are defined as asteroids or comets capable of ending life as we know it.

Today scientists believe there are about 1,100 NEOs within 200 million
kilometers of our home planet. Of those, they've identified some 650 and
plotted their orbits. The verdict: They're not on track for a collision with
Earth. But what about those remaining 450? Scientists still are trying to
nail down the threat. Even then, the guarantee is only good for a few
hundred years. "None of these orbits is predictable for more than a few
centuries," said David Morrison, an asteroid hunter for NASA.

If an asteroid or comet is found to be bearing down on Earth, what would you
tell the populace to avoid widespread panic? Buy duct tape? One panelist,
Geoff Sommer, wonders if authorities should say anything at all. Some
elements of society would thrive off such knowledge, he said, including
British tabloids, cultists long announcing the end of the world, and
potential survivors who might want to buy up land for a future tourist
attraction.

But limiting panic and avoiding the premature financial collapse of the
stock markets would be additional benefits to secrecy. "If you're my
neighbor, I really don't want you driving your pickup over my lawn because
you're upset the world is going to end," Sommer said.

Humans, said Clark Chapman of the Southwest Research Institute in Boulder,
react to low-probability events in different ways. Some who laugh off the
chances of a deadly asteroid also might play the lottery. On the other hand,
humans have a tendency to obsess over rare events. The media, he pointed
out, screamed headlines in 2001 over anthrax attacks that killed two people.
Meanwhile, stories about flu vaccinations were buried, and the flu kills
thousands of people in the United States annually.

===================================

PART II: SECRECY ISSUE AND MEDIA REACTIONS

-----------------------------------------------
The following four press stories, all from the UK (and taken from Benny
Peiser's CCNet) express strong negative reactions and imply a major crisis
in the NEO community.

----------------------------------------------

ARMAGEDDON ASTEROIDS 'BEST KEPT SECRET'
>From The Independent, 15 February 2003

A scientific adviser to the United States government has suggested that
secrecy might be the best option if scientists were ever to discover that a
giant asteroid was on course to collide with Earth. In certain
circumstances, nothing could be done to avoid such a collision and ensuing
destruction, and it would be best not to tell the public anything, said
Geoffrey Sommer, of the Rand Corporation in Santa Monica, California.

"When a problem arises with high uncertainty, there is an opportunity to
spin the problem to avoid global panic. If you can't do anything about a
warning, then there is no point in issuing a warning at all," Dr Sommer told
the association yesterday. If an extinction-type impact is inevitable, then
ignorance for the populace is bliss. As a matter of common sense, if you
can't intercept it and you can't move people out of the way in time, there's
nothing you can do in terms of reducing the costs of the potential impact,"
he said. "Overreaction not just by the public but by policy-makers scurrying
around before the thing actually hits because we can't do anything about it
anyway ... to a large extent you are better off not adding to your social
costs," said Dr Sommer, who is also an adviser on terrorism.


"DON'T TELL PUBLIC OF DOOMSDAY ASTEROID"
>From The Times, 15 February 2003

The public should not be told if scientists detect a huge asteroid on a
collision course with Earth that cannot be deflected, a disaster expert
said. Geoff Sommer, of the Rand Corporation in Santa Monica, California,
said that governments would be wrong to warn of an impending impact that
could destroy all life if there was no realistic prospect of stopping it.
The panic, misery and disruption that such a warning would cause would not
be worthwhile, he told the association.

His view was strongly disputed by Lee Clarke, Professor of Sociology at
Rutgers University, who said people had a right to be told about the
impending end of the world. "If we see a monster event coming, an extinction
event, common sense would tell me I want to know and that it's not up to
him, or up to some high-level bureaucracy, to decide whether I know or not,"
he said. "The reaction might not be what most people expect. Look at people
on death row, people in prison camps during the Holocaust, people with
terminal cancer," he said. "You might want to make peace with your God, for
example."


ASTEROID COVER-UP PROPOSAL CAUSES NEO COMMUNITY A CREDIBILITY CRISIS
>From Space Daily, 17 February 2003 by Benny Peiser

Just when you thought we had learned our lessons from past communication
debacles and PR fiascoes, bizarre statements at the Denver AAAS meeting have
plunged the NEO community into another crisis of credibility. "Don't tell
Public of Doomsday Asteroid", reads the headline in today's The Times, while
The Independent warns: "Armageddon Asteroids best kept secret." The Internet
(Drudge Report, etc.) and fringe websites are already brimming with gloating
links to this asteroid-cover-up story while doomsday prophets and
conspiracy-theorists can't believe their good fortune: "We've told you so!"

What happened? How could a harmless NEO panel generate conspiracy-advocating
headlines around the world that will seriously damage the integrity of the
NEO community?

The international media coverage is dominated by statements by Geoffrey
Sommer, a RAND researcher who has been studying the social and economic
implications of the impact hazard. S. Evidently, the 'extinction-type
impact' scenario is a red herring. So what really lies behind this thinking?
It would appear that Geoff Sommer is not so much concerned about the
cost-effective handling of the apocalypse but about the future management of
notoriously tricky impact risk uncertaintiesS.

While this whole argumentation looks utterly ridiculous to me, it does -
unintentionally - raise one fundamental (while highly unlikely) question:
Since there may be impact survivors, isn't it is our ethical obligation to
do everything in our power to inform the public as soon as necessary so to
increase the chances of human survival? I, for one, firmly believe it is!

Which brings me to my final point: Why bring up this conspiracy proposal
given that any attempted secrecy is totally futile in the first place?
Astronomers from around the world can easily access and confirm
observational data and calculations of any discovered NEO in any case.

The damage, however, of contemplating a cover-up stratagem will be immense:
it will strengthen the erroneous but widespread suspicion that some members
of the NEO community are more concerned about covering-up or "spinning" than
explaining the facts truthfully.

The price we will pay for the increased mistrust this episode is causing is
very high. In fact, it is much higher than any of the inadvertent asteroid
scares of the last 4 years. I fear it will also be more difficult to repair
the damage it has done to our integrity.

--------------------------------

The angriest reaction was expressed by David Whitehouse, the BBC reporter
who started the media hyperbole over asteroid 2002 NT7 last summer when he
reported that it was on a collision course with the Earth. Peiser's CCNet
published the following note from Whitehouse on February 17:

I am quite amazed that there are some in the NEO community who have the
audacity to think that if an NEO is found that is on, or suspected to be on,
a collision course with the Earth then the public should not be told at any
stage because if nothing can be done then why alarm people about something
they cannot do anything about. Let them be ignorant until the end, unless
perhaps they happen to live next door to a knowing NEO researcher!

I will leave to one side the debate about what could be done to deflect an
incoming NEO or the steps that could be taken to archive human achievements
or indeed the denial of the right of some people on the verge of death to
make their peace with their fellow humans and/or their God.

Who gives them the right to make such a decision? Who actually would make
such the decision? What would be their qualifications, their accountability?
Is this really regarded as being a responsible and accountable stance by
those whose salaries are paid out of the public purse? Indeed, I wonder if
this notion really has much support in the NEO community?

The ethics of such a stance are unsupportable. There are other areas of
science where the 'they don't need to know' argument has been debated and
discounted as unethical.

============================

POST-SYMPOSIUM COMMENTS FROM THE AAAS SPEAKERS

MORRISON: NEO searches and orbital predictions have always been carried out
openly. A few years ago there were delays of several days while scientists
compared their orbital predictions; today these predictions are done much
more quickly and posted on the web by the JPL and Pisa teams. It is
inconceivable to me that anyone involved in NEO surveys and orbital
predictions would want to keep the results a secret. It is also
inconceivable that astronomers could keep such a secret even if they wanted
to. A real impact prediction, even at low probability, would be known all
over the world in a matter of hours.

At the AAAS, Geoff Sommer mentioned the option of keeping a prediction
secret only in an extreme hypothetical case -- a very short warning of an
extinction-level impact. Such a case cannot arise today. We already know
there are no extinction-level asteroids in Earth-crossing orbits. Any comet
in this class would be visible in amateur astronomy telescopes all over the
world for months before it hit. This is a tempest in a teapot -- a comment
by one individual about a hypothetical situation that cannot today arise.
None of the other AAAS panelists supported the idea of secrecy even in this
extreme example. We are all committed to open sharing of our results with
the world, and we said so at the AAAS. Such openness is sometimes
temporarily embarrassing when the press play up a low probability
prediction, but that is far better than trying to impose secrecy.

SOMMER: I'm afraid that the AAAS press office quoted me rather severely out
of context.  Their press release (which I didn't get to see until two
minutes before the press conference) has me saying "if you can't do anything
about a warning, there is no point in issuing a warning at all.  If an
extinction-type impact is inevitable, then ignorance for the populace is
bliss".  It prefaces that by saying that I "take the controversial stance of
advocating silence and secrecy".  I most certainly would not take such an
absolute stand.

The primary purpose of a NEO survey is to enable a response, and absent a
mitigation capability that purpose is vitiated.  The context of all this is
an argument for mitigation. The "ignorance may be bliss" argument is not
trivial, however. Analytically, the question is whether the doom-warned
population has a negative discount rate - a "dread" factor. Does the
population as a whole have a "willingness to pay" to avoid bad news? It's
hard to say. Certainly, in the micro sense, the effect is real. Do we prefer
a quick (but ignorant) death for Columbia's crew, or do we wish for them
more time to "make peace with their God" before their inevitable end?  I
would guess the former.

In the context of astro-doomsaying, is there an absolute right to
information?  Many passionately believe so.  Yet, how many high-dread people
are outvoted by one "tell me the worst" person?  I don't know - hence, I
don't advocate "silence and secrecy" as absolutely as the AAAS press release
indicates.  It all depends, as I have said many times, on valuations.  What
gives the government the right to decide?  What gives the government the
right to decide on any issue of social welfare?


CLARKE:  My view is that for both moral and practical reasons, the benefits
of secrecy should be sacrificed for the benefits of democracy and informed
consent. It is true that Sommer and I disagreed about some things at the
AAAS meetings. We're intellectuals; that's what intellectuals do. It is
true, I think, that Sommer believes full secrecy is a possibility that
decision makers might have at their disposal. I think, as a practical
matter, that as soon as 3 people knew of a potentially dangerous situation
secrecy would no longer be possible because the information would spread as
quickly as a computer virus.

The AAAS session in which I participated was an intellectually engaging one,
in which many interesting and challenging things were said. It was, after
all, a session devoted to the idea that we should be talking about these
issues. One, but only one, of those issues is whether we should keep
information from the public. We should not keep secret information about any
impact, should astronomers discover one is imminent. But we, as a public,
should definitely be talking about the issues.

Geoffrey Sommer did the debate a great service by proposing a scenario that
needs to be talked about. Set aside what Sommer, as an individual, believes.
The issue itself is exceedingly important. Keeping secret something
potentially very dangerous is an idea that would resonate very well with the
current administration in Washington. It would probably resonate with most
high-level decision makers.

I denounce extreme secrecy about events and policies that redound negatively
to the populace. Geoffrey Sommer has said he holds similar sentiments. The
issue is big, but the individuals are not.


ROPEIK: Risk communication literature suggests that secrecy would be a
serious mistake. In the face of such an unlikely event as an impending
global extinction catastrophe we couldn't do anything about, it would still
be important for governments to maintain some order and avoid absolute
chaos. Secrecy, not telling people that they were about to die, would
destroy trust in government, presuming that such a huge secret would get
out, a pretty safe assumption. That would make the final days, weeks, or
months much worse. It's a bad idea.


CHAPMAN: I fear that when the small flames of these controversies get fanned
by those who prefer to see conflict than convergence and consensus, the real
messages that we have to deliver (such as at the AAAS Symposium) tend to get
lost in the noise.  I think that is unfortunate.  For sure, the individual
events (bad headlines about potential impacts of objects like NT7 last
summer) aren't explicitly remembered, even by the most attentive readers.
But repetition of such misunderstandings (and very low probability, high
consequence events are inherently difficult to intuit) has a toll.  Serious
consideration of the NEO hazard could even help us put things of urgent
concern to the nation (like the terrorism scale) in context, but that small
opportunity is diminished when much of the press coverage focuses on what is
really a non issue.

==============================

SUMMARY REPORT ON THE SECRECY ISSUE

ASTEROIDS AND SECRECY: IF END IS NIGH, DO YOU WANT TO KNOW?
By Robert Roy Britt, Space.com
24 February 2003

....

+++++++++++++++++++++++++++++++++++++++++++
NEO News is an informal compilation of news and opinion dealing with Near
Earth Objects (NEOs) and their impacts.  These opinions are the
responsibility of the individual authors and do not represent the positions
of NASA, the International Astronomical Union, or any other organization.
To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov.  For
additional information, please see the website: http://impact.arc.nasa.gov.
If anyone wishes to copy or redistribute original material from these notes,
fully or in part, please include this disclaimer.

===========
(3) IMPACT-GENERATED TSUNAMIS: AN OVER-RATED HAZARD

>From Michael Paine <mpaine@tpg.com.au>

Dear Benny

The abstracts for the 34th LPSC are available online at
http://www.lpi.usra.edu/meetings/lpsc2003/a-f.html

I see quite a few CCNet names in there. Jay Melosh has a paper about impact
tsunami. A copy is included below.

regards
Michael Paine

IMPACT-GENERATED TSUNAMIS: AN OVER-RATED HAZARD.

H. J. Melosh, Lunar and Planetary Lab, University of Arizona, Tucson AZ
85721 (jmelosh@lpl.arizona.edu).
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/2013.pdf

Introduction: A number of authors [1, 2] have suggested that oceanic waves
(tsunami) created by the impact of relatively small asteroids into the
Earth's oceans might cause widespread devastation to coastal cities. If
correct, this suggests that asteroids > 100 m in diameter may pose a serious
hazard to humanity and could require a substantial expansion of the current
efforts to identify earth-crossing asteroids > 1 km in diameter.

The debate on this hazard was recently altered by the release of a document
previously inaccessible to the scientific community. In 1968 the US Office
of Naval Research commissioned a summary of several decades of research into
the hazard proposed by waves generated by nuclear explosions in the ocean.
Authored by tsunami expert William Van Dorn, this 173-page report entitled
Handbook of Explosion-Generated Water Waves [3] affords new insight into the
process of impact wave formation, propagation, and run up onto the
shoreline.

Careful reading of the report suggests that previous work on
impact-generated tsunami has exaggerated the hazard posed by such waves. One
of Van Dorn's crucial points it that large explosions (and impacts) pro-duce
waves with periods in the range of 20 to 100 sec.
This is between the ranges of 5 to 20 sec for storm-generated ocean swell
and 100 sec to 1 hour for more common earthquake-produced tsunami. Thus,
impact-generated waves lie outside the frequency range of familiar
phenomena; our intuition from ordinary surf or earthquake tsunami is not a
good guide to the be-havior of these waves. In particular, large impact-generated
waves can be expected to break on the outer continental shelf and produce
little onshore damage. This phenomenon is known in the defense community as
the Van Dorn effect.

In the remainder of this abstract I summarize the basic points made by Van
Dorn and discuss why some previous work on impact tsunamis has greatly
overes-timated the hazard in each of three basic categories. Impact tsunami
formation and propagation in the deep ocean: An impact or explosion in the
ocean displaces a quantity of water. The displaced water piles up near the
rim of the crater. After the cratering flow has ceased, the rim collapses
and the crater is filled by the centripetal inflow of water from the rim and
adjacent ocean. A wave then propagates away from the site of the
disturbance.

There are two basic cases for impact wave generation. In the first, the
ocean is much deeper than the cavity opened by the impact. In this case
linear wave propagation theory is applicable and the evolution of the impact
tsunami can be analyzed by well-established methods [4]. On the other hand,
if the impact is so large that the excavated cavity exceeds the depth of the
ocean, the ocean is temporarily cleared away from the site of the impact, the seafloor itself is
cratered, and the ejected water falls onto the ocean surface. This case is
much more difficult to analyze analytically and can probably only be
addressed by hydrocode computations. At the moment, two recent hydrocode
computations have given widely divergent results [5, 6]. However, because
this limit is ap-proached only by asteroids more than about 1 km in diameter, it is not relevant
to the present hazard issue, which focuses on asteroids in the 100 to 1000 m
size range (it is already agreed that asteroids greater than about 1 km
diameter are a global threat [7]).

Because the volume of the rim and of the crater are approximately equal in
the case when the initial crater is less deep than the ocean itself, their
two effects tend to cancel one another, already limiting the size of the
disturbance propagated from the impact site. This differs from an
earthquake-generated tsunami in which the seabed either rises or sinks and a
net volume of water is transported across a large area of the ocean [8].

An important point emphasized by Van Dorn, but evidently neglected in
several publications [1, 2] is that, as the impact-generated waves
propagates away from the impact site, the wave amplitude can never exceed
the depth of the ocean. This elementary principle (actually, Van Dorn limits
the wave height to 0.39 times the ocean depth) is enforced by the breaking
and consequent energy dissipation of higher amplitude waves.

The group and phase velocities of waves propagating in water comparable in
depth to their own wavelength are strongly dependent on the wavelength (See
Fig. 1). The loner the wavelength, the faster the wave travels, up to the
limit of very long waves whose speed is [formula] , where g is the
acceleration of gravity and h0 is the ocean depth. Such waves are dispersed
as they travel. Although the period of the dominant wave group is constant, the
wavelength varies with water depth, as given by the dispersion relation
between wavelength and period. The amplitude of the maximum height wave in
the leading wave group declines as 1/(distance from the impact site). This
decline is due equally to the effect of dispersion and of spreading of the
energy over a larger area.

[Figure 1. Group and phase velocities of ocean waves as a function of
wavelength. Plot is constructed as-suming an ocean 4 km deep, the average
depth of Earth's oceans.]

Shoaling of impact tsunami: As an impact-generated wave approaches shore,
the decreasing water depth causes the wave amplitude to increase. The amplitude increase is
commonly given by the shoaling factor, S, which depends on the wave period w
and water depth h. Since wave energy is proportional to wave amplitude
squared, energy conservation requires that the shoaling factor equals the
square root of the ratio of group velocity vg(w, h0) in water of initial
depth h0 to the group velocity in shallow water of depth [formula] This
shoaling factor is substantially smaller for impact-generated waves than for
the very long-wavelength earthquake tsunami. Thus, whereas [1] cited shoaling factors of
10 to 20, based on experience with historical earthquake tsunami, [2, 9],
using the full equation above, find much more moderate shoaling factors of
less than 2, in agreement with the prescription of [3].

Breaking and run-in of impact tsunami: As waves approach shore, the water
depth approaches zero and the shoaling factor above mathematically approaches infinity. In
reality, the wave height increases until the wave becomes unstable and
breaks, dissipating its energy in turbulent eddies. Previous work on impact
tsunami has generally ignored wave breaking, but Van Dorn argues that it is
of overriding importance in limiting the damage that explosion-generated
waves can inflict on the coast. The very long-wavelength earthquake tsunamis
almost never break: the water depth simply increases by the offshore
shoaling factor and the run-in (the distance the water surges inland from
the initial shoreline) is simply given by S cot a, where a is the slope of
the shore (assumed to be the same above and below mean sea level, for
simplicity).

Normal ocean swell breaks within a few tens of meters of the shore,
depending upon the slope of the bottom in the near-shore zone and the period
of the breakers: As every surfer knows, long-period swells break farther
from the shore than short-period chop. Impact and explosion generated waves
are of much longer period than ocean swell (but not as long as earthquake
tsunami) and break still farther from the shore: at the edge of the
continental shelf, according to Van Dorn. In this case the run-in can be
drastically smaller than S cot a. The resulting turbulent zone between the
edge of the continental shelf and shore may be hazardous for coastal
shipping, but little damage is expected for most onshore structures (local
bottom topography may focus wave damage in harbors or along special
stretches of the coast, but this damage is not general).

Conclusion: The release of the Van Dorn report has saved the impact
community a great deal of effort in categorizing the impact tsunami hazard.
It appears that the defense community has already determined that
explosion-generated waves are neither a serious threat nor a promising
weapon. Although more work is needed on impact-generated tsunami, it appears
that such waves generated by asteroids in the 100 to 1000 m diameter range
may not pose as great a threat as previously believed.

References: [1] Hills, J.G., Nemchinov, I.V., Popov, S.P. & Teterev, A.V. in
Hazards from Comets and Asteroids (eds. Geherls, T.) 779 (Univ. of Arizona
Press, Tucson, AZ, 1994). [2] Ward, S.N. & Asphaug, E. (2000) Icarus 145,
64. [3] Van Dorn, W.G., LeMéhauté, B. & Hwang, L.-S. Handbook of
Explo-sion-Generated Water Waves, Volume I--State of the Art (Tetra Tech,
Pasadena, CA, 1968). [4] Kajiura, K. (1963) Bull. of the Earthquake Research
Inst. 41, 535. [5] Crawford, D.A. & Mader, C.L. (2003) submitted [6]
Shuvalov, V.V., Dypvik, H. & Tsikalas, F. (2002) J. Geophys. Res. 107,
10.1029/ 2001JE001698. [7] Morrison, D., Chapman, C.R. & Slovic, P. in
Hazards due to comets and asteroids (eds. Gehrels, T.) 59 (U. of Arizona
Press, Tucson, 1994). [8] Van Dorn, W.G. (1965) Advances in Hydroscience 2,
1. [9] Ward, S.N. & Asphaug, E. (2003) Geophys. Res. Lett. in press.

Acknowledgements: This work was supported by NASA grant NAG5-11493. Bill
Bottke and UA librarian Lori Critz played crucial roles in unearthing Van
Dorn's report.

============================
* LETTERS TO THE MODERATOR *
============================

(4) SUPPORT

>From Alain Maury <amaury@obs-azur.fr>

Dear all,

I am writing to ask you to support via a short email my request to borrow a
one meter telescope from the Observatoires de Marseilles in order to use it
to conduct an asteroid survey from northern Chile. Here are some details :

I have finished observing in La Silla, and am in vacations. The EROS2
program for which I have been working in the last 2 years will end at the
end of this month. We will dismount the experiment and ship the experiment
back to France in June.

I have purchased a 1ha land in San Pedro d'Atacama (latitude -23°) near the
triple border between Bolivia, Argentina and Chile, near the site of the
future ALMA telescope. It is a 300 nights/year site at 2400 meters of
altitude. I am going to leave at least temporarily my position at
CNRS and open a public observatory there (50000 tourists per year) in order
to survive and open a private observatory too. Since it is not realistic to
conduct an observatory survey in the french/european context, let's do it in
the private domain. Carolyn gave me the authorisation to name it the Gene
Shoemaker Observatory. We are a little group of 5 engineers working on an
asteroid survey project from there. I asked the Observatoire de Marseille to
loan me the 1m Ritchey Chretien telescope which is used in La Silla for the
EROS2 project where I work now. The scientific council accepted my request,
but then, other requests to use the telescope arrived, they are mainly for
amateur observatories/public observations, and the council feels it is fair
that these requests are examined too. There is another council on February
27th where the 3 projects are going to be examined. I have writen a complete
file concerning the scientific interest, the technical human and financial
means behind it. It is unfortunately in french. I have put it on the web
(http://www.astrosurf.com/maury/asteroides/spaceguard/BAT.html ). I think
it would not hurt to have some letters of support for this program. I know
you are very busy, but could you send an email of support to the scientific
council of the Marseille observatory to tell them it is important to have a
1 meter telescope searching for asteroids in the southern hemisphere. The
person who is going to centralize these emails is eric.maurice@oamp.fr. The
message does not need to be too long. Something in the lines of "I think it
is important to start a southern hemisphere search program as soon as
possible. In this context, I support the initiative of Alain Maury to obtain
a loan of the Marly telescope from your observatory,... ".

Thanks in advance,
Alain

PS1 : For now I have a 1K thinned camera, with which we will do follow up
for now at the F/8 focus, but we got hold of 2 2X4K thinned chips which we
will install behind a prime focus corrector (4 lenses) which has been
calculated, which we are going to build as soon as, and if, we have the loan
agreement. We already have all the required software for telescope
automation and asteroid detection.
PS2 : Please feel free to pass on this message to anybody you think would be
willing to sign it. Before February 26th.

============
(5) ARE WE BARKING UP THE WRONG TREE?

>From Michael Paine <mpaine@tpg.com.au>

Dear Benny

In seeking Australian government funds for Spaceguard I have tried the
portfolios of Defence (now much too busy spending money on Iraq
preparations), Science and Health. I never thought of higher education and
yet the Government has somehow found $20 million from our starved education
budget to rebuild Mt Stromlo Observatory. Now I fully support the use of
government money to rebuild Mt Stromlo - they deserve more than $20m for the
pioneering work they have been doing - but I am
concerned that higher education should bear the brunt. I will resist the
temptation to turn Spaceguard into an "education" issue.

regards
Michael Paine

Stellar grant for burnt observatory
By Aban Contractor (seriously?)
February 25 2003

The bushfire-ravaged Mount Stromlo Observatory will receive almost $20
million as part of the Government's package for higher education.

The cost of repairs to Australia's oldest active observatory has been
conservatively estimated at between $20 million and $40 million, about half
of which will be covered by insurance.

The observatory's main dome, workshops, eight staff houses and four
telescopes were destroyed by fires that swept through the ACT in January.
One of the telescopes lost was the 135-year-old Great Melbourne Telescope,
which, after an upgrade a decade ago, is one of the most
sophisticated in Australia.

It is still to be decided whether all of the observatory's facilities will
be rebuilt on the mountain.

After the fire, the Prime Minister, John Howard, assured observatory staff
that everything possible would be done to return it to its former glory.

This story was found at:
http://www.smh.com.au/articles/2003/02/24/1046063962499.html
c2003 Sydney Morning Herald

==========
(6) RE: THE GREAT IMPACT DEBATE

>From James Marusek <tunga@custom.net>

Dear Benny Peiser

I have read the latest in the series of the Great Impact Debate (Part III).
I would like to expand on Joe Veverka's discussion.

Expanding the NEO search efforts toward smaller NEOs, provides a good
roadmap for successfully mitigating large impactors. If we discovered a
large NEO that is on a collision coarse with Earth in say 800 years, what is
the probable engagement scenario? Governmental bodies will delay efforts to
divert or destroy the object immediately, because of questions concerning
the validity of the impact projections. Might additional observations alter
the probability equation? Might uncertainty factors such as solar radiation
effects alter the equation of motion? More likely the underlying issue would
be money. Why implement an expensive program to solve a problem that will
not affect our lives or the lives of our children, grandchildren or even
great-grandchildren. Let those that come after us resolve this issue. Will
not technology greatly evolve in the next 800 years; which will simplify the
mitigation approach? These factors will drive a wait-and-see attitude. At
what point in time will the world take the baton and run the race?

Small asteroids/comets fragments will likely strike Earth several times
prior to the impact from a large asteroid or comet. This observation
provides an opportunity: the opportunity to gain real world experience in
NEO deflection/destruction. A variety of mitigation approaches have been
introduced. Some of these approaches border on pure fantasy. But in the
brainstorming mode, all ideas are good. Reality will flesh out the best
approaches. Smaller impactors provide a proving ground to move from the
theoretical to the practical.

         James A. Marusek

===========
(7) SURVIVAL INSTINCTS

>From Linda Sloan <lksloan@informationuniverse.com>

Dear Benny Peiser

I would like to respond to the proposal of not informing the world's
population regarding an imminent extinction event. Survival instincts can be
one of our strongest assets of our species. I would tell the world of the
impending event with one caveat, you tell and do everything and anything
possible, or even impossible, to try to mitigate the event. Give people a
taste of hope and they will not go into panic mode, even if it looks
hopeless. I have  heard of people who would keep on trying until the very
end to try and avoid their inevetible fate. For some will be survivors and
they will try to keep the human species alive. Let's give them that chance
and let the world know when such an event occurs. Forgive me for my being so
much of an optimist but we might save our species by giving people a chance
to survive.

Sincerely,
--
Linda Kenny Sloan
Information Universe
http://informationuniverse.com


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*

CCNet EXTRA, 25 February 2003
-----------------------------


"We are now told that highly experienced science journalists from
the British media (who were in the room making notes and recordings and
asking questions) took Mr Sommer's remarks (concerning secrecy and NEO
impacts) made at the AAAS press conference, "severely out of context" and
that they "inaccurately described my position." I hope that those who feel
aggrieved will complain to the journalists concerned. I can imagine their
response. Some of my colleagues can be somewhat more forthright in
their defence than I!"
--David Whitehouse


(1) DON'T BLAME THE MEDIA FOR SELF-INFLICTED AAAS FIASCO
    David Whitehouse <davidwhitehouse@ntlworld.com>

(2) LESS CHATTER, PLEASE
    Oliver K. Manuel <oess@umr.edu>

(3) COMETS, METEORS AND METEORITES
    Margaret Penston <mjp@ast.cam.ac.uk>

============
(1) DON'T BLAME THE MEDIA FOR SELF-INFLICTED AAAS FIASCO

>From David Whitehouse <davidwhitehouse@ntlworld.com>

Dear Benny,

Politicians, who professionally live and die by the media, know how
important it is for anyone who wants to get a message across to the public
(and through them to the politicians) to have an understanding of how the
media works, as well as a realistic assessment of when things are not going
right and why. Many times we have all witnessed a politician leave the
public arena not because we, or almost anyone else, thinks they have done
something inherently wrong, but because they cannot attract anything other
than bad press that is always said to be distracting the government from the
important issues.

Is such a thing happening with the NEO issue I wonder?

There really ought to be a more constructive debate about how to learn to
communicate NEO issues better than blaming the media in a way which is often
selective, inaccurate and self-serving. It is also counterproductive as it
also fails to win friends and influence people in the media, something a
politician would never do.

Clearly, from one point of view, in terms of getting the message that many
wanted to get across to the public, the recent AAAS meeting and its coverage
was a disaster indicating a real communication problem. But who, if anyone,
was to blame?

We are now told that highly experienced science journalists from the British
media (who were in the room making notes and recordings and asking
questions) took Mr Sommer's remarks (concerning secrecy and NEO impacts)
made at the AAAS press conference, "severely out of context" and that they
"inaccurately described my position."

I hope that those who feel aggrieved will complain to the journalists
concerned. I can imagine their response. Some of my colleagues can be
somewhat more forthright in their defence than I!

While this may be a case of rewriting history after the event, I wonder why
others at the press conference failed to get their point across effectively,
and why Mr Sommer got only 2 minutes to review a press release about NEO's
which had already been distributed to reporters! I'm sorry to say that it
doesn't sound like a well prepared or run press conference to me and all in
the media know the risks when that happens. Consider what would happen if a
politician on a campaign employed someone to run a press conference where
the "message got lost in the noise" as has been said about the recent AAAS
meeting.

But if the AAAS fiasco was a self-inflicted wound does it do any real damage
to the NEO debate? Some scientists have said that individual headlines, good
or bad, are forgotten by the public but the accumulated drip-drip-drip of a
message or an impression does matter. Will, as it
has been suggested, the public come to distrust serious asteroid science and
turn away from supporting and funding it?

No, quite the contrary, as any media professional/lobbyist would tell you.

1997 XF11, 2000 SG344, 2002 EM7, 2002 NT7 and others are valuable events
that can teach a discipline how to interface with the public and benefit
from whatever coverage it receives in a positive way. Instead the debate,
for some, consists of moaning about the mote in the media's eye.

The examples of selective, inaccurate and deliberately misleading quoting
that is going on about 2002 NT7 by some dismays me. Only in the past day or
so the BBC article about 2002 NT7 was said to contain the direct quote "is
on an impact course with Earth." Actually, it does not, and the fact that
the headline is in qualified quotes that turns the headline into a question
is conveniently ignored.

Consider this, I have no records of any journalist during the 2000 SG344
'scare' (again self-inflicted when odds of 1 in 500 were described to the
media as 'very unlikely' - I wouldn't take a form of transport with those
odds) saying that further observations will almost certainly rule
out an impact with that object. Yet in the BBC's coverage of 2002 NT7 that's
exactly what paragraph 5, 12, 13 and 19 did.

The subject of NEO's and their issues are fascinating and full of unexplored
fertile land for researchers and the media. But it could end up sounding
like the media carping one sometimes reads in some former-politicians
biography. It could easily become a bad joke.

Regards,

David

==========
(2) LESS CHATTER, PLEASE

>From Oliver K. Manuel <oess@umr.edu>

Dear Benny,

Perhaps the scientific community should spend less time and energy on "what
if" scenarios and more time on "what is". What is accomplished by chatter
about "what if ....."?

With kind regards,

Oliver K. Manuel

============
(3) COMETS, METEORS AND METEORITES

>From Margaret Penston <mjp@ast.cam.ac.uk>

RAS-BAA ProAm Meeting
Comets, Meteors and Meteorites

Saturday 10 May 2003, 10.30-17.30
Berrill Lecture Theatre, Open University, Milton Keynes

The meeting gives professional and amateur astronomers who share a common
interest in comets, meteors and meteorites an opportunity to discuss recent
observations and developments in the field. The programme which includes the
BAA 'George Alcock Memorial Lecture' to be given by Dr Brian Marsden (SAO)
is on the website at http://www.ast.cam.ac.uk/~jds/proam.htm.  There is no
registration charge. Refreshments will be available for purchase. Please
notify Margaret Penston (mjp@ast.cam.ac.uk) if you wish to attend. For maps and information
on travel to the OU see http://www.open.ac.uk/maps/.

----------------------------------------------------------------------------
Dr Margaret Penston      Tel: 01223-766655 (with voice-mail)
Institute of Astronomy               Fax: 01223-337501
Madingley Road
Cambridge CB3 0HA
----------------------------------------------------------------------------



CCCMENU CCC for 2002

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