PLEASE NOTE:


*

CCNet DIGEST, 12 May 1998
-------------------------

(1) MINOR BODY PRIORITY LIST
    Sormano Astronomical Observatory <sormano@tin.it>

(2) ON THE AIRBURST OF LARGE METEOROIDS IN THE ATMOSPHERE
    Luigi Foschini <L.Foschini@fisbat.bo.cnr.it>

(3) DISCOVERY OF MAJOR IMPACT HORIZON AT THE EOCENE-OLIGOCENE
    BOUNDARY
    O. Pierrard et al., CEA, CNRS, France

(4) DIAMOND-BEARING IMPACTITES
    V.L. Masaitis, KARPINSKY GEOLOGICAL INSTITUTE, ST PETERSBURG

(5) THE LUNAR IMBRIUM IMPACT EVENT
    L.A. Haskin, WASHINGTON UNIVERSITY

(6) SMALL IS BEAUTIFUL, OR HOW TO SURVIVE THE K/T IMPACT EVENT
    H. Mai et al., UNIVERSITY OF BREMEN

(7) COMPARATIVE STRATIGRAPHY AT THE K/T/ BOUNDARY
    Z.C. Song & F. Huang, ACADEMIA SINICA, CHINA

(8) THE K/T BOUNDARY IN THE SOUTHERN PYRENEES (SPAIN)
    N. Lopez Martinez et al., UNIVERSITY COMPLUTENSE MADRID


========================
(1) MINOR BODY PRIORITY LIST

From Sormano Astronomical Observatory <sormano@tin.it>

Dear Dr. Peiser,

we include here a message that we would like to be distributed through
your CCNet mailing list. Thank you for your attention and your work.

Best regards

Piero Sicoli and Francesco Manca (sormano@tin.it)

-----
Subject: Minor Body Priority List

Within the framework of the activity that is performed in our
observatory in connection with The Spaceguard Foundation, we have
prepared a list of minor bodies for which observations and/or
identifications are most desirable, because hazardous close encounters
with our planet can be predicted or at least (taking into account the
present uncertainty of orbital elements) cannot be entirely ruled out
(over a timespan of the order of one hundred years).

We have selected the objects on the basis of their MOID (Minimum
Orbital Intersection Distance) and have computed their close approaches
with the Earth over a time interval spanning one century in the past
and two centuries in the future.

The results are available at our homepage
(http://www.brera.mi.astro.it/sormano/mbpl.html)

Piero Sicoli and Francesco Manca
Sormano Astronomical Observatory (sormano@tin.it)
MPC code 587

=========================
(2) ON THE AIRBURST OF LARGE METEOROIDS IN THE ATMOSPHERE

From Luigi Foschini <L.Foschini@fisbat.bo.cnr.it>

Dear Friends and Colleagues,

I would like to inform you that at the xxx Eprint server
(http://xxx.lanl.gov/) a preprint on a reanalysis of the "Lugo" bolide
of January 19, 1993, is now available:

L. Foschini: On the airbursts of large meteoroids in the Earth's
atmosphere, eprint astro-ph/9805124.

ABSTRACT: On January 19, 1993, a very bright bolide (peak magnitude -23)
crossed Northern Italy, ending with an explosion approximately over the
town of Lugo (Emilia Romagna, Italy). The explosion (14 kton) generated
shock waves that were recorded by six local seismic stations. A
reanalysis of collected data allows us to hypothesize that the
meteoroid was a porous carbonaceous chondrite somehow like the asteroid
253 Mathilde. (41kb)

Comments are welcome. 
Thank you very much for your attention.

Cordially,
Luigi Foschini

CNR - Institute FISBAT
Via Gobetti 101, I-40129 Bologna (Italy)
tel. +39 51 639.9620/9622; fax  +39 51 639.9654
E-mail: L.Foschini@fisbat.bo.cnr.it
WWW: http://www.fisbat.bo.cnr.it/homepp/dinamica/foschini.html

=========================
(3) DISCOVERY OF MAJOR IMPACT HORIZON AT THE EOCENE-OLIGOCENE
    BOUNDARY

O. Pierrard*), E. Robin, R. Rocchia & A. Montanari: Extraterrestrial
Ni-rich spinel in upper Eocene sediments from Massignano, Italy.
GEOLOGY, 1998, Vol.26, No.4, pp.307-310.

*) CEA, CNRS, LAB MIXTE, CTR FAIBLES RADIOACT, F-91198 GIF SUR
YVETTE, FRANCE

Evidence of a major cosmic event at the end of the Eocene is given by
the finding of at least one, possibly two or more, impact horizons
containing microtektites, microkrystites, shocked quartz, and
unusually high iridium concentrations. We report here the discovery,
in the global stratotype of the Eocene-Oligocene boundary at
Massignano in Italy, of Ni-rich spinel, a mineral that forms by the
interaction of meteoritic bodies with the Earth's atmosphere. A
maximum concentration of approximate to 800 crystals mg(-1),
corresponding to a flux of 2 x 10(7) crystals cm(-2), is observed in
a well-dated layer (35.7 +/- 0.4 Ma) that also contains shocked
quartz and iridium. The crystals are found clustered in flattened
spheroids, the probable relic of their host bodies. The chemical and
physical characteristics of the spinel crystals indicate that the
spheroids formed by interaction of dust particles in the upper part
of the atmosphere rather than by ablation of large objects, as
proposed for the spinel-bearing spheroids found at the
Cretaceous-Tertiary boundary. The most likely explanation is that the
dust particles were generated by a large cometary impact. Whether
this impact is the one that produced microtektites and/or
microkrystites, or another one that may have occurred shortly after
or before, is still questionable. Additional searching for Ni-rich
spinel at other upper Eocene sections may help to answer this
question. Copyright 1998, Institute for Scientific Information Inc.

===========================
(4) DIAMOND-BEARING IMPACTITES

V.L. Masaitis: Popigai crater: Origin and distribution of
diamond-bearing impactites. METEORITICS & PLANETARY SCIENCE, 1998,
Vol.33, No.2, pp.349-359

KARPINSKY GEOLOGICAL INSTITUTE, SREDNY PROSPEKT 74, ST PETERSBURG
199106, RUSSIA

About three decades ago, a formerly unknown genetic type of natural
diamonds was discovered in impact craters. Impact diamonds are
currently known from a number of impact structures in Europe, Asia and
North America, and it's likely that the number of finds will increase
with time. The Popigai crater, Northern Siberia, where impact diamonds
were first found, was specifically Investigated in terms of geology,
geophysics, petrography and mineralogy. Large resources of industrial
impact diamonds were discovered, and these minerals were studied in
detail. Authigenic impact diamonds occur in situ in shocked graphite-
bearing gneisses that are found as inclusions in impact melt rocks:
tagamites and suevites. According to the observed transformation of
coexisting minerals, the lower estimated pressure of the coherent
martensite transition of graphite to diamonds is 35 GPa. Impact
diamonds inherit the original shape of graphite crystals and are
composed of a polycrystalline structured aggregate of cubic and
probably hexagonal carbon microcrystals 1-5 mu m across. Numerous
properties of diamonds depend on the high density of defects in the
crystal lattice. Allothigenic impact diamonds occur in rocks produced
by the homogenization and solidification of impact melt, which
originated from the complete fusion of graphite-bearing precursor
gneisses. These diamonds usually reflect the influence of the hot melt
and are strongly corroded. Diamond-bearing tagamites and suevites in
the Popigai crater interior occur as extended lens and sheets bodies
and also as irregular small bodies. Diamond distribution depends on the
original abundance of precursor graphite in the target rocks, on the
superimposed shock-metamorphic zonation, and on the character of the
ejection of shocked and melted material along different trajectories
and azimuths. This has resulted in radial and concentric
inhomogeneities in diamond distribution in the crater interior. On a
second order, the distribution depends on the scale of melt
contamination by clasts and fragments and by the duration of cooling of
certain melt bodies and their constituents. Enrichment in diamonds at
the margins of thick tagamite sheets is the result of rapid cooling,
which prevents combustion of diamonds. A positive correlation between
diamond content and the amount of phosphorus pentoxide in impactites
indicates links to C and P probably in organic matter of the primary
sedimentary rocks, which were subjected to granulitic metamorphism 2.4
Ga ago and melted at the time of impact 35.7 Ma ago. Copyright 1998,
Institute for Scientific Information Inc.

========================
(5) THE LUNAR IMBRIUM IMPACT EVENT

L.A. Haskin: The Imbrium impact event and the thorium distribution at
the lunar highlands surface. JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS,
1998, Vol.103, No.E1, pp.1679-1689

WASHINGTON UNIVERSITY,DEPARTMENT OF EARTH & PLANETARY SCIENCES, CAMPUS
BOX 1169, 1 BROOKINGS DR, ST LOUIS, MO, 63130

Late in the Moon's heavy bombardment period, the impact that formed the
Imbrium Basin excavated and melted a tremendous volume of material that
was subsequently distributed over most of the Moon's surface. The
Apollo orbiting gamma ray experiments [Metzger et al., 1977] show that
the Imbrium projectile struck in a Th-rich area, called the High-Th
Oval Region here and regarded as a unique lunar geochemical province.
Imbrium primary ejecta were thus probably rich in Th. It is shown here
using ejecta deposit modeling that the distribution of Th in the
highlands surface along the ground tracks of the gamma ray
spectrometers is consistent with the distribution expected for Imbrium
ejecta deposits. Deep basins other than Imbrium appear to have
excavated regions of lower crust that were mafic and Fe-bearing but not
Th-rich. The possibility that the surface Th distribution arises mainly
from Imbrium ejecta has implications for the nature of the Moon's
igneous differentiation and the nature of the proposed 'cataclysm' or
late bombardment with large meteoroids. Copyright 1998, Institute for
Scientific Information Inc.

=========================
(6) SMALL IS BEAUTIFUL, OR HOW TO SURVIVE THE K/T IMPACT EVENT

H. Mai*), K.V. Perch Nielsen, H. Willems, T. Romein: Fossil
coccospheres from the K/T boundary section from Geulhemmerberg, the
Netherlands. MICROPALEONTOLOGY, 1997, Vol.43, No.3, pp.281-302

*) UNIVERSITY OF BREMEN, DEPARTMENT OF GEOLOGY, KLAGENFURTER STR, D-
   283539 BREMEN,GERMANY

The recent discovery of well preserved, complete spheres of
Biantholithus sparsus in a clay layer from the K/T boundary interval
in the Geulhemmerberg section resulted in a search for coccospheres
of other taxa. Applying the same new preparation-and SEM techniques,
coccospheres of over 30 Cretaceous and Tertiary species were found;
they are illustrated and briefly described in this paper. Based on
the excellent state of preservation of the coccospheres of several
Cretaceous species it is suggested that they survived the K/T
boundary event(s). Copyright 1998, Institute for Scientific
Information Inc.

=============================
(7) COMPARATIVE STRATIGRAPHY AT THE K/T/ BOUNDARY

Z.C. Song & F. Huang: Comparison of palynomorph assemblages from the
Cretaceous/Tertiary boundary interval in Western Europe, northwest
Africa and southeast China. CRETACEOUS RESEARCH, 1997, Vol.18, No.6,
pp.865-872

ACADEMIA SINICA, NANJING INSTITUE OF GEOLOGY & PALAEONTOLOGY, NANJING
210008, CHINA

The composition of palynomorph assemblages from selected sections
through the Cretaceous/Tertiary (K/T) boundary interval in Western
Europe, northwest Africa and China is discussed. Similarities are
emphasised and widespread trends noted, including the evolutionary
development of the porate group of pollen grains, palynomorph
extinctions within the boundary interval, and links with a climatic
cooling trend. The comparative analysis revealed numerous taxonomic
and; nomenclatural problems, as a list of 71 forms recorded from five
papers on European and North African topics demonstrates. These taxa
are considered to be similar or identical to palynomorphs documented
in four Chinese papers, despite the fact that almost all of the
identifications differ at either generic or specific level, or both.
(C) 1997 Academic Press Limited.

======================
(8) THE K/T BOUNDARY IN THE SOUTHERN PYRENEES (SPAIN)

N. Lopez Martinez*), L. Ardevol, M.E. Arribas, J. Civis, A. Gonzalez
Delgado: The geological record in non-marine environments around the
K/T boundary (Tremp formation, Spain). BULLETIN DE LA SOCIETE
GEOLOGIQUE DE FRANCE, 1998, Vol.169, No.1, pp.11-20

*) UNIVERSITY COMPLUTENSE MADRID, DEPARTMENT OF GEOLOGY, E-28040
   MADRID, SPAIN

In the Ager basin and Benabarre area (southern Pyrenees, Spain), the
Cretaceous-Tertiary (K/T) boundary is recorded in a succession of
non-marine to coastal deposits (Lower Tremp Formation). Abundant
diverse dinosaur tracks have been found at two localities on top of
an estuarine sandstone body. A few meters above, grey marls at two
localities contain Palaeocene mammals and fish. Both levels are
correlated with the latest part of chron C29R. These data have led to
the location of the K/T boundary within a 3 m thick stratigraphic
interval with no major breaks in the sedimentation. A rapid fall in
delta(13)C content is recorded shortly after the KT boundary. The
delta(13)C curve does nor support the hypothesis of a gradual shift
due to volcanic activity. Both fossil vertebrates and isotope data
are compatible with an abrupt change in the continental ecosystems
close to the K/T boundary. Copyright 1998, Institute for Scientific
Information Inc.

----------------------------------------
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*

DEEP IMPACT SPECIAL: REVIEWS, COMMENTS AND SUGGESTIONS
-------------------------------------------------------

(1) NATIONAL SPACE SOCIETY AND CREATORS OF "DEEP IMPACT" ANNOUNCE
    CAMPAIGN TO COLLECT ONE MILLION NAMES FOR COMET MISSION
    Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>

(2) ASTEROIDS, COMETS AND COSMIC DISASTERS IN GENRE FILMS: 1951-1998
    Steve Koppes <SKoppes@aol.com>

(3) ONLINE REVIEWS OF DEEP IMPACT
    Phil Burns <pib@nwu.edu>

(4) VARIOUS REVIEWS OF DEEP IMPACT [Morrison, Cowing, Chapman, Durda]
    David Morrison <david.morrison@arc.nasa.gov>

(5) ESTIMATED MAY 8-10 GROSS FOR DEEP IMPACT IN US CINEMAS
    David Morrison <david.morrison@arc.nasa.gov>

(6) FIVE % OF DEEP IMPACT OFFICE TAKE SHOULD BE DONATED FOR    
    IMPROVED NEO SEARCHES
    Greg Bear <grbear@ix.netcom.com>

(7) A LETTER TO 100 NEWSPAPERS AROUND THE WORLD
    Michael Martin-Smith <martin@miff.demon.co.uk>

(8) JUPITER SCIENTIFIC REPORT ON THREATS FROM HEAVEN

From Victor D. Noto" <vnn2@phoenixat.com>


=======================
(1) NATIONAL SPACE SOCIETY AND CREATORS OF "DEEP IMPACT" ANNOUNCE
CAMPAIGN TO COLLECT ONE MILLION NAMES FOR COMET MISSION

From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>

Contact:  Karen Rugg
National Space Society
202-543-1900, ext. 77

Warren Betts
Paramount Pictures
310-479-1305

NATIONAL SPACE SOCIETY AND CREATORS OF "DEEP IMPACT" ANNOUNCE CAMPAIGN
TO COLLECT ONE MILLION NAMES FOR COMET MISSION
Public invited to go to <http://www.nss.org/impact> to "Make an IMPACT"

(Washington, DC) -- May 7 -- The National Space Society, along with
Paramount Pictures and DreamWorks Pictures, today announce a joint
online campaign to collect one million names to be placed on board a
spacecraft that will intercept an actual comet.  The campaign, "Make an
IMPACT," is being launched in time for tomorrow's nationwide release of
the film, "DEEP IMPACT," and will continue through the summer or until
the one million mark is met.

The spacecraft, STARDUST, is being prepared for launch by NASA and the
Jet Propulsion Laboratory to intercept Comet Wild-2, collect samples
and return to Earth. The names will be printed onto a microchip to be
placed aboard the craft later this year. Already on the chip are the
names of every member of the National Space Society, and the names of
the cast and crew of "DEEP IMPACT."  Names can be submitted by going to
the National Space Society website at nss.org/impact or to the film's
website at deep-impact.com.

"We are firm believers in the idea that, today, fact can be as
spellbinding as fiction," said Ms. Pat Dasch, executive director for
the National Space Society. "In this case, a film tells a fictional
story of an impending comet collision while, in fact, NASA and JPL are
preparing a craft to intercept a comet and learn more about it. We are
very pleased to be partnering with Paramount on this project; with a
one million name goal, we're committed to making a real 'impact.'"

The National Space Society is also producing a slide set for educators
on comets and asteroids, featuring text prepared by leading scientists.
The set will include several images from "DEEP IMPACT."

The National Space Society, founded in 1974, is an independent,
nonprofit space advocacy organization headquartered in Washington, DC. 
Its 23,000 members and 90 chapters around the world actively promote a
spacefaring civilization. Information on NSS and space exploration is
available at <http://www.nss.org/>.

"DEEP IMPACT" is a contemporary action thriller about the chaos that
ensues when it is discovered that a comet is on a deadly collision
course with the Earth. DreamWorks Pictures and Paramount Pictures
present "DEEP IMPACT," a Zanuck/Brown production, directed by Mimi
Leder. The executive producers are Oscar-winner Steven Spielberg, Joan
Bradshaw and Walter Parkes. The film is written by Michael Tolkin and
Bruce Joel Rubin.  DreamWorks SKG is a multi-faceted entertainment
studio formed in October 1994 by Steven Spielberg, Jeffrey Katzenberg
and David Geffen.  Paramount Pictures is part of the entertainment
operations of Viacom Inc.

======================
(2) ASTEROIDS, COMETS AND COSMIC DISASTERS IN GENRE FILMS: 1951-1998

From Steve Koppes <SKoppes@aol.com>

On this opening weekend for "Deep Impact," I'd like to take a few
moments to remember some of the more obscure movies of the genre.

Last week David Morrison gave us a technical-accuracy appraisal of "A
Fire in the Sky" (1978), "Meteor" (1979), "Asteroid" (1997), "Deep
Impact" (1998) and "Armageddon" (1998), while also mentioning "When
Worlds Collide" (1951). And last summer Phil Burns reviewed "Doomsday
Rock" (1997) for us. But I know of at least six other movies of this
type: "The Day the Sky Exploded" (1958), "On the Comet" (1970), "Night
of the Comet" (1984), "Without Warning" (1994), "Within the Rock"
(1996), and "Falling Fire" (1997).

"The Day the Sky Exploded" was a French-Italian production. This is the
darkest film I have ever seen (I'm talking lighting here, not mood).
The first man in space, riding a nuclear-powered rocket to the moon,
experiences a malfunction. He aborts his mission and ditches his
rocket, which blows up, sending a cluster of asteroids toward Earth.
The Earth is saved when, in an international, coordinated effort, all
the militaristic nations of Earth destroy the oncoming asteroid swarm
in a barrage of nuclear (and conventional!?) missiles.

I haven't seen "On the Comet," but it is based on Jules Verne's "Off On
a Comet" (1877). In this one, a comet explodes on the shores of
northern Africa, knocking a substantial chunk of land and its surviving
inhabitants into space.

"Night of the Comet" is one of my all-time favorite films. It's a
comedy that can get away with all kinds of absurdity because it

obviously doesn't take itself seriously. If I remember correctly, the
comet doesn't actually collide with Earth. Rather, the Earth passes
through its tail, which reduces those not properly protected into a
dehydrated pile of chemicals. Among the survivors are two sisters in
Los Angeles, valley girls, who prevail over zombies, evil scientists,
and then, apparently, live happily ever after with their new-found
boyfriends.

"Without Warning" was a TV movie that aired the night before Halloween,
1994. The movie was intended to have the same feel that led millions of
people to believe that Orson Welles' "War of the Worlds" radio
presentation on Halloween, 1938, was real. Real-life TV reporter Sander
Vanocur appears in this one, along with Ed Marinaro, the former NFL
football player who also would star in "Doomsday Rock."  Also appearing
briefly was U.S. Representative George Brown of California, the
chairman of the House Science, Space and Technology Committee. This
time it's asteroids, not comets, raining down on Earth. I rather
enjoyed this one until it turned out that aliens were sending the
asteroids as part of their strategy to take over the world.

"Within the Rock" aired on the Sci-Fi Channel. Again my memory may be a
bit hazy, but an asteroid is headed for Earth. A crew of miners are
sent to remove enough of the asteroid's mass to deflect its course.
Their mission is complicated by a predatory creature from another
galaxy who millions of years ago was subdued, encased in some solid,
high-tech material, then launched into space. Over the millennia the
creature's prison accretes an asteroid around it. The  miners have the
misfortune of exhuming and releasing the creature, which somehow
revives after millions of years encased in the rock. I rate this film
quite highly for its suspenseful plot. The miners have a deadline to
meet, but the creature keeps killing them off. Aside from the creature,
it's fairly accurate (as far as I can tell -- I'm a science writer, not
a scientist).

I can't say much about "Falling Fire" because I haven't seen it. It
appeared on the Movie Channel a few months ago. The newspaper listing
said it was about a spaceship officer who seeks a killer who is
murdering his crew and causing an asteroid to speed toward Earth.

By my count that's 13 movies, and I haven't even mentioned the TV shows
(Rocky Jones, Space Ranger: "Crash of the Moons" (1953), and "Bobby's
Comet (1954?), and Star Trek: "The Paradise Syndrome"  (1968).

Happy viewing.
Steve Koppes

=======================
(3) ONLINE REVIEWS OF DEEP IMPACT

From Phil Burns <pib@nwu.edu>

I have not yet seen DEEP IMPACT but there are a few reviews of the
movie's science now available online. David Morrison provides one at:

     http://impact.arc.nasa.gov/news/1998/may/05.html

Morrison's sobering observation that

   "It is interesting that the complete Spaceguard survey could be
    accomplished for the cost of either one of these films: Deep Impact or
    Armageddon."

should give everyone pause.

Randall Brooks, curator of physical sciences and space for the National
Museum of Science and Technology in Canada, offers another review at:

   http://www.ottawacitizen.com:80/entertainment/980508/1696666.html

Brooks ends his review by stating:

   "Fortunately, we will have to wait millions or tens of millions of
    years to get first-hand experience of the psychological and physical
    effects of an impending impact of the scale depicted in Deep Impact."

with which I would disagree. While the average time between impacts of
1-2 km objects may be a few hundred thousand (not millions) of years,
there is no reason why such an impact could not happen tomorrow, or next
week, or at any other time. This seems to me to be one of the most
difficult ideas to get across to the general public. That the -average-
elapsed time between impacts of a given size is a few hundred thousand years,
does not mean that the -actual- elapsed time between any two specific
impact events of a given size will ncessarily be a few hundred thousand
years.

-- Phil "Pib" Burns
   Northwestern University, Evanston, IL.  USA
   pib@nwu.edu
   http://pibweb.it.nwu.edu/~pib/

==========================
(4) VARIOUS REVIEWS OF DEEP IMPACT [NEO NEWS 5/11/98]

From David Morrison <david.morrison@arc.nasa.gov>

I saw Deep Impact twice this weekend, and I think it is terrific!
Unfortunately the two reviews I read were not very favorable, and both
took the position that the movie was too thoughtful and didn't have
enough action and special effects. I suppose those critics will prefer
Armageddon, which makes no sense but spent twice as much ($130M versus
$60M) on the production. This week I was filmed by ABC for a show they
will show in July dealing with the reality (?) behind Armageddon, and
they commented that the special effects were much better in Armageddon.
I can believe it. The special effects in Deep Impact are pretty good in
terms of realism, but probably below state-of-the-art in a purely
technical sense. For example, some of the computer-generated images
have slightly lower resolution that the photographic images. And I felt
the water often didn't look right; the big breaking waves are terrific,
but the water sloshing about over the landscape doesn't look much
better that the "crossing the red sea" scene from The Ten Commandments
in the pre-computer age.

NASA supported Armageddon, which asked to film at Kennedy Space Center,
but the Agency had little to do with Deep Impact. Former Johnson Space
Center Director Gerry Griffin is credited with technical advice and
appears briefly in the film, however. Deep Impact uses stock footage of
a Shuttle launch, and the mission control room set looks just right --
small and high-tech, consistent with current Agency efforts to shrink
operations staff and depend more on modern information technology in
running flight missions.

One can always nitpick the science, but in my opinion there is not one
serious error in this film -- nothing that damages its basic
credibility. There is a great deal left unsaid, and this is in fact an
understated film, so the audience is free to fill in the details in
part according to how much you know. For example, it seems as if the
astronauts get instantly to the comet, but it is entirely consistent
with the film to imagine that several months have passed -- they simply
don't say how long this flight takes. And the President uses some loose
language in describing the origin of the comet in terms of
billiard-balls in the Oort cloud, but in fact we can all easily imagine
a public official not quite getting it right technically. At least no
scientists or NASA officials in this film say anything incorrect.
(Actually they don't say much at all). Probably the most questionable
science comes at the beginning and the end. At the beginning the comet
is discovered with a small amateur telescope at a star party, but then
apparently not seen again for several months. This could be explained
in terms of the comet moving into the daylight sky, except for the
little matter of it appearing at discovery in Ursa Major, a north
circumpolar constellation. And at the end the 8-km diameter comet is
blown to smithereens by a nuclear charge of a few megatons that seems
way too small to do the job. The one other problem takes place on the
surface of the comet itself, which comes to life with strong outgasing
entirely too quickly after local sunrise. The idea is fine but the
realization greatly exaggerated. Other aspects of the comet are good,
especially the use of anchors to hold the spacecraft down in the
ultra-low gravity of the surface. And the overall framework of the film
is entirely plausible, from the perspective of planetary science as
well as the impact hazard.

Certainly this is much better science that any of the previous impact
films -- there is no idiocy of a comet knocking an asteroid into an
impact trajectory, or of small fragments getting through the atmosphere
and hitting individual buildings, or of impacts targeted precisely at
cities such as New York, Phoenix, or Dallas. The Deep Impact
film-makers took the trouble to find out what the real impact danger is
-- both from a tsunami due to a mile-wide impact into the ocean, and an
Extinction Level Event from a 10-km land impact. And the two-year lead
time for a comet discovery is also just about right. Gene and Carolyn
Shoemaker are listed as technical advisors in the credits, and they
should be proud!

I found that Deep Impact is very impressive, thoughtful, even moving.
It focuses in the entire middle section of the film on the reaction of
people to impending doom. The approach is often subtle, based on a
closeup of fingers nervously tapping, or an exchanged glance, or an
involuntary head movement. Morgan Freeman gives a sensitive portrayal
of the President, Tea Leoni draws our sympathy as a young reporter in
way over her head, and Robert Duval turns in one of his finest
performances as the old astronaut --  a hero without the histrionics.
One reviewer refers to Duval's projection of "simple goodness -- an
unclouded spirit". Unfortunately, it is the subtlety of the film that
was criticized in the reviews I read. I am reminded of last year's
Contact, which was also criticized as too cerebral by many reviewers,
who perhaps wanted to see aliens from Central Casting. One critic of
Deep Impact wrote that "director Mimi Leder focuses on the anguish,
fear and overwhelming grief that's provoked by an approaching
cataclysm. She couldn't have picked a harder trajectory for a season
when people mainly want to see things that go boom . . . maybe people
go to cataclysm movies for the cataclysm . . . the tidal wave seems
welcome when it arrives." Another review concluded as follows: "When
the tidal wave comes, its not a moment too soon. Still, when the comet
enters the atmosphere -- a yellow fireball across the sky -- its hard
not to feel just a bit excited that its coming. That they're all
coming. Armageddon, Godzilla, all of them".

See this film. It may do more to alert the thinking public to the
impact hazard than anything else in the past. And its images may even
keep you up at night wondering if we are doing enough to protect our
planet against this threat.

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

From Keith Cowing:

This movie deals with two impacts - the slow-to-build human impact of
realizing  that immutable oblivion will happen at a set date and time
and the swift and  awesome impact which occurs when planets and comets
collide.

Despite the blockbuster hype which  "Deep Impact" is being given, it is
actually a rather small story set against a huge backdrop - not unlike
"Titanic". Take the technology out of the picture and alter the source
of the impending disaster and the plot would still work. This movie is
not about things being blown to smithereens but rather about the
choices you make when you have the power to save someone else's life,
the way you spend your remaining days when the exact time of your death
is a certainty, and the legacy you relay to those who will survive.

Given Hollywood's chronic habit of violating the laws of physics, this
movie is a rather notable exception.  Speaking as a former NASA rocket
scientist, the technology is portrayed quite realistically, the
celestial scenery is done very well, and the cataclysmic effects of a
cometary impact are masterfully realized. This film also manages to use
subtle means of conveying titanic events - such as a fleet of ICBMs
exploding on a comet but having no effect on its trajectory.  You never
see it happen, you only see the disappointment on the president's face
and in his voice as he goes on TV to relay the bad news.

This movie is about a devastating cometary impact - you know that
walking in the theatre.  What amazes me is how a number of movie
critics who profess to know and seek out  good movies - and good story
telling - are critical of this movie because it "waits until the last
15 minutes" to deliver its punch. All I can say is that each of these
critics is showing that they too are suckers for special effects.  For
me, the plot build-up is what makes this movie's "impact" as powerful
as it is.

This movie is well worth seeing.  It allows you to place your own
existence in both a human and a cosmic perspective - something far too
few films ever allow you to do.

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

From Clark Chapman:

As a movie, we rate "Deep Impact" to be fairly good...about 7.5 on our
scale of 0 to 10. Scientifically, it was fairly good. There were
essentially no "dumb" mistakes, like those that proliferated during the
"Asteroid" miniseries. There were many things that weren't right, but
can be generously chalked up to "artistic license". Most seriously
wrong were:

* violent comet activity commences within seconds of "sunrise"

* dispersal of the larger comet fragment that close to Earth is represented
as a 4th of July-type fireworks display, rather than the deadly holocaust
it would have been

* the two comet fragments are seen in broad daylight as bright objects
weeks before impact

More forgivable, taking account of the simplification necessary for a
plot in a reasonable length movie, is the sudden orbit computation by
the astronomer in the dome (rather than Brian Marsden), omission of
other effects (besides tsunami) of the impact, apparent discovery of a
comet as bright as Mizar and Alcor that is then kept secret for a year,
the extremely tangential angle (and long time to traverse the
atmosphere) of the impacting comet fragment (and its lack of
brilliance), apparent failures to predict locations of impact earlier
(but after XF11, who knows?), and the extraordinary violence of the
comet (spitting boulders) but then who knows what a comet really looks
like?

Elements of the plot also strain credulity, from our informed
point-of-view.  Especially, I mean keeping secret the comet, the
construction of the space mission, and the construction of the caves in
Missouri.

But the movie was at least 100 times better than "Asteroid" and a
reasonable movie to watch by any standard. The Indianapolis newspaper
reporter I talked with yesterday (who had seen the preview with the paper's
movie critic) said "wait for the video". But the special effects in the
final minutes are worth seeing on the big screen.

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

From Dan Durda:

I enjoyed the movie as well. They got enough of the major science so
right that I can overlook the nit-picky errors as dramatic or artistic
license. I think it might be worth sharing with our colleagues that we
might consider emphasizing the following as we talk with the public
about the movie: for the price of making the movie, we could survey to
completeness within a couple decades the near-Earth environment for objects
which might pose a global catastrophe. (Granted, it wouldn't help much
for the problem of long-period comets, presumably the scenario of the
movie, but...) If people enjoyed the movie and were moved to think a
little more about the scenario, would they be willing to spend the
price of admission to better understand and prevent the real thing?

=====================
(5) ESTIMATED MAY 8-10 GROSS FOR DEEP IMPACT IN US CINEMAS

From David Morrison <david.morrison@arc.nasa.gov>

The following information on Deep Impact is from Steve Ostro:
------------------------------------------------
Estimated May 8-10 gross in North American theaters:

1.  Deep Impact    $41.9 million  (3156 theaters)
2.  City of Angels   4.7 million
3.  He Got Game      3.8 million
4.  Titanic          3.0 million
5.  Les Miserables   2.7 million

Deep Impact posted the highest-ever pre-Memorial Day single-weekend
gross, beating Twister ($41.1 million in 1996). It also accounted for
more than half of the weekend's total.
------------------------------------------------

I (Morrison) note that this means nearly 7 million people have already
seen Deep Impact.  I wonder what impact it had on them.  Also I must
add that with a little extrapolation, the first week's gross from Deep
Impact would be enough to implement the Spaceguard Survey (detectors
and operations for 10 years), assuming availablility of the USAF GEODSS
telescopes.

David Morrison

===========================
(6) FIVE % OF DEEP IMPACT OFFICE TAKE SHOULD BE DONATED FOR    
    IMPROVED NEO SEARCHES

From Greg Bear <grbear@ix.netcom.com>

Just saw DEEP IMPACT with my son this morning. A very effective
film--beautifully made and at least acceptable on the technical level.
(The last shotgun blast impact does seem extremely underrated, of
course, in terms of destruction--would probably cook one side of the
Earth!)

I suggested in a NY NEWSDAY opinion piece last year that perhaps
Dreamworks SKG should donate five percent of the box office take for
improved sighting and tracking... No announcement yet from them!

Greg Bear

========================
(7) A LETTER TO 100 NEWSPAPERS AROUND THE WORLD

From Michael Martin-Smith <martin@miff.demon.co.uk>

Meanwhile last night, Spielberg's DEEP IMPACT is opening, with a piece
on News at Ten last night, featuring an interview with Spaceguard-UK's
founder, Jay Tate. Trevor MacDonald, although anxious not to be a scare
monger, gave due weight to the magnitude of the disaster which would
result from an actual hit. I have sent a letter to 100 newspapers world
wide, in severral different languages, making the case that the true
lesson form this newly discovered thrweat is NOT counter attck with
nuclear  weapons, but orderly human dispersal into Space utilizing these
same potential inpactors to our own profit

For the moment a radical idea, but one which I intend to make widely
accepted within 10-15 years . The exploration of Space is a matter of
scientific and intellectual interest- its development and colonization
is an evolutionary necessity! If we work to put communities into Space,
the space probes will come easily and cheaply enough. The Lifespan of
an advanced civilization is now beyond doubt inversely proportional to
the cost of Space travel! For interst, my letter appears below!

Re:- "Deep Impact"

Dear Editor,

Mr Spielberg's film, "Deep Impact", shows  the disastrous potential of
an impact on Earth by a comet or asteroid - indeed, it is most likely
an understatement. The end of civilization, perhaps Humanity, would
most likely result. Events like "Deep Impact", or greater, have
occurred often in Earth's history, and will happen again.

Detection by dedicated telescopes and  compositional study by space
probes is essential reconnaissance  and should be established without
delay. Despite this, some will give us months' warning at best, and so
are not amenable to Earth based nuclear strikes. Lunar based lasers
could react more rapidly , but the only true insurance for Humanity is
the timely development and settlement of Space by self sustainable
populations, supported from these same threatening asteroids and
comets. It is wiser to consume an enemy for profit than to destroy him.
Impact is the only disaster threat offering such a huge potential
pay-off!

We can and should move out into the new ecological niche before us.
Those who question the value of Human Intelligence and science now 
have a clear  answer; we exist to take Life and Mind out into Space, as
surely as lions exist to eat wildebeestes - or face deserved
extinction!

Yours sincerely,

Dr Michael Martin-Smith,BSc,MRCGP,FBIS President, Space Age Associates,
http://www.astronist.demon.co.uk/index.html
Spaceguard-UK  http://dspace.dial.pipex.com/town/terrace/fr77/

=========================
(8) JUPITER SCIENTIFIC REPORT ON THREATS FROM HEAVEN

From Victor D. Noto" <vnn2@phoenixat.com>

Jupiter Scientific Reports on Threats from Heaven: Dangers to Earth
from Solar System Debris at
http://ajanta.sci.ccny.cuny.edu/~jupiter/pub/sciinfo/impact.html.
Foregoing is an Interesting read. Would like your opinion on this
report.

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