PLEASE NOTE:
*
CCNet 130/2000 - 11 December 2000
--------------------------------
"A Defense Department briefing paper prepared last month
also cited
a 'strong government desire to avoid having more than 70
satellites
de-orbit within 14 months,' as had been planned by Motorola. A
U.S.
interagency group led by the Justice Department feared that this
'might
create widespread anxiety and lead to a public outcry for
ill-considered
government action,' the Pentagon paper said."
-- Jim Wolf, Reuters, 10 December 2000
"The Geminids are a mystery. Most meteoroids that we know of
come
from comets. They are set free by solar vaporization of
[cometary]
ice. Geminid meteoroids, on the other hand, appear to come from
3200
Phaethon, an asteroid. We're not sure why an asteroid should have
a
debris trail, but this one does."
--Brian Marsden, Minor Planet Center, 8
December 2000
"A trawl through CCNet records, including refereed journal
papers,
shows that panspermia is currently regarded by significant
numbers of
practitioners as a "working hypothesis." [...] That's
been true since NASA
claimed to have detected signs of fossilised life in a Martian
meteorite.
But in fact, ever since SNC meteorites were established as
originating from
Mars and Chassigny was shown to have been only lightly shocked in
transit, in the 1980s, panspermia has served as a working
hypothesis that
was very amenable to scientific experimentation and theoretical
analysis."
--Max Wallis, Cardiff Centre for
Astrobiology, 11 December 2000
(1) TWO DAYLIGHT FIREBALLS OBSERVED FROM SPAIN
Josep M. Trigo <trigo@exp.uji.es>
(2) NASA APPLIES NEW IMPACT HAZARD SCALE FOR SATELLITE RE-ENTRY
Exite News, 10 December 2000
(3) 'LIFE-FROM-SPACE' BALLOON READY FOR LAUNCH IN INDIA
The Times of India, 11 December 2000
(4) THE BAFFLING METEOR SHOWER THAT SEEMS TO COME FROM A CURIOUS
ASTEROID
NASA Science News for December 8, 2000
(5) MYSTERY OF THE FIREBALL FROM THE SKY DEEPENS
Concord Monitor, 7 December 2000
(6) NEW EVIDENCE AGAINST NANOBACTERIA
Science-Week <prismx@scienceweek.com>
(7) IMPACTS AND THE EARLY EARTH
Iain Gilmour & Christian Koerberl
(8) PANSPERMIA AND UNSCIENTIFIC NOTIONS
Max Wallis <wallismk@Cardiff.ac.uk>
(9) VISCOUS MAGMA FLOW RATES AND CONTINENTAL ACCRETION RATES ARE
NOT THE
SAME THING
Andrew Glikson <geospectral@spirit.com.au>
===============
(1) TWO DAYLIGHT FIREBALLS OBSERVED FROM SPAIN
From Josep M. Trigo <trigo@exp.uji.es>
Press release from the Spanish Fireball Network (SPMN):
http://www.spmn.uji.es/
Two impressive fireballs, probably of cometary origin, were
observed from
Spain on November 28 and 29. Both events were of short duration
and happened
in diurnal hours. As consequence our network only has collected
eye witness
reports.
Initially our team thought in the artificial nature of both
fireballs. In
fact, these events just remind us the 27th Nov. 1999 fireball
caused by the
Chinese Shenzhou Long March rocket. The atmospheric path of this
impressive
reentry was analysed by us the past year (for more details please
see the
SPMN homepage). Despite of these first impressions, the
trajectory data and
luminous path characteristics suggested us a solar system origin
for both
fireballs. This suspicion was confirmed by several specialist in
satellite
decays such as: Alan Pickup and Harro Zimmer. They inform us that
no reentry
events were expected for these days on Spain.
At this moment we are still collecting data of the 28th November
fireball.
It was observed at midday from several cities in Andalucia and
the visual
reports suggest that its absolute magnitude was close to -15. At
this moment
we have only poor reports but probably in the next weeks we can
elucidate
its nature and origin.
November 29th fireball has been analysed in more detail. In fact,
this event
was observed from Mallorca (Balearic Islands) by several
eyewitnesses. High
quality trajectory data of the fireball was obtained by Francisco
Sáez
Isern, a experienced meteor observer member of the UMA team of
the Mallorca
Astronomical Observatory (OAM). These high quality data were
provided us by
Enric Coll showing that the fireball appeared in the evenfall at
16h41m31s
+-3s UTC. The fireball appeared from Mallorca close to the Moon
and Venus,
the only celestial bodies visible at this time. The reported
apparent
magnitude was -10 although probably it could have been more
impressive in
the night sky. The fireball exhibited several flares along its
trajectory.
At the end an impressive green flare signaled the full
desintegration of the
incident body. The luminous trajectory and the ending flare
suggests us a
cometary origin. Moreover, analysing the angular velocity and the
apparent
trajectory in the sky we have strong evidences that this fireball
was
produced by a late Leonid meteoroid.
Additional information and trajectory data can be obtained in our
homepage.
We will be grateful with whoever provide us additional
information on these
two big events.
********************************************
Josep M. Trigo-Rodríguez / Jordi Llorca Piqué
SPANISH PHOTOGRAPHIC METEOR NETWORK (SPMN)
Institut d'Estudis Espacials de Catalunya (IEEC)
Dept. Astronomy & Astrophysics, Univ. of Valencia
Dept. Experimental Sciences, Univ. Jaume I
Dept. Inorganic Chemistry, Univ. Barcelona
SPMN homepage: http://www.spmn.uji.es/
E-mails: trigo@exp.uji.es /
jllorca@kripto.qui.ub.es
*********************************************
================
(2) NASA APPLIES NEW IMPACT HAZARD SCALE FOR SATELLITE RE-ENTRY
From Exite News, 10 December 2000
http://news.excite.com/news/r/001210/15/science-tech-satellites-dc
NASA: SATELLITE ODDS OF HITTING SOMEONE 250-1
By Jim Wolf
WASHINGTON (Reuters) - U.S. space scientists put the odds at
nearly 1 in 250
that debris from the proposed burn-up of the world's first global
satellite
telephone mesh would hit someone on Earth.
The prospects of a casualty from the now-averted mass
"de-orbiting" of the
system known as Iridium were spelled out in a previously secret
study by the
National Aeronautics and Space Administration.
The analysis was done in April as a government task force weighed
fears that
a hurry-up, 14-month schedule for bringing back cast-off hardware
might
trigger "widespread anxiety."
"With the information currently available, the probability
of someone being
struck by surviving Iridium debris is assessed to be 1 in 18,405
per reentry
and 1 in 249 for all 74 spacecraft combined," NASA
calculated.
The study was made available to Reuters by the Federal
Communications
Commission under the Freedom of Information Act. It found four
types of
Iridium components were likely to survive a flaming reentry into
the
atmosphere -- 10-kg titanium fuel tanks, 30-kg batteries, 6.3-kg
structural
brackets and 116-kg electronic control panels.
Last week, the Pentagon, citing its own needs, stepped in to
rescue the
necklace of 66 cross-linked, low Earth orbiting satellites plus
its spares
from the ashes of bankruptcy court.
Motorola Corp., which built, bankrolled and operated the $5.5
billion
system, had said it would begin nudging the 560-kg satellites
into decaying
orbits this month in the absence of a buyer.
In staving off a fiery end for now, the Pentagon signed a
$3-million-a-month
deal for unlimited air time for up to 20,000 U.S. government
users of
wireless satellite telephones, including military forces
worldwide.
The deal could be worth as much as $252 million if the Defense
Department
picks up options for service through 2007. It was a condition for
court
approval of the purchase of Iridium, for $25 million, by an
investors group
led by Dan Colussy, president of Pan American World Airways from
1978 to
1980.
The Pentagon already owned about 1,600 Iridium satellite phones.
The State
Department has another 2,000. They have been used by Navy ships
at sea,
polar teams, special operations forces and combat
search-and-rescue missions
in areas without U.S. military satellite coverage or when
military channels
are full.
Iridium "will provide a commercial alternative to our purely
military
systems," said Dave Oliver, principal deputy under secretary
of defense for
acquisitions, technology and logistics. The Navy, for example,
needed more
than twice as much such point-to-point secure communications
capability as
was available, the Pentagon said.
But a Defense Department briefing paper prepared last month also
cited a
"strong government desire to avoid having more than 70
satellites de-orbit
within 14 months," as had been planned by Motorola.
A U.S. interagency group led by the Justice Department feared
that this
"might create widespread anxiety and lead to a public outcry
for
ill-considered government action," the Pentagon paper said.
In its study, NASA said a total mass equal to 300 Iridiums, or
more than
168,000 kilos, fell to Earth last year alone in
"natural," or untargeted,
re-entries from decaying orbits.
Since the Soviets launched the basketball-sized Sputnik I on Oct.
4, 1957,
no one has ever been reported hurt by falling debris, though
there have been
4,100 natural re-entries, said Nicholas Johnson, NASA program
manager for
orbital debris and author of the report.
The bottom line, he added in an interview, is that the Iridium
satellites
would plunge back to Earth if not now, then in about 108 years
given their
current orbits.
The risk to life and limb, while statistically small, would
increase
"somewhat" due to projected world population growth in
the next 100 years,
Johnson concluded.
Copyright 2000, Reuters
MODERATOR'S NOTE: It would appear that NASA have come up with an
interesting
new "Impact Hazard Scale." In the case of the re-entry
of Iridium satellites
(which will not happen now for some time), the probability of
risk is
related to the likelihood that surviving debris from the
de-orbited
satellites will hit a person. This is an interesting approach to
risk
assessment (and risk announcement) if we compare it, for example,
to the
information provided by the Torino Scale. Here, a certain impact
of a small
NEO (level 8 on the Torino Scale) is described as "a
collision capable of
causing localised destruction." While this is certainly
correct, it does not
tell us anything about the probability that such an impact will
actually
occur in or over a populated area. There can be no question about
it: the
next Tunguska-type impact is going to happen at some time in the
forseeable
future. Given that we might even detect the object approaching
Earth before
its entry into the atmosphere, it would be wise to study the
Iridium case
carefully. After all, if the re-entry of tiny satellites
"might create
widespread anxiety and lead to a public outcry for ill-considered
government
action," can you imagine what may happen if a Tunguska-type
object were
predicted to hit the Earth in a matter of days? BJP
===========
(3) 'LIFE-FROM-SPACE' BALLOON READY FOR LAUNCH IN INDIA
From The Times of India, 11 December 2000
http://www.timesofindia.com/111200/11hlth15.htm
HYDERABAD: A scientific balloon carrying a special payload that
will find
out if life came from space, is all set for a midnight launch
from the
national balloon facility here, scientists said.
Sixteen super cooled sterilised containers -- that from the heart
of the
payload - will collect air samples from heights of 10 to 35 km
and bring
them back eight hours later.
"A helicopter is standing by to recover the precious cargo
seconds after the
balloon made the touch down," Pushapa Bhargava, former
director of Central
for Cellular and Molecular Biology (CCMB) and one of the
investigators of
this experiment, said.
The balloon is being launched from the National Facility run by
the Tata
Institute of Fundamental Research, Mumbai, one of four such
facilities in
the world.
Scientists said the balloon experiment is being carried out to
confirm their
discovery of an unknown form of bacteria in air samples brought
by a balloon
last April. "Exhaustive microbiological analysis" had
then established that
the bacteria was a new strain never before recorded on earth,
they said.
"It is tempting to speculate that these micro organisms came
from space, but
their terrestrial origin cannot be ruled out", Bhargava
said. (PTI)
Copyright 2000, Times of India
=============
(4) THE BAFFLING METEOR SHOWER THAT SEEMS TO COME FROM A CURIOUS
ASTEROID
From NASA Science News for December 8, 2000
http://science.nasa.gov/headlines/y2000/ast08dec_1.htm
Most meteor showers are caused by comets, but the Geminid meteor
shower,
which peaks next Wednesday morning, seems to come from a curious
near-Earth
asteroid.
December 8, 2000 -- Early risers who venture outdoors before dawn
next week
are in for a treat. The Geminid meteor shower peaks on Wednesday
morning
when sky watchers could spot as many as 3 to 5 shooting stars
every minute.
Geminids look like most meteors -- they tend to be fast-moving
and yellow in
color. But there's something special about them. Other meteor
showers happen
when Earth passes through the debris trail of a comet. Tiny bits
of dust no
bigger than a grain of sand disintegrate high in our atmosphere
and leave
behind dazzling streaks of light. But the parent of the Geminids
isn't a
comet at all. It appears to be a curious near-Earth asteroid
known as 3200
Phaethon.
"The Geminids are a mystery," says Brian Marsden of
Harvard's Minor Planet
Center. "Most meteoroids that we know of come from comets.
They are set free
by solar vaporization of [cometary] ice. Geminid meteoroids, on
the other
hand, appear to come from 3200 Phaethon, an asteroid. We're not
sure why an
asteroid should have a debris trail, but this one does."
Sky watchers first noticed the Geminids in the mid-1800's, but
for more than
a century the shower's source was unknown. Then, in 1983, NASA's
Infrared
Astronomy Satellite spotted a new asteroid: 3200 Phaethon.
Astronomer Fred
Whipple quickly realized that Phaethon and the Geminid meteoroid
stream
follow nearly identical orbits. They move around the Sun in a one
and a
half-year elliptical path that stretches from inside the orbit of
Mercury
outward to the asteroid belt.
Every year in mid-December when the Geminid meteor shower is
active, Earth
is barely eight lunar distances (~0.021 AU) from Phaethon's
orbit. That
makes Phaethon a "potentially hazardous" near-Earth
asteroid (NEA).
In most respects Phaethon appears to be an ordinary NEA, says
Marsden, but
it is remarkable because it comes so close to the Sun. Its
distance from the
Sun ranges from 0.14 AU at perihelion to 2.4 AU at aphelion.
"The small
aphelion distance would be unusual for a defunct comet," he
explained.
Phaethon's sungrazing orbit might be responsible, in part, for
the Geminids.
"You could argue that a lump of dusty ice on the surface of
Phaethon was
uncovered at some point and then vaporized by solar
heating," he speculated.
Such an event might produce meteoroids in the style of a comet.
Phaethon doesn't have a tail now and there's no evidence that
jets of
vaporizing debris are pushing the asteroid around. Whatever
liberated the
Geminid meteoroids probably happened long ago.
"The Geminid meteor shower is very stable from one year to
the next," notes
Robert Lunsford, Secretary General of the International Meteor
Organization,
"and there is no evidence for outbursts that follow close
encounters between
Earth and Phaethon." The debris trail seems to be spread
rather uniformly
around Phaethon's orbit -- another indicator that the meteoroids
are old.
In July 1996 astronomers saw something in the asteroid belt that
could be
relevant to the past experiences of 3200 Phaethon.
"Four years ago Eric Elst contacted us from the European
Southern
Observatory and reported a strange object (now known as
'Elst-Pizarro' after
its discoverers)," recalled Marsden. "It had a tail,
like a comet, but no
coma. We calculated an orbit and it seemed to be a perfectly
ordinary minor
planet in the asteroid belt. Furthermore, we found some older
images of it
from 1979 and '85. There was no tail in those photos and by 1997
the tail
Elst saw a year earlier was gone."
Despite its brief appearance as a comet look-alike, Elst-Pizarro
is probably
an asteroid, says Marsden. "We may have been seeing a cloud
of dust that was
ejected by an impact with another asteroid or, perhaps, a small
ice deposit
became uncovered and vaporized."
Elst-Pizarro spends all of its time in the main asteroid belt
where
asteroid-asteroid collisions are most likely to happen. Phaethon
spends less
time there, but it does visit the asteroid belt every 17 months
when it
reaches its farthest point from the Sun. A collision between
Phaethon and
some smaller object in the asteroid belt might account for the
Geminid
debris stream. Detailed studies of Geminid orbits, however,
indicate that
the meteoroids more likely crumbled away while Phaethon was close
to the
Sun. Once again, there's no clear solution to the Geminid riddle.
The mysterious Geminids will be on display Wednesday morning,
Dec. 13th,
when the ongoing shower reaches its day-long peak. Most years
stargazers in
rural areas can see as many as 140 Geminids per hour. That number
will be
substantially reduced by the glare of a nearly-full Moon on
Wednesday.
"The brutal moonlight will prevent us from enjoying the
Geminids as much as
usual," laments Lunsford. "I would estimate that rates
will average 20 to 30
per hour for most observers."
No matter where you live, the best time to watch will be during
the hours
before dawn on Wednesday. Meteors will streak away from a point
(called the
"radiant") in the constellation Gemini. Geminids can
appear anywhere in the
sky, but their trails will point back toward the radiant, which
will lie
some 60 degrees above the southern horizon at 4 am as seen from
mid-northern
latitude observing sites.
Even if the 2000 Geminids produce fewer meteors than usual,
they're still
worth watching. The morning sky this month features an array of
bright stars
and planets including Jupiter, Saturn, Sirius, the constellation
Orion, and
even the subtle Pleiades. A trip outdoors before breakfast on
Wednesday is a
no-lose proposition (weather permitting!).
And if you see a smattering of Geminids, just remember, each and
every one
is a bona-fide enigma -- baffling and dazzling in equal measure!
Tune in to SpaceWeather.com for more information about the
ongoing Geminid
meteor shower.
==============
(5) MYSTERY OF THE FIREBALL FROM THE SKY DEEPENS
From Concord Monitor, 7 December 2000
http://www.concordmonitor.com/stories/front0400/salisbury_fireball.shtml
If Monday's fire wasn't caused by a meteorite, what was it?
By STEPHANIE HANES
Monitor staff
SALISBURY - Ron Baalke of NASA's Jet Propulsion Lab saw the story
about the
meteorite in a small New Hampshire town online. It seemed a
spectacular
occurrence - meteorites are rare to begin with, but it's unheard
of to see
one land on Earth still burning. So, on his California computer,
he
forwarded the news to a London-based electronic network that
disseminates
information on catastrophic asteroids and cosmic disasters.
The "CCNet" published Baalke's post about the supposed
Granite State
meteorite, and sky-minded scientists across the world read the
news.
Salisbury, New Hampshire, was famous.
Since Paul Kornexl and Donna Ayoub saw a fireball plummet from
the sky into
the woods behind their houses Monday evening, Salisbury and its
potential
meteorite have gained worldwide attention. While Kornexl, Ayoub
and her
husband, Dave, continued to scour the muddy ground yesterday for
extraterrestrial signs, scientists from New Mexico to Moscow -
aided by the
more-familiar science of the Internet - were conjecturing on just
what
happened behind quiet Hensmith Road.
The first report that had come out of Salisbury said a meteorite
had landed
in the woods behind 129 and 137 (which are next to each other)
Hensmith
Road. The blazing softball-sized object had started two small
fires in the
dried leaves Monday evening, and neighbors had rushed to douse
the flames.
"It's a little weird for my book," said the fire
dispatcher Monday. "I've
never had anything drop out of the sky on my watch."
By the time firefighters arrived on scene the blaze was
extinguished. But
the curiosity wasn't.
Kornexl had been standing next to his shed when he saw the
fireball land.
"I was dumbfounded," he said.
The next day, when a scientist from the Christa McAuliffe
Planetarium
examined the scene, and other experts pieced together the
reported details,
the explanation of a meteorite seemed less and less plausible.
A meteorite would not have been burning when it hit the ground,
scientists
said. It would have left a crater when it landed and it would not
have come
in on an arc like residents described.
But the woods were deserted. Kornexl, who spent six years in the
Army, said
the scene didn't fit with any weapon he knew of. And air control
and
military officials said there was nothing overhead at the time.
So the question lingered. What sort of unearthly visitor had
shown up in
Salisbury?
The conjectures started coming in yesterday morning. Robin
Griffith, who
lives outside Houston, Texas, said the New Hampshire fireball was
similar to
a flash of light she saw from her deck back in July.
"If it had streaked I would have thought it was a shooting
star," she said.
But she added that her siting was exactly the same - she didn't
see her ball
of light fall to the horizon.
"I don't believe mine was what y'all had," she said.
She gave the name of a
scientist in Russia who had studied her incident. Andrei
Ol'khovatov had
read the posting on CCNet and had asked her to get more
information about
the New Hampshire incident.
Ol'khovatov had his own opinion. "It was probably not a
meteorite," he wrote
in an e-mail, "but a geophysical meteor (high-speed ball
lightning). I
investigate these events for some years."
Ol'khovatov's Web page has scores of information about incidents
of
geographic meteors, what he describes as a rare type of electric
atmospheric
discharge like ball lightning. He suggests TWA Flight 800 and
other airline
disasters may have been caused by this natural phenomena.
Salisbury's fire
could be just the latest incident.
Richard Spalding, a senior engineer at the Sandia National
Laboratories in
New Mexico, a U.S. Department of Energy national security lab,
had his own
theory. Apart from the lab, Spalding has studied flashes in the
atmosphere -
of which meteors are one sort and lightning another.
"This particular article is reminiscent of quite a number of
events I've
looked into in which people claim they've seen a fireball come
all the way
to the ground," he said. "I think they are an
electrical manifestation -
akin to lightning but with nothing to do with
thunderstorms."
Spalding said evidence of this sort of event could be gained by
analyzing
some leftover material at the site.
"It's quite possible there are some radioactive trace
elements that are
formed by the ions," he said. The Ayoubs, he said, agreed to
send him some
ground samples. "If found, there's no mistaking something
very strange had
occurred. There's only one way those elements could be created.
It requires
high energy radiation."
Scientists conjecturing on the Salisbury mystery got more
information from
residents yesterday as more people came forward with reports of
seeing the
fireball.
Phil Plait, who works at NASA's Goddard Space Flight Center in
Maryland and
who developed the badastronomy.com Web site to clear up
misconceptions about
his science, said he spoke to more Hensmith Road residents who
saw the
flame.
"I really, strongly feel it's not a meteorite," he said
after hearing the
residents' descriptions. "I, unfortunately, don't have a
good alternative
explanation. Unless it was something thrown from a distance.
Sometimes these
things are mysteries forever."
But if the bright light New Durham resident Ron Nordquist saw
Monday night
was the same fireball, it couldn't have been an object simply
thrown over
the trees.
Nordquist said he saw the glowing ball as he walked his dog
around 5 p.m.
"It was like the brightest star you've ever seen," he
said. "It was going
down instead of going across the sky. It seemed like it was going
in slow
motion, even though it happened in seconds. I looked at the dog
and I said
'did you see that?' "
Nordquist mentioned the site to his brother on the phone that
night. It
wasn't until he read the paper that he made a connection.
"I got my map book and looked for Salisbury. And right away,
when I saw M6
or whatever the page was, right away I started getting goose
bumps. I looked
up New Durham, I looked at Salisbury. And I said to myself, 'my
goodness,
I'd seen that.' "
The scientific search is still on.
Sandt Michener, a scientist at the planetarium, said while he
still doesn't
believe the object was a meteorite, he thinks the incident is
worth
investigating further.
"There are a lot of ideas, but it's just so many
possibilities," he said.
"If it is a meteorite, or if it's something else, it's
unusual enough to
merit an investigation."
© Concord Monitor and New Hampshire Patriot
==============
(6) NEW EVIDENCE AGAINST NANOBACTERIA
From Science-Week <prismx@scienceweek.com>
ScienceWeek Abstracts Edition - December 8, 2000
BACTERIOLOGY: NEW EVIDENCE AGAINST NANOBACTERIA
Although the presence of fossils of living nanoscale forms in
known
meteorites now seems questionable if not refuted, there has
recently been
some interest in reports of living nanoscale
entities present as pathogens in mammalian host systems including
humans.
But new experimental evidence does not provide plausible support
for the
existence of a previously undiscovered genus of
"nanobacteria". Instead,
experiments provide evidence that biomineralization previously
attributed to
nanobacteria may be initiated by nonliving macromolecules and
transferred on
"subculture" by self-propagating microcrystalline
apatite.
Copyright (c) 1997-2000 ScienceWeek; All Rights Reserved
============================
(7) IMPACTS AND THE EARLY EARTH
Edited by Iain Gilmour & Christian Koerberl
Springer (Berlin, Heidelberg, New York 2000)
ISBN 3-540-67092-0
List Price DM 198 (ca.£60.00)
Preface
This volume is the first one to result from the activities of the
new
scientific program on "The Response of the Earth System to
Impact Processes"
(IMPACT) of the European Science Foundation (ESF). The ESF is the
European
association of national funding organizations of fundamental
research, with
more than 60 member organizations from more than 20 countries.
One of the
main goals of the ESF is to bring European scientists together to
work on
topics of common concern. The ESF IMPACT program deals with all
aspects of
impact research, mainly through the organization of workshops,
exchange
programs, short courses, and related activities. An important
aspect of the
program is to bring people together to help stimulate
interdisciplinary and
international research.
Impacts of asteroids or comets on the Earth surface have played
an important
role in the evolution of the planet. The ESF IMPACT program is an
interdisciplinary program aimed at understanding impact processes
and their
effects on the Earth System, including environmental, biological,
and
geological changes, and consequences for the biodiversity of
ecosystems. The
program is geared towards understanding of the linkage between
impact
processes and the Earth System, i.e., defining and studying the
effects of
impact events on the environment, including atmospheric,
climatic, biologic,
and geologic effects and interactions between these subsystems.
Important
aspects of future research regard also the consequences of the
high-energy
impact events for the biodiversity of ecosystems. Comprehending
the
processes that are responsible for these interactions is the key
goal of the
program. Currently 12 countries sponsor the program, which was
launched in
1998, but an expansion to 14 countries is anticipated.
The first workshop to be organized as part of the ESF-IMPACT
program was
held at Robinson College, Cambridge, United Kingdom, from
December 13th to
15th, 1998, in. A total of 56 scientists from 10 European
countries, the
United States, Russia and South Africa attended.
Contributions at the meeting covered the following themes:
* Impacts and the Origin of Life on Earth and Mars
* Late heavy bombardment and impact processing of the Earth
* The Earth's Early Cratering Record
* Micrometeorites and Spherule layers
* Impacts through geological time
A selection of 17 papers resulting from this meeting is included
in the
present volume. Manuscripts were reviewed by two referees and
were
considered for publication on the basis of originality and the
themes
discussed at the workshop.
There is currently some discussion on the present state of
scientific
understanding of the role impacts may have played in the
biological and
geological evolution of the Early Earth. There is good evidence
that simple
single celled life forms were already present at the start of the
Archean,
which means that chemical evolution must have occurred during the
Hadean and
life had probably originated at around 4 Ga. Since there are no
Hadean
rocks, our knowledge of the Earth's history during this period is
necessarily based on indirect evidence. The Earth acquired an
oceanic-type
crust formed shortly after the process of core-mantle separation
occurred
some 4.5 Ga, although we have no record of it in the rocks. By
3.8 Ga light
granitic continental crust had formed from the mantle. Proof of
this comes
from the 3.8 Ga granites and associated metamorphosed volcanic
and
sedimentary rocks at Isua in western Greenland, which represent
the oldest
piece of primitive crust known to geologists. Conditions at the
Earth's
surface and in the atmosphere during the Hadean must have had a
powerful
influence on chemical evolution. Estimates for the growth of
continents on
the early Earth cover a wide range of parameters save that there
were no
continents at the beginning. This results in most scientists
assuming that a
global ocean existed in which the pre-biotic chemistry that led
to the
origin of life to place.
The possibility of continued intense bombardment by meteorites
long after
the Earth had formed has led some scientists to conclude that the
emergence
of life could have been deterred for hundreds of millions of
years. Many of
the projectiles would have been much large enough that they would
have
generated enough heat to boil the surface of the oceans as well
as throwing
large clouds of dust and molten rock into the atmosphere. The
implication of
this hypothesis is that the impacts would have deterred the
emergence of
life anywhere near the surface of the oceans until perhaps as
late as 3.8
billion years ago. On the other hand, comets and meteorites may
have
delivered important organic molecules to the Earth. The question
of how this
delivery could have influenced the development of life on the
early Earth,
and if bacterial life forms could survive the forces of an
impact, are
discussed in the paper by Burchell et al. The macromolecular
organic
materials present in meteorites and their role in the origin of
life on
Earth are subsequently discussed by Sephton and Gilmour, and in a
related
paper, Wright et al. discuss the effects of atmospheric heating
on carbon
compounds in meteorites and micrometeorites.
Only 10% of the 150 or so known impact craters on Earth date from
the
Precambrian, an Era spanning some 88% of the Earth's history. The
Precambrian encompasses fundamental events in the origin and
evolution of
our planet from the origin of life itself, the development of
continents, to
the development of eukaryotic organisms and the vast
diversification of life
that occurred at the end of this Era. We know from the lunar
cratering
record that the Earth was subject to intense bombardment by
asteroids and
comets early in its history on a scale far greater than anything
it has
experienced since. Koeberl et al. discuss their search for
evidence of such
a heavy bombardment on Earth in about 3.8 to 3.9 million-year-old
rocks from
Greenland.
Another hot topic is the geological evidence for Early Archean
impact
events, in particular the occurrence of spherule layers in the
Precambrian
Barberton formation (South Africa), which may represent the
remnants of
large-scale impact events. This is a controversial area, because
many of the
normally accepted criteria for the identification of impact
structures, such
as shock metamorphism in rock-forming minerals, are not
preserved.
Shukolyukov et al. present new data based on chromium isotopic
ratios that
they argue proves that the large platinum group element
enrichments
associated with these spherule layers are extraterrestrial in
origin. In
contrast, Reimold et al. argue that the enrichments are too great
to be of
primary origin and suggest that the mineralogical and geochemical
features
of the spherule layers are the result of (secondary)
mineralization.
The importance of the recognition of an impact record in the
Precambrian
sedimentary succession is also emphasized by Simonson et al.
Impact
structures per se, as well as their proximal ejecta blankets, are
limited to
areas on the order of a few hundred kilometers in diameter,
whereas distal
ejecta from the largest impacts can be distributed globally.
These authors
examined various late Archean to Paleoproterozoic formations from
Australia
and South Africa that contain preserved spherule layers. They
interpreted
these layers as altered microtektites and microkrystites and
therefore
inferred that they have an impact origin.
A different type of extraterrestrial deposit is described by
Kettrup et al.,
who discuss occurrences of fossil micrometeorites from about 18
to 1.9
billion year old sediments in Finland. It is astonishing that
these
materials have survived with only little alteration.
A major theme of the workshop was the need for the better
recognition of
ancient impact events in the geological record. Vishnevsky and
Raitala
describe the use of impact-produced diamonds as indicators of
shock
metamorphism in Precambrian rocks. Gibson and Reimold provide a
useful
review of the Vredefort impact structures in South Africa (with
an age of
2.02 billion years the oldest, and by chance also the largest
known, impact
structure on Earth) as a case study for old, deeply eroded impact
structures. Kenkman and co-workers cover techniques of structural
geology in
their contribution that might be applied in future from a better
understanding of the geology of large ancient impact structures.
In a
related paper, Abels et al. describe the use of remote sensing
techniques in
the study of old and deeply eroded impact structures.
More general topics follow. Hughes provides a review of cratering
rate
investigations, and Jones et al. discuss rarely studied features
of
carbonate rocks that result of from impact-induced melting
processes. At the
end is a trio of papers by Lilljequist, Suuroja and Suuroja, and
Puura et
al., describing various Scandinavian structures as case studies
of more
recent impact events.
From these contributions, and from the discussions at the
workshop, it is
clear that impact cratering events have played a major role in
the very
early history of our planet. We are only beginning to try and
decipher the
evidence of such early events, as we currently do not even have
good
criteria for the recognition of Early Archean impact events, and
a lot
remains to be done. We hope that the current volume is a first
step in the
right direction.
Iain Gilmour, Open University University of Vienna , Milton
Keynes, UK
Christian Koeberl, Vienna, Austria
December 1999
For further information, please contact:
Dr Iain Gilmour
Planetary and Space Sciences Research
Institute
The Open University
Milton Keynes, MK7
6AA
United
Kingdom
I.Gilmour@open.ac.uk>
Url: http://pssri.open.ac.uk
============================
* LETTERS TO THE MODERATOR *
============================
(8) PANSPERMIA AND UNSCIENTIFIC NOTIONS
From Max Wallis <wallismk@Cardiff.ac.uk>
Konrad Ebisch on CCNet of 4 December sarcastically contrasted
Andrew
Glikson's assertion
"...there can be little doubt that life abounds
throughout the
universe...."
with Glikson's put-down for panspermia as an "Extraordinary
claim" and "a
philosophical notion rather than a scientific theory" (CCNet
essay of 1
December).
The description of one hypothesis makes it sound like an accepted
theory,
while the other sounds like a nut-case notion, commented Konrad,
finishing
with a plea for open minds. While polemical essays have a place,
I'd comment
more strongly about Glikson's loose terminology.
Classification of ideas as 'notions', 'hypotheses', 'theories' or
'paradigms', with or without the descriptor 'scientific', is
amenable to
philosophical and linguistic analyses. A trawl through CCNet
records,
including refereed journal papers, shows that panspermia is
currently
regarded by significant numbers of practitioners as a
"working hypothesis".
That's been true since NASA claimed to have detected signs of
fossilised
life in a Martian meteorite. But in fact, ever since SNC
meteorites were
established as originating from Mars and Chassigny was shown to
have been
only lightly shocked in transit, in the 1980s, panspermia has
served as a
working hypothesis that was very amenable to scientific
experimentation and
theoretical analysis.
Evidently there were cultural inhibitions up till the last few
years, but
the stages summarised by Matthew Genge (CCNet last week)
- ejection from Mars
- survivability during ejection and transport
- planetary landing
were all topics of scientific study in the 1980s. Theoretical and
experimental developments over the last few years have served to
confirm the
picture - which is the method whereby hypotheses turn into
theories, and
eventually into paradigms.
What of Andrew Glikson's starting point that "life abounds
throughout the
universe"? Myself I give that higher status than a
"nut-case notion", taking
it as a working hypothesis that leads to comparing interstellar
transfer
(panspermia again) with spontaneous generation on individual
sites through
the galaxy. But others may accept it on general grounds, eg. a
dislike of
geocentric ideas. For them it is a philosophical notion.
As further example, take Andrew Glikson's "the biosphere is
founded on yet
little understood universal quantum information laws". One
problem with such
a statement is that philosophers view "laws" as human
constructs. And
Newton's laws, for example, had limited lifetime (or
applicability).
I'm more concerned with the "quantum information"
reference, which as we all
know is based on mind-boggling concept of entanglement - that
quantum
objects separated by macroscopic distances have faster-than-light
linkage.
I say "mind-boggling" because that is the description
of one of the foremost
experimentalists of their explanation of photon coherence
experiments with a
pair of optical crystals [1,2]. From the viewpoint that a
'photon' can be on
two paths simultaneously but when detected is only on one of the
paths, they
inferred from the two-crystal experiment that "what is
knowable in principle
rather than what is known" determines the photon path.
A mind-bogglingly
anthropocentric explanation!
Quantum information "laws" based on entangled photons
are inconsistent with
the wave theory of light and run up against fundamentals of
locality and
causality, that ensure time sequence and require signals to have
a finite
speed [3]. The basis is the mystical or even crazy [4]
interpretation of
quantum physics espoused by Paul Davies, as cited by Glikson. So
the quantum
information law foundation of Glikson's biosphere may be in
fashion, but is
in conflict with basic scientific concepts. That surely excludes
it as a
scientific hypothesis and puts it more in the category of a
"notion".
Why Glikson and scientists in general adopt unscientific notions
is a
sociological and cultural question, as were
"inhibitions" on panspermia
mentioned above. I wouldn't address that, apart from noting that
scientists
are human.
[1] Greenberger D M, Horne MA, Zeilinger A, Physics Today, 46,
22, 1993
[2] Wallis M K, Contemporary Phys. 39, 483-486, 1998; New
Scientist letters,
23 May 1998
[3] Marshall T W, webpage - www.keyinnov.demon.co.uk/antiqm.htm
[4] Greenberger D, Zeilinger A, "Quantum theory still crazy
after all these
years" Physics World, 8, 33-38, 1995.
Max Wallis < wallismk@cardiff.ac.uk
>
Cardiff Centre for Astrobiology
================
(9) VISCOUS MAGMA FLOW RATES AND CONTINENTAL ACCRETION RATES ARE
NOT THE
SAME THING
From Andrew Glikson <geospectral@spirit.com.au>
Dear Benny
I refer to the news item "Another blow to geological
gradualism: continental
land masses created in fast bursts" (CCNet 7.12.00). While I
have not as yet
seen the original article, I suggest that rather than
constituting "ANOTHER
BLOW to geological gradualism ... " etc., the way this news
item is
presented is ANOTHER BLOW to the accurate reporting of scientific
results,
as follows:
1. Continental masses form by a variety of mechanisms, including
(a) lateral
accretion along ocean margin subduction zones and arc-trench
accretional
wedges; (b) intercontinental collisions, for example the
Himalaya, where
sediments, volcanics and intrusive plutons accumulate and undergo
partial
fusion, and (c) production and emplacement of magmas at a range
of crustal
levels consequent on partial melting of the subcontinental mantle
and deep
crustal anatexis, magmatic underplating and intrusion.
2. The rates of continental accretion are determined by the
time-integrated
interval/s over which the various components (sedimentary,
volcanic,
plutonic) are added laterally and vertically to
the continental crust, as measured by isotopic age determinations
of
accreted terrains - a relevant example being the subducted
northeast Pacific
margins. The distribution pattern of isotopic age data does in
fact reveal
episodic continental accretion rates, including periods of
intense thermal-igneous-tectonic events represented by peaks on
isotopic age
frequency plots. Examples are magmatic-tectonic maximae about 1.8
Ga
(billion years), 2.7 Ga , 3.2 Ga, 3.5 Ga. The factors underlying
this
episodicity remain subject of a range of geotectonic models.
3. The viscous flow rate of any individual magmatic increment,
for example
the mobile crystal/melt mass which forms a granitic pluton,
depends on
factors such as the composition of the magma, degree of
crystallisation,
water content, attendant lithostatic pressures and tectonic
stress field,
and so on. However, the consequent magmatic viscous flow rates
have nothing
to do with the overall temporally protracted or episodic rates of
continental accretion.
Andrew Glikson
Austrtalian National University
Canberra, ACT 0200
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