PLEASE NOTE:
*
CCNet DIGEST 13 July 1998
-----------------------------------------
(1) FRENCH CONVINCINGLY CORRECT ENGLISH IMPACT PREDICTION
Alain Maury <maury@obs-azur.fr>
(2) SPACEGUARD UK
Jonathan TATE <fr77@dial.pipex.com>
(3) DON'T BE CRUEL TO AMERICANS
Andrea Milani Comparetti <milani@copernico.dm.unipi.it>
(4) TSUNAMI INSURANCE
Duncan Steel <dis@a011.aone.net.au>
wrote:
(5) ASTEROID 239 ADRASTEA
Alan W. Harris <awharris@lithos..jpl.nasa.gov>
(6) GREENLAND IMPACT
Henrik Persson <henrikp@image.dk> [as
posted on the meteorite-list]
(7) X-RAY SPECTRA OF COMETS
M. Uchida et al., OCHANOMIZU UNIVERSITY,
JAPAN
(8) NO DEATH STAR - FOR NOW
J.A. Frogel & A. Gould, OHIO STATE
UNIVERSITY
==================
(1) FRENCH CONVINCINGLY CORRECT ENGLISH IMPACT PREDICTION
From Alain Maury <maury@obs-azur.fr>
1982 Italy
1978 Argentina Argentina 1986
1974
Germany
Germany 1990
1970
Brazil
Brazil 1994
1966
England
FRANCE !!! 1998
Sorry. Couldn't resist.
Alain
================
(2) SPACEGUARD UK
From Jonathan TATE <fr77@dial.pipex.com>
INTRODUCTION TO IMPACT 4
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
leaders!
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
_________________________________________________________________
DEEP IMPACT – MYTH OR REALITY?
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
predictable).
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
occurs.
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.
=======================
(3) DON'T BE CRUEL TO AMERICANS
From Andrea Milani Comparetti <milani@copernico.dm.unipi.it>
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
http://copernico.dm.unipi.it/~milani/preprints/preprint.html
the last paper which I was mentioning is at
http://copernico.dm.unipi.it/~milani/ident3/
(HTML)
http://copernico.dm.unipi.it/~milani/preprints/ident3.ps.gz
(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
56127 PISA ITALY
tel. +39-50-844254 fax +39-50-844224
E-mail: milani@dm.unipi.it
WWW: http://virmap.unipi.it/~milani/homemilani.html
================================================
(4) TSUNAMI INSURANCE
From Duncan Steel <dis@a011.aone.net.au>
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.
Regards,
Duncan Steel
==========================
(5) ASTEROID 239 ADRASTEA
From Alan W. Harris <awharris@lithos..jpl.nasa.gov>
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.
Cheers,
Al
====================
(6) GREENLAND IMPACT
From Henrik Persson <henrikp@image.dk>
[as posted on the meteorite-list]
>(1) GREENLAND IMPACT ZONE OF GIANT METEORITE CONFIRMED
> CNN Interactive
> http://cnn.com/TECH/space/9807/08/metorite.dust/index.html
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:
http://www.astro.ku.dk/tycho/tbe98/english/
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:
http://www.dr.dk/ddr/color/meteor/eng/meteor.htm
Holger Pedersen, a member of the scientist team involved,
maintains a
regularly updated site at:
http://www.astro.ku.dk/~holger/
On behalf of Copenhagen Astronomical Society I maintain
some pages at:
http://www2.dk-online.dk/users/hpersson/meteor/meteor.htm
These pages are not updated anymore, but they contain some
eyewitness
reports and drawings, if you have not seen them already.
greetings
Henrik
================
(7) X-RAY SPECTRA OF COMETS
M. Uchida*) M. Morikawa, H. Kubotani, H. Mouri: X-ray spectra of
comets.
ASTROPHYSICAL JOURNAL, 1998, Vol.498, No.2 Pt1, pp.863-870
*) OCHANOMIZU UNIVERSITY, DEPT PHYS, BUNKYO KU, TOKYO 112, JAPAN
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.
===================
(8) NO DEATH STAR - FOR NOW
J.A. Frogel & A. Gould: No death star - For now.
ASTROPHYSICAL JOURNAL, 1998,
Vol.499, No.2 Pt2, pp.L219-L222
OHIO STATE UNIVERSITY, DEPT ASTRON, SMITH LAB 5040, 174 W 18TH
AVE,COLUMBUS, OH,
43210
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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