PLEASE NOTE:
*
CCNet 131/2002 - 15 November 2002
--------------------------------
"The lack of a mass extinction suggests that in large
impacts, where
the collision occurs is just as important as its
size."
--Gordon Walkden, Aberdeen University, 14 november 2002
"It may well be that we might get devastating meteorite
impacts in
the future but it is unlikely that there will be a repeat of the
impact
that saw the end of the dinosaurs."
--Simon Kelley, Open University 14 November 2002
"At the time, 214 myrs ago, early dinosaurs and mammals
lived in,
what was then, the red arid deserts of Southwest Britain. The
fall of the
spherules, which may have still been molten, and the other
effects of the
impact did not, however, cause a mass extinction. The animals of
the
Triassic period were not affected and survived until 13 million
years later
when many became extinct for an, as yet, unknown reason."
--Matthew Genge, NEO Information Centre, 14 November 2002
(1) FIRST UK IMPACT LAYER DISCOVERED
Matthew Genge <m.genge@ic.ac.uk>
(2) IMPACT 'SHOWERED DEBRIS OVER BRITAIN'
BBC News Online, 14 November 2002
(3) NASA PREPARES FOR "LAST CHANCE" METEOR SHOWER
NASANews@hq.nasa.gov
(4) ESA'S SHORTCUT TO A COMET
Andrew Yee <ayee@nova.astro.utoronto.ca>
(5) ONLINE LEONID EXPRESS FORM
Rainer Arlt <rarlt@aip.de>
(6) SCIENTISTS GENERATE 'LABORATORY EARTHQUAKES'
Ananova, 15 November 2002
(7) RE: MIRROR MATTER MYSTERY
Robert Foot <foot@physics.unimelb.edu.au>
============
(1) FIRST UK IMPACT LAYER DISCOVERED
>From Matthew Genge <m.genge@ic.ac.uk>
First UK Impact Layer Discovered
Matthew Genge, NEO Information Centre
http://www.nearearthobjects.co.uk
In an article published today in the journal Science researchers
led by Dr
Gordon Walkden of Aberdeen University have reported the discovery
of a 214
myr old impact layer in the rocks of the west of England. The 2cm
thick
layer consists of millimetre-sized green spherules that were
formed as
molten droplets of rock in the impact of a large asteroid or
comet with the
Earth. The droplets formed by condensation from gases generated
by
vaporisation of rocks at enormous temperatures and were scattered
over the
entire Earth surface.
Speaking to the NEO Information Centre, Walkden said "I
discovered the layer
in 1983 but didn't realise it was an impact layer until the late
1990s." Mr
Julian Parker, from Aberdeen, studied the spherule layer with
Walkden and
discovered quartz grains that had been deformed by intense
pressures. "The orientation of the distorted planes through
the grains
showed they had been shocked," said Walkden, "and prove
the layer was formed
as debris thrown out from a giant collision."
Dr Simon Kelly, from the Open University, measured the age of the
west
country spherule layer using the decay of radioactive potassium,
that is
found in all potassium-bearing minerals. The age of 214 myrs is
the same as
the 100 km wide Manicouagan Crater in Canada which is, therefore,
the likely
source of the impact layer. Kelly, however, suspects that a
number of
craters that have similar ages may have formed at the same time
as a string
of impacts.
At the time, 214 myrs ago, early dinosaurs and mammals lived in,
what was
then, the red arid deserts of Southwest Britain. The fall of the
spherules,
which may have still been molten, and the other effects of the
impact did
not, however, cause a mass extinction. The animals of the
Triassic period
were not affected and survived until 13 million years later when
many became
extinct for an, as yet, unknown reason.
"The lack of a mass extinction," says Gordon,
"suggests that in large
impacts, where the collision occurs is just as important as its
size." The
impact at Chicxulub 65 myrs ago, that is widely believed to have
caused the
extinction of the dinosaurs, occurred into carbonate and sulphate
rocks and
it is thought that the gases generated by the impact caused
climatic
changes that resulted in the extinction.
The location of the impact layer is currently being kept secret
in order to
protect it. Specimens of the layer, however, are being put on
public
exhibition at the Natural History Museum in London, at the NEO
Information
Centre at the National Space Centre in Leicester, and the
National Museum of
Scotland, Edinburgh. Dr Gordon Walkden is also taking part in a
public
discussion on impacts and mass extinctions, together with Dr
Matthew Genge
from Imperial College, at 2.30 pm GMT on Nov 15 at the Darwin
Centre of the
Natural History Museum. This discussion will be broadcast live on
the
internet and at the National Space Centre, Leicester and the
National Museum
of Scotland, Edinburgh.
===========
(2) IMPACT 'SHOWERED DEBRIS OVER BRITAIN'
>From BBC News Online, 14 November 2002
http://news.bbc.co.uk/1/hi/sci/tech/2472903.stm
By Helen Briggs
BBC News Online science reporter
Evidence has emerged of how Britain's history was shaped by an
asteroid
collision 214 million years ago.
Rock blasted out of the ground by an asteroid hitting the Earth
has been
found for the first time in the southwest of England.
Canada still bears the scars of the explosion, which splattered
hot rock and
dust across the British Isles.
The space rock hit what is now Manicouagan, Quebec, opening up a
100-kilometre-wide (62-mile-wide) crater that can be seen by
astronauts from
space.
The Atlantic Ocean had not appeared at the time, so the two land
masses
(Europe and North America) were much closer than they are today.
The rock was found near Bristol by geologists at the University
of Aberdeen.
Dr Gordon Walkden said: "We have found evidence of a massive
shockwave
carrying molten rock and dust that has left a thin layer of glass
beads and
shattered mineral grains across the ancient British land
surface."
Nuclear bomb
The material has the distinctive hallmark of an asteroid slamming
into the
planet.
The space body, about five km (three miles) wide, generated a
shockwave 40
million times larger than the Hiroshima blast.
The impact material was found among sediments of the late
Triassic Period
Molten rock and debris were hurled high into the Earth's
atmosphere, some of
it falling on to Britain.
The landscape 214 million years ago was very different to the
rolling green
fields of today.
It was largely arid desert, sparsely populated by ferns,
reptiles, lizards,
and small mammals.
"Anything standing would have been flattened by the
blast," said Dr Walkden,
who discovered the rock in the 1980s.
He knew at once there was something unusual about the sample,
which he
describes as tiny green balls embedded in pinky-coloured rock,
but its
ancient origins have only just come to light.
"It was very clearly something strange that I wasn't able to
identify at the
time," the senior geology lecturer told BBC News Online.
"It sat in a drawer
for a long time."
It was to be 20 years before he realised its scientific value,
when he saw
similar deposits from a crater in Mexico, where the asteroid
blamed for
killing off the dinosaurs landed.
Dark skies
According to Dr Simon Kelley, of the Open University in Milton
Keynes, who
dated the Bristol sample, it is the first recorded example of
such an impact
deposit in Britain.
The rock was found at an outcrop near Bristol
"If you had been in Britain at the time, the Sun would have
been blotted out
by the dust and gases from the impact," he told BBC News
Online.
"First you would have seen a big flash over the horizon.
Then the skies
would have gone dark; then it would have rained hot dust and
rocks. The
effects would have lasted for years."
The shock wave from the asteroid would have carried molten rock
and dust
thousands of kilometres.
Scientists are now searching for other remnants of the blast to
study what
happened to biodiversity on Earth.
Public display
The Canadian impact does not seem to have had as devastating an
effect as
the impactor that signalled the downfall of the dinosaurs.
This is thought to be because it hit normal rock, rather than
salt deposits
capable of releasing poisonous gas.
"It may well be that we might get devastating meteorite
impacts in the
future but it is unlikely that there will be a repeat of the
impact that saw
the end of the dinosaurs," said Dr Kelley.
A piece of the material discovered by Dr Walkden will be on
display at the
Darwin Centre at the Natural History Museum, London, on 15
November.
Specimens will also be on display at the National Space Centre in
Leicester,
the National Museum of Scotland, Edinburgh, and at the University
of
Aberdeen.
The research is published in the journal Science.
Copyright 2002, BBC
==========
(3) NASA PREPARES FOR "LAST CHANCE" METEOR SHOWER
>From NASANews@hq.nasa.gov
Donald Savage/Nancy Neal
Headquarters,
Washington
November 14, 2002
(Phone: 202/358-1547)
RELEASE: 02-221
The early morning hours of Nov. 19 may be your last chance to see
the
spectacular Leonid meteor shower in its full glory, according to
astronomers.
"Even with the full moon, this year's Leonids will probably
be better than
any other for the next hundred years," said Dr. Don Yeomans,
an astronomer
at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "If
you're ever going
to see them, this might be the year to try," he said. NASA
is taking
advantage of the event for several research efforts around the
world.
The shower is predicted to have two peaks, each a couple of hours
long,
during which the most meteors can be seen. The shower's second
peak, most
prominent in North American skies, is expected at around 5:30
a.m. EST Nov.
19, and promises the rare spectacle of a few meteors every minute
or even
more. "Observers in good locations away from city lights
might see a few
hundred per hour. You'll only get to see the bright ones because
the
moonlight will wash out the ones that aren't as bright,"
said Yeomans. Last
year, observers did not have to contend with the Moon and saw
meteors at a
pace of several hundred per hour.
An earlier peak is expected over Europe and Africa the night of
Nov. 18, and
observers in North America might see a few grazers -- meteors
skimming the
top of the atmosphere -- from this first peak starting around
11:30 p.m. EST
Nov. 18.
The Leonids are grains of dust from comet Tempel-Tuttle colliding
into the
Earth's atmosphere. Most Leonid particles are tiny and will
vaporize very
high in the atmosphere due to their extreme speed (about 44 miles
per
second, or almost 71 km/sec), so they present no threat to people
on the
ground or even in airplanes. As it progresses in its 33-year
orbit, the
comet releases dust particles every time it comes near the Sun.
Earth
intersects the comet's debris trail every year in mid-November,
but the
intensity of each year's Leonid meteor shower depends on whether
Earth
ploughs through a particularly concentrated stream of dust within
the
broader debris trail.
The dust that Tempel-Tuttle shed in 1866 forms the stream
predicted to give
Americans a good show this year. Last year, people in Asia saw
the plentiful
collisions within that stream. A dust stream from 1767 provided
last year's
peak hour of viewing in North America and will provide this
year's peak hour
of viewing in Europe. After 2002, Earth won't hit either of those
streams
again for decades to come, and is not predicted to encounter a
dense Leonid
stream until 2098 or 2131.
The golden rule for watching the Leonids -- or any meteor shower
-- is to be
comfortable. Be sure to wrap up warmly -- a sleeping bag placed
atop a lawn
chair facing east is a good way to enjoy the show. Put your chair
in a
clear, dark place with a view of as much of the sky as possible.
Don't stare
at any one place -- keep your eyes moving across the sky. Most
Leonids will
appear as fleeting streaks of light, but watch for the bigger
ones that
produce fireballs and trails -- some trails will remain visible
for several
minutes or more.
The Leonids get their name from the constellation where they
appear to
originate; the meteors will be radiating from the Sickle pattern
in the
constellation Leo the Lion, which will be rising out of the
east-northeast
sky. Don't look directly at the constellation, but at the area
above and
around it. And, though you don't need them to see the Leonids, a
pair of
binoculars could come in handy.
Researchers think meteors might have showered the Earth with the
molecules
necessary for life's origin. A two-aircraft campaign, led by
astronomer Dr.
Peter Jenniskens of the SETI Institute and NASA's Ames Research
Center,
Moffett Field, Calif., will investigate this possibility.
"We are looking
for clues about the diversity of comets and their impact on the
chemistry of
life's origin on Earth," Jenniskens said.
"We are eager to get another chance to find clues to two
puzzling questions:
What material from space rains down on Earth, and what happens to
the
(meteor's) organic matter when it interacts with the
atmosphere?" said Dr.
Michael Meyer, senior scientist for astrobiology at NASA
Headquarters in
Washington.
On Nov. 15, a team of 42 astrobiologists from seven countries
will depart
from southern California's Edwards Air Force Base on a mission to
Spain to
observe this year's two Leonid storm peaks. The DC-8 Airborne
Laboratory,
operated by NASA's Dryden Flight Research Center, Edwards,
Calif., will
carry high-speed cameras; a radio receiver to listen to upper
atmosphere
molecules; and a team of meteor observers, who will keep track of
the meteor
activity for satellite operators concerned about impact hazards.
"This final deployment of the Leonid Multi-instrument
Airborne Campaign
program promises an important and unique database for the
development of
instruments targeted at in situ sampling of cometary materials
and for the
future definition of comet missions," said Dr. John Hillman,
lead scientist
for planetary astronomy at NASA Headquarters. "It is hoped
that these
scientific data will provide new insights for the comparative
studies of
comets," he said.
Although the meteors are harmless to people, there is a slight
chance that a
satellite could be damaged if it was hit by a Leonid meteoroid.
The
meteoroids are too small to simply blow up a satellite. However,
the Leonids
are moving so fast they vaporize on impact, forming a cloud of
electrified
gas called plasma. Since plasma can carry an electric current,
there is a
risk that a Leonid-generated plasma cloud could cause a short
circuit in a
satellite, damaging sensitive electronic components.
NASA's Goddard Space Flight Center, Greenbelt, Md., is
responsible for
controlling a large number of satellites for NASA and other
organizations
and is taking precautions to mitigate the risk posed by the
Leonids. These
include pointing instrument apertures away from the direction of
the Leonid
stream, closing the doors on instruments where possible, turning
down high
voltages on systems to decrease the risk of a short circuit, and
positioning
satellites to minimize the cross-section exposed to the Leonids.
Minimizing the threat meteoroids pose to satellites is the second
major area
of NASA's Leonid research. From five key points on the globe and
from the
International Space Station, NASA researchers will use special
cameras to
scan the skies and report activity around the clock during the
Leonid
shower. Led by Dr. Rob Suggs of the Engineering Directorate at
NASA's
Marshall Space Flight Center in Huntsville, Ala., the research is
part of a
long-term goal to protect spacecraft from potentially damaging
meteoroids.
Using "night-vision" image-intensifier video systems
and sky-watchers
outfitted with Palm computer software developed to record visual
counts,
NASA engineers and astronomers will record their observations for
later
analysis. Another tool at Marshall's disposal is
"forward-scatter radar" --
an early warning system built by Suggs, Dr. Jeff Anderson, also
of
Marshall's Engineering Directorate, and Dr. Bill Cooke, an
astronomer at
Marshall.
"Our system is pretty simple," said Suggs. "We use
an antenna and a
computer-controlled shortwave receiver to listen for 67 MHz
signals from
distant TV stations." The transmitters are over the horizon
and normally out
of range. When a meteor streaks overhead, the system records a
brief ping --
the echo of a TV signal bouncing off the meteor's trail. Like the
image-intensified cameras, this system is capable of detecting
meteors too
dim to see with the unaided eye.
The research data from the Leonids shower will be analyzed to
help NASA
engineers refine their forecasts for spacecraft; by better
determining
where, when and how the meteors will strike, NASA can improve
protective
measures to prevent or minimize damage to spacecraft.
For more information, including predicted peak times for major
cities and
NASA media contacts, refer to:
http://www.gsfc.nasa.gov/topstory/2002/1114leonid.html
==========
(4) ESA'S SHORTCUT TO A COMET
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
ESA Science News
http://sci.esa.int
14 Nov 2002
ESA's shortcut to a comet
Night owls across Europe, get ready. On the night of 18-19
November 2002,
you may see a spectacular sky show. As tiny particles in Comet
55/P
Tempel-Tuttle's tail enter Earth's atmosphere, they will pierce
through it,
heating up, and finally explode. Welcome to one of the most
spectacular
natural fireworks displays of the year: a meteor shower called
the Leonids.
Unlike in 2001, this year the Leonids will be very well visible
from Europe.
The meteor showers are expected every night between 13 and 21
November 2002.
Scientists expect the Leonids meteor shower to reach its peak at
04:00 CET,
in Europe, and 10:30 on the night of 18-19 November 2002.
Die-hards willing to travel each year all around the planet look
for the
best location to witness the shooting-star show. Some years that
can be in
the middle of a desert. This year, that will be on top of a cold
mountain
close to Pico Veleta in Granada, Spain. The scientists aim to
obtain
information about the meteor shower, the structure of our own
atmosphere,
and comets.
"It's like a cheap comet mission," says Detlef Koschny,
a member of the ESA
team. "The behaviour of the particles left in past orbits
tells us things
about comets, even without having to go there."
Koschny has led the ESA Leonids campaigns since 1998. The team
has observed
the meteors in The Netherlands, Spain, Germany, and Australia.
This year the
location is once again Spain. Why? Statistically it is one of the
places
where there are higher chances of good weather. Secondly,
scientists can use
a professional observatory, from which the visibility conditions
are
optimal. Lastly, technicians are at hand to help these
Leonid-chasers solve
possible engineering problems.
Scientific models predict the intensity and the maxima of the
storms, and
this year's shower appears promising. Scientists are expecting
about 3000
events per hour in the stronger, first peak. However, the light
of the near
full moon will make observations more difficult and may
reduce the apparent number by 10%.
The 2002 Leonids show could be the last one for many years to
come.
Calculations of the comet's path predict that the next
perihelions, or
closest points of approach, of the comet in 2031 and 2065 could
be
significantly less dramatic. Jupiter's gravitational pull is
pushing the
orbit of the comet further away from Earth's orbit.
The path of our planet intersects the comet's trails twice this
year.
Firstly, Earth's atmosphere will encounter the trail the comet
left in 1767,
seven comet journeys ago. These particles will create a shower
storm visible
from Europe. A few hours later, a second trail Comet
Tempel-Tuttle left in
1866, about four cycles ago, will cause another shower. North
American
sky-watchers will benefit from this second shower.
Koschny is also involved in the Rosetta mission, the ESA
spacecraft to Comet
Wirtanen due for launch in January 2003. "The composition of
the particles
belonging to the two different trails can tell us a lot about the
structure
of the comet. If we observe different chemical properties,
we can conclude that the particles are coming from different
parts of its
surface." Knowing whether a comet is homogenous or not is
very useful since
scientists have to decide on a landing site for the Rosetta
lander touchdown
on the comet in 2011.
The Leonids enter Earth's atmosphere at a speed around 70
kilometres per
second -- nearly twice as fast as other meteors. Why? Comet
Tempel-Tuttle
orbits the Sun roughly in the opposite direction than the Earth's
orbit of
the Sun. There are therefore almost head-on collisions between
Earth and
comet-trail debris. However, this is much less dangerous than it
sounds.
"The biggest pieces can't exceed 0.5 metres in
diameter," says Koschny. "The
gases vaporising from the nucleus of the comet would not be able
to lift
anything bigger than that. These rocks are small enough to be
vaporised by
the Earth's atmosphere and really do not constitute a risk for
the
observers. More worrying is the effect they may have on
satellites, which
could be seriously damaged by such collisions."
For video animations, see:
http://sci2.esa.int/leonids/leonids2001/video.htm
USEFUL LINKS FOR THIS STORY
* Meet the team
http://spdext.estec.esa.nl/content/doc/cb/30923_.htm
* Typical Leonids puzzles
http://spdext.estec.esa.nl/content/doc/d0/30928_.htm
* Previous Leonids campaigns
http://sci2.esa.int/leonids/leonids2001/links.htm
* Listening to the Leonids
http://spdext.estec.esa.nl/content/doc/dd/30941_.htm
* Video animations
http://sci2.esa.int/leonids/leonids2001/video.htm
* Chasing meteors on-board airplanes
http://spdext.estec.esa.nl/content/doc/cf/30927_.htm
* More about Rosetta
http://sci.esa.int/rosetta/
IMAGE CAPTIONS:
[Image 1:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=1&cid=1&oid=30921&ooid=30942
]
The Leonids as seen in 2001. Copyright © 2001 Shigemi Numazawa,
Japan
Planetarium Laboratory; courtesy Sky & Telescope
[Image 2:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=1&cid=1&oid=30921&ooid=30936
]
Spanish radio telescope ready for the Leonids. Copyright ©
"Observers", AlltheSky.com
============
(5) ONLINE LEONID EXPRESS FORM
>From RainerArlt <rarlt@aip.de>
Dear meteor enthusiasts,
As every year, we are trying to compile reliable information
about the
Leonid peaks soon after the events. I created a small ONLINE
reporting form
to help here.
http://www.imo.net/leo02/online.html
The structure of the form is as simple as possible. All amateurs
are invited
to contribute with their counts. It is not necessary to have a
long-term
observing experience. Just be careful to determine a Stellar
Limiting
Magnitude representing the sky quality.
The form sends an e-mail message to me, and possibly to people
responsible
for data utilization and the quick generation of results
(probably Mark
Davis, Marc Gyssens, Vladimir Krumov).
Giving your e-mail address in the form is optional, but is
helpful if
questions arise.
All those of you who record more information than required in the
form, are
kindly asked to send their usual observing report later in
November. The
main point is of course meteor magnitudes which do not feature in
the ONLINE
form.
I hope the form is helpful and wish clear skies!
Rainer
www.imo.net/leo02/
Rainer Arlt -- Astrophysikalisches Institut Potsdam
-- www.aip.de
Visual Commission - International Meteor Organization -- www.imo.net
rarlt@aip.de -- phone:
+49-331-7499-354 -- fax: +49-331-7499-526
=======
(6) SCIENTISTS GENERATE 'LABORATORY EARTHQUAKES'
>From Ananova, 15 November 2002
http://www.ananova.com/news/story/sm_709644.html?menu=news.scienceanddiscovery
Scientists have for the first time generated "laboratory
earthquakes".
It will help them pinpoint the origins of some of the largest and
most
violent tremors ever to hit the earth.
Experts at University College London are now able to recreate the
exact
pressure and temperature conditions of a quake.
They say it will assist them in their quest to answer questions
that have
baffled scientists for years.
Focusing their research on "deep earthquakes", which
occur between 40 and
400 miles deep, researchers found quakes can be generated from at
least 130
miles down.
Dr David Dobson, who led the study, said: "Understanding the
processes
behind deep earthquakes is vital in helping scientists understand
how plate
motions are related to the convection in the deep Earth which
drives plate
tectonics.
"Deep and intermediate focus earthquakes are an important
and mysterious
class of earthquakes. Understanding these deep earthquakes could
be the key
to unlocking the remaining secrets of plate tectonics."
During the study the scientists compressed rocks similar to those
found deep
in the earth to pressures and temperatures of extreme magnitude,
recreating
the conditions hundreds of miles below.
Experts were then able to watch rocks and minerals under the
unique
conditions, witnessing them "dehydrate" as they heated
up, fractured and
then split - contributing to the overall effect of an earthquake.
The largest ever recorded deep earthquake was at magnitude 8.3
and occurred
375 miles below Bolivia in 1994.
Copyright 2002, Ananova
============================
* LETTERS TO THE MODERATOR *
============================
(7) RE: MIRROR MATTER MYSTERY
>From Robert Foot <foot@physics.unimelb.edu.au>
Hi Benny,
I remember at one point i was going to e-mail you... but i didn't
get around
to it... I think someone asked you about the mirror matter
theory.. and I
didn't think what you replied was correct... I think it was to do
with how
mirror matter could interact with ordinary matter. Basically, it
is possible
for small non-gravitational interactions to exist coupling
ordinary and
mirror matter together. This is a new `fundamental' interaction.
Its not ad
hoc, because if you look at the particle physics then theortical
constraints
imply only one possible force... so its form is fixed, but its
strength
depends on a (theoretically) free parameter.. (which is the case
for all the
other forces we know about).
If you would like more details, please read the relavent chapters
to my
book, available at
http://www.ph.unimelb.edu.au/~foot/harder.pdf
(the first page is blank.. just scroll down...).
Best regards,
Robert
--------------------------------------------------------------------
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.
DISCLAIMER: The opinions,
beliefs and viewpoints expressed in the articles and texts and in
other
CCNet contributions do not necessarily reflect the opinions,
beliefs and
viewpoints of the moderator of this network.
----------------------------------------------------------------------------