CCNet DIGEST 27 May 1998


    Ron Baalke <>

    Michael Gerrad <>


    Stephen Ashworth <>



Statement on The Threat of Impact by Near-Earth Asteroids by
Dr. Clark R. Chapman Southwest Research Institute

before the Subcommittee on Space and Aeronautics of the Committee on
Science of the U.S. House of Representatives
at its hearings on "Asteroids: Perils and Opportunities"

May 21, 1998

Mr. Chairman and Members of the Subcommittee:

I am pleased to discuss with you the threat to our civilization from
impacting asteroids. The threat is something I think we should all
think about, but I am happy to report that I feel that we can still
sleep well at night......

List members can find Clark's entire statement on his website at


From Ron Baalke <>

University News Services
University of Iowa
100 Old Public Library
Iowa City, IA 52242

Contact: Gary Galluzzo
(319) 384-0009; fax (319) 384-0024

Release: Tuesday, May 26, 1998

UI's Louis Frank finds "small comets" are seasonal

IOWA CITY, Iowa -- University of Iowa space physicist Louis A. Frank
today, Tuesday, May 26, presented a new study supporting his "small
comet" theory that more than 25,000 snow comets weighing 20 to 40
tons each disintegrate in the Earth's atmosphere every day. The
study, presented at the spring meeting of the American Geophysical
Union (AGU) in Boston, is based upon data gathered by NASA's Dynamics
Explorer 1 and Polar satellites and shows that the number of snow
comets observed varies with the seasons.

Frank and his UI colleague John B. Sigwarth analyzed 1981 data
collected by Dynamics Explorer 1 and compared it to data gathered by
Polar in 1997. In both cases, they found a mid-January lull in the
data, a seasonal phenomenon that would refute the contention of some
skeptics who claim that evidence of small comets is merely electronic
"noise" appearing on satellite photographic images.

"We have finished our analysis of the seasonal variations during the
same months [winter], but 16 years later with the Polar spacecraft
Earth Camera. Even though the camera is totally different and the
orbit is different, the Earth Camera also detects the same seasonal
variations as the Dynamics Explorer 1 spacecraft camera, including
the dramatic mid-January minimum," Frank says. "Obviously, the
possibility of an instrument artifact is not even remotely possible."

Despite mounting evidence supporting the small comet theory, doubters
remain in the scientific community. Several papers refuting the
theory were scheduled for presentation at the spring 1998 AGU
meeting, one of them suggesting that measurements made by another
satellite show that the atmosphere some 15 to 35 miles above the
Earth is much drier than the small comet theory would suggest.

Frank says that what may be needed to resolve the debate is a space
mission to meet the small comets 600 miles out. Frank, Sigwarth and a
group of former critics -- including Thomas Donahue and Michael Combi
of the University of Michigan; Paul Feldman of Johns Hopkins
University; Robert Meier, George Carruthers and Charles Brown of the
Naval Research Laboratory; and Ralph Bohlin of the Space Telescope
Science Institute -- have proposed a spacecraft to look for emissions
of carbon, oxygen and simple organic gases coming from these objects.

Last December, Frank presented a study at the AGU fall meeting
showing that dark spots (called "atmospheric holes" because of their
appearance on film) captured in June 1997 on Polar photographs
decrease in size and number as the satellite's altitude and distance
from the holes increases -- just what one would expect to find if the
cameras are taking pictures of a real phenomenon.

At the May 1997 AGU meeting, Frank revealed a series of Polar
satellite photographs, ranging from a picture of a small comet the
size of a two-bedroom house disintegrating thousands of miles above
the Atlantic Ocean to an image of light emitted by the breakup of
water molecules from a small comet less than 2,000 miles above the
Earth. Frank and Sigwarth, who co-discovered the small comets and
designed and built the three Visible Imaging System (VIS) cameras
aboard Polar, offered the pictures as proof of their 12-year-old
theory, which holds that small snow comets, over the age of the
Earth, could have provided enough water to fill the oceans. Also,
last August, a satellite trailing the Space Shuttle Discovery was
reported to have detected significant amounts of high-altitude water
vapor, a finding that would seem to support the small comet theory.

Frank first announced his small comet theory in 1986, after examining
images recorded in photographs taken by Dynamics Explorer 1. Frank
and his colleagues had designed and built a specially-made camera to
take pictures of the northern lights, including the first images of
the complete ring of the northern lights from above the north pole.
But some of the images contained unexplained dark spots, or
atmospheric holes. After eliminating the possibility of equipment
malfunction and numerous other explanations, Frank and Sigwarth
concluded that the atmospheric holes represented clouds of water
vapor being released high above Earth's atmosphere by the
disintegration of small comets composed mostly of snow.

They calculated that about 20 comets enter the atmosphere each
minute. At that rate, the steady stream of comets would have added
about one inch of water to the Earth's oceans every 20,000 years --
enough to fill the oceans over billions of years. The theory was
immediately controversial, with people asking why such objects hadn't
been observed previously. Frank countered that not only their small
size -- 20-to-30-feet in diameter -- makes observation difficult, but
also that water striking the upper atmosphere glows very faintly as
compared to the bright glow of metal and rock in solid meteors. The
1996 launch of Polar, carrying two sensitive visible light cameras
and one far-ultraviolet light camera, made it possible to photograph
the small comets with greater resolution.

For further information, see the small comets web site which is
embargoed until 1 p.m. EDT, Tuesday, May 26 at:


From Michael Gerrad <>

Benny -- The attached may be of interest.

News Release                  Contact: Diane Noserale 703-648-4333
U.S. Department of the Interior     
U.S. Geological Survey
Office of the Eastern Regional Geologist
953 National Center
Reston, VA 20192
Release Upon Receipt:  May 27, 1998

The Caribbean is not renowned for its potential to generate the huge
waves known as "tsunamis" that often occur in the Pacific.  And
scientists worldwide refer to them by their Japanese name "tsunami,"
which means "harbor wave." Yet these long-period waves are not
confined to the Pacific Ocean. Historically, tsunamis have occurred
in the Caribbean and the Atlantic, resulting in deaths and property
damage. USGS scientist William Dillon will present new evidence for
the cause of several historical tsunamis near Puerto Rico at the
American Geophysical Union meeting, scheduled for May 26-29 in

"We reprocessed data from a seismic line provided by Shell
International," said Dillon.  "It shows tilting of the small portion
of the Earth's crust, known as the Puerto Rico microplate, upon which
Puerto Rico sits. The tilting is probably caused by interaction with
the North American tectonic plate as it dips in downstepping fault
blocks beneath the Puerto Rico microplate and is overrun by another
tectonic plate, the Caribbean, moving eastward. Submarine slope
failure and sliding of limestone slabs on the northern insular margin
of Puerto Rico resulted, and these submarine slides may have
generated some of the historical tsunamis near Puerto Rico,"
according to Dillon.

Tsunamis are more commonly known by the misnomer "tidal waves."  They
are not, however, related to tides, which are caused by gravitational
forces from the Moon and the Sun. "It has been known for many years
that tsunamis are generated by disturbances of the sea floor from
events such as submarine landslides, earthquakes, and volcanic
eruptions,"  said Dillon. "These disturbances can generate
long-period waves that begin to pile up into a wall of water as they
approach shallow water near shorelines.  Our data indicate that the
Puerto Rico tsunamis may have been caused by the landslides that
appear on the nearby sea floor," said Dillon.

Will people in Boston ever need to flee from a tsunami?  "I doubt it.
By far, nor'easters, the occasional hurricane, and beach erosion from
the constant surf are more worrisome.  However, a major earthquake
hit offshore near Cape Ann, north of Boston, during colonial times. 
So a tsunami in this area isn't completely impossible," said Dillon,
who will present his findings at 8:30am on Wednesday, May 27 in
Convention Center Room 201. As the nation's largest water, earth and
biological science and civilian mapping agency, the USGS works in
cooperation with more than 2000 organizations across the country to
provide reliable, impartial, scientific information to resource
managers, planners, and other customers. This information is gathered
in every state by USGS scientists to minimize the loss of life and
property from natural disasters, contribute to the conservation and
the sound economic and physical development of the nation's natural
resources, and enhance the quality of life by monitoring water,
biological, energy, and mineral resources.

This press release and in-depth information about USGS programs may
be found on the USGS home page: To receive the
latest USGS news releases automatically by email, send a request to
<>.  Specify the listserver(s) of
interest from the following names:  water-pr; geologic-hazards-pr;
biological-pr; mapping-pr; products-pr; lecture-pr.  In the body of
the message write: subscribe (name of listserver) (your name). 
Example: subscribe water-pr joe smith.


H. Schulz*), U. von Rad, H. Erlenkeuser: Correlation between Arabian
Sea and Greenland climate oscillations of the past 110,000 years.
NATURE, 1998, Vol.393, No.6680, pp.54-57


Palaeoclimate studies have revealed the general high-frequency
instability of Late Pleistocene climate-for example, the so-called
Dansgaard-Oeschger and Heinrich events-on timescales of a few
millennia, centuries or even decades(1-11). Here we present evidence
for a general relationship between low-latitude monsoonal climate
variability and the rapid temperature fluctuations of high northern
latitudes that are recorded in the Greenland ice records. Sediment
cores from the northeastern Arabian Sea show laminated,
organic-carbon-rich bands, reflecting strong monsoon-induced
biological productivity, that correlate with the mild interstadial
climate events in the northern North Atlantic region. In contrast,
periods of lowered southwest monsoonal intensity, indicated by
bioturbated, organic-carbon-poor bands, are associated with intervals
of high-latitude atmospheric cooling and the injection of melt water
into the North Atlantic basin. Our records suggest that
Dansgaard-Oeschger and Heinrich events are strongly expressed in
low-latitude (monsoonal) climate variability, suggesting the
importance of common forcing agents such as atmospheric moisture and
other greenhouse gases. Copyright 1998, Institute for Scientific
Information Inc.


From Stephen Ashworth <>

Dear Benny Peiser,

Thank you for subscribing me to the Cambridge-Conference Network.

If I may, I would like to comment on point (iii) of CCNet's interests
-- "the development of a planetary civilisation capable of protecting
itself against cosmic disasters".

I suggest we might more profitably understand the focus to be upon
the development of an *interplanetary* civilisation as opposed to the
monoplanetary one we enjoy at present.  This is because the potential
threats operate in the general environment of the Solar System, and
reaching out to comprehend and avert them is, I suggest, a natural
accompaniment to the economic growth that is likely eventually to
utilise natural resources and opportunities for expansion on a
Solar-System-wide scale.

For example, the mission to avert asteroid or comet collision with
the Earth is obviously complemented by research on the likely utility
of asteroids and comets for mining the materials that may make
large-scale space construction possible.

Stephen Ashworth
Fellow of the British Interplanetary Society
Space Age Associates

The CCNet is a scholarly electronic network. To subscribe, please
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Information circulated on this network is for scholarly and educational
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The electronic archive of the CCNet can be found at



From Sir Arthur C Clarke

Dear Benny,

Herewith my convocation address. It's for a lay audience so I've
made it simple as possible.

All best,




Convocation Address


Sir Arthur C Clarke, Kt., CBE

Chancellor, University of Moratuwa, Sri Lanka

26 May 1998

Less than four years ago, in October 1994, I devoted my Convocation
Address to something which probably few people had ever worried about -
the danger to our planet of impacts from space. Well, during those four
years so much has happened that I make no apologies for returning to
the subject.

If you spend a few hours at night under a perfectly clear sky  - 
which, alas, I haven't done for years - you are almost certain to see a
few meteors sliding silently  across the stars; there  are times,
indeed, when you may see hundreds. One such occasion is due in November
1999: a Space Shuttle launch has been rescheduled, and the owners of
communications satellites are already rushing to take out insurance.
For though that 'shining furrow', as Tennyson called it, is caused by
an object not much larger than a pea burning up as it enters the
atmosphere, that has enough energy to damage, or even destroy, delicate
orbiting equipment costing hundreds of millions of dollars. Tennyson,
who a century and a half ago saw 'the heavens filled with commerce'
could never have imagined that one day this would be literally true.

Quite often, one of these cosmic fragments is large  enough to survive
passage through the atmosphere, and falls to earth. We then call it a
'meteorite'; the word 'meteor' applies merely to the streak of light
across the sky.    

That meteorites did fall -  sometimes in large numbers over
considerable areas - had been known from time immemorial; indeed, it
has been suggested that they were the only source of iron for early
man. Yet two hundred years ago, in what has been called the Age of
Enlightenment, there was great scepticism about their existence. Thomas
Jefferson, widely considered the most brilliant President ever to sit
in the White House, once remarked  after hearing that a couple of
academic gentlemen had witnessed a shower of meteorites: "I would
rather believe that two Yankee professors lied, than that stones fell
from the sky." Well, now we know that mountains can fall from the sky.

The evidence is overwhelming, yet only in  the  last  few decades has
this been accepted: as someone once said: "The obvious we see

Perhaps the best example of this phenomenon is the famous Meteor Crater
in Arizona - a huge hole in the ground more than a kilometre across.
Despite the perfectly accurate name that the locals had given to it,
for years most geologists argued that the crater was home-grown - some
kind of volcanic formation! Now we know that it was produced by the
impact some 50,000 years ago of a nickel-iron  mass about as large as
this building. Once they removed their  mental  blindfolds, geologists
started finding impact craters all over the world. About two hundred
have now been identified, and there must be many more hidden in the
ocean depths. We live in a very dangerous neighborhood: what has
happened countless times in the past will, inevitably, occur again
in the future.

What did most to focus the attention of the scientific - and
non-scientific - community on this fact was a paper published in 1980
by the American physicist Luis Alvarez and his geologist son Walter,
suggesting  that the extinction of the dinosaurs was linked with the
impact of an asteroid on Earth, about 65 million years ago*.
* Luis was a good friend of mine, and I dedicated my 1963 novel Glide
Path  to him. This work of barely disguised  fiction was based  on my
experiences as an RAF officer when I took  over the GCA (Ground Control
Approach) radar blind-landing  system  which 'Luie' had invented at the
Massachusetts Institute of Technology. The  main  protagonist was
modelled on him, and I am  very happy that  my  prediction  of his
Nobel Prize came true  a  few years later.

The word 'asteroid' is unfortunate, because it  means 'small star' -
and asteroids are in fact only small planets, most of  them  between
Mars and Jupiter. The largest, Ceres, is  just under a thousand
kilometres across, but they come in  all sizes down to ones that would
sit comfortably on the Galle Face Green (what there is left of it.) So
where one draws the line  between meteorites and asteroids is a matter
of definition; they all bits of debris left over from the formation of
the Solar System.

And so are comets, which are enormously larger but no heavier than
asteroids, since they are almost entirely clouds of extremely thin gas,
surrounding a small, solid nucleus. When, after many trips round the
sun, all its volatile material has boiled off into space, only this
core is left - and the comet becomes a normal asteroid.

I am proud to say that the International Astronomical Union, which is
in charge of such matters, recently named  an asteroid (previously
known only by a number, 4923) after me. It's about ten kilometres in
diameter, and spends most of its time near the orbit of Mars, so I'm
afraid its climate is rather chilly. The IAU apologised to me because
Number 2001 was no longer available. Apparently it had been allocated
several years ago, to somebody named A. Einstein. 

As far as the resulting damage to planet Earth was concerned, it would
not make the slightest difference whether the impactor was a comet or
an asteroid. However, because it is such an impressive astronomical
object, we could see a  comet months before it hit. But an asteroid

might give only two minute's warning, when the sky suddenly exploded...

This happened over a remote part of Siberia in 1908. Luckily, though  a
huge area of forest was devastated, there was no loss of human life.

There have been several other major events since then, again in
uninhabited  areas, and in 1972 there was a hair-raising near-miss. On
10 August, a large meteorite streaked half way across the United States
and was seen not only by thousands of people, but recorded by many
amateur photographers. It came within a mere 58 kilometres of ground
level; had its  trajectory been slightly different, some American city
might have emulated Hiroshima.

I'm  not sure if this provided any inspiration for my novel Rendezous
with Rama, which opened with the destruction of Northern Italy by
asteroid impact in the year 2077. This disaster resulted in the
establishment of a warning system, to which I gave the name -
SPACEGUARD. Well, fact has followed fiction. When the U.S. House of
Representatives asked NASA to study the problem, I was delighted when
the resulting 1992 report was entitled THE SPACEGUARD SURVEY, with due

That same year, a senior editor of TIME wrote to me saying that though
the magazine  had never deliberately published  fiction, they'd like me
to write a short story for a special issue. The result was The Hammer
of God, in which I attempted to answer the question: what could we do
to save ourselves if we see a killer rock headed this way?

The novel-length version of The Hammer of God  appeared in 1993 - and
just one year later, the whole world had a grandstand view of the most
spectacular collision ever observed in our Solar System. The impact of
Comet Shoemaker-Levy 9 on Jupiter in July 1994 made holes in the giant
planet's atmosphere larger than the Earth; they could be seen even in
the smallest telescope, and the after-effects lingered for months.

Only a few weeks ago, there was a great deal of alarm when the initial
orbit calculated for the newly-discovered asteroid 1997 XF11 suggested
that it might collide with Earth in the year 2028. Luckily, after a
hunt through the thousands of photographic plates collected by
astronomers over many decades, an earlier image of XF11 was discovered.
This made it possible to compute a much more accurate orbit, and we now
know that there is  no danger from this particular asteroid - at least
for millions of years!

This rather embarrassing affair - the correction came only a day after
the initial report - has triggered a major debate in the astronomical
community. A protocol is now being drawn up to reduce the chance of any
premature and perhaps inacurate announcement. And I am happy to say
that NASA is now in the process of establishing a new office to deal
with the  problem, with  an initial annual budget of $3,000,000.   

Among the members of NASA's SPACEGUARD Committee is my old friend the
Dutch-American astronomer Tom Gehrels, one of the world's leading
experts on asteroids. He has visited Sri Lanka on several occasions,
hoping to establish an observatory here  - so far without success,
because of a deplorable lack of interest in astronomy (as opposed to

This situation, I hope, may be rectified now that the Japanese 
Government has made an extraordinarily generous gift of a half-million
dollar observatory-class telescope, currently located at the Arthur
Clarke Centre. Although this is far from  being an ideal location, the
best observing sites are currently inaccessible and good work can still
be done at Moratuwa - if we can find experienced and enthusiastic
staff. I might add that most comets and many asteroids are discovered
by amateurs working with telescopes considerably smaller than the one
we now possess.

Some might argue that, in a world already nervous about global warming,
poisoned oceans, DIY nuclear bombs,  etc.  etc., any discussion of
protection from asteroids amd comets is a massive exercise in
irrelevancy. Yet there is much that can - and should - be done, as is
proved by the current intense  debate among astronomers, space
scientists, and under-employed Star Warriors looking for new targets.

It is an old idea - going back at least to  Andre  Maurois' "The War
Against The Moon" (1927) - that only a threat  from beyond the Earth
could unify the quarrelsome human species. So it may indeed be a stroke
of luck that such a threat has been discovered, at just the period in
history when we can devise technologies to deal with it.

Although some suggested cures may sound worse than the disease (Dr
Edward Teller has proposed a bodyguard of orbiting H-bombs) there are
several plausible  alternatives. They all depend on the length of the
warning time available.

Of the many defences proposed, the most elegant (and environmentally
friendly!) one is to rendezvous with any asteroid on an orbit liable to
impact Earth, and to persuade it to make a slight change of course. If
there was sufficient warning time, only a modest amount of rocket
propulsion would be necessary. This was the scenario I developed in The
Hammer of God, which was later optioned by a promising young
movie-maker named Steven Spielberg. I don't know how much of my story
he has used, but I have a double interest in Deep Impact, as he is
calling the film. The role of the first black President of the United
States is played by Morgan Freeman, now considered by many to be the
finest actor in America. Well, Morgan has just optioned my own
Rendezvous with Rama, which started the whole SPACEGUARD business. I
can't wait...

Meanwhile SPACEGUARD Foundations have been set up in the UK, the US 
and Australia, to persuade goverments to fund a  survey which would,
for the first time, give us some idea of the real extent of the danger.
At the moment, we probably do not know even one tenth of the NEO's -
Near Earth Objects - which must exist.

In one of his last books, Carl Sagan pointed out that no really
long-lived civilization could survive unless it develops space travel,
because major asteroid impacts will be inevitable in any solar system
over the course of millennia. Larry  Niven summed up the situation with
the memorable phrase: "The dinosaurs became extinct because they didn't
have a space programme." And we will deserve to become extinct, if we
don't have one.

CCCMENU CCC for 1998