PLEASE NOTE:
*
CCNet 72/2001 - 29 May 2001
----------------------------
"In the early darkness of April 23, as Washington was
beginning to
relax after the spy plane crisis in China, alarm bells began to
go off
on the military system that monitors the globe for nuclear
blasts.
Orbiting satellites that keep watch for nuclear attack had
detected a
blinding flash of light over the Pacific several hundred miles
southwest of
Los Angeles. On the ground, shock waves were strong enough to
register
halfway around the world. Tension reignited until the Pentagon
could
reassure official Washington that the flash was not a nuclear
blast. It
was a speeding meteoroid from outer space that had crashed into
the
earth's atmosphere, where it exploded in an intense fireball.
[...]
Preliminary estimates, Dr. ReVelle said, are that the cosmic
intruder was
the third largest since the Pentagon began making global
satellite
observations a quarter century ago. Its explosion in the
atmosphere
had nearly the force of the atomic bomb dropped on
Hiroshima."
--William J. Broad, The New York Times, 29 May 2001
(1) LISTENING FOR NUKES: A METEOR DETECTION PROJECT
Space.com, 24 May 2001
(2) MILITARY WARNING SYSTEM ALSO TRACKS BOMB-SIZE METEORS
The New York Times, 29 May 2001
(3) ASTEROID FLYBY NOT TOO CLOSE
Albuquerque Journal, 26 May 2001
(4) JAPANESE SCIENTIST FINDS CLUES OF EALIER MASS EXTINCTION
Andrew Yee <ayee@nova.astro.utoronto.ca>
(5) PLUTO HAS BIG SHINY COLLEAGUE
Andrew Yee <ayee@nova.astro.utoronto.ca>
(6) NEW WORLD RIVALS PLUTO
BBC News Online, 24 May 2001
(7) NASA TO BLAST HOLE IN COMET
The Guardian, 26 May 2001
(8) NEO NEWS
David Morrison <dmorrison@arc.nasa.gov>
(9) IMPACT SEQUENCE IN THE GEOLOGICAL RECORD
Hermann Burchard <burchar@mail.math.okstate.edu>
(10) SHAPE OF PYRAMIDS
David W. Hughes <D.Hughes@sheffield.ac.uk>
(11) AND FINALLY: CHINESE MAKE A BIG THING OF VEGETABLES FROM
OUTER SPACE
The Sunday Times, 27 May 2001
=============
(1) LISTENING FOR NUKES: A METEOR DETECTION PROJECT
From Space.com, 24 May 2001
http://www.space.com/scienceastronomy/solarsystem/nuke_meteor_010524.html
By Robert Roy Britt
Senior Science Writer
If anyone tries to secretly test a nuclear weapon, anywhere in
the world,
the U.S. Department of Energy will know about it. Same goes for
any large
space rocks that try to sneak past our planet's natural defense
system.
The technology that monitors both of these potentially hazardous
events is
amazingly simple. A handful of microphones positioned around the
United
States listen for a telltale atmospheric pressure wave, a
phenomenon that
circles the globe at a frequency too low for the human ear to
detect.
A similar system is now under construction worldwide, designed to
help
monitor and enforce compliance with the Comprehensive Nuclear
Test Ban
Treaty. A recent study, however, questions whether the technology
is up to
the task.
The sensitive but simple detection system, which officials say
can pinpoint
the source of a nuclear blast by noting when the pressure wave
arrives at
each microphone, also routinely detects giant space rocks that
slam into
Earth's atmosphere, vaporizing and producing a similar pressure
wave.
On April 23, researchers monitoring the set-up from the Los
Alamos National
Laboratory detected an explosion out over the Pacific Ocean.
After comparing
the data with other monitoring stations, they determined it was
not a rogue
nation setting off a bomb, but rather an object the size of a
small car
burning up as it raced through the atmosphere toward the planet.
Quite a show
The object plunged into the atmosphere several hundred miles
(kilometers)
west of the northern portion of Baja California. It's possible no
one saw
it. But that doesn't mean it wasn't there.
The explosion was equivalent to at least 6,000 tons of TNT,
according to Los
Alamos scientists Rod Whitaker and Doug ReVelle. Once a space
rock enters
our atmosphere, it is called a meteor. And based on the incoming
meteor's
energy and speed, the researchers figure it was at least 12 feet
(3.6
meters) in diameter.
Whitaker and ReVelle say it would have created a very visible
fireball in
the sky, something scientists call a bolide.
"Had anyone seen the April 23 event, they would have seen
quite a show,"
ReVelle said. "That meteor was one of the five brightest
meteors that have
ever been recorded."
The event, along with a similar one on August 25, 2000, was
confirmed by
U.S. Department of Defense (DOD) satellites. Whitaker and ReVelle
told
SPACE.com that DOD satellites are able to spot different
characteristics in
a meteor or nuclear explosion. "Nuclear explosions would
leave radioactive
debris, which could be picked up by radionuclide air
samplers," they said.
It's raining rocks
ReVelle said that on the average, 10 or more meteors, each wider
than the
average person is tall, enter the atmosphere every year.
Typically, they do
not make it to the ground. Some do, however, and every hundred
years or so
researchers estimate that one large enough to cause local death
and
destruction reaches the planet.
So, of course, scientists who study asteroids appreciate the
government's
listening efforts.
"We are bombarded daily by smallish debris, but it is the
larger chunks that
can easily penetrate our atmospheric shield and cause physical
damage on the
Earth's surface," said Benny Peiser, a researcher at
Liverpool John Moores
University who studies how natural catastrophes might affect
Earth and its
inhabitants.
Peiser said the DOD and other researchers have routinely
published detection
data of atmospheric impacts since the end of the Cold War.
"This data is vital for assessing the impact rate and a
better understanding
of the overall impact hazard," he said. But he also noted
that the
information contributes to international stability by helping to
distinguish
space rocks from nuclear tests.
Leftover technology
During the 1960s, before satellites were common, the U.S. Air
Force operated
a network of infrasound stations, as they are called, as a first
line of
defense and to listen for nuclear-weapon tests.
The Los Alamos listening devices, four around the country, were
installed in
1983. They remain, at least for now, the only infrasonic network
left in
full-time operation in the world. Because the system is simple,
officials
say it costs very little to maintain.
But it is highly sensitive, able to detect meteors as small as a
baseball.
The sonic waves created by such a meteor, or a faraway nuclear
explosion,
are well below the range of human hearing, but are detectable as
small
changes in atmospheric pressure. The system is like a
hypersensitive
barometer used by meteorologists to note incoming storm fronts.
Cheap insurance
The Los Alamos listening devices would not provide advance
warning of an
incoming meteor. The pressure wave takes several minutes to hours
to reach
the stations. But the stations do have tremendous potential for
detecting
clandestine nuclear weapons tests, the researchers say.
Whitaker said other technologies, including satellites, sometimes
miss
events that the ground-based microphones pick up.
"Consequently, infrasound is inexpensive insurance for
cost-effective
monitoring, and it is something that's available to the entire
international
community," he said.
And, interestingly, nature's meteors help the Feds calibrate
their
nonproliferation technology efforts.
"Because those two [meteor] events were detected by our four
arrays and by
five other arrays operated by the International Monitoring
System, we are
able to use the space platform data to calibrate our instruments,
and
analyses, to make them better able to pinpoint the exact location
where
these events occurred," Whitaker said. "Every time we
hear a bolide, we
learn something about this technology and are better able to
fine-tune it."
Nuke or meteor?
The International Monitoring System is a developing worldwide
network of 321
monitoring stations that use various techniques to make sure no
one violates
the Comprehensive Nuclear Test Ban Treaty (CTBT), in which
nations agree to
ban all nuclear explosions.
Though the U.S. Senate has not ratified the signed treaty, many
other
nations have.
As part of the monitoring system, construction has begun on a
global array
of 60 infrasound listening devices. And about 100 stations using
other
techniques have been built.
But infrasound technology can also detect explosive volcanoes,
meteorological events and even rocket launches and supersonic
aircraft. It
is therefore questionable how accurate it is in monitoring
nuclear tests.
A pair of Dutch researchers got some surprising results when they
set up a
similar device. On a November night in 1999, a flash of light
brightened the
skies above northern Germany. In the Netherlands, Läslo Evers
and Hein Haak
detected the sonic boom associated with the explosion, but could
not
distinguish it from the expected signature of a nuclear
explosion.
In January of this year, the researchers reported their results
in the
journal Geophysical Research Letters, suggesting that the devices
might not
be capable of distinguishing between a natural attack from space
and a
clandestine nuclear test.
Nonetheless, the worldwide monitoring plan moves forward.
Last month, a CTBT commission announced that the first infrasound
station,
in Germany, had been certified for use. The system was
constructed deep in
the Bavarian forest, which officials say will help cut down on
wind noise
that might fool the microphones. And each sensor is surrounded by
a network
of baffles to further block the wind.
More methods
Infrasound will not be the only technology used to enforce the
treaty.
Some 170 seismic sensors and 11 underwater listening devices will
be used as
well, plus 80 devices that can detect radioactive debris.
Information from
all these sensors will funnel via satellite into the
International Data
Center in Vienna, where automated results are released two hours
after the
data rolls in.
A spokesperson at Los Alamos said the lab "has always
maintained that
infrasound is only one tool in the entire nonproliferation
toolbox and
probably should not be regarded as a standalone nonproliferation
technology," but that it can help make other systems more
effective.
The CTBT, adopted in 1996, has been signed by 160 nations, but
ratified by
only 76. An additional 33 have not signed on at all.
Arms control advocates had campaigned for the adoption of a test
ban treaty
since the early 1950s. The first one was adopted in 1963 -- a
Partial Test
Ban Treaty that banned nuclear tests in the atmosphere,
underwater and in
space.
Neither China nor France signed that first international test-ban
treaty,
and negotiations for stricter treaties have continued ever since.
Copyright 2001, Space.com
==========
(2) MILITARY WARNING SYSTEM ALSO TRACKS BOMB-SIZE METEORS
From The New York Times, 29 May 2001
http://www.nytimes.com/2001/05/29/science/29ROCK.html
By WILLIAM J. BROAD
In the early darkness of April 23, as Washington was beginning to
relax
after the spy plane crisis in China, alarm bells began to go off
on the
military system that monitors the globe for nuclear blasts.
Orbiting satellites that keep watch for nuclear attack had
detected a
blinding flash of light over the Pacific several hundred miles
southwest of
Los Angeles. On the ground, shock waves were strong enough to
register
halfway around the world.
Tension reignited until the Pentagon could reassure official
Washington that
the flash was not a nuclear blast. It was a speeding meteoroid
from outer
space that had crashed into the earth's atmosphere, where it
exploded in an
intense fireball.
"There was a big flurry of activity," recalled Dr.
Douglas O. ReVelle, a
federal scientist who helps run the military detectors.
"Events like this
don't happen all the time."
Preliminary estimates, Dr. ReVelle said, are that the cosmic
intruder was
the third largest since the Pentagon began making global
satellite
observations a quarter century ago. Its explosion in the
atmosphere had
nearly the force of the atomic bomb dropped on Hiroshima.
The episode shows how the system that warns of missile attack and
clandestine nuclear blasts is fast evolving to detect bomb-size
meteors as
well. Now, it finds them about once a month, on average. But Dr.
ReVelle, a
scientist at the Los Alamos National Laboratory in New Mexico,
said in an
interview that the developing system was likely to find many more
of the
natural blasts in the years ahead.
"The real number is probably bigger," he said.
"There's no doubt about that.
But we don't know how much bigger."
Already, the system has shown that the planet is being
continually struck by
large speeding rocks, and that the rate of bombardment is higher
than
previously thought. The blasts light the sky with brilliant
fireballs but
people seldom see the blasts because they usually occur over the
sea or
uninhabited lands.
The rocky objects are anywhere from a few feet to about 80 feet
wide. They
vanish in titanic explosions high in the atmosphere, their
enormous energy
of motion converted almost instantly into vast amounts of heat
and light.
The Air Force did not publicly disclose its imaging of the recent
blast
until late May, more than a month afterward. In a terse release
on May 25,
its Technical Applications Center, at Patrick Air Force Base in
Florida,
said the flash was "non- nuclear" and consistent with
past observed meteor
explosions.
A Defense Department satellite, the Air Force said, detected
bright flashes
over a period of more than two seconds.
After that disclosure, Los Alamos got the military's permission
to reveal
its own detection of the April event. Its ground-based sensors
are even more
sensitive than orbiting satellites to the repercussions of meteor
blasts.
The ground-based sensors work like sensitive ears to detect very
low-frequency sound waves, which radiate outward from an
exploding rock over
hundreds and thousands of miles.
The sensors record sounds well below the range of human hearing,
including
those from underground nuclear tests as well as atmospheric
blasts.
Dr. ReVelle said four arrays of the lab's sound sensors had
picked up the
April blast. In addition, he said, sound detectors in Los
Angeles, Hawaii,
Alaska, Canada and Germany had picked up its shock waves. Two
sensors in
South America made tentative detections, he added.
"It was a big event," he said. "There are people
worrying about impacts on
the earth, and these things are giving us a better understanding
of the
impact rate. That's the real byproduct scientifically."
The speeding boulder was perhaps 12 feet wide, he added.
An even more sensitive global ear is emerging as the world's
nations try to
monitor the Comprehensive Test Ban Treaty, a tentative accord
that seeks to
end the exploding of nuclear arms and to police compliance. When
finished in
the next year or so, the global acoustic system is to consist of
60 arrays
that give complete global coverage, increasing the odds that even
more large
meteor impacts will be detected.
The disclosure of such intruders is seen as bolstering the idea
that the
earth is periodically subjected to strikes by even larger
objects, including
doomsday rocks a few miles wide. Objects this size are predicted
to hit once
every 10 million years or so, causing mayhem and death on a
planetary scale.
Copyright 2001, The New York Times
===========
(3) ASTEROID FLYBY NOT TOO CLOSE
From Albuquerque Journal, 26 May 2001
http://www.abqjournal.com/scitech/344358scitech05-26-01.htm
By John Fleck
Journal Staff Writer
Astronomers are tracking an asteroid making a close pass by Earth
this
weekend, and Albuquerque-area stargazers will have the chance
tonight to see
it for themselves.
The asteroid became doubly interesting this week after
observations by a
team at NASA's Jet Propulsion Laboratory found the 2-mile-wide
space rock
has a smaller "moon" orbiting around it.
The asteroid will be at its brightest this evening, according to
Kevin
McKeown of The Albuquerque Astronomical Society.
It made its closest approach to Earth on Friday, according to
Brian Marsden
of the International Astronomical Union.
It was 3 million miles from Earth - 12 times farther than the
distance to
the moon.
While that might seem far on human distance scales, it is
extraordinarily
close in astronomical terms - just one-thirtieth the distance
between Earth
and the sun.
It is not unusual for asteroids to come this close to Earth. It
happens
several times a year.
But it is unusual for one to be this bright and easily visible to
astronomers, said McKeown.
Marsden said there is no chance the asteroid could hit Earth.
The asteroid's close approach coincides with the society's first
Astronomy
Night of the season. That means the public has a chance to peer
through one
of the organization's telescopes to see it, said Astronomical
Society member
Brock Parker.
The asteroid is not visible to the naked eye, but through a
telescope it
looks like a bright point of light moving against the background
of the
stars, said McKeown, who has been watching it all week.
"You could actually see it move through the star
field," McKeown said after
a night watching the object earlier this week.
The asteroid, known as 1999 KW4, was discovered by New Mexico
researchers.
Astronomers using an Air Force telescope at the north end of
White Sands
Missile Range found it in May 1999 during a routine asteroid
hunt.
McKeown's Albuquerque Astronomical Society Colleagues will be
sharing their
telescopes with the public this evening, weather permitting, to
see the
asteroid and interesting stars and planets.
The viewing, at Oak Flat picnic area in the Manzano Mountains,
begins after
sunset, which comes at 8:12 p.m.
The asteroid is in a perfect spot in the sky for easy early
evening viewing,
as it moves through the constellation of Ophiucus, the Serpent
Bearer. "As
soon as it gets dark, it'll be high enough to be visible to
people at Oak
Flat," McKeown said.
With advance warning that 1999 KW4 would be close to Earth this
month,
National Aeronautics and Space Administration scientists set up a
special
observing campaign to study it. The scientists bounced radar
signals off the
asteroid, using giant radio telescope antennas in California and
Puerto Rico
to watch the results.
Their observations, carried out Monday, Tuesday and Wednesday,
revealed not
one but two objects orbiting one another, according to Steven
Ostro of
NASA's Jet Propulsion Laboratory.
Observations by Czech astronomer Peter Pravec offered "a
hint of the
possibility" that 1999 KW4 was not one rock but two.
But until they trained their radar on it the scientists could not
be sure,
Ostro said Friday in a telephone interview from Puerto Rico,
where he was
carrying out the asteroid observations using the Arrecibo radio
telescope.
Ostro and his colleagues reported that the smaller of the two is
about a
third the size of the main asteroid.
The scientists plan to continue bouncing radar off of the
asteroid all
weekend, he said, allowing them to create a detailed
three-dimensional
picture. "If there are craters, we will see them," he
said.
The asteroid is on an unusual orbit that takes it around the sun
every 188
days, meaning it crosses the path of Earth's orbit roughly twice
a year. But
orbital calculations show it will not come this close to Earth
again,
Marsden said. "This is as close as it comes," he said.
Copyright 2001 Albuquerque Journal
===========
(4) JAPANESE SCIENTIST FINDS CLUES OF EALIER MASS EXTINCTION
From Andrew Yee <ayee@nova.astro.utoronto.ca>
[ http://www.japantimes.co.jp/cgi-bin/getarticle.pl5?nn20010529a5.htm
]
Tuesday, May 29, 2001
Japanese scientist finds clues of earlier mass extinction
A mass extinction of life on Earth may have occurred 10 million
years before
the largest known extinction took place around 250 million years
ago, a
Japanese scientist said Monday.
Yukio Isozaki, professor of life extinction history at the
University of
Tokyo, said he made the discovery along with Ayano Ota, a
graduate student.
They studied the fossils of fusulinidae, a unicellular organism,
in a
40-meter-thick layer of limestone in Takachiho, Miyazaki
Prefecture.
A study in southern China, which was a shallow sea some 250
million years
ago, has led scientists to believe that mass extinction on Earth
occurred in
two stages. Isozaki said his findings help verify this two-stage
hypothesis.
He said he will report the findings at an academic conference on
Earth and
planet science beginning next Monday in Tokyo.
The limestone found in the town bears traces of coral reefs that
piled up
near the surface of the sea during a period of some 10 million
years prior
to Earth's largest mass extinction. In the largest extinction, 96
percent of
all invertebrate life in seas -- such as trilobites --
disappeared between
the Paleozoic and Mesozoic eras some 250 million years ago.
Isozaki said he and Ota paid close attention to fusulinidae,
which became
extinct after living in coral reefs or shallow seas during the
Paleozoic
era.
The study found that larger fusulinidae, measuring up to 1 cm in
length,
became extinct about 260 million years ago, he said.
It also found that smaller fusulinidae, measuring less than 1 mm,
survived
at that time, he said.
But the smaller fusulinidae became extinct about 250 million
years ago,
underscoring the two-stage theory of extinction. Scientists say
they believe
extinction occurred at those times due to a lack of oxygen caused
by unusual
volcanic activity.
Isozaki said he suspects such volcanic activity occurred twice
and that
larger fusulinidae were unable to cope with environmental changes
brought on
by the first wave.
(C) 2001 The Japan Times. All rights reserved.
=========
(5) PLUTO HAS BIG SHINY COLLEAGUE
From Andrew Yee <ayee@nova.astro.utoronto.ca>
[ http://www.nature.com/nsu/010524/010524-16.html
]
Thursday 24 May 2001
Pluto has big shiny colleague
By JONATHAN TROUT
Astronomers in Hawaii have measured the size and shininess of
Varuna, an
object in the Kuiper belt, the ancient ring of icy bodies
orbiting the Sun
beyond Neptune, home also to Pluto and its satellite, Charon [1].
They are
interested in the belt's composition, as it may have remained
more or less
unchanged since the birth of the Solar System.
Being cold, slow-moving and almost black, Kuiper-belt objects
(KBOs) are
very hard to see. David Jewitt of the Institute for Astronomy,
Honolulu, and
his colleagues used the James Clerk Maxwell Telescope -- the
largest
astronomical telescope in the world -- to pick up Varuna's faint
thermal
image.
They compared this image with simultaneous optical images from
the
University of Hawaii's telescope to determine how much of the
object's
brightness is due to its reflectance, and how much to its large
diameter.
The measurement of the thermal emission of such cold objects has
proved
difficult because their emissions are absorbed in the Earth's
atmosphere.
Thanks partly to the fact that the James Clerk Maxwell Telescope
is more
than 4 km above sea level, the researchers could view Varuna
through
'windows' in the far infrared.
They found that Varuna reflects around 7% of the sunlight that
hits it. This
figure for Varuna's albedo -- the percentage of sunlight it
reflects -- is
greater than researchers had assumed and more than that of most
other
asteroids for which accurate measurements are available.
"The higher-than-guessed albedo may be due to the presence
of some ice on
the surface, but nothing like as much as Pluto can command,"
speculates
Brian G. Marsden of the Harvard Smithsonian Observatory.
Also known as the trans-neptunian belt, the Kuiper belt consists
of more
than 70,000 objects, the largest and best known of which is the
planet
Pluto. Pluto has long been visible owing to of its high albedo:
because of
its frost covering and thin atmosphere it reflects around 60% of
the
sunlight that hits it.
Varuna has a diameter of 900 km, Jewitt's team also calculates.
This makes
it the third largest known KBO, after Pluto (2,200 km) and Charon
(1,200
km).
Steve Tegler of Northern Arizona University sees this as
significant:
"Varuna closes the gap between the largest previously known
Kuiper-belt
object (around 600 km in diameter) and Pluto. Pluto and Charon
are not so
unique in size now. Perhaps more Pluto-sized objects or even
larger objects
remain undiscovered in the outer reaches of the Solar
System."
[1] Jewitt, D., Aussel, H. & Evans, A. The size and albedo of
the
Kuiper-belt object (20000) Varuna. Nature 411,
446-447 (2001).
Web Links:
* Kuiper Belt Homepage
http://www.ifa.hawaii.edu/faculty/jewitt/kb.html
* James Clark Maxwell Telescope
http://www.jach.hawaii.edu/JACpublic/index.html
© Macmillan Magazines Ltd 2001 - NATURE NEWS SERVICE
=========
(6) NEW WORLD RIVALS PLUTO
From the BBC News Online, 234 May 2001
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1347000/1347031.stm
By BBC News Online science editor Dr David Whitehouse
Detailed observations of a recently discovered large object is
prompting a
reappraisal of the myriads of icy worlds that live in the cold,
outer
reaches of our Solar System - the Kuiper Belt.
The observations are of Varuna, which was discovered in November
2000. It
was immediately recognised as a very large object, probably the
largest in
the Kuiper Belt except for Pluto and its moon Charon.
Combining data obtained from two different types of telescope,
the
researchers have calculated Varuna's diameter to be 900 km (550
miles).
Varuna's large size threatens Pluto's status as a fully-fledged
planet as it
now seems to be merely the largest of a swarm of similar large
worlds in
deep space.
More reflective
Writing in the journal Nature, David Jewitt of the Institute for
Astronomy,
Honolulu, Hawaii, US, and colleagues report simultaneous optical
and
sub-millimetre wavelength measurements of Varuna, determining its
size and
reflectivity for the first time.
Veruna was seen in 1953 but not recognised at the time
Until now, Pluto and its moon Charon were the only members of
this ancient
ring of icy bodies for which accurate sizes were known.
At 900 km (550 miles) across, Varuna is only slightly smaller
than Charon
(1,200 km or 750 miles in diameter), the tiny moon that orbits
Pluto (2,400
km or 1500 miles in diameter), the most distant of the Sun's
planets.
The data also indicates that Varuna is more reflective than most
other small
worlds for which accurate measurements are available - though it
is less
reflective than Pluto or Charon.
Shuttle telescope
Scientists say that Varuna goes some way to vindicate the views
held by the
late US astronomer Clyde Tombaugh. He discovered Pluto in 1930
looking for
what he called Planet X. He continued his search after its
discovery
believing there were other worlds out there waiting to be
discovered.
Stephen Tegler, of Northern Arizona University, said: "This
work raises the
possibility that Pluto is not the only Planet X, but perhaps one
of several.
"We can now imagine that bodies even larger and more distant
than Pluto will
be found. Such objects have so far escaped detection because of
their
extreme faintness, due in part to the feeble illuminating light
from the Sun
and in part to their very dark surfaces."
Astronomers are hopeful that further discoveries could be made in
the Kuiper
Belt, following the launch of a telescope attached to the cargo
bay of the
space shuttle.
The Shuttle Infrared Telescope Facility will be deployed in 2002
and is
expected to measure the diameters and reflectivities of dozens of
Kuiper
Belt objects.
Copyright 2001, BBC
==========
(7) NASA TO BLAST HOLE IN COMET
From The Guardian, 26 May 2001
Scientists to study results of Deep Impact mission
James Meek, science correspondent
The Guardian (Manchester & London)
Saturday May 26, 2001
It may go down in history as the earliest act of deliberate
cosmic
vandalism, mankind's first halting steps at preventing its own
extinction,
or - as the scientists involved modestly hope -
an explosive, useful experiment in the wilds of space.
Whatever it is, the Deep Impact mission, just given the go-ahead
by Nasa,
will be unlike any previous space venture in the scale of the
planned damage
to a celestial object, a comet called Tempel 1.
Scientists will fire a 350kg bullet into the heart of the comet
as it passes
between Earth and Mars, gouging out a crater seven storeys deep
and 100
metres wide.
The blast, to be broadcast on television and the internet from
cameras
mounted on the mother ship, is scheduled for July 4 2005. With a
mission
price tag of about £200m, it will be the
most expensive Independence Day fireworks.
The "bullet" itself, known as an impactor, will have a
camera to record its
last moments as it slams into the comet at 10km a second
(22,300mph).
The scientific goal is to gain the first glimpse of a comet's
interior by
studying the walls of the crater and the debris thrown out by the
impact.
That is if there is a crater. Astronomers' best guess is that the
nuclei of
comets are a cocktail of ice, frozen alcohol and methane, with a
sprinkling
of rock and dust.
But they cannot be sure. Tempel 1, discovered in 1867, orbits the
sun every
five-and-a-half years and is only about 1km wide. The impactor
could shoot
straight through or break the comet into large pieces.
"I wouldn't be at all surprised if it broke into several
chunks - comets are
pretty fragile," said Duncan Steel, a comet specialist at
the University of
Salford, Greater Manchester. "We see several of them of them
breaking apart
every year."
This would pose no danger to Earth, he added. "The chunks
would still follow
the comet's orbit, which is outside Earth's orbit," said Dr
Steel.
Around 40,000 tonnes of space debris rain down on Earth each
year, and the
destruction of a small comet close to the planet would risk
doubling that.
Dr Steel said Nasa had sensibly gone for a comet far enough away
to avoid
that problem. "The chances of being hit by a big lump are
essentially zero.
We've got much worse things to worry about, like all the
asteroids we
haven't found yet."
He dismissed any aesthetic or moral objections that space
environmentalists,
a largely unformed body as yet, might have to gouging holes in
pristine
parts of the solar system.
"As soon as we landed on the moon and made footprints you
could say we were
polluting the moon," he said. "A lot of these airy
fairy ideas are pretty
absurd, aren't they."
Deep Impact is due to be launched in January 2004 and orbit the
sun for a
year before swinging out to intercept Tempel 1 in July 2005. It
will release
the cylindrical impactor into the comet's
path before moving to watch the crash from a safe distance.
The US scientists involved claimed they came up with the title
Deep Impact
long before the writers of the 1998 film of the same name. In the
movie,
astronomers discover a comet on a collision course with Earth. A
manned
spacecraft is sent to intercept it, plant nuclear charges and
destroy or
deflect it before it can wipe out human life. Nasa's Deep Impact
is not a
trial run for such an emergency, but the knowledge gained will
inevitably be
useful if a planetary defence programme is set up.
Nasa recently landed a space probe on a small, peanut-shaped
asteroid, Eros,
and in 2011 the European space agency will try to land its
unmanned Rosetta
craft on a comet. Deep Impact will go further than either of
these missions
in altering the course of a comet, or breaking it up.
There is thought to be a one in a thousand chance of an
undiscovered
asteroid or comet 1km or more across hitting earth in the next
century.
In the 1990s Nasa planned a mission called Clementine-2, a mother
ship
carrying three 1.5-metre harpoons to be fired into three
asteroids at 10km a
second, to test the technology.
But President Bill Clinton vetoed the project in 1997, on the
grounds that
it was an overly aggressive hangover from the Star Wars era which
would
needlessly alarm the Russians and Chinese.
© Guardian Newspapers Limited 2001
============
(8) NEO NEWS
From David Morrison <dmorrison@arc.nasa.gov>
NEO News (5/27/01) Deep Impact & 2 letters
Dear Friends & Students of NEOs:
This edition includes a press release announcing that the Deep
Impact comet
mission has passed Preliminary Design Review. Also printed are
two letters
commenting on earlier stories. Andrew Glickson discusses the
end-Triassic
mass extinction, and Al Harris and Rick Binzel discuss the
relationship
between the Spaceguard metric, which is based on finding NEAs
with absolute
magnitude brighter than H=18, and the underlying goal to survey
NEAs larger
than 1 km diameter.
For those who do not wish to read their detailed essay, I provide
the
following summary of the conclusions from Harris & Binzel.
They write that
the missing parameter in transforming between H magnitude and
diameter is
the albedo or reflectivity of the object. The canonical
translation of H=18
to 1 km diameter assumes an average albedo of about 0.1 for all
discovered
objects. In this essay, they examine how well this 0.1 average
albedo
assumption is likely to fit the actual discovered population. The
relevance
of this work is that we must be aware of the corresponding
uncertainties in
where the goalpost resides for a survey goal (such as the
Spaceguard goal)
specified as completeness with regard to diameter, rather than
completeness
with regard to observed H magnitude.
Harris & Binzel conclude that the often assumed population
mix of roughly
equal fractions of light and dark NEAs leads to completion models
that lie
within a couple tenths of a magnitude, or equivalently a couple
percent of
completion, of a simple equivalence of H = 18.0 equal to D = 1 km
for the
entire population. The biggest current uncertainty is in the
population
model, not the implementation of it. We barely know the relative
distributions of the different compositional types that make up
the NEO
population, and the number of well-determined albedos of NEAs is
very small.
For the moment, the largest uncertainty in relating survey
efforts to the
"Spaceguard Goal" is in the population fractions and
albedos of the various
constituents. Only by further physical observations to
characterize the
population of NEAs in terms of taxonomic class and, most
importantly albedo,
will we be able to reliably say how we are doing toward achieving
the
Spaceguard Goal. Nailing down the 1 km goalpost for the
Spaceguard survey
requires knowing the albedo distribution of the population for
securing the
H magnitude value where the goal of 90% completeness must occur.
Note that since many of us will be attending several professional
meetings
dealing with NEOs during coming weeks, it is unlikely that there
will be any
editions of NEO News during the month of June.
David Morrison
=================================================
MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
FOR IMMEDIATE
RELEASE
May 24, 2001
NASA GIVES GO-AHEAD TO BUILD 'DEEP IMPACT' SPACECRAFT
The Deep Impact mission, the first
mission to ever
attempt to impact a comet nucleus in order to answer basic
questions about the nature of comets, has successfully
completed its preliminary design phase and has been approved
by NASA to begin full-scale development for a launch in
January 2004.
The Deep Impact team of
scientists, engineers and mission
designers, from the University of Maryland, NASA's Jet
Propulsion Laboratory and Ball Aerospace and Technologies
Corporation, Boulder, Colo., have been working for more than
18 months designing the mission, the dual spacecraft and three
science instruments. The encounter with Comet Tempel 1 on
July 4, 2005 will reveal clues to the origin of comets and the
composition and structure of perhaps the most mysterious
objects in our solar system.
Now the Deep Impact team is
completing the final design
details and will begin building the mission's two spacecraft:
a flyby spacecraft and a 350-kilogram (771-pound) impactor
spacecraft. They will be launched together in early
2004 and
travel to Comet Tempel 1's orbit where they will separate and
operate independently. The flyby spacecraft will release
the
impactor into the comet's path, then watch from a safe
distance as the impactor guides itself to collide with the
comet, making a football field-sized crater in the comet's
nucleus.
"This is a major milestone
for us," said Dr. Michael
A'Hearn, the prinicipal investigator and director of the Deep
Impact mission, from the University of Maryland, College Park,
Md. "We have now shown NASA that we have a viable
design for
the spacecraft and the mission to carry out a truly rare,
large-scale experiment on another body of the solar system."
"The Deep Impact mission
follows in the tradition of
other Discovery missions like Mars Pathfinder and the Near-
Earth Asteroid Rendezvous by doing first of a kind science on
a low-cost, highly focused project," said Brian Muirhead,
the
manager of the Deep Impact mission, of NASA's Jet Propulsion
Laboratory, Pasadena, California. "The project team is fully
prepared to implement this technically challenging and
scientifically unique mission."
As the gases and ice inside the
comet are exposed and
expelled outward by the impact, the flyby spacecraft will take
pictures and measure the composition of the outflowing gas.
The images and data will be transmitted to Earth as quickly as
possible. Many observatories on Earth should be able to see
the comet dramatically brighten just after the impact on July
4, 2005.
Scientists refer to comets as time
capsules that hold
clues about the formation and evolution of the solar system.
Comets are composed of ice and dust, the primitive debris from
the solar system's earliest and coldest formation period, 4.5
billion years ago. They would also like to learn much
more
about a comet's composition, structure and how its interior is
different from its surface. The controlled cratering
experiment of the Deep Impact mission will provide answers to
these questions.
Comet Tempel 1 was discovered in
1867. Orbiting the Sun
every 5.5 years, it has made many passages through the inner
solar system. This makes it a good target to study
evolutionary change in the mantle, or outer crust, of a comet.
"Ball Aerospace is pleased
and proud to be involved with
JPL and the University of Maryland in working on this first of
a kind deep space mission," said Ball's John Marriott,
deputy
project manager.
Principal investigator A'Hearn
oversees Deep Impact's
scientific investigations. Project manager Brian Muirhead, of
NASA's Jet Propulsion Laboratory manages and will operate the
Deep Impact mission for NASA's Office of Space Science,
Washington D.C. JPL is managed by the California Institute
of
Technology, Pasadena, Calif., for NASA. John Marriott of
Ball
Aerospace and Technology Corporation manages the spacecraft
development in Boulder, Colo.
=====================================================
LETTER: ON THE END-TRIASSIC EXTINCTION
Dear David Morrison,
I refer to the T-J boundary mass extinction, where it is stated
(NEO News
13-05-01) "There is no direct evidence of an impact".
The end-Triassic constitutes a major extraterrestrial bombardment
period,
the cluster consisting of Manicouagan (Quebec; D=100 km; 212+/-2
Ma),
Puchezh-Katunki (Russia; D=80 km; 220+/-10 Ma), Saint Martin
(Manitoba; D=40
km; 220+/-32 Ma), Redwing (Dakota; D=9 km; 200+/-25 Ma) and
possibly
Kara-Kul (Tajakistan; D=52 km; ?190-220 Ma).
The end-Triassic is also the time of onset of the Atlantic
oceanic split,
accompanied by intense volcanic activity along the incipient
ocean
rift/suture, as well as rifting in several other parts of the
Earth (V.
Courtillot, C. Jaupart, I. Manughetti, P. Tapponnier, J.
Besse. On causal
links between flood basalts and continental breakup. Earth
Planet. Sci.
Lett. 166 (1999) 177-196. W.J. Morgan, Hotspot tracks
and the opening of
the Atlantic and Indian oceans. in: C. Emiliani (Ed.), The Sea,
vol. 7,
Wiley Interscience. New York, 1981, pp. 443-487). These
papers interpret
the volcanism as due to endogenic mantle plumes, however it is
possible the
volcanic activity rifting and ocean splitting may have been
triggered by the
impacts (Glikson, 1999; Glikson, in press).
A major extinction at the end-Triassic has been established
earlier (Newell,
1967; Stanley, 1987; Sepkoski, 1993; Hallam, 1997). This is
supported by
the organic carbon and light carbon enrichment (the so-called
"graveyard
shift") reported by Ward et al. (2001), a diagnostic
signature of extinction
also observed along several other impact boundaries
(Frasnian-Famenian [late
Devonian], Permian-Triassic, K-T). Genetic links between
the impact cluster
and the mass extinction remain a distinct possibility to be
tested by
further precise isotopic age determinations of the above impact
craters.
Andrew Glikson
Australian National University
Canberra, ACT 0200
geospec@webone.com.au
==============================================
LETTER: NAILING DOWN THE SPACEGUARD SURVEY GOALPOST:
UNDERSTANDING THE RELATIONSHIP BETWEEN H MAGNITUDE AND DIAMETER
As well described by David Morrison ("Origin and Meaning of
the NASA
Spaceguard Goal", NEO News 5/12/01), there are good reasons
from the hazard
point of view for setting 1 km diameter as the goal for the
Spaceguard
Survey. Of course, we are discovering and vigorously
cataloging numerous
objects below this size,and prudence dictates that we should
indeed continue
to achieve completeness well below 1 km. The
"Spaceguard Goal" is a metric
for tracking the overall progress of our survey efforts.
When objects are discovered, we determine only their H magnitude,
not their
diameter. The missing parameter in transforming between H
magnitude and
diameter is the albedo of the object. The canonical
translation of H=18 to
1 km diameter assumes an average albedo of about 0.1 for all
discovered objects.
In this essay, we examine how well this 0.1 average albedo
assumption is
likely to fit the actual discovered population. The
relevance of this work
is that we must be aware of the corresponding uncertainties in
where the
goal post resides for a survey goal (such as the Spaceguard goal)
specified
as completeness with regard to diameter, rather than completeness
with
regard to observed H magnitude.
In establishing an equivalent, or average, relation between
absolute
magnitude and diameter, one must consider whether you mean a mean
albedo
with respect to what may hit you, or a mean albedo with respect
to what you
see in the sky. The mean albedo of the objects that strike
the Earth, for
any given size, is the weighted mean according to the relative
fraction of
the population (at that size) that has a given albedo. The mean
albedo of
what is discovered in the sky, when considered at a specific
limiting
magnitude, will be biased toward higher albedo objects. This is
because for
any magnitude limited survey, for any two equally sized objects
the one with
the higher albedo appears brighter and is more easily discovered.
Consider the following example (for the moment, the first four
columns):
Population Fraction:
Of a Given Of a Given H
magnitude Completeness
Class Albedo
Diameter H Magnitude @ 1 km
Dia [1] [2]
C-like
0.06
0.45
0.16
18.67 0.794 0.831
S-like
0.18
0.45
0.62
17.48 0.946 0.957
M
0.12
0.05
0.04
17.92 0.909 0.928
E,V
0.40
0.05
0.18
16.61 0.975 0.978
------------------------------------------------------------------------
<albedo>
-
0.112
0.172
0.112
- 0.093
H(D=1 km) -
18.00
17.51 18.00
<Completeness>
0.877 0.900
H(C=0.90)
18.00 18.20
The column "Given Diameter" is an assumed population
fraction similar to
what one often sees claimed for the makeup of NEAs, or for that
matter
main-belt asteroids, roughly equal numbers of S and C types with
small
components (~5%) of metalic objects, very high albedo E-class,
"Vestoids",
and miscellaneous others. As noted above, higher albedo objects
are more
easily discovered. In addition to this, as you go to smaller
sizes the
number of objects increases. Thus, aa fixed value for the H
magnitude,
smaller objects having high albedos tend to be more
abundant than larger objects having low albedos.
The column labeled "Of a Given H Magnitude" gives the
relative fractions of
discovered objects in each of the four albedo categories for an
assumed
population index of -2.4, i.e. N(>D) = A*D^-2.4. Within
this last column
can be seen that the population fraction with respect to H is
dominated by
higher albedo "S-like" objects relative to lower albedo
"C-like" objects,
even though the total population postulated to exist (in this
model) is
equal between these two categories. Even more noticable is
that the
ultra-high albedo objects (labeled here as the "E,V"
group) contributes
equally to the fraction in the last column as do the C-types,
even though
the "E,V" group has only about 10% of the number (0.05
versus 0.45) of
objects within our total model population.
On the line immediately below the dashes is listed the geometric
mean albedo
of this assumed population, weighted according to the fractions
with respect
to size, and with respect to H. The last line gives the value of
H that
corresponds to D = 1 km for that value of albedo. If your
interest is in
"what may hit you", the diameter weighting is more
representative, and is
extremely close to the equivalence of H = 18.0 to 1 km diameter.
However, if
one asks what is the mean albedo of a sample of discovered
objects
(remembering that absolute magnitude H is the primary measure of
whether an
object is discovered or not), the mean albedo is much higher,
0.17 in this model. Thus when a new object is discovered
and you are asked
"how big is it?", the best probabilistic guess would be
to assume the higher
albedo (that is, H = 17.5 corresponding to D = 1 km).
How does this relate to the Spaceguard Goal of 90% completion of
all objects
larger than 1 km in diameter? In the next column of the
table we list the H
magnitude of a 1 km diameter NEA for the assumed albedo of each
class. Thus
a 1 km diameter low albedo C-class object has H = 18.67, while
the same diameter high albedo (E,V) asteroid has H = 16.61. For
each of the
H magnitudes we can estimate the expected fraction completion of
a survey at
that value of H, and then weight those completions by the assumed
fractions
in the total population to obtain an estimate of the average
completion for the total population. In the last two columns we
do this for
two assumed completion levels, using the survey completion model
of Harris
(Planet. Space Sci. 46, 283-290, 1998, see fig. 4). The first one
is
normalized to 90% completion at H = 18.00, and the second is
normalized to
90% completion at H = 18.20. These are the values listed on
the very last
row below these two columns. Just above those entries are
listed the
average completeness for the entire population. We can see
from these
numbers that the usual equivalence of 1 km diameter equivalent to
H = 18.0
is not quite right. For the normalization where 90%
completion at H = 18.0
is achieved for a single albedo (0.112), for our assumed model of
albedo
populations the completion is only 87.7%. To achieve 90%
completion of the
model population requires 90% completion to H = 18.2, as
enumerated in the
last column. The very last number to note is the
<albedo> given in the last
column, just below the dashed line, 0.093. This is the
albedo which relates
H = 18.2 equivalent to D = 1 km. This can be thought of as
an effective
albedo relating D to H such that a survey to 90% completion in
terms of H is
also 90% complete in terms of the related value of D.
One final item of note is that the above completion figures
relate to
differential completion, that is, completion at a given H or D
value. The
"Spaceguard Goal" is usually assumed to be an integral
completion, that is,
90% completion of objects larger than 1 km. Since completion is
greater for
larger objects, the integral completion is higher than the
differential
values given above. In fact, in the range of completion
from ~0.85 to 0.90,
the integral completion for the assumed population index of -2.4
is about 5%
higher than the differential value. Thus the integral
completion
represented by the normalization used in the next-to-last column
is
probably already more than 90%, and in fact one might move in the
other
direction to a normalization of H(C=0.90) = 17.80 to yield an
integral
completion of 90% for the assumed population.
In conclusion, it appears that the often assumed population mix
of roughly
equal fractions of light and dark objects leads to completion
models that
lie within a couple tenths of a magnitude, or equivalently a
couple percent
of completion, of a simple equivalence of H = 18.0 equal to D = 1
km for the
entire population. The biggest current uncertainty is in the
population
model, not the implimentation of it. We barely know the relative
distributions of the different compositional types that make up
the NEO
population, and the number of well-determined albedos of NEAs is
very small
and such as they are seem to be systematically much higher than
measured
main-belt albedos. Is this a real difference, or something due to
observational circumstances (typically larger phase angles) or
model errors
(faster rotation, lack of regolith). We don't know yet, and
only further
observations will tell. For the moment, the largest
uncertainty in relating
survey efforts to the "Spaceguard Goal" is in the
population fractions and
albedos of the various constituents. Only by further
physical observations
to characterize the population of NEAs in terms of taxonomic
class and, most
importantly albedo, will we be able to reliably say how we are
doing toward
achieving the Spaceguard Goal. Nailing down the 1 km
goalpost for the
Spaceguard survey requires knowing the albedo distribution of the
population
for securing the H magnitude value where the goal of 90%
completeness must
occur.
Alan Harris (JPL) and Richard Binzel (MIT)
============================
* LETTERS TO THE MODERATOR *
============================
(9) IMPACT SEQUENCE IN THE GEOLOGICAL RECORD
From Hermann Burchard <burchar@mail.math.okstate.edu>
Dear Benny,
recently on CCNet, new light has been shed on the Tr/J boundary
events.
Andrew Glikson discussed known craters from cosmic impacts near
that time of
about 200+\-10 Ma in a recent note. The very precise new results
by Peter
Ward et al, likewise reported on CCNet, have demonstrated an
exceedingly
narrow time horizon for the Tr/J extinction events, using
biostratigraphy
from British Columbia. This is not inconsistent with impact
causation.
At that time also, it is thought the N Atlantic Ocean began to
open up, in a
major tectonic convulsion that led to the eruptions of the Tr/J-
related
Central Atlantic Magmatic Province (CAMP). CAMP basalts occur in
N and S
America, Europe, and Africa. Paul Renne et al recently discovered
basalt
eruptives in Brazil forming a part of the CAMP. This province now
turns out
to cover an area greater than either the Deccan or Sibirian
traps. In
addition, the Azores mantle hotspot is conveniently located near
the center
of the CAMP, hence it is reasonable to ask if this hotspot is
impact
related, as after any major cosmogenic impact we must expect some
mantle involvement.
The sequence of events would be similar to those at other mantle
hotspots.
Examples are mentioned in an essay by geophysicist Michael
Wysession:
"..Regions of continuous volcanism, called hot spots, have
long been
both a blessing and a curse to plate tectonics. These hot spots,
which
include Hawaii, Iceland, Tahiti, Galapagos, Yellowstone and many
others, appear to be fixed relative to the deep mantle. Despite
the
vagaries of plate movements, the 40 or so major hot spots do not
move
relative to each other. This means that they are not tied to the
motions of the plates; they originate deeper than the
lithosphere. ...
It is an unusual feature of surface hot spots that they always
seem to
begin with a giant outpouring of basaltic volcanism. For example,
the
Deccan Traps that covered much of mid-India around 65 million
years ago were
the surface emergence of the hot spot that is now at the site of
Reunion
Island in the Indian Ocean. Likewise, the giant basalt lava
floods that
covered much of the state of Oregon were the emergence of the hot
spot now under Yellowstone National Park."
In a paper by Nikishin, Ziegler, et al, we find more on these and
other
examples:
"Classical long-lived plumes are the Rajmahal-Kerguelen,
Deccan,
Tristan da Cunha, St. Helena, Iceland and Hawaiian plumes (Coffin
and
Eldholm, 1992, 1994; Storey et al., 1992). The Rajmahal-Kerguelen
plume
caused the eruption of the Rajmahal Traps in India close to 117
Ma, the
Kerguelen-Broken Ridge oceanic plateau (close to 88-114 Ma), then
the
Ninetyeast Ridge (close to 82-38 Ma), and new magmatism within
the Kerguelen
Plateau (ñ40-0 Ma; Kent et al, 1997). Correspondingly, its
plume-related
magmatism lasted for 117 My years. The Deccan plume generated the
Deccan-Seychelles Traps at 65 Ma, then the Maldives- Chagos and
Mascarene
oceanic ridges, and finally the Reunion volcanic area. The
duration of this
magmatic activity spans 65 Myr and may be related rather to
fracture
propagation than to the drift of the lithosphere over a
stationary
plume (Sheth, 1999). The Tristan da Cunha plume caused the
eruption of
the Parana-Etendeka flood-basalts (137-125 Ma), thereafter the
intraoceanic
Walvis Ridge and Rio Grande Ridge, and finally the Tristan da
Cunha oceanic
island (Wilson, 1992). This plume was active during the last 137
Myr. The
St. Helena plume lit up at about 145 Ma, controlled the
development
of the Helena sea-mount chain and is at present still active
(Wilson, 1992). The Iceland plume was responsible for the
development of
the North Atlantic Thulean igneous province (64-52 Ma), and,
after crustal
separation between Europe and Greenland, for the development of
the
Faeroe-Greenland Ridge and the present volcanic activity of
Iceland
(Ziegler, 1988, 1990; Larsen et al, 1999). Thus, this plume was
active
during the last 64 Myr. The Hawaiian plume was active during the
last 75
Myr or longer (Coffin and Eldholm, 1994)."
The Deccan/Reunion Island hotspot is the cause also of rifting
along the
Carlsberg ridge. The Yellowstone hotspot caused incipient,
but inhibited,
rifting in Idaho, Nevada and Utah. leaving a track along the
Snake River
valley, rather than forming a ridge.
We note that impacts are not considered in these quotes. After
major
impacts, several kinds of structures related causally with each
other should
be found as a regular sequence in the geological record:
1) Crustal impact structures leave a remnant crater on the
surface
or buried beneath sediment or later eruptives.
2) After impact there is deep involvement of the mantle in the
form
of pressure relief melting and/or some other kind of pressure
relief
phase transition. Due to high viscosity a considerable delay of
up to
several million years (?) seems likely in the formation of any
eruptives,
be these basalt or granite.
3) There results a mantle hotspot of some sort that likely
persists
for some time, in some sort of circulation pattern with reduced
pressure in
a vertical column maintained causing eruptions by pressure relief
melt or
phase transition, a process that's not so easy to understand.
4) The crust or the lithosphere (?) will move over the mantle
hotspot with local plate tectonics dictating speed and direction
of
the motion. Therefore, in time, mantle hotspot and crustal impact
remnant
(crater) will no longer be found at the same longitude and
latitude.
5) Mantle hotspot and crustal impact structure remnant remain
connected by a crustal hotspot track. On the ocean bottom
this would be a
series of islands or sea mounts. Various situations will
arise
depending on erupted volumes. On a continent the results seem
much less
well-known.
6) Basalt eruptions or granitic intrusives occur near the crustal
impact structure remnant, and elsewhere along the hotspot track,
depending on oceanic or continental position of the hotspot.
7) Rifting can occur and basalts erupt along linear faults
starting
from points situated on the hotspot track.
How does this play out at the Azores for Tr/J times, 200+\-10 Ma
in the
past? Rifting along the Mid Atlantic Ridge is the best-known
feature, and
could be impact related, although continental crust may have been
thinned by
eons of erosion prior to impact.
A hotspot track, if preserved and found, would lead us right to
the elusive
crustal impact structure remnant or crater. On some maps a
fairly obvious
track goes in a SSE direction from the Azores: The
Atlantis, Cruiser, and
Great Meteor Sea Mounts are lined up along it. The last
name is probably a
coincidence, in fact, on some maps the sea mount chain or ridge
appears to
extend farther south than the Great Meteor Mount. Because of
plate tectonics
and a widening Atlantic Ocean, we must expect older parts of the
hotspot
track not to be preserved. Crustal impact structure
remnants would likely
be buried under CAMP basalts, possibly on four continents!
It would be
interesting to learn about any geological research on this.
Regards,
Hermann Burchard
===========
(10) SHAPE OF PYRAMIDS
From David W. Hughes <D.Hughes@sheffield.ac.uk>
Dear Benny,
Many pyramids were built so that the angle of inclination between
their
sides and the horizontal was equal to the co-latitude of the
site. This ment
that the Sun could (from a convenient vantage point) be seen to
role up and
then down the slope on the morning and evening of the equinox.
All the best
David
D W HUGHES, SHEFFIELD
===========
(11) AND FINALLY: CHINESE MAKE A BIG THING OF VEGETABLES FROM
OUTER SPACE
From The Sunday Times, 27 May 2001
http://www.agbios.com/_NewsItem.asp?parm=neIDXCode&data=1896
Sunday-Times.co.uk
Michael Sheridan
Sunday -- May 27, 2001
WE can forget about little green men from outer space; it is the
giant green
vegetables from China that should concern us. British and
American
scientists have been left perplexed by claims emanating from the
world`s
most populated country that it has managed to grow extra-large
marrows and
peppers from seeds sent into orbit.
While western scientists scoff and champion vegetable growers
look on in
disbelief, the Chinese claim they have achieved their feat by
exposing seeds
to high radiation levels and low gravity in space. The resulting
vegetables,
they say, easily outgrow their terrestrial counterparts.
The giant vegetables have started appearing in markets in Beijing
and
Shanghai. Space Daily, a Chinese journal, reports that a tomato
from one
farm weighed in at 28oz. The average tomato found in a British
supermarket
weighs 4oz.
The company which has produced the vegetables claims they come
from a
programme carried out by space scientists to boost yields and
increase
production in the country`s constant search for new ways to feed
a
population thought to have reached 1.3 billion.
At the Greenhome company`s farm, near the southern city of
Guangzhou, the
peppers are reported to have an unusually high vitamin C content
and their
seeds yield 30% more vegetables than normal.
Similar claims are made for strains of rice modified in space.
Some types of
melon are said to grow larger and taste sweeter. ``The seeds are
carried
into space by a rocket and returned to earth after three or four
days, then
they are carefully cultivated by experts,`` said Xie Zhongqing,
manager of
the Greenhome farm.
Xie seems even more baffled by the phenomenon than western
experts. ``It`s
quite difficult to say how it changes. I myself am not a
scientist, just a
businessman,`` he said.
China Today magazine says scientists began experiments in 1987 to
breed
plant forms up to 250 miles beyond the earth`s atmosphere.The
article claims
it was discovered that low levels of gravity and high radiation
in space
irreversibly changed the genetic make-up of the seeds.
For China`s leaders, the potential of space seeds outweighs any
discernible
risk. Space Daily revealed last year that under State Project 863
the
country has launched eight recoverable spacecraft and five
high-altitude
balloons containing more than 70 varieties of crop seeds
including rice, oil
seeds, cotton, vegetables and fruit.
In November 1999, the Shenzhou space capsule was sent up with
seeds of
tomatoes, watermelon, Chinese radishes, green pepper, corn,
barley, wheat
and more than 30 types of traditional medicine.
Chinese leaders are now considering the launch of the first
satellite
dedicated to modifying crops in space. ``Breeding seeds in space
is expected
to become a strong driving force behind Chinese agriculture in
the 21st
century,`` Liu Luxing, a senior government scientist on the
project, told
Space Daily.
Last week Dr Simon McQueen Mason, of York University, who was
appointed a
fellow of the Royal Society for his work on plant growth, said he
considered
the Chinese claims extremely dubious.
``I cannot think of any reason why seeds should grow better by
being exposed
to space,`` he said. ``Nasa has done some work on growing plants
in orbit
and found that growth rates were just the same in space and later
on the
ground.``
Peter Glazebrook from Halam, Nottinghamshire - who holds world
records for
the size of his cucumbers, parsnips and beetroots - said there
was a simpler
way to grow giant vegetables than the ``suspicious`` claims of
the Chinese.
``The best technique is to get the seed from a previous champion
vegetable,`` he said.
-- Copyright © Sunday-Times.co.uk --
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