Date sent: Mon, 16 Mar 1998 12:02:32 -0500 (EST)
From: Benny J Peiser
Subject: CC DIGEST, 16/03/98
Priority: NORMAL


March the 12th 1998 will go down in history as the day the entire
human race became aware of our precarious place in space. While many
scientists and lay people interested in natural and biological
sciences have known about past impact catastrophes and the threat
due to comets and asteroids at least since the late 70s or early 80s,
last week's events have catapulted this vital information into the
living rooms of billions of city slickers and villagers from around
the globe. Suddenly, we have become a global village of NEO experts
and NEO catastrophists.

From a historical perspective, the events of last week will be viewed
as a major turning point in human and societal evolution. The real
issue at stake was never whether the 'newly' detected asteroid 1997
XF11 will miss us by 30.000 or 600.000 miles - but rather becoming
aware of the uncomfortable fact that a similarly large object can -
and at some unknown point in the future will - impact the earth,
thereby causing widespread devastation.

Compared to the long and bumpy evolution of Homo sapiens, it took
just over two hundred years for this knowledge to slowly emerge
and to sink in. It was in 1794 that Cladni found out that meteorites
do fall from the sky, a highly controversial theory which was
confirmed by Biot in 1803.

Knowledge of the first Earth-approaching asteroid only became
available in 1898 whereas the first Apollo asteroid on a Earth
crossing orbit was discovered only some 60 years ago (in 1932). It's
only 18 years ago that Luis Alvarez and his team published their
findings which confirmed that a cosmic impact occurred some 65
million years ago, leading to the extinction of the dinosaurs.

And it's not even three years ago that the collision of comet
Shoemaker-Levy 9 with Jupiter in 1994 occurred in front of our
noses. This event made us fianlly realise just how hazardous giant
impacts can be for planets in our solar system.

Now, our attention has become focused on the asteroids and comets
which might be on collision course with our own world. The so-called
giggle factor displayed by 'enlightened' scientists for more than 150
years and which has stood in the way of any serious debate and
research on cosmic catastrophes has gone for good. Instead, it's time
to start laughing about all our pompous attempts to escape from or
deny the reality of our vulnerable existence. The challenge ahead, as
far as I am concerned, is: what are we going to do with our newfound
awareness? Is there intelligent life on Earth fit enough to start an
effective fight for survival?

In his recent book VISIONS (see further below), Michio Kaku
speculates about the reasons why astrophysicists have been unable to
detect any signs of intelligent life in nearby star systems, 'even
though Drake's equations predict the existence of thousands of
intelligent civilizations in our galaxy.' One possibility which Kaku
fails to mention in this context is that our galaxy might be filled
with the ruins of civilisations which were either unable or unwilling
to develop a system of planetary defense and which might have helped
prevent their demise.

Below, I have attached a number of responses to last week's events
as food for thought. Please feel free to contribute to this debate
should you wish to add any relevant insights,comments and thoughts on
related issues or simply if you want to report about the discussions
taking place in your part of the world.

Benny J Peiser



It is an impending catastrophe that lurks in outer space. It probably
killed millions and wiped out civilisations, and the chance that it
will do the same to us is ridiculously high. Yet when astronomers
warn of cataclysmic asteroids heading this way, most people simply

The chance of being killed, directly or indirectly, by a meteorite is
greater than that of wild animals, fireworks, terrorist bombs and
airline hijackings, according the Nasa's Ames Research Centre in

The chance of being "seriously effected" by such an impact is one in
280 each year, according to some astronomers. That translates to a
one-in-four lifetime risk. Compared with the one-in-200 risk of dying
from smoking 10 cigarettes a day, the threat from the skies seems
almost certain.

There are several reasons for the disparity. Comet and asteroid
statistics are largely the result of hughely-destructive events that
happen extremely rarely. One that kills perhaps a quarter of the
world's population happens only once every half a million years.

But there is no reason for complacency, according to Dr Victor Clube
of Oxford University and the Armagh Observatory, a prominent
campaigner on the threat from outer space. Civilisations have a good
chance of being devastated by a celestial catastrophe every three our
four thousand years, he says, highlighting the 1908 cometary
explosion above Lake [sic] Tunguska in Siberia. It killed no one but,
had it arrived half an hour earlier, it would have eliminated st

One difficulty in assessing the risk from the skies is deciding what
to put into the equation. The chance of being struck on the head by a
fist-sized meteorite is small. They land in their hundreds every day
but the only known casualty has been a small dog.

An important element is not the effect of the initial impact but the
massive dust plumes that could blanket Earth as a result of
explosions in the upper atmosphere. These could block out sunlight
for decades so that crops would not grow.

The greatest problem in predicting the risk stems from disagreements
over the regularity of asteroid and comet showers. Experts are
divided. Those from the mainly British "Catastrophist School" believe
that they come in clusters. Some [4300] years ago, urban societies
collapsed around the world simultaneously. Scientists have recently
found a series of impact craters that date from that period.

The "Uniformitarian School" - mainly Americans - gaze skywards rather
than studying Earth'e geology. They believe asteroids appear
regularly, not cyclically. If their predictions are correct, the
frequency with which an asteroid the size of 1997 XF11 will hit us is
once every million years. (C) The Daily Telegraph

From: David Morrison

NEO News (3/14/98)


Near-Earth asteroid 1997XF11, discovered on December 6 1997 by James
Scotti of the Arizona Spacewatch Program, will come very close to the
Earth in 2028. However, contrary to preliminary reports, there is no
danger of its colliding with the Earth in 2028. Like all Earth-crossing
asteroids, XF11 may someday hit our planet, but this seems to be an
event for the distant future, and at present we are more at risk from
some unknown asteroid colliding with the Earth than from XF11 or any
other object already discovered.

The orbit of XF11 will bring it close to the Earth many times. In
October 2002 it will be an excellent target for detailed radar
observations, and in 2028 it may even be bright enough to be seen
without telescopic aid.

The special interest in this object began when International
Astronomical Union minor planet notice #6837 released by Brian Marsden
on March 11 estimated a miss distance of only 50,000 km in its passage
near Earth on October 26 2028. Marsden wrote in a press release
reproduced below:

"Recent orbit computations indicate it is virtually certain that it
will pass within the Moon's distance of the Earth a little more than 30
years from now. The chance of an actual collision is small, but one is
not entirely out of the question."

The story was widely reported, with the following AP coverage typical:

WASHINGTON (AP) - An asteroid large enough to cause widespread
destruction may be heading toward a 2028 collision with the Earth and
will certainly pass closer to the planet than any such space object in
modern times, astronomers said Wednesday. ``The chance of an actual
collision is small, but one is not entirely out of the question,''
according to a notice filed by the International Astronomical Union.
``It has enormous destructive potential,'' said Steven Maran of the
American Astronomical Society, but he added it will take several more
years of observations before experts are certain of its path. ``It
scares me. It really does,'' said Jack G. Hills, an asteroid specialist
at the Los Alamos National Laboratory. ``An object this big hitting the
Earth has the potential of killing many, many people.''

The London Times reported in a lead article by Nigel Hawes: Apocalypse
could be just 30 years away, astronomers said yesterday. They have
identified an asteroid a mile across on a near-collision course with
Earth. It is by far the most alarming object yet identified in the
search for asteroids and comets with Armageddon potential.

Following this announcement several astronomers searched older
photographic records to try to locate previously unrecognized
observations of 1997XF11. Eleanor Helin and her colleagues from the Jet
Propulsion Lab soon found images taken in 1990 that permitted
calculation of an improved orbit for the asteroid. Based on this
expanded observation set, Don Yeomans and Paul Chodas at JPL
recalculated the orbit and found that the 2028 close approach
circumstances are: Time: 2028 Oct 26.26732 (06:24 UT) +/- 63 minutes;
closest approach distance = 0.00638 AU = 954340 km +/- 0.00058 AU;
relative velocity at closest approach = 13.914 km/s. This means that
the asteroid will pass by the Earth at about twice the distance of the
Moon, and that the probability of impact with Earth is effectively
zero. The JPL press release providing this information is included

The discovery of 1997XF11 illustrates several aspects of the asteroid
impact hazard.

(1) When astronomers carry out searches, they typically
find even threatening asteroids decades to centuries before their
actual impact with the Earth. If it had turned out that XF11 posed a
threat to Earth in 2028, we would have had three decades to deal with
this threat.

(2) With a diameter of about a mile, XF11 is near the threshold for
global disaster. The impact of an object this size with the Earth would
release a million megatons of energy and would probably lead to the
death of hundreds of millions of people.

3) Most of the asteroids that could strike the Earth and cause a global
catastrophe have not yet been found. For the year 2028 (or any other
year) the chances of an unknown asteroid hitting the Earth are much
greater than the chances of this particular asteroid hitting.

(4) if an unknown asteroid should hit us, we would likely have no
warning at all. The first we would know of the danger is when we saw
the flash of light and felt the ground shake.

(5) At the current rate of discovery, it will take more than a century
to find 90% or more of the objects this large with Earth-crossing

(6) For better or for worse, the astronomers who carry out these
searches and orbit calculations work in the public eye. The idea that a
threatening asteroid could be kept secret (or that anyone would want
to keep it secret) is ludicrous

For further information see the NASA asteroid and comet impact hazard
website at:

David Morrison

From: Robert H. McNaught"

[...] If you "keep it private", you are blamed by the media for
"covering it up" and you don't get the observations made usually, as
there are so few people involved at the actual observational end (I
was employed in NEO discovery and observation from 1990-1996 until
the Australian govt. cut our funds; not important enough although we
discovered 16% of the 108 potentially hazardous asteroids). By
keeping quiet, eventually someone will come up with the story and you
have no control over how it is used. Even in this case, despite the
measure words of Marsden and others, the comments of the news anchors
introducing the story irreversibly color it "Astronomers disagree
about the danger posed..." "Some astronomers predict a collision of
an asteroid with the Earth...".

I was a little annoyed in seeing various NASA representatives stating
that the danger was "zero" being interposed with Marsden and others
saying the threat was small. The NASA statements were made after the
1990 precovery by the Helin's JPL team, and the statements were
either chosen by the media to create a false tension, or the NASA
folks involved really were trying to put one over.

Wayne's point on the errors from the first estimate, not including
the more accurate estimate of miss distance can be explained by two
factors. Firstly, an error estimate in such a circumstance is
probabilistic and I guess Marsden took a suitably large figure to
include perhaps a 99% probability. However the wings of the remaining
1% can be very large. The second point is that the error estimates
assume that the observational errors are random. This will not be
true for two reasons. Each observatory that contributed observations
(and only a handfull did with this object) can introduce small
systematic errors due to their observation or reduction techniques,
or small timing errors (a few seconds can count). Perhaps more
importantly, the star catalogue used, especially if not the latest,
will have systematic position errors in different parts of the sky.
I have had experience with this myself. 10 days after the discovery
of comet Hale-Bopp, I would a tiny faint smudge of the comet on a
plate taken a year and a half-earlier (in the same sort of precovery
process that Ken Lawrence used for 1997 XL11). It was initially about
7 arcmins from the predicted position based on the small arc.
Marsden trusted me and published this. As time went on, the
discrepancy dropped, but eventually that last 30 arcsecs or so would
not disappear. JPL made an announcement, without discussing the issue
with me, that there was a problem with my precovery observation, and
they had excluded it from their orbital analysis to have the highest
accuracy. However, the comet was moving so slowly during that time
that the observed arc since discovery was in one small portion of the
sky, and most astrometrists were using the low-accuracy Hubble Star
Catalog. The huge number (thousands) of observations which included
systematic errors due to the star catalog, were the cause of the
problem and Marsden was the first to discover this by suitably
weighting the observations. It has not been shown (with astrometry
from discovery to present day) that my precovery measure is accurate
to around 1 arcsecond.

Cheers, Rob

From: Victor D. Noto

So here we go again analyzing another fireball only this time it's a
media press release by a very hard working and respected member of the
science community that went around the world like a burning rock.
Will there be an impact from this press release fireball or not will be
answered very quickly at the 29th Lunar and Planetary Conference
dedicated to the memory of Eugene M. Shoemaker held on March 16-20,
1998 in Houston, TX.

There are a small group of NEO researchers that have been manning the
trenches in a very forward post in defense of the planet and Brian
Marsden of cfa Harvard Smithsonian and International Astronomical Union
is one of their Generals with his hand on the very trip wire of early
warning. Brian has been at this task a very long time and has seen many
large and small rocks close approach calculation and literal events to
this old planet. This close approach grabbed the attention of a person
familiar and perhaps a little jaded to close approaches of asteroids
and comets. Brian took action as he should have. Who are we to second
guess his opinion of such events for which he spends his every waking
moment studying. In fact the world did take notice of Brian's words
because it came from a highly respected member of the science community
and the ultimate insider of near Earth asteroid survey and research.
As Tom Gehrels said just today "Brian is the insider who does most of
the work and for that he works night and day, literally, because
whenever we need him, he's always there."

NASA JPL went to work immediately on his word of close approach as they
should - hunting old images taken by astronomical observations back in
the archives to finally in 1990 something turned up. The calculation
made by Brian's associate Gareth Williams at cfa Harvard with this new
data showed that the orbit was slightly different than calculated with
limited data originally used and thus the miss turned out to be
greater. Does anyone realize that this calculation could have just as
well showed that this asteroid XF11 could have impacted Earth on that
same day in 2028. No. But there are those in the US government who do
know and were very relieved because they have been planning a for over
a year on what to do if such an event as an asteroid predicted impact
should arise. Thus far the people studying this question have no

There was a general relief at NASA and the US Pentagon that it fizzled
this time, and a greater awareness that it could be for real next time.
Brian is a hero if this added awareness leads to additional action.

From: Zhu Jin

I think that the 1997 XF11 stuff was announced in two IAUCs is good
at least in this aspect: Both works of Jim Scotti (discover the
object) and K. J. Lawrence (find prediscovery images) are important,
and each of their works worth a seperate item in IAUC - it makes
later researchers on this object easier to reference the discovers'
contributions and also make the discovers easier to complete their
paper-works to their funds providers (where discovery itself may not
be enough, but some publications and citations are also necessary).

I'll try to observe that object if we have good weather next week. It
will always be an interested thing to see whether the orbit could be
changing slightly from further observations. Of course there might be
less chance for those new data to appear in IAUC again. :)

Clear Skies, Jin



From: Michio Kaku (1997) Visions: How Science will Revolutionize the
21st Century, Anchor Books, Doubleday

"On this cosmic scale, we are a Type 0 civilisation - we derive our
energy from dead plants (e.g. fossil fules). We are like infants,
just beginning to contemplate the vast universe of possible
civilizations. Our civilization is so new that even a hundred years
ago we still got most of our energy from burning wood and coal, and
any discussion of extraterrestrial energy sources would have been
considered madness.

Of these three transitions [from Type 0 to Type III civilizations],
perhaps the most perilous one is the transition from a Type 0 to a
Type I civilization. Like a child learning how to walk, it suddenly
becomes aware of new life-threatening dangers in its quest to explore
and master its world. The more it learns about the universe around
it, the more it learns of potential dangers, such as ice ages, meteor
and comet impacts, supernova explosions, and environmental threats,
such as the collapse of its atmosphere or the proliferation of
nuclear weapons.

Furthermore, a Type 0 civilization is like a spoiled child, unable to
control it self-destructive temper tantrums and outbursts. Its
immature history is still haunted by the brutal sectarian,
fundamentalist, nationalist, and racial hatreds of the past
millennia. A Type 0 civilization is still split along deep fracture
lines created thousands of years in the past. [...]

Given the fact that astrophysicists do not see evidence of life in
nearby star systems, even though Drake's equations predict the
existence of thousands of intelligent civilizations in our galaxy, it
is possible that our galaxy is filled with the ruins of Type 0
civilizations which either settled old grudges and jealousies via
element 92 [i.e. uranium] or else uncontrollably polluted their

The Cambridge-Conference List is a scholarly electronic network
moderated by Dr Benny J Peiser at Liverpool John Moores University,
United Kingdom. It is the aim of this network to disseminate
information and research findings related to i) geological and
historical neo-catastrophism, ii) NEO research and the hazards to
civilisation due to comets, asteroids and meteor streams, and iii) the
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