PLEASE NOTE:
*
CCNet 97/2000 - 28 September 2000
---------------------------------
"Ah well, without 1997 XF11, where
would we be today? Would NASA have
established its NEO Office and increased its NEO funding? Would
we have LINEAR and
Spaceguard initiatives around the world? And finally, and more to
home, would both
Houses of Parliament have debated the impact hazard and would the
UK Government,
subsequently, have set up the NEO Task Force; indeed, would we
have the NEO Task
Force Report without the XF11 Affair? I somehow doubt it.
-- Benny J Peiser
(1) LIFE-ON-MARS HOPES DENTED BY METEORITE CONTAMINATION
SpaceDaily, 27 September 2000
(2) WORSENING URBAN AIR POLLUTION WON'T INCREASE GLOBAL
TEMPERATURE OVER
NEXT 100 YEARS
Ketrina Jackson <kjackson@nsf.gov>
(3) A GLOBAL TSUNAMI IN 200 AD?
D.J. Lowe & W.P. de Lange
(4) NATURE AND DESTRUCTION OF THE TUNGUSKA COSMICAL BODY
V.A. Bronshten
(5) RE-EVALUATION OF THE CAUSE & LOCALIZATION OF THE LATE
LUNAR BOMBARDMENT
G. Arrhenius & A. Lepland
(6) NEW 2.5 KM IMPACT STRUCTURE DISCOVERED IN NW AUSTRALIA?
J.D. Gorter & S.W. Bayford
(7) CAN SELF-ORGANISED TUNGUSKAS PREVENT THE BIG ROCK?
B.D. Malamud & D.L. Turcotte
(8) NATURAL HAZARDS: SOCIOPOLITICAL AND HUMANITARIAN
CONSIDERATIONS
J.V. Smith
(9) MICKEY MOUSE SCIENCE:
HOW WALT DISNEY'S ACCOUNT OF THE XF11 AFFAIR
IS FOSTERING AN URBAN MYTH
Benny J Peiser <b.j.peiser@livjm.ac.uk>
(10) 1946 TSUNAMI
Michael Paine <mpaine@tpgi.com.au>
(11) MEA CULPA!
Phil Plait <badastro@badastronomy.com>
(12) INVENTION OF IMPACT CRATERING
Duncan Steel <D.I.Steel@salford.ac.uk>
(13) MOON HAS SQUARE CRATERS TOO
Ian Tresman <ian@knowledge.co.uk>
=================
(1) LIFE-ON-MARS HOPES DENTED BY METEORITE CONTAMINATION
From SpaceDaily, 27 September 2000
PARIS (AFP) - September 27th, 2000 - Suggestions that life, or
the potential
for it, existed on Mars have been dealt a blow by a new question
mark that has been
placed over one of the main pieces of evidence -- Martian
meteorites found in
Antarctica. Of the 15 Martian meteorites so far retrieved on
Earth, six have been found in the dry
valleys of Antarctica.
The most famous one, ALH-84001, found in 1984 in the Allan Hills,
sparked
worldwide headlines in 1996 when a NASA team declared its
microscopic grooves had been
gouged by microorganisms on the Red Planet 3.6 billion years
earlier.
That theory has since been repeatedly attacked by other
scientists who
suggested the grooves could have been simply caused by a chemical
process or by Earth
bacteria.
Another argument for the meteorites was that they hold high
sulphur ratios
and atmospheric gases -- including an isotope of oxygen that, it
was suggested,
became trapped in magma billions of years ago when the Martian
atmosphere reacted
with water.
But, say a team led by Huiming Bao of the University of
California at San
Diego, the meteorites may have been contaminated by the
peculiarly salty soils of
dry-valley Antarctica.
An analysis of those soils shows them to have extremely high
levels of the
same oxygen isotope, the researchers say.
The isotope was derived from a reaction long ago between the
atmosphere and
local gaseous sulphur compounds, they believe. The isotope was
then deposited by
precipitation onto surface rock.
The results were found among samples far inland, which ruled out
airborne
particles of sea salt as the source for the sulphur compound.
The data "suggests a possibility that anomalous isotopic
signatures detected
on meteorites could come from terrestrial contamination,"
the scientists say, publishing
their work in Thursday's issue of Nature.
ALH-84001, about the size of a potato, landed in Antarctica
around 13,000
years ago, presumably after it had been knocked off Mars by a
colliding space wanderer
such as an asteroid. Martian meteorites have been identified as
such because their
chemical profile matches that of rocks analysed by US space
probes.
NASA announced on June 22 it had found photographic evidence of
the recent
presence of water on Mars, a discovery said to have resounding
implications for the
prospect of life on the planet.
All rights reserved. © 2000 Agence France-Presse.
==================
(2) WORSENING URBAN AIR POLLUTION WON'T INCREASE GLOBAL
TEMPERATURE OVER
NEXT 100 YEARS
From Ketrina Jackson <kjackson@nsf.gov>
Media Contact:
September 27, 2000
Cheryl Dybas
NSF PR 00-66
(703) 292-8070/cdybas@nsf.gov
Program Contact:
Anne-Marie Schmoltner
(703) 292-8522/aschmolt@nsf.gov
WORSENING
URBAN AIR POLLUTION WON'T INCREASE
GLOBAL TEMPERATURE OVER NEXT 100 YEARS
Researchers funded in part
by the National Science
Foundation (NSF) and affiliated with the Massachusetts
Institute of Technology have found that although urban air
pollution is expected to increase significantly in the coming
century, it will not have a big effect on global temperature
change.
While there may be temperature increases
in certain regions,
global mean surface temperature will not go up significantly
because of urban air pollution, researchers at MIT's Joint
Program on the Science and Policy of Global Change wrote in a
paper to be published in the September 27 issue of the Journal of
Geophysical Research--Atmospheres.
"It is very important to understand
the interplay between
air quality and climate, and recent advances in coupled chemistry
climate models make that possible," says Anne-Marie
Schmoltner,
program director in NSF's division of atmospheric sciences.
"Changes in air quality could affect global climate, and
conversely, climate change could affect air quality. The
results
presented by the MIT group provide insight into these complex
interactions."
Using a method that allows global
coupled-chemistry climate
models to take urban air pollution into account in a new way, MIT
researchers found that compared to a reference run excluding
urban air pollution, the average tropospheric ozone concentration
decreases while high concentrations of ozone are projected in the
urban areas. As a consequence of the change
in the chemical composition of the troposphere, the lifetime
of methane increases. This leads to higher ambient methane
concentrations, even if emissions are unaltered.
"People thought things would go in
this direction, but
they couldn't quantify it before," said Monika Mayer,
research scientist at MIT and lead author on the paper,
"Linking local air pollution to global chemistry and
climate."
While scientists agree that urban air
pollution can alter
concentrations of greenhouse gases such as ozone in the
troposphere, they have left the complicated chemistry of
urban air pollution out of global climate models.
"Global-scale models that do not take into account urban
areas' highly nonlinear atmospheric chemistry most likely
overestimate tropospheric ozone production due to
unreasonably high background nitric oxide concentrations,"
the authors write.
Yet, "high-resolution climate models
don't have chemistry
coupled to them," said Mayer. "It takes months just to
run a
global climate model without the chemistry."
Population projections show that in the
next 100 years,
the concentration of people in urban areas will increase
dramatically. While 30-40 percent of air pollution currently
comes from urban areas, as much as 70 percent may originate
from cities in the future. The researchers carried out three
simulations of 100year projections that factored in the
effects of increased urban air pollution tied to population
increases and economic development in these areas. They found
that even with significant increases in air pollution, global
mean temperature should not change much, although there may be
more pronounced regional effects.
=================
(3) A GLOBAL TSUNAMI IN 200 AD?
D.J. Lowe & W.P. de Lange: Volcano-meteorological tsunamis,
the c. AD 200
Taupo eruption (New Zealand) and the possibility of a global
tsunami.
HOLOCENE 10: (3) 401-407 MAY 2000
Meteorological tsunamis are long-period waves that result from
meteorologically driven disturbances. They are also generated by
phase
coupling with atmospheric gravity waves
arising through powerful volcanic activity. The AD 1883 Krakatau
eruption
generated volcano-meteorological tsunamis that were recorded
globally. Because of its
extreme violence and energy release (greater than or equal to 150
+/- 50 megatons explosive
yield), and by analogy with the Krakatau event, it is highly
possible that the
ignimbrite-emplacement phase of the c. AD 200 Taupo eruption of
North Island, New Zealand,
generated a similar volcano-meteorological tsunami that may have
reached coastal areas
worldwide. Tsunami deposits of identical age to the Taupo
eruption occur in
central coastal New Zealand and probably
relate to that event; definitive evidence elsewhere has not yet
been found.
In theory, volcano-meteorological tsunamis are likely to be
produced during comparable
eruptive events at other explosive volcanoes, and thus represent
an additional
volcanic hazard at coastal sites far from source. We suggest that
evidence for such tsunamis,
both for marine and lacustrine environments, may be preserved in
geological records, and
that further work searching for this evidence using a facies
approach is
timely.
Addresses:
Lowe DJ, Univ Waikato, Dept Earth Sci, Private Bag 3105, Hamilton
2001, New
Zealand.
Univ Waikato, Dept Earth Sci, Hamilton 2001, New Zealand.
Copyright © 2000 Institute for Scientific Information
===============
(4) NATURE AND DESTRUCTION OF THE TUNGUSKA COSMICAL BODY
V.A. Bronshten: Nature and destruction of the Tunguska cosmical
body
PLANETARY AND SPACE SCIENCE 48: (9) 855-870 AUG 2000
The problem of the nature of the Tunguska Cosmical Body (TCB) is
closely
related to the mechanism of its disintegration which ended with
an explosive disburse. The
only hypothesis capable of explaining such a process is the idea
that TCB
was a fragment of a comet. Three alternative hypotheses are
considered here.
They assume the TCB to be: (i) a fragment of a
stony asteroid; (ii) a porous snowball; and (iii) a plasmoid. It
is shown
that the first of them is not plausible because the fragmentation
and explosion of an asteroid
should result in the scattering of numerous fragments over the
ground. They, however, have
not been found on the terrain for many years by many tens of
explorers who
have carried out a cartful analysis of the soil and peat. Bodies
like a
porous snowball or a plasmoid cannot exist in the Solar
system (they should be unstable). The history of the cometary
hypothesis is
followed in the article, starting from its original formulation
in a book by
the well-known astrophysicist H. Shapley (1930. Flights from
Chaos. A Survey
of Material Systems from Atoms to Galaxies. N.Y.: McGraw-Hill, p.
57-58.
Russian translation: From Atoms to Milky Ways. Moscow: ONTI,
1934),
who has priority over F. J. W. Whipple [the latter having put
this
hypothesis 4 years later (Whipple, 1934. On phenomena related to
the Great
Siberian meteor. Quart. Journ. of the Roy. Meteorol. Sec. 60,
505-513)].
Simultaneously with the evolution of this hypothesis our ideas
of the structure of cometary nuclei have also varied. Estimates
of the main
parameters of the TCB - its initial mass m, initial velocity v
and energy of explosion E-e -
are examined. The following quantities are assured to be the most
plobable:
m = 2 x 10(6) t, v = 31 km/s, E-e = 5 x 10(23) erg. The mentioned
value of v corresponds to the
Zotkin-Kresak hypothesis that the TCB was a fragment of the Encke
comet. Sekanina's criticism against
this hypothesis is examined. During recent years, three
analytical theor ies of the
sequential disintegration of large bodies in the atmosphere have
bern put forward by Grigoryan (1979:
Motion and disintegration of meteorites in the planetary
atmospheres. Cosmic
Res. 17(6), 875-893), Hills and Goda (1993. The fragmentation of
small asteroids in the atmosphere.
Astron. J. 105(3) 1114-1144) (their theory is physically
equivalent to
Grigoryan's theory), and by Chyba et al. (1993. The Tunguska 1908
explosion:
atmospheric disruption of a stony asteroid. Nature, 36 (1)
40-44.). The
comparison of all the three theories is presented. It is shown
that the
theory of Chyba et al. overestimates the altitudes of disruption
of the
meteoroid compared to other theories. The results of the
numerical
simulations of the process in the free-Lagrangian and the
Eulerian
approximation (Svettsov V.V., Nemchinov I.V., Teterev A.V., 1995.
Disintegration of large meteoroids in Earth's atmosphere:
theoretical
models. Icarus 116, 131-153) are also analysed.
The results of numerous studies examined either do not contradict
the
cometary hypothesis of the TCB nature or the discrepancies (e.g.
in the case of Chyba et al., 1993)
can simply be explained. An interpretation is presented fur the
anomalous
sky glow observed after the TCB fall, west of the treefall
epicenter, in Russia and in West Europe. It was
first put forward by the author (Bronshten, 1991. Nature of the
anomalous illumination of the
sky related to the Tuuguska event. Solar System Res. 25(4), 490
504) and considers the
secondary scattering of solar light by the dust of the head of
the comet that entered the Earth's
atmosphere simultaneously with the TCB. (C) 2000 Elsevier Science
Ltd. All
rights reserved.
Addresses:
Bronshten VA, 16-130 Varshavskoye Shosse, Moscow 113105, Russia.
Russian Acad Sci, Comm Meteorites, Moscow 117975, Russia.
Copyright © 2000 Institute for Scientific Information
================
(5) RE-EVALUATION OF THE CAUSE & LOCALIZATION OF THE LATE
LUNAR BOMBARDMENT
G. Arrhenius & A. Lepland: Accretion of Moon and Earth and
the emergence of
life
CHEMICAL GEOLOGY 169: (1-2) 69-82 AUG 15 2000
The discrepancy between the impact records on the Earth and Moon
in the time
period, 4.0-3.5 Ga calls for a re-evaluation of the cause and
localization of the
late lunar bombardment. As one possible explanation, we propose
that the time coverage
in the ancient rock record is sufficiently fragmentary, so that
the effects of giant,
sterilizing impacts throughout the inner solar system, caused by
marauding
asteroids, could have escaped detection
in terrestrial and Martian records. Alternatively, the lunar
impact record
may reflect collisions of the receding Moon with a series of
small, original satellites
of the Earth and their debris in the time period about 4.0-3.5
Ga. The effects on Earth
of such encounters could have been comparatively small. The
location of
these tellurian moonlets has been estimated to have been in the
region around 40 Earth radii. Calculations
presented here, indicate that this is the region that the Moon
would traverse at 4.0-3.5 Ga,
when the heavy and declining lunar bombardment took place. The
ultimate time limit for the
emergence of life on Earth is determined by the effects of
planetary accretion - existing
models offer a variety of scenarios, ranging from low average
surface temperature at slow accretion
of the mantle, to complete melting of the planet followed by
protracted
cooling. The choice of accretion model affects the habitability
of the
planet by dictating the early evolution of the atmosphere and
hydrosphere.
Further exploration of the sedimentary record on Earth and Mars,
and of the
chemical composition of impact-generated ejecta on the Moon, may
determine
the choice between the different interpretations of the late
lunar bombardment and cast
additional light on the time and conditions for the emergence of
life. (C) 2000 Elsevier Science
B.V. All rights reserved.
Addresses:
Arrhenius G, Univ Calif San Diego, Scripps Inst Oceanog, San
Diego, CA 92093
USA.
Univ Calif San Diego, Scripps Inst Oceanog, San Diego, CA 92093
USA.
Tallinn Tech Univ, Inst Geol, EE-0001 Tallinn, Estonia.
Copyright © 2000 Institute for Scientific Information
================
(6) NEW 2.5 KM IMPACT STRUCTURE DISCOVERED IN NW AUSTRALIA?
J.D. Gorter & S.W. Bayford: Possible impact origin for the
Middle Miocene
(Serravallian)
Puffin Structure, Ashmore Platform, Northwest Australia.
AUSTRALIAN JOURNAL
OF
EARTH SCIENCES 47: (4) 707-714 AUG 2000
The Puffin Structure is interpreted from high-quality 3D seismic
data as a
small multiringed impact structure formed by collision of a
meteorite or
small asteroid with unconsolidated, water-saturated
shallow-marine shelf carbonates during the Middle Miocene
(mid to late Serravallian). The impact created a dish-shaped
structure about
2.5 km in diameter with annular rings and no central uplift.
Addresses:
Gorter JD, British Borneo Australia Ltd, POB 1265, W Perth, WA
6872,
Australia.
British Borneo Australia Ltd, W Perth, WA 6872, Australia.
Copyright © 2000 Institute for Scientific Information
===============
(7) CAN SELF-ORGANISED TUNGUSKAS PREVENT THE BIG ROCK?
B.D. Malamud & D.L. Turcotte: Self-organized criticality
applied to natural
hazards
NATURAL HAZARDS 20: (2-3) 93-116 NOV 1999
The concept of self-organized criticality evolved from studies of
three
simple cellular-automata models: the sand-pile, slider-block, and
forest-fire
models.
In each case, there is a steady "input'' and the
"loss'' is associated with
a fractal (power-law) distribution of "avalanches.'' Each of
the three
models can be associated with an important natural hazard: the
sand-pile model with
landslides, the slider-block model with earthquakes, and the
forest-fire model with
forest fires.
We show that each of the three natural hazards have
frequency-size
statistics that are well approximated by power-law distributions.
The model behavior suggests
that the recurrence interval for a severe event can be estimated
by extrapolating the
observed frequency-size distribution of small and medium events.
For example, the
recurrence interval for a magnitude seven earthquake can be
obtained directly from the
observed frequency of occurrence of magnitude four earthquakes.
This concept leads to
the definition of a seismic intensity factor. Both global and
regional maps of
this seismic intensity factor are given. In addition, the
behavior of the models
suggests that the risk of occurrence of large events can be
substantially reduced if
small events are encouraged. For example, if small forest fires
are allowed to
burn, the risk of a large forest fire is substantially reduced.
Addresses:
Malamud BD, Cornell Univ, Dept Geol Sci, Ithaca, NY 14853 USA.
Cornell Univ, Dept Geol Sci, Ithaca, NY 14853 USA.
Copyright © 2000 Institute for Scientific Information
=============
(8) NATURAL HAZARDS: SOCIOPOLITICAL AND HUMANITARIAN
CONSIDERATIONS
J.V. Smith: Natural hazards: Geology, engineering, agriculture,
and
sociopolitical/humanitarian considerations for the
twenty-first century.
INTERNATIONAL GEOLOGY REVIEW 42: (7) 617-656 JUL 2000
Dangers from natural hazards have been characterized
quantitatively by
national and international committees of geoscientists
based on technical advances in
geochemistry and geophysics (sensu lato). The current status of
knowledge on
natural hazards is reviewed with particular emphasis on
comet/asteroid impact, earthquakes, and
volcanoes. All these hazards are survivable by the world's
population if appropriate measures are
taken over the next century and millennium. Ideas for mitigation
include: general use of
weathered volcanic ash and power-station fly ash to make
pozzolana cement for strengthening
buildings, and stabilizing weak ground and hillsides prone to
slumping;
long-term storage of grains under nitrogen, together with other
techniques
for maintaining viability of stored food; drilling
of tunnels under major cities to facilitate traffic flow, and for
protection
against impact of bolides and bombs; design of sea and lake
fronts to guard against
tsunamis from earthquakes and asteroid impact. The food-storage
proposals
could be tailored to help farmers obtain a regular income while
producing a
higher crop yield than needed for current food supply. The
land modification plans would provide technical challenges and
new business
activities for civil engineers, lawyers, real-estate
professionals, and city planners. It
is truly tragic that genuine ideas for mitigation of natural
hazards are being implemented
at a snail's pace while funding for weapons nourishes around much
of the
world. The early development of my thinking on hazards is an
example of the
typical disconnection between "scientific expertise"
and actual day-to-day planning decisions. As a farmer's boy
interested in
civil engineering and land planning in an ecological context, I
summarize old and new ideas in
an effort to bridge this disconnection, and facilitate the
planned transfer of funding
from weapons to actions that enhance human well being. Because
the actions are international
in their basic nature and ecological in character, I hope that
they will
help to generate a feeling of "One world that must be loved,
not abused." We
belong to one biological species, Homo supposedly sapiens
sapiens. We must
progress beyond tribal, ethnic, and other divisive matters
associated with wars and civilian conflicts. The rich must help
the poor.
Geology and civil engineering can provide important worldwide
cooperative
connections.
Addresses:
Smith JV, Univ Chicago, Dept Geophys Sci, 5734 S Ellis Ave,
Chicago, IL
60637 USA.
Univ Chicago, Dept Geophys Sci, Chicago, IL 60637 USA.
Univ Chicago, Ctr Adv Radiat Sources, Chicago, IL 60637 USA.
Copyright © 2000 Institute for Scientific Information
===================
* LETTERS & OPINION
===================
(9) MICKEY MOUSE SCIENCE:
HOW WALT DISNEY'S ACCOUNT OF THE XF11 AFFAIR
IS FOSTERING AN URBAN MYTH
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
You know that intellectual standards are going down the drain
when
scientists start to promote the cartoon versions of populist
science. This is certainly
the case with the recent promotion of Walt Disney's account (or
should I say:
blunder) of the events surrounding the announcement of asteroid
1997 XF11
way back in March of 1998.
A couple of days ago, Alan Harris (JPL/NASA) re-opened the
unfortunate
XF11 affair with another public broadside against Brian Marsden.
In a
message to the MPML mailing list on 26 September, Al Harris
posted a cutting from
Discover Magazine's list of "Twenty of the Greatest Blunders
in Science in the Last
Twenty Years" which included what Al calls "the 1997
XF11 fiasco."
Brian Marsden, Harris continued, "shares company with quite
a few other
planetary and space stories: the Challenger disaster, failed Mars
missions, the Mars
Rock story and the Iridium satellite constellation. I'm not sure
I would make the
same choices, but in any case Marsden is in pretty select
company. You can
check it all out at:
http://www.discover.com/oct_00/featblunders.html"
-------------------------------------------------------
Twenty of the Greatest Blunders in Science in the Last Twenty
Years
What were they thinking?
By Judith Newman
The Sky Is Falling Again
Um, never mind. On March 12, 1998, on the front page of The New
York Times,
a headline read: "Asteroid Is Expected to Make a Pass Close
to Earth
in 2028." Brian G. Marsden, director of the Central Bureau
for Astronomical
Telegrams at the Smithsonian Astrophysical Observatory, predicted
that on
October 26, 2028, an asteroid about a mile in diameter would come
within
30,000 miles of Earth. That's within spitting distance,
spacewise, which
evoked comparisons to the asteroid that crashed on the Yucatàn
peninsula 65
million years ago, allegedly wiping out all the dinosaurs.
"When you first
discover a comet, or any kind of body, you start measuring its
position,"
notes Robert Park. "From that you extract its trajectory.
The more
measurements you make, the more accurate your trajectory
gets." Marsden issued his
warnings based on very early trajectory measurements. Now he
anticipates
the asteroid will pass Earth at a safe distance of 600,000 miles.
--------------------
So what's wrong with exposing this kind of "scientific
blunder" on a mailing
list for NEO observers? For a start, Discover.com, as Victor Noto
has
correctly pointed out, is a small Disney Company entertainment
website and
not, as Harris seemed to believe, identical to the science
journal Discovery.com.
This then raises the question as to whether Walt Disney really
understand
what their writing about. After all, if you want to expose a
scientific blunder
and wish to take the mickey out of scientists, you'd better get
your facts
right.
Nobody, I am sure, will be surprised to learn that Disney's
mini-story about
the XF11 affair has to be taken with a pinch of salt.
The first crucial mistake in the Discover cartoon is at the
beginning of
line 5:
The announcement stated that asteroid 1997XF11 could come within
30,000
miles of the earth, not "would." I fear that this
difference, which is to scientists
as that between night and day, is very frequently misrepresented
(or simply
misunderstood) by journalists. One could venture say that the
could/would
confusion is frequently the principal problem from which
journalism - even
science journalism - suffers.
Roberta Park's quoted statement is also incorrect. After all,
it's not the
number of observations that matters in this respect, but the
length of time
they span. And rather than issuing "warnings", Brian
Marden, as we know, was
noting the apparent apathy of observers to what was obviously an
interesting object
by urging them to make that timespan longer, both by means of
continuing new
observations and the search for possible observations on old
plates.
It is also interesting that the writer feels that "30,000
miles" is indeed
worrisome - "within spitting distance" - yet the now
"anticipated" 600,000
miles is "safe". (remember the 3 million miles of 2000
QW7 that made
global headlines recently as "near miss"?) NEO
researchers did not seem to
consider a minimum miss distance of 30,000 miles in any way
worrisome, even
if it would have turned out to be correct: to them, clearly,
"a miss is as
good as a mile". But it was precisely the possibility that
the 2028 miss
distance was about 500,000 miles (allegedly "safe", in
the mind of
Discover.com) that an object such as 1997 XF11 could (*not
would*) have hit the earth 12
years later.
If there was a scientific blunder at all, it was rather made by
Alan Harris
himself when he calculated, on 11 March 1998, that, in 2028,
"the probability of
impact [of XF11] is probably greater than 0.1%." That
calculation was indeed a
blunder.
I have always wondered why Alan Harris never stopped his camapign
against
Marsden's XF11 announcement. He appeares driven and almost
obsessed by the
whole affair. Historians of the XF11 affair and its long-term
implications on NEO
research and NEO politics may be interested to known that it was
Al himself who, on
the day of the MPC release, congratulated Marsden on the tone and
format of the
XF11 announcement:
"I think Brian is to be commended for restraint and
discretion in the
wording of the announcement below. Let me add a couple more
sensational
details that could have been added, but thankfully weren't: [...]
For
the first time, we have an object with a significantly non-zero
probability of impacting the Earth."
Ah well, without 1997 XF11, where would we be today? Would NASA
have
established its NEO Office and increased its NEO funding? Would
we have LINEAR and
Spaceguard initiatives around the world? And finally, and more to
home, would both
Houses of Parliament have debated the impact hazard and would the
UK Government,
subsequently, have set up the NEO Task Force, indeed, would we
have the NEO Task Force
Report without the XF11 Affair? I somehow doubt it.
Benny J Peiser
================
(10) 1946 TSUNAMI
From Michael Paine <mpaine@tpgi.com.au>
Dear Benny,
The article explains the most likely source of the 1946 tsunami
'Fryer
said the earthquake alone doesn't explain the large waves, but it
shook
loose a huge submarine landslide into the Aleutian Trench.' The
diagram
in the Star-Bulletin article clearly shows a source in that
trench.
http://starbulletin.com/2000/09/23/news/story9.html
Submarine landslides can cause tsunami that are much larger than
ones
caused by earthquakes alone. It is an interesting event but I
suspect it
but has nothing to do with asteroid-generated tsunami, other than
providing a good case study for tsunami modeling.
regards
Michael Paine
=============
(11) MEA CULPA!
From Phil Plait <badastro@badastronomy.com>
In the CCNet from 22 September 2000, James Oberg says
about heating meteors:
>Actually, friction has nothing to do with it -- although
>this is a common, careless, misconception. The source of
>heat on an entering object is the shock compression of the
>air piled up in front of it
Mea Culpa!
He is correct. The hypersonic passage of the meteoroid compresses
the
air tremendously, which heats it. Radiant energy from the shocked
air
heats the forward surface of the meteor, melting it. There is a
standoff zone of relatively dead air in front of the meteor, and
friction with that ablates off the melted material.
I would define friction as the force of air moving laterally over
a
surface, so the heating is not really friction-induced.
References
on the actual heating mechanism of the air in front of a meteor
(at least, the ones I could find) are maddeningly vague, but John
Lewis
at the University of Arizona set me straight, and I thank him for
it. If
there are any remaining errors in my comments, they are mine and
not his.
-Phil
* * *
* The Bad Astronomer
* * * *
Phil
Plait
badastro@badastronomy.com
The Bad Astronomy Web Page: http://www.badastronomy.com
=============
(12) INVENTION OF IMPACT CRATERING
From Duncan Steel <D.I.Steel@salford.ac.uk>
Dear Benny,
I am not sure about your start dates in:
"...early researchers on impact cratering processes found
themselves
between the mid 19th and the mid 20th centuries. It
should be recalled
that it took more than 100 years before the initial impact
hypothesis for
many lunar and terrestrial craters could be finally
verified..."
Although Edmond Halley suggested in the 1690s that comets must
hit the
Earth from time to time, and he suggested that the Caspian Sea
might be
the scar from such an event, the real beginning of the impact
hypothesis
might really be judged to have occurred around 1890 when Daniel
Barringer
(in Arizona) and Alexander Bickerton (in New Zealand) mooted
ideas that
were thought crazy at the time. If one goes back to the mid-19th
century,
one finds people being totally bewildered by the craters of the
moon.
For example, Charles Babbage (no idiot he) suggested in the late
1840s
that they were similar in origin to coral atolls, left high and
dry
after the lunar seas (maria) had dried up; he was influenced by
Charles
Darwin's description of tropical atolls as observed in the 1830s
on the
famous voyage of the Beagle. I might point out that in the same
discussion
Babbage put forward what might well be regarded as the first
description
of the greenhouse effect in the planetary context (that is, he
discussed
how different planets might have elevated temperatures due to the
effects
of their differing atmospheres trapping more of their re-emitted
infra-red
radiation). I discussed this in:
D. Steel, 'Charles Babbage, the craters of the Moon, and the
Greenhouse
Effect,' Journal of the British Astronomical Association, 102,
246-247
(1992).
Kind regards,
Duncan Steel
MODERATOR'S NOTE: The invention of the impact cratering idea goes
back to
1802 and is mainly a German invention. The idea emerged as a
direct consequence
of the discovery of the first two asteroids in 1801 and 1802.
Once it was
realised that such small bodies existed in the solar system, it
was clear that they
may occassionally collide with the moon or earth. Thus, in 1802,
the von
Bieberstein brothers in Germany and again in 1815 K.E. von Moll
suggested that the lunar
craters were caused by asteroidal impacts. The idea was picked up
and
expanded by F. von Gruithuisen in 1829 but completely
overshadowed by the emerging
uniformitarian/anti-catastrophist paradigm which took shape in
the 1830s and
1840s.
While Richard Proctor revived the impact hypothesis in his 1878
book on the
Moon, the whole issue was dropped when the second edition was
published a couple
of years later. Altogether it took some 160 years for the impact
hypothesis to become
a scientific fact, beginning from its original invention in 1801
until its
verification in the early 1960s.
BJP
=============
(13) MOON HAS SQUARE CRATERS TOO
From Ian Tresman <ian@knowledge.co.uk>
RE: HOLY SMOKE: SQUARE CRATERS DETECTED ON EROS
Apparently the moon has square craters too. See
1. http://members.home.net/bill2space/square-craters.html
2. http://www.lunaranomalies.com/double_craters_in_hort.htm
Regards,
Ian Tresman, Compiler, Catastrophism! CD-Rom Disc
9 Ashdown Drive, Borehamwood, Herts. WD6 4LZ. UK.
Fax: 0870 284 8769. Email: ian@knowledge.co.uk
Web: http://www.catastrophism.com
----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The CCNet is a scholarly electronic network. To
subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied
or
reproduced for any other purposes without prior permission of the
copyright holders. The fully indexed archive of the CCNet, from
February 1997 on, can be found at http://abob.libs.uga.edu/bobk/cccmenu.html