CCNet DIGEST 13 July 1998

      Alain Maury <>

     Jonathan TATE <>

     Andrea Milani Comparetti <>

      Duncan  Steel <> wrote:

     Alan W. Harris <>

      Henrik Persson <> [as posted on the meteorite-list]


     J.A. Frogel & A. Gould, OHIO STATE UNIVERSITY


From Alain Maury <>

                                                  1982 Italy
                           1978 Argentina     Argentina 1986
                     1974 Germany                  Germany 1990
                 1970 Brazil                                     Brazil 1994
           1966 England                                          FRANCE !!!  1998

Sorry. Couldn't resist.



From Jonathan TATE <>


Welcome to the fourth edition of “Impact”.  After the rather busy time
following the XF11 affair, I had hoped that things would calm down a bit.
However, to the despair of my lords and masters at work, nothing could be
further from the case!

The opening of Steven Spielberg’s “Deep Impact” has generated a rash of
interest in the impact hazard, and also considerable ramblings in various
Internet newsgroups on the scientific accuracy (or otherwise) of the film.
I have seen it twice now, and I can honestly say that it’s very good!  OK,
there are some technical bloopers, but remarkably few. And, after all, it’s
designed as entertainment and not a science lecture.  As a piece of
entertainment it is first class, and as a carrier of the Spaceguard message
it will be excellent.

Apart from the smashing special effects, I felt that the film was also very
thoughtful, raising some interesting issues, (which is possibly why the
critics are not too happy with it – not enough blood). One of the most
important, and current, is the morality of concealing news of an impending
impact from the public. While I think that it would be impossible to conceal
the facts for the length of time postulated in the movie, I am also less
confident in human nature than a lot of the scientific community who
advocate complete openness. Should an early announcement be made of a
definite event (assuming such calculations are possible to the necessary
levels of accuracy), I think it unlikely that the human race will quietly
settle down to straighten out its affairs before catastrophe.  A fuller
examination of the film, and the issues that it raises can be found later in
this issue.  Let’s hope that we can be as enthusiastic about the next
Hollywood offering, “Armageddon”, due to be released in July.

Spaceguard UK is in good fettle at the moment. There have been a couple of
good “airings” on the television over the past couple of months, and I have
been travelling the country lecturing to astronomy clubs and societies.  The
message seems to be getting across, and membership is rising steadily!

Other news from abroad is good.  In the Unite States NASA has decided to
double its NEO budget from $1.5 million to $3 million per year.  An extra
$1.5 per year may not be a lot, but it’s certainly a step in the right
direction, and the ball has begun to roll. The news from Japan is even
better with the funding of their new telescope for NEO/debris studies at a
cost of about $15 million.

Sadly of course, the British government still has its head firmly embedded
in an uncomfortable part of its anatomy. I sometimes despair of our elected

However, all is not lost!  There are a number of ongoing initiatives both
here and abroad.  Here, Sir Crispin Tickell has written to the Prime
Minister, encouraging him to look at the threat posed to the United Kingdom
by impacts, and, in the United States there are further moves afoot to
persuade Congress and the Pentagon to take the problem seriously.  Let’s
hope that some or all of these initiatives manage to produce some results.

Jay Tate


For the past few months the NEO community has been waiting with some
trepidation for the release of the latest Spielberg blockbuster, “Deep
Impact”. The story line is based on the impending impact of a large (seven
mile diameter) comet on the Earth, and the measures taken to prevent or
mitigate the effects of the catastrophe.
Contrary to the natural concerns of the real experts, the science is
surprisingly good.  Before descending to the level of minor “nit-picking
detail”, the first thing to appreciate is that the film was made to
entertain, and not to educate.  That being the case, I believe that the
scientific inaccuracies contained in the piece are almost insignificant,
except for the most rabid critic.  The overall picture presented in the film
is very realistic, and portrays the threat in a balanced and cogent fashion.
This is definitely a film to see, and to encourage others to see.
The first question that anyone seeing the film is likely to ask is “could
this really happen?”  The answer is clear – not only could it happen, but it
will happen.  It has happened before, and the statistical probability of it
happening again is exactly one.
The threat portrayed in the film – that of a long period comet approaching
the Earth, giving us only two years warning of impact – is completely
realistic.  In fact, it is the worst case scenario.  The threat from
asteroids and short period comets is likely to be easier to deal with as,
once detected, these bodies are likely to orbit the Sun a number of times
before becoming a direct threat.  For example, with Asteroid 1997 XF11 we
would have had thirty years to prepare for impact.  In addition, asteroids
and short period comet orbits are confined to a band of sky close to the
plane of the ecliptic, making search programmes significantly simpler.
Assuming that these bodies can be detected in good time (a rather optimistic
assumption at present) there should be plenty of time to prepare counter
measures.  The original Spaceguard Survey proposed by Eugene Shoemaker in
1994 was designed to catalogue all Earth threatening objects within 25
years, so, even in the worst case we would have that much warning, and at
best, up to 100 years (beyond that, orbits become increasingly less
On the other hand, the long period comet can come from any direction, with
typical warning times of 18 months to two years.  Since their arrival in the
inner solar system is completely unpredictable, this poses a serious problem
for Spaceguard-type surveillance programmes.
In “Deep Impact” the news of the impending collision is withheld from the
public, while the United States and Russia plan their countermeasures.  In
real life, as shown during the XF11 affair, it would be virtually impossible
for any government to conceal the facts.  The expanding use of the Internet
for the passage of astronomical data makes the keeping of secrets almost
impossible.  The requirement for follow-up observations of a suspect object
would involve a considerable number of individuals and organisations
worldwide, any one of which could (and probably would) blow the whistle.
After the XF11 affair, the International Astronomical Union Working Group on
Near Earth Objects (IAU WGNEO) studied in some detail the passage of
information that led to the press release.  A concurrent study, commissioned
by NASA, concluded that there should be a short delay in the publication of
any warning, to allow for the confirmation of the data.  The wording of this
proposal is somewhat suspect, as it implies United States government control
over the data.  The thought of any “censorship” or concealment of truth is
abhorrent to the vast majority of the scientific community, and there has
been considerable opposition to the NASA proposal.  An alternative solution
would be to have another, non-governmental institution conduct the peer
review and confirmation, such as the IAU WGNEO.  Whoever is selected will
have to have the trust and respect of the scientific community, and the
resources to carry out its task in a very short time.
But why should the news be delayed in the first place?  Deep Impact
portrayed, albeit briefly, a world that had lost hope, that had lost all
sense of civilised responsibility, had lost all moral decency; all in the
panic caused by impending mass death.  Sadly this portrayal is likely to be
nearer to the truth than most of us would like to believe.  Is it the act of
a responsible profession to precipitate mass panic and hysteria without
being absolutely sure of the accuracy of its data?  The XF11 affair clearly
demonstrated that the less responsible sections of the press are more than
willing to whip themselves into a frenzy at the slightest excuse, and with
no regard for the accuracy of their statements.  The main lesson learned is
that any data released to the media, and thence to the public, must have
been checked scrupulously beforehand.  Later retractions will be too late.
So, do we opt for honesty and openness, thereby risking mass hysteria (with
the possibility of serious social unrest, casualties and loss of
credibility) for no reason, or do we agree to delay publication (by 48 to 72
hours) until the data has been thoroughly checked and verified?  It is a
Catch-22 situation, but one that must be resolved by astronomers in
particular, and the scientific community as a whole before the next incident
So, could “Deep Impact” really happen?  The simple answer is “possibly.”  In
the situation of a long period comet being discovered on a collision course,
and with only two years warning, it is unlikely that there is anything that
we could do, except hunker down, and hope to ride out the impact.  The
technology to deflect an approaching comet exists – the launch vehicles, the
spacecraft, the guidance systems and the nuclear weapons – but there are no
integrated systems available, and the technology is largely untested.  The
US Air Force had planned to send its Clementine 2 spacecraft to rendezvous
with two near Earth asteroids, and to fire instrumented penetrators into
them.  This mission would have “space rated” the technology required for
interception, but the mission was curtailed by Mr. Clinton last autumn.
With more warning time, missions such as “Messiah” could doubtless be
mounted, and the ground preparations could be made.
The devastation wrought by the comet fragment that strikes the Earth is very
accurately portrayed in “Deep Impact”.  Indeed, it was perhaps somewhat
understated.  The massive risk posed by tsunami effects is still not well
understood, but since any impact has a 70% chance of occurring at sea, the
threat is very real.  The longer term effects of the impact were not
detailed, but it should be remembered that it is these later effects,
including the loss of light at the Earth’s surface, the acidification of
land and sea, the mixing of warm and cold ocean layers and the toxification
of the atmosphere that are the chief killing mechanisms.  The “Deep Impact”
tsunami may have looked good, but the slower acting, more insidious after
effects of the impact would be the real villains of the piece.
The theme that runs through any discussion about Planetary Defence is the
prime requirement for surveillance.  Without the ability to detect a
threatening object before impact there is no chance of doing anything about
it.  The ability to deflect an incoming impactor is directly proportional to
the warning time available, so surveillance is of paramount importance.  At
the moment, there are simply not enough people searching for NEO’s, and, all
things being equal, the warning time that we can reasonable expect is about
six seconds.  The late Gene Shoemaker recommended the Spaceguard Project to
the US Congress in 1994.  This consisted of a global network of six
ground-based telescopes, and a data processing centre.  The total cost?  $50
million (32 million) to establish, and $10 million (6.25 million) per year
to run.  Now that sounds like a lot of money, but think on.  Firstly, the
programme must be international, so the total amount will be spread amongst
the participating countries.  Secondly, in government terms, 32 million is
not a lot, especially when you consider that the British government is
willing to spend 758M on the Millennium Dome - more than enough to pay for
the entire global surveillance programme twenty times over.
In fact, governments other than ours are taking the threat very seriously,
and things are beginning to happen abroad.  In the USA, NASA has announced a
doubling of its NEO budget, from $1.5 million per year to $million.  This
may still not be a lot, but at least it is a step in the right direction.
In Japan, the construction of a dedicated NEO/space debris search telescope
and a radar system has recently been announced, at a cost of 2 billion yen
(around $15 million).  In the UK, a proposal has been submitted to the
Particle Physics and Astronomical Research Council for 2 million to fit a
sophisticated CCD camera system to the UK Schmidt Telescope, which is
located at the Anglo-Australian Observatory.  The UKST is about to be
decommissioned, and donated to Australia.  However, used for surveillance,
this system would be the most powerful search tool in the world, and the
only one in the Southern Hemisphere.  Again, 2 million is a lot of money,
as is the 450,000 per year that it would cost to run, but when compared
with the actuarial cost (the cost of doing nothing, and accepting the
inevitable devastation) to the UK of 120 million per year (in lives only,
not property or heritage), it doesn’t seem so much!  The proposal has been
shelved.  The United Kingdom is doing nothing to protect itself from the
inevitable threat, but according to a government spokesman, “the Government’s
view is that the scale of action taken so far is commensurate with the
known threat”.  The current scale of action (none) can only mean that there
is no threat in the government’s view.
Spaceguard UK has been working with the scientific community for nearly two
years to persuade the “establishment” that the impact threat is real, and
deserves some action.  Our message is clear.  Asteroidal and cometary
impacts are rare, but are unlimited in their destructive potential.
However, one thing sets this potential catastrophe apart from other natural
disasters like earthquakes, volcanoes or floods – it is avoidable.
So far the message has fallen on deaf ears, despite the clarity of the data.
Nothing is likely to be done until one of two things happens – either a
major impact somewhere on the Earth, involving the massive loss of life
and/or property, or a groundswell of public concern over the government’s
lack of responsible action.
“Deep Impact” is going to bring the threat of cosmic impacts into sharp
relief, so help us to persuade the government to face up to their
responsibilities and to do something about it.  Write to your local MP,
requesting a statement of his or the government’s policies on the impact
threat (contact Spaceguard UK for a draft letter if you wish).  Do not be
fobbed off by talk of ESA contributions (that was worth 5928.57p), “plans
made by the emergency planning community” (there are none for the scale of
potential damage), or claims that this is an international problem that can
only be dealt with by international bodies (other countries are forging
ahead with national programmes that all contribute to the international
effort).  We at Spaceguard UK would be most interested to hear about any
replies that you may receive.

Next Issue

In the next issue, I hope to publish an up to date membership list.  It does
not appear in this issue due to something of a "surge" in membership that
would render any list out of date within a day of printing.


From Andrea Milani Comparetti <>

Dear Dr. Tate,

Yes, I am willing to become a Visiting member of Sapceguard UK. Although,
as you can imagine, I can not take very strict commitments, I am willing
to contribute, at least with my advice,  to your work and public action,
since it is not in my style to be a purely passive member of any society.
Thus, let me start now.

I have been appalled, in reading the Cambridge Conference mailings (which
are otherwise very useful), by the lack of attention to the events concerning the
research on NEO which have taken place in Great Britain. First, the UK has
cancelled the actual effort to track NEO at the anglo-australian observatory; it
needs to be stressed that the recovery/follow up work done there was vital, as
the 1997 XF11 event (where the opportunity to improve the orbit by finding
observations at another opposition was critical) should have taught. Among the
disgusting results of this insane decison, D. Steel has been fired and there is
now no NEO search/follow up telescope in the southern hemisphere. 

More recently I understand that the British government is threatening once more
the dissolution of the Nautical Almanac Office; Andrew Sinclair has now been
pushed to early retirement. I know that the people interested in the NEO threat
are inclined to give more value to the observational work rather than to
computations, but they are wrong. There is no purpose in being able to collect
data if the culture and know how for processing them is not available; the
process leading from raw observations to asteroid/comet orbits, and to assessment
of risk, is far from trivial. Just to collect data without understanding them,
and then  sending the raw data to some processing center overseas, is not really
taking part in the research on NEO. Now A. Sinclair is (was?) the leading UK
expert of orbit determination for celestial bodies, with a precious experience
not inferior to the one of B. Marsden; if anything, if Brian does not take
offence, I would say that the experience of A. Sinclair was broader in scope,
since he has also been in charge of processing the satellite laser ranging data,
including the one of the UK station (which is now left useless, since who is
going to use the data)? And this is happening in Cambridge; I believe it would be
appropriate  for a mailing list referring even in the name to Cambridge to take
notice of what is happening at home!
This, in my opinion, should replace a little bit of the 'bash the americans'
attitude which has been common in the public statements of both you and B.
Peiser. The americans are hatefully arrogant, NASA wants to control everything,
this is true, but they are doing it: something like 95% of the present effort to
detect hazardous NEO's is done in the USA and with US taxpayer dollars. If we
want the Spaceguard Survey to be truly international in nature, it is our
responsability to be up to the challenge, and yes, maybe even defy the americans
on their own ground by attempting to be competitive with them in our research. If
we fail to do this, our statements on what they should do appear frankly useless,
and  the UK involvement will be represented by the idiotic statement by one UK
junior minister, to the effect that in case a 1 mile asteroid hits the Earth, the
UK government will then take appropriate action (given the long standing
tradition of the UK government in preparations for the nuclear war, as reported
in D. Campbell's "War plan UK", this probably means keeping law and order so that
people can die in a an orderly fashion).     

Having requested action from others, I feel it is my duty to show what I am
personally doing to improve the situation. I have just completed a paper (with
G.B. Valsecchi) to reassess the 1997 XF11 case, and more to the point to make
sure that we are not caught imprepared by another similar event which sooner or
later will return.  The paper is available in my preprint home page at

the last paper which I was mentioning is at  (HTML) (PostScript)

Both the paper and the free software announced therein are recommended  to those
wishing to maintain, and even reintroduce after the destructive action of the
british governments, the capability to understand the problems posed by the NEO
threat in the UK. Frankly, I would have liked more the partecipation to the
intense debate on 1997 XF11 by people who could claim to have performed their own
computations, rather than being just willing to argue about other people's work.
The availability of free software, distributed on internet, allowing to compute
asteroid orbits (with an estimation of the uncertainty), and even to analyse in
real time the impact risk, should be considered a step in the right direction.

Sincerely yours

Andrea Milani

Andrea Milani
Dipartimento di Matematica
Via Buonarroti 2

tel. +39-50-844254 fax +39-50-844224

From Duncan  Steel <> wrote:

Dear Benny,

I note the interesting message from Ted Bryant of the University of Wollongong
regarding recent (on the geological and astronomical time-scales) tsunamis
afflicting the coasts of Australia.  Of course members of this list
have previously been alerted to his interesting web pages on this topic.

I wonder how many readers have house and contents insurance policies which
mention tsunamis?  I do.  The policy DEFINES a tsunami as:

"An unusually high wave or series of high waves caused by an earthquake or
volcanic eruption."

Thus if there were an impact-induced tsunami (like that/those Bryant believes may
have occurred ~400 years ago) then the surviving residents of Wollongong, Sydney,
Newcastle, Brisbane, and all around the coasts of Australia and elsewhere, would
have no claim on the losses of their houses: the event would be due to neither
earthquake or volcano.


Duncan Steel


From Alan W. Harris <>

Dear Duncan,

RE. your note on naming Earth-interior asteroids, there already is one named
Adrastea, with the embarrassingly low number of 239.  Interesting suggestion,
none the less.




From Henrik Persson <> [as posted on the meteorite-list]

>      CNN Interactive

Hi Lew,

This is a mild exaggeration by the press, I believe. The Danish scientists
involved have stated that a relation between the December meteorite and the
meteoritic dust sampled from the ice is suspected but *not* confirmed.

For more information check the homepage of Tycho Brahe Planetarium at:

Unfortunately they are reconstructing their English pages right now, so
unless you understand Danish.....
However the link might come in handy, since the Planetarium organizes the
search expedition that leaves Copenhagen on July 22nd and probably will post
news here.

It is rumoured that Danish television (DR) will transmit a 5 minute status
report each day. My source has also mentioned negotiations between DR and
BBC and/or Discovery Channel, but I don't know the outcome. Sometimes DR
puts a program on the net. If this happens, I'll post the URL here.
In the meantime you can find the information DR has at:

Holger Pedersen, a member of the scientist team involved, maintains a
regularly updated site at:

On behalf of Copenhagen Astronomical  Society I maintain some pages at:
These pages are not updated anymore, but they contain some eyewitness
reports and drawings, if you have not seen them already.



M. Uchida*) M. Morikawa, H. Kubotani, H. Mouri: X-ray spectra of comets. 
ASTROPHYSICAL JOURNAL, 1998, Vol.498, No.2 Pt1, pp.863-870


X-rays from a comet have been discovered for the first time in C/Hyakutake by
Lisse et al. We discuss the excitation mechanism and the energy source of these
cometary X-rays. We compute the intensity and the spectrum of bremsstrahlung
X-rays and characteristic X-rays induced by nonthermal energetic electrons in the
coma Our results are compared with the X-ray data of C/Hyakutake, and the number
density and kinetic energy of the electrons are evaluated. The electron density
is found to be consistent with the in situ observation of P/Halley. The energy
flux required to generate the observed X-ray luminosity is well explained by the
solar-wind power falling on the coma. Hence, we suggest that the nonthermal
electrons accelerated by the interaction of the comet with the solar wind are
responsible for the X-ray emission. Copyright 1998, Institute for Scientific
Information Inc.


J.A. Frogel & A. Gould: No death star - For now. ASTROPHYSICAL JOURNAL, 1998,
Vol.499, No.2 Pt2, pp.L219-L222


A star passing within similar to 10(4) AU of the Sun would trigger a comet shower
that would reach the inner solar system about 0.18 Myr later. We calculate an a
priori probability of similar to 0.4% that a star has passed this close to the
Sun but that the comet shower has not yet reached the Earth. We search the
Hipparcos catalogue for such recent close-encounter candidates and, in agreement
with Garcia-Sanchez et al., find none. The new result reported in this Letter is
an estimation of the completeness of the search. Because of the relatively
bright completeness limit of the catalogue itself, V similar to 8, the search is
sensitive to only about half the stars that could have had such a near encounter.
On the other hand, we show that the search is sensitive to nearly all of the past
encounters that would lead to a major shower in the future and conclude that it
is highly unlikely that one will occur during the next 0.5 Myr. Copyright 1998,
Institute for Scientific Information Inc.

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