PLEASE NOTE:
*
CCNet 48/2002 - 16 April 2002
----------------------------
"In a recent study published by the Iowa Law Review, Policy
Analyst
Evan R. Seamone has addressed the duty to mitigate asteroid and
comet
impacts from the perspective of international law. The report
argues
that the nature of the dangers posed by asteroids and comets
place the
threat in the category of certain types of disasters for which
the
international community is unprepared."
-- Elizabeth Davis, Iowa Law Review
(1) NEW COMET DETECTED BY SOHO - VISIBLE THE REST OF THE WEEK
Paal Brekke <pbrekke@esa.nascom.nasa.gov>
(2) LEGAL DUTY TO "MITIGATE" ASTEROID OR COMET
COLLISIONS WITH THE EARTH
INVOLVES MUCH MORE THAN
STARGAZING, SAYS POLICY ANALYST
Elizabeth Davis, http://www.uiowa.edu/~ialawrev/
(3) CRASH COURSE: SCIENTISTS STEP UP EFFORTS TO TRACK ASTEROIDS
The Dallas Morning News, 15 April 2002
(4) EUROPEAN SPACE AGENCY TO PROBE ASTEROID BLIND SPOT
Karen O'Flaherty <Karen.O'Flaherty@esa.int>
(5) MISSIONS TO PLUTO, EUROPA CANCELED
Andrew Yee <ayee@nova.astro.utoronto.ca>
(6) MECHANISM THAT CREATES NEAR-EARTH BINARY ASTEROIDS
Andrew Yee <ayee@nova.astro.utoronto.ca>
(7) RADAR REVEALS FIVE DOUBLE ASTEROID SYSTEMS ORBITING EACH
OTHER NEAR
EARTH
Andrew Yee <ayee@nova.astro.utoronto.ca>
(8) A LAST WAVE GOODBYE
The Guardian, 11 April 2002
(9) DAVE RODDY, 1932 - 2002
U.S. Geological Survey
(10) THE REAL THREAT TO THE PLANET
Tech Central Station, 9 April 2002
(11) ROCKET FRAGMENT, NOT METEORITE, LANDED IN UGANDA
Ron Baalke <baalke@jpl.nasa.gov>
(12) AND FINALLY: CHINA METEOR MAY (OR MAY NOT) SOLVE MYTHICAL
DEATH OF
MYTHICAL EMPEROR
Ron Baalke <baalke@jpl.nasa.gov>
=================
(1) NEW COMET DETECTED BY SOHO - VISIBLE THE REST OF THE WEEK
>From Paal Brekke <pbrekke@esa.nascom.nasa.gov>
The comet SOHO-422 was first reported on Friday, April 12, by
XingMing Zhou
of China, who discovered the comet while watching SOHO real-time
images on
the Internet. The comet is a new comet, not belonging to
any known group of
comets. It will be visible in LASCO C3 images until
Saturday, April 20. The comet was first visible late in the day
on Thursday,
April 11. It enters the FOV at the bottom edge, almost
directly under the
Sun. It is moving upwards, first to the left. It will
eventually move back
towards the right, exiting from the LASCO C3 field of view at the
top edge,
to the right of the Sun.
It will reach perihelion on April 17 at about 6:30 UT, at a
distance of 17.7
solar radii. At this time, the apparent distance in LASCO
will be about 13
solar radii. As the week goes on, the comet will move
through the field of
view more quickly.
It's officially designated as C/2002 G3 (SOHO) in MPEC 2002 G51.
Updating mpegs where people can follow the comet across the LASCO
field of
view:
http://sohowww.nascom.nasa.gov/data/LATEST/current_c3.mpg
http://sohowww.nascom.nasa.gov/data/LATEST/current_c2.mpg
Stills:
http://sohowww.nascom.nasa.gov/data/realtime-images.html
In all these images the shaded disk is a mask in the instrument
that blots
out direct sunlight. The white circle added within the disk
shows the size
and position of the visible Sun.
NOTE: AROUND 08:18 UT TODAY the comet went behind the pylon (the
metal rod
holding the occulting disk in front of the Sun). It will reappear
around
15:18 UT.
SOHO has discovered more than 420 comets in just under 6 years
which makes
SOHO the most prolific comet finder in the history of astronomy.
Most of the
comets were first spotted by amateurs around the world
downloading our real
time images to their home computers. All the SOHO images are
freely
available on the SOHO web site: http://sohowww.nascom.nasa.gov/
THUS, ANYONE WITH INTERNET ACCESS CAN TAKE PART IN THE HUNT FOR
NEW COMETS
AND BE A COMET DISCOVERER. To read more about sungrazing comets
and how to
spot new ones visit: http://sungrazer.nascom.nasa.gov/
Solar radiation heats the comet which in turn causes the
outgassing of the
water molecules and dust. The dust scatters sunlight at visible
wavelengths,
making the comet bright in LASCO images. The water
molecules break down
into oxygen and hydrogen atoms, and the hydrogen atoms interact
with the
coronal plasma.
IMAGE CREDITS: SOHO (ESA/NASA)
Launched almost 6 years ago as a project of international
cooperation
between the European Space Agency and NASA, the Solar and
Heliospheric
Observatory has revolutionized the science of the Sun.
Webstories on:
http://sohowww.nascom.nasa.gov/hotshots/
----------------------------------------------------------------------------
-
Paal Brekke,
SOHO Deputy Project Scientist (European Space Agency - ESA)
NASA Goddard Space Flight Center,
Email: pbrekke@esa.nascom.nasa.gov
Mail Code 682.3, Bld. 26, Room 001, Tel.:
1-301-286-6983 /301 996 9028
(cell)
Greenbelt, Maryland 20771, USA.
Fax:
1-301-286-0264
----------------------------------------------------------------------------
-
SOHO WEB: http://soho.nascom.nasa.gov/
----------------------------------------------------------------------------
-
=====================
(2) LEGAL DUTY TO "MITIGATE" ASTEROID OR COMET
COLLISIONS WITH THE EARTH
INVOLVES MUCH MORE THAN STARGAZING, SAYS POLICY ANALYST
Dateline: April 13, 2002 ...
Iowa City, Iowa
Contact Name: Elizabeth Davis
Contact Phone: 319-335-9132
Web Address: http://www.uiowa.edu/~ialawrev/
Iowa City, Iowa - April 13, 2002 - In the 1960's, a period that
many called
the "Golden Age of Space," the public began to doubt
the writings of lawyers
who addressed space-related topics. Too many had "jumped on
board the ship,"
so to speak. Today, one area where the attention of lawyers is
desperately
needed relates to the mitigation of threats posed by asteroid or
comet
collisions with the Earth.
Aside from the efforts of nations to conduct sky searches and
catalogue
potential threats, there exist few, if any, plans to evacuate
nations,
educate the public about the nature of a significant impact, or
deal with
the rationing of scarce resources, in the event that scientists
or military
personnel are unable to destroy or deflect an oncoming space body
of
significant mass.
In a recent study published by the Iowa Law Review, Policy
Analyst Evan R.
Seamone has addressed the duty to mitigate asteroid and comet
impacts from
the perspective of international law. The report argues that the
nature of
the dangers posed by asteroids and comets place the threat in the
category
of certain types of disasters for which the international
community is
unprepared. Similar threats include the mutation of the Acquired
Immune
Deficiency Syndrome into an airborne virus or the collapse of the
Cumbre
Vieja volcano in the Canary Islands, which would devastate
multiple nations
simultaneously.
Seamone argues that mitigating asteroid or comet threats
necessarily
involves preventive measures including the commitment of
resources and
personnel. He first explains the three major obstacles that must
be overcome
before mitigation efforts will succeed. First, the public must be
educated
to treat the threat seriously, an objective attainable by
developing
international protocols, especially involving warning mechanisms
and the
verification of actual threats. Second, the dangers posed by
these unique
threats must be situated in policies that extend beyond
traditional disaster
response measures at the international level, which often suffer
from a lack
of coordination.
Third, duties to commit resources preventively must rest on
principles other
than the allocation of blame, which characterizes much of the
corpus of law
dealing with international responsibilities to mitigate
transboundary harm.
Next, recognizing the danger posed to governments in the absence
of serious
preventive coordination, the report associates the duty to
mitigate asteroid
and comet impacts with General Principles of International Law,
as
recognized by the Statute of the International Court of Justice.
The legal
precedents supporting international cooperation hinge on the duty
to
self-preserve as articulated by philosophers such as Vattel and
Hobbes and
in numerous State Constitutions guaranteeing essential
necessities such as
air, food, and water, and the extension of that duty, which would
require
nations to cooperate in order to secure the survival of their own
populaces,
as indicated in legal opinions such as the Island of Palmas case.
After pointing out manifestations of nations' adherence to the
principle of
"cooperative preservation," through duties to warn
other nations of
impending danger, such as Article 28 of the International Law
Commission's
Draft Articles on the Law of Non-Navigational Uses of
International Water
Courses, and duties to mitigate impending danger, such as
Principle VII of
Principles Relevant to the Use of Nuclear Power Sources in Outer
Space,
Seamone recommends international collaboration similar to the
Scientific
Committee on Antarctic Research (SCAR), which deals with issues
facing the
Antarctic region, endowed with certain unique powers to influence
legislation and the allocation of resources.
IF INTERESTED in receiving an offprint of Evan R. Seamone's
"When Wishing on
a Star Just Won't Do: The Legal Basis for International
Cooperation in the
Mitigation of Asteroid Impacts and Similar Transboundary
Disasters," the
author has reserved 100 complementary copies for interested
individuals. The
Iowa Law Review can facilitate such orders. The author may be
contacted
directly at (319) 358-6422 or eseamone@blue.weeg.uiowa.edu.
====================
(3) CRASH COURSE: SCIENTISTS STEP UP EFFORTS TO TRACK ASTEROIDS
>From The Dallas Morning News, 15 April 2002
http://www.dallasnews.com/health/stories/041502dnlivasteroid.a8e99.html
By ALEXANDRA WITZE / The Dallas Morning News
Like a clay pigeon, Earth serves as the moving target in a cosmic
shooting
gallery.
Flying chunks of rock and ice - asteroids and comets - constantly
wallop the
planet. The small ones burn up or explode in the atmosphere. But
someday,
scientists worry, a really big one could hit with the force that
killed the
dinosaurs 65 million years ago.
The last few months have brought some scary reminders.In January,
an
asteroid the size of a football field zoomed by a month after it
was
discovered. In March, a smaller rock made headlines when it was
spotted four
days after passing Earth. This month, astronomers announced an up
to
1-in-300 chance that another big asteroid could hit in the year
2880.
The good news is that this asteroid, called 1950 DA, is helping
scientists
better understand the risk of collision - and what to do if a big
rock is
discovered heading for Earth.
"I was hoping this case would move the discussion to a
higher level," says
Jon Giorgini, leader of the team that announced the possible
future impact.
"In the past it's all been about primal fear issues: Is it
going to hit, is
it not going to hit?"
Researchers now know more about 1950 DA's path than they do about
any other
near-Earth asteroid.
"The exciting thing is the science coming out of this,"
says Steven Chesley,
an asteroid expert at NASA's Jet Propulsion Laboratory in
Pasadena, Calif.
For instance, scientists are learning about the subtle physical
forces that
can nudge asteroids onto a path toward, or away from, Earth.
Dangerous
asteroids can also come in pairs, other new work has shown -
doubling the
trouble for scientists trying to save the planet.
Not all asteroids are bad. Most of the 40,000 identified so far
orbit the
sun between Mars and Jupiter, in the asteroid "main
belt." But sometimes
gravitational tugs from planets or other celestial bodies send
main-belt
asteroids closer to the Earth. The same thing can happen to
comets, icy
bodies from farther out in the solar system.
The Earth is pockmarked with scars - impact craters - from
previous meetings
with asteroids and comets. And every year, scientists monitor
dozens of
explosions in the atmosphere caused by rocks several feet across.
Meanwhile, a rock on the order of several hundred feet across
might hit
every few centuries to 100,000 years, scientists estimate. A
really big
asteroid, measuring two-thirds of a mile across or more, might
hit about
once every million years - possibly causing global devastation by
enshrouding the planet in dust.
Researchers are most worried about the biggest objects, like the
estimated
1,000 Earth-threatening asteroids that are two-thirds of a mile
across or
more.
Congress has asked NASA to find 90 percent of those objects
before the end
of 2008, says Don Yeomans, manager of the near-Earth object
program office
at the Pasadena lab. Five U.S.-led search teams, along with some
now-defunct
programs, have identified just under 600 of those asteroids.
"That looks pretty good on paper, but it's like the old
Easter egg problem,"
says Dr. Yeomans. "The first ones are a lot easier to find
than the
subsequent ones."
Also of concern are smaller asteroids, which could still wipe out
a city if
they hit.
"Those are bullets out there that can really ping us, too,
and we can't
overlook those," says longtime asteroid hunter Eleanor Helin
of the Jet
Propulsion lab.
The closest known near-miss was a small asteroid, about the size
of a flying
couch, that zoomed by in 1994 at a distance of about 70,000
miles, or
three-tenths of the way to the moon. In contrast, the asteroid
that got so
much attention in March, known as 2002 EM7, passed at about
290,000 miles
away, farther than the moon.
"Objects like that pass around those distances on the order
of every single
week of every single year," says Dr. Chesley.
The sun's glare obscures objects coming toward Earth from the
direction of
the sun, so scientists often won't spot an asteroid until after
it's passed,
he says.
More intriguing - not just because it was immortalized in a
column by
humorist Dave Barry - was the football-field-sized asteroid 2001
YB5.
Discovered in December by Dr. Helin's team, 2001 YB5 whizzed
within 520,000
miles on Jan. 7.
Now, scientists are most worried about an object called 2002
CU11, which has
a small chance of hitting Earth in August 2049. That risk that
will probably
disappear as astronomers get more observations to pin down the
asteroid's
path, says Dr. Yeomans.
Unlike many other near-Earth asteroids, 2002 CU11 has a stable
orbit that
doesn't get perturbed by other planets. "It avoids all the
planets except
Earth," Dr. Yeomans notes.
As of last week, 2002 CU11 was the only object rated a
"1" on the Torino
scale, which was devised to communicate asteroid risk to the
public. The
scale runs from 0 (which includes all other asteroids) to 10
(indicating a
certain collision with global consequences).
But on another risk scale, 2002 CU11 has been rated as less
threatening than
the general, or background, risk of any other impact; as of last
week, it
had a value of minus 1.28 on the Palermo scale.
Last summer, scientists introduced the Palermo scale to help
prioritize the
many asteroids that were showing up as 0 on the Torino scale.
With only the Torino scale, "we don't have a way of
categorizing these
hundreds of potential impact events," says Dr. Chesley. The
Palermo scale
uses 0 to represent the background risk of impact; numbers can
range below
or above 0 depending on relative risk.
The only object to receive a positive Palermo rating so far -
meaning its
risk is above the background - is 1950 DA, with a rating of plus
0.17.
Like other asteroids, 1950 DA will probably be marked as safe
once it
reappears and astronomers can observe it, says Dr. Chesley. But
just in
case, asteroid experts are busy dreaming up Armageddon-like
schemes for
deflecting a rock heading for Earth.
Strategies might include blowing up the asteroid with a nuclear
or
conventional explosive; blasting off enough small pieces to
change the
asteroid's trajectory; or exploiting a little-known effect caused
by the
sun's heat.
The "Yarkovsky effect" describes how, as the afternoon
side of an asteroid
rotates into darkness, it reradiates heat from its warmed surface
and pushes
slightly in the opposite direction. It is this effect that serves
as the
greatest uncertainty about where 1950 DA might be in 2880, says
Mr.
Giorgini, of the Pasadena lab.
The Yarkovsky effect may be responsible for making some asteroids
dangerous
in the first place; the subtle radiation may help nudge asteroids
from the
main belt into Earth-crossing orbits, some scientists think.
Other researchers believe that harnessing the effect might be the
best way
to save Earth. Some astronomers, including Andrea Milani of the
University
of Pisa in Italy and Joseph Spitale of the University of Arizona,
have
independently suggested methods for altering an asteroid's
heat-absorbing
properties. This might involve changing the asteroid's color - by
painting
or covering it in black or white substances.
"There are obviously engineering problems with taking so
much talcum powder
out into space," Dr. Chesley notes.
Saving the planet might be twice as hard if the incoming asteroid
were
actually in two pieces.
One in six near-Earth asteroids is probably a binary, which means
two rocks
travel together, says a new paper published last week in the
online version
of Science magazine. The scientists, led by Jean-Luc Margot of
the
California Institute of Technology, say that five such pairs have
been found
so far. Twinned rocks have hit Earth before; several of the
impact craters
on Earth are double craters formed by two asteroids at the same
time.
Whether one or two asteroids is approaching, astronomers want as
much lead
time as possible to prepare for any impact. At least several
decades would
be needed to plan a strategy, says Benny Peiser, a social
scientist at
Liverpool John Moores University in England who studies impact
risks.
Dr. Peiser says that the public may have to learn to live with
uncertainty.
Even with the best predictions, he says, "we could have this
prolonged
period of anxiety and uncertainty when we don't know what is
going to
happen."
Fortunately, scientists are working hard now so that they won't
be too
surprised in the future.
"The problem is being handled, at least at some level,"
says Dr. Yeomans.
"Whereas 10 years ago, people didn't even know there was a
problem."
E-mail awitze@dallasnews.com
Copyright 2002, Dallas Morning News
===============
(4) EUROPEAN SPACE AGENCY TO PROBE ASTEROID BLIND SPOT
>From Karen O'Flaherty <Karen.O'Flaherty@esa.int>
In the past five weeks two asteroids have passed close by Earth,
at
distances of 1.2 and 3 times the distance to the Moon. Another
asteroid has
recently been shown to be on course for a collision with Earth in
2880.
Monitoring known asteroids allows astronomers to predict which
may collide
with Earth. But that is only true for the asteroids we know of.
What about those
that lie in the asteroid blind spot between the Sun and Earth?
The European Space
Agency is studying ways in which its missions can assist in
monitoring these
unseen but potentially hazardous asteroids.
It is difficult to estimate the danger posed by asteroids. This
is, in part,
because astronomers do not yet know how many asteroids there are.
A recent
discovery, made using data from ESA's Infrared Space Observatory
(ISO),
showed that there could be nearly two million asteroids larger
than one
kilometre in the main asteroid belt, between Mars and
Jupiter. That is more
than twice as many as previously thought.
In addition, even when an asteroid is identified many
observations must be
made before it is known whether or not it will come close to, or
even
collide with, Earth.
If the asteroids remained in the main-belt, they would pose no
danger to
Earth. However, they can be thrown into different orbits by
collisions with
other asteroids or by the influence of Jupiter's gravitational
field. If
their new orbits cross the Earth's orbit, they could one day
collide with
our planet, inflicting unprecedented devastation.
A number of ground-based searches are already underway to find as
many
potentially hazardous asteroids (PHAs) as possible but there is a
notorious
'blind spot' that telescopes on Earth can never peer into. It is
the region
of space inside Earth's orbit, towards the Sun. From Earth,
astronomical observations close to the Sun are almost impossible
because it
means observing during the daytime when only the brightest
celestial objects
stand out from the blue sky. That means asteroids lurking in this
region of
space can 'sneak up' on the Earth undetected. Asteroid 2002 EM7,
which
passed close by the Earth on 8 March this year, was one such
object and was
only detected after it crossed Earth's orbit to appear briefly in
the night
sky, before it crossed back into the glare of the Sun.
About 550 similar asteroids are known. They are called the Atens
and spend
most of their time inside Earth's orbit, close to the Sun.
Traditional
estimates suggest there may be several thousand in total and
tracking them
from Earth is next to impossible. However, a study
performed for ESA has
shown that the Gaia spacecraft will be able to see clearly into
this
'blind spot' and keep precise track of the Aten population.
François Mignard of Observatoire de la Côtes d'Azur, France,
conducted the
study. He found that Gaia would be ideal because it is designed
to measure
the position of celestial objects with unprecedented accuracy. In
addition,
since there is no atmosphere in space to scatter the Sun's rays
and create a
blinding blue sky, Gaia can see close to the Sun without
disturbance.
Gaia is expected to be launched around 2010. Even if ground-based
searches
have spotted more Atens by that time, the mission still has an
essential
role to play because it will reveal their orbits to a precision
30 times
better than any observation from the ground, thus identifying
whether any
pose a danger to Earth.
"To know how close these objects will come to Earth is very
dependent on how
accurately one can measure their orbits. That's the main
contribution that
Gaia can be expected to make," says Michael Perryman,
project scientist for
Gaia, at ESA's European Space Research and Technology Centre in
the
Netherlands.
Gaia's data will also provide astronomers with a first estimate
of these
objects' composition. This knowledge could help to
determine methods to
divert or destroy asteroids that are set on a collision course
with Earth.
Several ESA missions are contributing, or will contribute, to our
understanding of minor bodies of the Solar System: these include
ISO, Gaia
and Rosetta, which will study asteroids Siwa and Otawara. ESA is
also
considering the addition of an asteroid spotting telescope to its
BepiColombo mission.
================
(5) MISSIONS TO PLUTO, EUROPA CANCELED
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
[ http://www.latimes.com/news/nationworld/nation/la-000026460apr13.story
]
Saturday, April 13 2002
Missions to Pluto, Europa Canceled
By USHA LEE McFARLING, LOS ANGELES TIMES STAFF WRITER
NASA's on-again, off-again mission to Pluto appears to be off, at
least for
now. And a JPL mission to Jupiter's watery moon Europa --
considered the
most likely spot for extraterrestrial life -- also has been
canceled for
budget reasons.
Top NASA officials said Friday it was highly unlikely that a
mission to
Pluto would launch by 2006 -- the final date set by scientists to
be able to
reach the planet in time to study its atmosphere before it
becomes
inaccessible for a century. The Europa mission was canceled
after its projected cost more than doubled.
Though a darling of schoolchildren and a long-elusive target of
scientists,
a Pluto expedition is not favored by the White House. For the
second year in
a row, the administration budget has included no money to explore
the
distant world. Last year, Congress added $30 million to NASA's
budget to
develop plans for a Pluto mission after a flood of letters and
calls from
distraught children and concerned citizens. But this year,
scientists at the
Applied Physics Laboratory
at Johns Hopkins University in Baltimore were refused the $122
million they
say is necessary to continue developing a $500-million mission.
Even if Congress again restores funding at the last minute, the
unmanned
mission faces two significant hurdles, said Chris Scolese, NASA's
deputy
associate administrator for space science.
It has yet to be proved, he said, that the distant mission is
feasible. In
addition, the use of plutonium in the spacecraft, to power its
instruments,
remains controversial.
In other spacecraft, including Cassini, which is bound for
Saturn, it has
generally taken about eight years to receive permission to use
plutonium,
Scolese said. Opponents of using the radioactive material fear
contamination
from a spacecraft accidentally returning to Earth; NASA says the
plutonium
is well shielded, minimizing any risk.
Finally, the mission is scheduled to leave Earth aboard a new
rocket --
either a Boeing Delta IV or a Lockheed Martin Atlas V. Both
rockets have yet
to take their maiden voyage; NASA officials would want the
rockets to be
well proved before using them to launch spacecraft.
Life on Europa Thought Possible
The mission to Europa was canceled after its $650-million budget
swelled to
$1.4 billion. The mission could compete for funding in the new
NASA budget
if its cost is trimmed back to $650 million. But scientists think
it is
unlikely that they could conduct an effective mission to probe
the icy
moon's subsurface oceans for traces of life for less than $1
billion.
Most of the staff working on the Europa mission at the Jet
Propulsion
Laboratory -- 80 to 90 people -- are continuing to work on a new
generation
of faster, smaller radiation-hardened electronics that were part
of the
project and will now be used to improve future missions. Others
have been
redeployed to work on a Mars rover project. Lab officials said
the move
resulted in no layoffs.
Planetary scientists and those in favor of exploration are
angered by NASA's
move. Reaching Pluto and Europa is among the top priorities for
solar system
exploration. Pluto was considered especially urgent because it is
entering a
distant, colder part of its elliptical orbit. This means the
atmosphere will
freeze completely and could be unavailable for study for roughly
100 years.
Lou Friedman, executive director of the Planetary Society, called
the
decisions shortsighted and called them the equivalent of
"recalling the
fleet."
Colleen Hartman, who directs solar system exploration for NASA,
said it may
still be possible to reach Pluto and Europa in the near future as
technologies such as nuclear propulsion evolve. "We're doing
things now that
seemed impossible five years ago," she said.
Hartman was also awaiting a survey, done once a decade by the
National
Academy of Sciences and due out in August, that will set
priorities among
scientific goals for planetary exploration. A strong push to get
to Pluto or
Europa from the respected organization could resurrect funding
for the
projects.
==============
(6) MECHANISM THAT CREATES NEAR-EARTH BINARY ASTEROIDS
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
Media relations
Caltech
Contact:
Robert Tindol, (626) 395-3631
4/11/2002
Researchers find evidence for mechanism that creates near-Earth
binary
asteroids
About one in six of all near-Earth asteroids are binaries -- in
other words,
two bodies that travel in close companionship as they orbit the
sun. A new
study reveals that binaries most likely form when a single
asteroid swings
close to Earth, is ripped apart by the planet's tidal
attraction, and eventually reforms into separate bodies.
In a refereed article to be released Thursday, April 11 on the
Science
Express Web site of the journal Science, California Institute of
Technology
astronomer Jean-Luc Margot and his co-authors report detailed
information on
the near-Earth asteroid currently assigned the rather unpoetic
name 2000
DP107, and also on four other binary asteroids. 2000 DP107
comprises two
bodies that are about three kilometers apart, the larger of the
two being
about 800 meters in diameter and the other about 300 meters.
Using
particularly detailed radar data, the study is a description of
the system
and explains how both these particular bodies and near-Earth
binaries in
general can be formed.
Near-Earth asteroids were formed between Mars and Jupiter, like
all other
asteroids, but are kicked into elliptical orbits by the
gravitational
influence of Jupiter and occasionally pass near Earth. An
Earth-crossing
orbit is one in which the asteroid actually crosses
the path that Earth follows around the sun, which means the two
bodies could
eventually collide.
Margot, a postdoctoral researcher in the Division of Geology and
Planetary
Science at Caltech, led the observations in October 2000 that
uncovered 2000
DP107's binary nature, just months after the asteroid was first
discovered
by MIT researchers. The current study, of which Margot is lead
author,
employs data obtained from the 70-meter Goldstone NASA tracking
telescope
and the Arecibo Observatory's radio telescope in Puerto Rico,
which is funded by the
National Science Foundation with additional support from NASA and
operated
by Cornell University, to yield a much more detailed picture of
the two
orbiting bodies and their dynamics.
Other details from the radar data show that the two bodies are
probably in a
tidal lock, which means that a person standing on the larger body
would
always see the same face of the smaller body, but a person on the
smaller
body would see the larger body spinning. This is exactly like the
tidal lock
of the Earth-moon system.
Further, the research suggests that the tidal force applied to an
asteroid
by a larger planet can be the cause of its breaking apart. The
process,
known as "spin and fission," means that a body
approaching Earth is made to
change its spin rate. Specifically, the tidal force tends to make
an
asteroid passing nearby spin at the orbital rate, which can
increase rather
substantially in a close approach to a planet. This increase in
spin rate,
coupled with the tidal pull itself, can cause a loosely-bound,
gravel-like
accumulation such as the near-Earth asteroids, to sling off
material. Later,
the weak gravitational attraction of the particles allows the
material to
reform in a second body.
But the most important issue raised by the paper is that
near-Earth binaries
are so common, says Jet Propulsion Laboratory researcher Steve
Ostro, one of
the authors. "The discovery of the existence and substantial
abundance of
binary asteroids in Earth-crossing orbits is a major one,"
says Ostro, an
expert on the radar characterization of asteroids.
"Presumably, binary
asteroids have hit Earth in the past, and will do so in the
future."
"Of course, the most important thing to know about any
(potentially
hazardous asteroid) is whether it is two objects or one, and this
is why we
want to observe these binaries with radar whenever
possible."
"The use of radar allows precise measurements of asteroid
densities, a very
important indicator of their composition and internal
structure," says
Margot.
"Getting (near-Earth asteroid) densities from radar is
dirt-cheap compared
with getting a density with a spacecraft," Ostro explains.
In addition to Margot and Ostro, the other authors are Michael
Nolan of the
Arecibo Observatory; Lance Benner, Raymond Jurgens, Jon Giorgini,
and Martin
Slade, all of JPL; and Donald Campbell of Cornell University.
The article will be available Thursday on the Science Express Web
site at
http://www.sciencemag.org/cgi/content/abstract/1072094v1
Related Links
* More on Binary Asteroids
http://www.gps.Caltech.edu/~margot/2000DP107
* Science Express
http://www.scienceexpress.org
=============
(7) RADAR REVEALS FIVE DOUBLE ASTEROID SYSTEMS ORBITING EACH
OTHER NEAR
EARTH
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
News Service
Cornell University
Contact: David Brand
Office: 607-255-3651
E-Mail: deb27@cornell.edu
EMBARGOED FOR RELEASE: 2 p.m. Eastern Time, April 11, 2002
Radar reveals five double asteroid systems orbiting each other
near Earth,
likely formed in close encounters with planet
ITHACA, N.Y. -- Binary asteroids -- two rocky objects orbiting
about one
another -- appear to be common in Earth-crossing orbits,
astronomers using
the world's two most powerful astronomical radar telescopes
report. And it
is probable, they say, that these double asteroid systems have
been formed
as a result of gravitational effects during close encounters with
at least
two of the inner planets, including Earth.
Writing in a report published by the journalScience on its
Science Express
web site (April 11, 2002), the researchers estimate that about 16
percent of
so-called near-Earth asteroids (NEAs) larger than 200 meters (219
yards) in
diameter are likely to be binary systems, with about a
three-to-one relative
size of the two encircling bodies. To date, five such binary
systems have
been identified by radar, says lead researcher Jean-Luc Margot,
an O.K. Earl
postdoctoral fellow in the Division of Geological and Planetary
Sciences at
the California Institute of Technology.
Margot, who at the time of the observations was a research
associate in the
planetary studies/radar group at the National Science
Foundation's (NSF)
Arecibo Observatory in Puerto Rico (managed at Cornell
University), says
that theoretical and modeling results show the binary asteroids
appear to be
formed extremely close to Earth -- within a distance equal to a
few times
the planet's radius (6,378 kilometers or 3,963 miles). "The
fact that one
out of every six large NEAs is a binary and that they typically
survive on the order
of 10 million years, implies that these close encounters must
happen frequently compared
to the lifetime of the binary asteroids," says Margot.
The Science article, "Binary Asteroids in the Near-Earth
Object Population,"
is coauthored by Michael Nolan, research associate at Arecibo;
Lance Benner,
Steven Ostro, Raymond Jurgens, Jon Giorgini and Martin Slade at
the Jet
Propulsion Laboratory (JPL); and Donald Campbell, professor of
astronomy at
Cornell. The observations were made at the 70-meter Goldstone
NASA tracking
telescope in California and at Arecibo Observatory.
NEAs are formed in the asteroid belt, between the orbits of Mars
and
Jupiter, and nudged by the gravitational attraction of nearby
planets,
largely Jupiter, into orbits that allow them to enter the Earth's
neighborhood. Most of the asteroids are the remnants of the
initial
agglomeration of the inner planets.
Astronomers have long speculated about the existence of binary
NEAs, based
in part on impact craters on Earth. Of about 28 known terrestrial
impact
craters with diameters greater than 20 kilometers, at least three
are double
craters formed by impacts of objects about the same size as the
newly
discovered binaries. Astronomers also have noted the changes in
brightness
of reflected sunlight for some NEAs, indicating a double system
was causing
an eclipse or occultation of
one by the other.
In 2000, Margot and his co-researchers, using measurements from
the
Goldstone radar, found that a small, roughly 800-meter-diameter
(half-a-mile) asteroid, 2000 DP107 (discovered only months before
by a team
from the Massachusetts Institute of Technology), was a binary
system.
Observations over eight days last October with the much more
sensitive
Arecibo telescope clearly established the physical
characteristics of
DP107's two asteroids as well as their orbit
about each other. The smaller object called the secondary, it was
found, is
about 300 meters (1,000 feet) in diameter and is orbiting the
larger
asteroid, the primary, every 42 hours at a distance of 2.6
kilometers (1.6
miles). The two asteroids appear to be locked in synchronous
rotation, with
the smaller always with the same face oriented to the larger.
Since that observation, says Margot, four more binary NEAs have
been
discovered, all in Earth-crossing orbits and each with a main
asteroid
significantly larger than the smaller body. "The primary is
rotating much
faster than most NEAs in all five binaries that have been
discovered," says
Cornell's Campbell. The Science Express article speculates that
the most
likely way the binaries are created is by close encounters of
asteroids with
the inner planets Earth or Mars. Of the five binary NEAs
discovered to date,
none has an orbit that brings it as close to the sun as Venus or
Mercury.
NEAs, basically piles of rubble held together by gravity, are on
trajectories that bring them within a few thousand miles of the
planets,
where tidal forces -- essentially the pull of gravity -- can
increase the
spin rate of the asteroid, causing it to fly apart. The ejected
rubble then
reforms in orbit around the larger asteroid.
"The asteroid is already rotating very quickly as it
approaches the planet.
A little extra boost from tidal forces can be enough to exceed
its breakup
limits, and it sheds mass. This mass can end up forming another
object in
orbit around the asteroid. Right now this seems the most likely
explanation," says Margot.
There is an important reason for studying binary asteroids, says
JPL's
Ostro: their potential for colliding with Earth. Knowing the
density of
so-called PHAs (for potentially hazardous asteroids), he
observes, "is an
extremely important input to any mitigation plans." He says,
"Getting NEA
densities from radar is dirt cheap compared with getting a
density with a
spacecraft. Of course, the most important thing to know about any
PHA is
whether it is two objects or one, and this is why we want to
observe these
binaries with radar whenever possible."
Margot notes, "Radar gives us very precise measurements of
the size of the
objects and their shape. The radar measurements of the distance
and velocity
of each component allows us to obtain precise information on
their orbits.
>From this we can obtain the mass of each of the objects
allowing, for the
Þrst time, measurements of NEA densities, a very important
indicator of
their composition and internal structure."
Arecibo Observatory is operated by the National Astronomy and
Ionosphere
Center at Cornell under a cooperative agreement with the NSF. The
research
was supported by the NSF, with NASA providing
additional support for the planetary radar program at Arecibo.
Related World Wide Web sites:
The following sites provide additional information on this news
release.
Some might not be part of the Cornell University community, and
Cornell has
no control over their content or availability.
* Science Express
http://www.sciencemag.org/cgi/content/abstract/1072094v1
* Images of binary asteroid 2000 DP107
http://www.gps.caltech.edu/~margot/2000DP107
-30-
IMAGE CAPTION:
[ http://www.news.cornell.edu/photos/DP107.sum6.300.gif
(698KB)] A montage of
radar images, captured with the Arecibo Observatory radar
telescope, of
binary asteroid 2000 DP107, showing the smaller body (about 300
meters in
diameter) circling the larger body (about 800 meters) at a
distance of 2.6
kilometers every 42 hours. Jean-Luc Margot, Caltech.
===============
(8) A LAST WAVE GOODBYE
>From The Guardian, 11 April 2002
http://www.guardian.co.uk/Archive/Article/0,4273,4391088,00.html
An asteroid landing in the ocean would produce the tsunami to end
them all,
says Duncan Steel
Throw a stone into a pond and the ripples take just seconds to
spread to the
banks. Drop an asteroid into the Atlantic and you get much the
same effect,
but on a grander scale. Hours later, the coastlines are deluged.
When the possible consequences of cosmic impacts on our planet
are
discussed, people take comfort from the fact that 70% of the
Earth's surface
is ocean. In reality, we would not want a small asteroid to land
in the open
sea: it would cause more damage and kill more people.
Consider a lump of space rock 200 metres in diameter, colliding
with our
planet at 12 miles per second, a typical speed. As it is brought
to an
abrupt halt, it releases its kinetic energy in an explosion
equivalent to
600 megatons of TNT, 10 times the yield of the most powerful
nuclear weapon
tested (underground). The asteroid vaporises, and the rapidly
expanding
shock wave carries away its energy. For a land impact, the area
devastated
would be about 10,000 square miles: everything within a 60-mile
radius would
be obliterated. Beyond that, the destruction would still be
substantial.
However, the implications for humanity would likely be worse if
the open
ocean were struck instead. An asteroid landing in an ocean
produces a
phenomenal tsunami (often mistakenly called a "tidal
wave"). Even though
only about 10% of the energy of the impactor would be transferred
to the
tsunami, such waves are effective at carrying that energy over
the large
distances to the coastlines. They therefore cause destruction
over a much
wider area than is the case for a land impact. In the latter, the
interaction between the blast wave and the irregularities of the
ground
(hills, buildings, trees) limits the area damaged, but on the
ocean, the
wave propagates until it runs into something.
Paradoxically, ships at sea are little affected by tsunamis. They
simply
ride the waves that move outward from the epicentre at well over
100mph. On
the open ocean, a major tsunami may be only 10 to 50cms high; it
is the
run-up that occurs as the wave reaches the continental shelf that
causes the
wave height to increase markedly, and they can penetrate miles
inland.
During the past century, several significant tsunamis have swept
across the
Pacific, provoked by undersea landslips, earthquakes or volcanic
eruptions.
A major rumble off the coast of Chile in 1960 induced a series of
waves that
killed more than a thousand people on the mainland. The waves
reached Hawaii
15 hours later, drowning more than 60 people. As the main wave
smacked Hilo
harbour it was over 10 metres high. Seven hours later, it killed
hundreds in
Japan. In July 1998, an earthquake-generated tsunami in Papua New
Guinea
swept more than 2,000 coastal dwellers to their deaths.
Dr Steven Ward, who works in the Institute of Geophysics and
Planetary
Physics at the University of California at Santa Cruz, modelled a
200-metre
asteroid slamming into the Atlantic about 700 miles west of the
tip of
Cornwall. The transient crater formed in the three-mile deep
ocean is about
four miles wide and a mile-and-a-half deep. It's like throwing a
big rock
into a vast pond, although at hypervelocity. One hour later, the
outermost
edge of the wave has spread about 300 miles from the epicentre.
The greatest
wave amplitude is further back, because the tsunami continues to
be boosted
by the water oscillating up and down at the epicentre. To see
what happens,
over a much shorter time scale, drop a sugar cube into a cup of
coffee.
After two hours, the tsunami is just reaching the south-western
tip of
Ireland. The distortion of the wave from circularity is clear,
due to the
crossing of the continental shelf, where the water is much
shallower. This
slows the wave, but considerations of conservation of momentum
say that it
must get taller. This is called "shallow water
shoaling". Three hours
post-impact, the west coast of Ireland is inundated: goodbye
Galway and
Donegal, although Limerick and Cork may survive, shielded by
their natural
harbours. In this scenario, Ireland provides a singular service
to the rest
of the British Isles, bearing the brunt of the tsunami. Five to
six hours
after the strike, Cornwall, Devon and south Wales are hit, as are
the
Western Isles of Scotland, but the ports lining the Irish Sea
escape the
worst.
Further south, the news is not so good. The shallow waters of the
English
Channel cause the wave to elevate, and seaside resorts to
Brighton and
beyond would be swept away. One must hope that eight hours - the
time the
tsunami would take to reach the Isle of Wight - are enough to
organise an
evacuation. Shortly after, the wave would penetrate between Dover
and
Calais, and the dykes of the Netherlands would provide little
resistance.
With no offshore shield, the coasts of France, Spain and Portugal
are
pummelled by the tsunami.
The shadowing effect provided by islands is most obvious in the
case of the
Azores. When a tsunami hits a coast, it ramps up in height by a
factor that
depends upon the profile of that coastline and, in particular,
the gradient
of the sea bottom. That factor may be only two or three, but it
may be more
than 10. The latter would mean that waves 10 metres in amplitude
on the open
sea would attain a height of 100 metres as they hit land. We are
not talking
of a simple flood, then. We are talking about a coastline swept
clean.
How often does such an event occur? Asteroids around 200 metres
in size
strike the Earth about once every couple of thousand years. The
Atlantic has
about a one-in-10 chance of being the next target.
A parting thought. Last time I checked my house insurance, I was
covered for
tsunami damage. Trouble is, tsunamis were defined in the small
print as
being large sea-waves produced by sub-oceanic volcanoes,
landslips or
earthquakes. Asteroid impacts don't count, it seems.
· Duncan Steel conducts research on asteroids at the University
of Salford.
Guardian Unlimited © Guardian Newspapers Limited 2002
================
(9) DAVE RODDY, 1932 - 2002
http://astrogeology.usgs.gov/About/People/DaveRoddy/
U.S. Geological Survey, Astrogeology Team Emeritus David John
Roddy passed
away at 9:40 in the morning, March 21 at St. Louis hospital while
on a short
trip. He had gone into the hospital complaining of chest pains
and ruptured
an aorta while undergoing a heart scan. He died immediately.
Dave was a world-renowned scientist at the forefront of
investigators
studying impact and explosion craters. His field mapping of Flynn
Creek was
the first mapping detailed enough to demonstrate the impact
origin of an
ancient structure in North America. David was an authority on the
Meteor
Crater impact structure, east of Flagstaff. Dave's work has
assisted in the
recognition of large-body impact as an important geologic process
on Earth.
His study of explosion craters led to longtime involvement with
the
Department of Defense and was of critical value in strategic
military
planning. His specialties were the mechanics of hypervelocity
impacts,
nuclear- and explosion-cratering processes, and high-pressure
shock-wave
deformation of natural materials, and the geologic and
geophysical
applications of the science to terrestrial and planetary
research. He was
also a U.S. Air Force flight navigator and instructor, and a
qualified
private and commercial pilot for most of his life.
David was born in Springville, Ohio, in 1932 to Jack and Nellie
Roddy. He
attended the U.S. Air Force School in Harlington, Texas, from
1957 to 1958.
Dave got his A.B. and M.S. degrees from Miami University in Ohio
in 1955 and
1957, respectively. He was a distinguished graduate of the U.S.
Air Force
ROTC program at Miami University. From 1957-1960, he was in
active service
as an Air Force navigator. He attended California Institute of
Technology in
southern California from 1960 to 1966, receiving a Ph.D. on the
dissertation
topic of "Impact-cratering mechanics of Flynn Creek,
Tennessee" working
under Dr. Gene Shoemaker. In 1962, he was induced by Gene to work
in an
interim capacity at the USGS in the newly-formed Branch of
Astrogeology. He
joined the Astro Team full time in 1965. Dave was Associate
Branch Chief of
the Astrogeology Team from 1983-1984. He retired from the USGS in
1992, but
remained with the Team as an Emeritus and was extremely active in
Science to
the very end. David was a member of Sigma Gamma Epsilon, the
Geological
Society of America, the Mineralogical Society of America, Sigma
Xi, American
Geophysical Union, and the American Society of Industrial
Security.
He was the recipient of the U.S. Department of Interior Unit
award for
Pacific Enewetak Atoll Crater Explosion Program. He received
several letters
of appreciation and commendation from Generals at the Department
of Defense
and from the Secretary of the Air Force for his work with Desert
Storm. He
was cited by the Secretary of the Interior for a Meritorious
Service Award.
The prestigious Barringer Award was presented to David Roddy at
the
International Meteoritic Society Meeting in Prague,
Czechoslovakia, on
August 3, 1994, in recognition of his outstanding scientific
contributions
and lifetime work in the field of impact crater mechanics.
Co-workers at the USGS remember a caring, kind, loyal friend with
a sharp
sense of humor. Dave was a good listener, who could always be
trusted to
keep confidences. Extremely honest and ethical, he was always
willing to
help someone in need. Throughout the 1980s and early 1990s his
constant
companion was a small white terrier named Michelle. Clad in
sunglasses and
leather pilot jacket with Michelle trotting at his side, Dave was
a driven
scientist with a Colonel Flag persona, who aspired to the highest
of
standards, but usually had time for lunch with friends.
Most of his life Dave was a vital man with a passion for running
and staying
fit. Although the last ten years of his life were marked by a
battle with
Parkinson's disease, he fought it every inch of the way. In 2000,
he ran 2.5
miles in the annual Flagstaff 4th of July 10K/fun run. Last year,
he walked
the entire 10K. It was hot as hell and Dave came in last,
receiving the red
caboose award and another for being the oldest participant, but
he still had
enough energy to walk over and view the 2-hour parade, eat lots
of my
daughter's candy, and then beg us to join him for lunch. Lunches
with Dave
were always memorable, a meal rarely ended without his ordering
one dessert,
that we all had to share. David was a practical joker. He
probably pulled
his last one on me, a week before his death, in Houston at the
Lunar and
Planetary Science Conference. We were going out to lunch in a
group of 5:
Bevan French and Wylie Poag in a small car and David, John
McHone, and I
were to use the LPI van service. Inside the van, Dave wasn't
happy with the
lax schedule of the driver. He pointed out an open-door car
across the
parking lot and asked me to jump out and run over there, to see
if we could
all squeeze in Wylie Poag's car. I sprinted across the lot,
glanced at the
empty back seat, and asked if we could join them, only to find
that the two
men in the front seat were not French or Poag. Bill Casidy, on
the passenger
side, wanted to know what my companions looked like. Mortified, I
apologized
and walked back to the van to find Dave and John laughing their
heads off.
Dave said, "I knew it wasn't them all the time, you should
have seen the
looks on their faces, but don't worry - you made their day."
Dave was married twice. First to Andrea Biehler of Riverside,
California,
with whom he had 3 sons. His second marriage was to Jeannie Swan
Roddy of
Halifax, Nova Scotia. His mother Nellie, 3 sons: David M., Mark
R., and
Matthew J. Roddy, as well as stepsons, Glen and Kevin Swan and 3
grandchildren survive Dave. He was active in his community and is
sorely
missed by numerous friends, co-workers, and peers.
A memorial service will be held 11:00 a.m. on Saturday, May 18 in
Wettaw
auditorium (building #88, room #130) on the Northern Arizona
University
campus in Flagstaff, Arizona. The Wettaw building is the new
biology-biochemistry building near the corner of DuPont and
Beaver. The
entrance is on the west side, and parking is available in lot P-1
northwest
of the building. The family has asked that in lieu of flowers,
donations may
be made to the Parkinson's Foundation, 1250 Hylan Blvd., Suite
4B, Staten
Island, NY 10305, or to an animal care organization of the
donor's choice.
By Mary G. Chapman
26 March 2002
Selected Publications
Roddy, D.J., Boyce, J.M., Colton, G.W., and Dial, A.L., Jr.,
1975, Meteor
Crater, Arizona, rim drilling with thickness, structural uplift,
diameter,
depth, volume, and mass-balance calculations: Lunar Science
Conference, 6th,
Proceedings, New York, Pergamon Press, p. 2621-2644.
Roddy, D.J., 1976, Impact cratering and its record on the planets
and Moon,
in Greeley, R., and Schultz, P. eds., Planetary Geology Short
Course, April
1976, p. 100-157.
Roddy, D.J., 1977, Tabular comparisons of the Flynn Creek impact
crater,
United States, Steinheim impact crater, Germany, and Snowball
explosion
crater, Canada, in Impact and explosion cratering: Planetary and
terrestrial
implications, Roddy, D.J., Pepin, R.O., and Merrill, R.B., eds.,
New York,
Pergamon Press, p. 125-162.
Roddy, D.J., 1977, Large scale impact and explosion craters:
Comparisons of
morphological and structural analogs, in Roddy, D.J., Pepin,
R.O., and
Merrill, R.B., eds., Impact and explosion craterering: Planetary
and
terrestrial implications: New York, Pergamon Press, p. 185-246.
Roddy, D.J., 1977, Pre-impact conditions and cratering processes
at the
Flynn Creek crater, Tennessee, in Roddy, D.J., Pepin, R.O., and
Merrill,
R.B., eds., Impact and explosion cratering: Planetary and
terrestrial
implications: New York, Pergamon Press, p. 277-308.
Roddy, D.J., and Davis, L.K., 1977, Shatter cones formed in large
scale
experimental explosion craters, in Roddy, D.J., Pepin, R.O., and
Merrill,
R.B., eds., Impact and explosion cratering: Planetary and
terrestrial
implications: New York, Pergamon Press, p. 715-750.
Roddy, D.J., and Pepin, R.O. 1977, Introduction, in Roddy, D.J.,
Pepin,
R.O., and Merrill, R.B., eds., Impact and explosion cratering:
Planetary and
terrestrial implications: New York, Pergamon Press, p. xi-ix.
Roddy, D.J., Pepin, R.O., Merrill, R.B., eds., 1977, Impact and
explosion
cratering: Planetary and terrestrial implications: New York,
Pergamon Press,
1301 p.
Ullrich, G.W., Roddy, D.J., and Simmons, G., 1977, Numerical
simulations of
a 20-ton TNT detonation on the Earth's surface and implications
concerning
the mechanics of central uplift formation, in Roddy, D.J., Pepin,
R.O., and
Merrill, R.B., eds., Impact and explosion cratering: Planetary
and
terrestrial implications: New York, Pergamon Press, p. 959-982.
Roddy, D.J., 1978, Pre-impact geologic conditions, physical
properties,
energy calculations, meteorite and initial crater dimensions and
orientations of joints, faults and walls at Meteor Crater,
Arizonz: Lunar
and Planetary Science Conference, 9th, Proceedings, Houston,
Geochimica et
Cosmochimica Acta, v. 3, Supplement 10, p. 3891-3930.
Roddy, D.J., 1979, Structural deformation at the Flynn Creek
impact crater,
Tennessee: A preliminary report on deep drilling: Lunar and
Planetary
Science Conference, 10th, Proceedings, p. 2519-2534.
Roddy, D.J., Watson, R.D., and Theisen, A.F., 1980, Shock-induced
luminescence at Meteor Crater, Arizona, measured by laboratory
and airborne
Fraunhofer line discriminator systems: Meteoritics, v. 15, no. 4,
p.
356-357.
Roddy, D.J., Schuster, S.H., Kreyenhagen, K.N., and Orphal, D.L.,
1980,
Computer code simulations of the formation of Meteor Crater,
Arizona:
Calculations MC-1 and MC-2: Lunar and Planetary Science
Conference, 11th,
Proceeding, p. 2275-2308.
Roddy, D.J., Schuster, S.H., Rosenblatt, M., Grant, L.B., Hassig,
P.J., and
Kreyenhagen, K.N., 1987, Computer simulations of large asteroid
impacts into
oceanic and continental sites--Preliminary results on
atmospheric, cratering
and ejecta dynamics: International Journal of Impact Engineering,
v. 5, nos.
1-4, in Hypervelocity Impact, Proceedings of the 1986 Symposium,
Anderson,
C.E., ed., Pergamon Press, p. 525-541.
===============
(10) THE REAL THREAT TO THE PLANET
>From Tech Central Station, 9 April 2002
http://www.techcentralstation.com/1051/envirowrapper.jsp?PID=1051-450&CID=1051-040902B
By Sallie Baliunas 04/09/2002
"...[G]lobal warming [is] the most serious threat that we
have ever
faced..." (Al Gore, Earth in the Balance, p. 40)
"...[A large asteroid striking the earth is a] serious and
surprising danger
posed to our global civilization from outer space." (Carl
Sagan)
Two global threats - one supposedly human-made, the other
natural. How much
worry should be parceled to each? Calamitous global warming from
human
activities like fossil-fuel burning finds little support in
reliable
measurements of the temperature of the earth - either at the
surface or in
the sensitive lower atmosphere. On the other hand, an eventual
asteroid
strike is a dead certainty.
Just discovered is the threat of asteroid 1950 DA, which might
endanger the
earth in 878 years. The risk of comet or asteroid strike is not
unusual - it
is ever present. However, for the first time in the history of
life on
earth, science may allow Homo sapiens to see and deflect a cosmic
destroyer.
Natural catastrophes have always pounded the earth and its
precious life. As
the plates of the crust of the earth ride the underlying molten
flow of
magma, land masses smash together only to tear apart. Crumpled
ridges jut
into high mountain ranges, and crushes of volcanoes emit choking
dust and
gases, plus waves of lava that blanket continent-sized regions.
Today the lever of science helps to measure, classify and
comprehend past
calamities. But the action of continental drift, winds, seas and
volcanoes
blurs the evidence, making scientists' detective work hard.
Still,
geologists gaze, for example, at the Himalayas and see the
1,800-mile long
wrinkling of land produced by the enormous force of the collision
between
the roughly 75-mile thick Eurasian and Indian tectonic plates
around 50
million years ago.
Through the 4.5 billion years of the earth's existence, internal
actions
have jostled, jolted, smoothed and havocked the earth, with life
and its
Darwinian process forced to respond.
And then there is the moon.
Thoughts of the moon run first to its strangeness compared to the
earth. A
verdant, sapphire-blue, cloud-dappled and dynamic planet brimming
with life,
orbited by a satellite starched in gradations of unrelenting
gray, arid,
airless, lifeless - and anciently cratered. The craters attest to
the early
phase of intense bombardment as the planets nearer the sun grew
out of the
amalgamation of rocky bits built in turn from the sticky
collisions of dust
motes over eons. How can two bodies so seemingly disparate end up
orbiting
each other?
By accident! About 4.5 billion years ago, two planets that had
formed -- the
earth and a planet about the size of Mars - collided. The debris
of the
disintegrated smaller body collected in a nearby gaseous ring
whose
particles collided, stuck together and grew to form another
planetesimal -
this time the moon in orbit around the earth.
Just north of Los Angeles sits Mount Wilson Observatory with its
deliberately time-frozen exhibits in the Astronomical Museum.
Built in 1936,
the Museum displays splendid backlit glass photographs of
astronomical
objects, many taken with the Observatory's 100-inch Hooker
Telescope, then
the largest in the world. The early captions describe the 1930's
state of
astronomical knowledge. Accompanying a glorious close-up of the
pocked
lunarscape is the best science of that period: "Lunar
craters are probably
of volcanic origin, although some of the smaller ones may have
been caused
by impacts from meteors."
Thanks to science, that notion has been revised. Lunar craters
reveal the
chaos to which both the earth and the moon must have been
subjected in the
inner solar system during the first billion years or so. Lacking
the great
erosive forces of wind, ocean, vulcanism and plate tectonics, the
moon's
surface preserves a record of early solar system history. On
earth, that
record has been all but obliterated.
Fossil evidence on earth from about 3.5 billion years ago
suggests that life
persisted and flourished soon after the early pummeling by
asteroids and
comets ceased. On the arid, airless moon, life must not have even
begun -
there is no hint of evidence favoring lunar life.
The scarred lunar regolith warns of exo-terrestrial hazards that
have
endangered the earth and its life. While the early chaos has long
since
calmed, asteroids and comets continue to strike the planets,
including the
earth. One line of evidence is the remnants of recent craters on
the earth,
like Barringer Meteor Crater in Arizona, an awful sight near
Interstate 40.
There, an exo-terrestrial projectile about 150 feet across
exploded and
disintegrated upon impact with the ground about 50,000 years ago,
leaving a
crater three-fourths of a mile across.
More evidence of strikes comes from recent impact sightings, some
historically described. NASA researcher John S. Lewis speculates
in Rain of
Fire and Ice that the Bible's Joshua (Chapter 10) may tell of a
deadly
asteroid strike ca. 1400 B.C.E., when a rain of "great
stones out of the
heavens" killed Joshua's battlefield enemies. Just a few
verses later sits
the astonishing line, "and the sun standeth in the midst of
the heavens, and
hath not hasted to go in - as a perfect day." Rather than
the rotation of
the earth temporarily stalling, the exploded debris of an
asteroid or comet
that decimated the men must also have lit the sky with
long-burning glows
that would have seemed like sunlight and full moonlight
persisting long
beyond sunset. To the ancient mind, bright, nighttime light from
the debris'
disintegration equaled the sun's standing still - and the timing
and
consequence of the asteroid strike would have seemed a miracle.
Television history was made with the broadcast of the 1994
collision of
Jupiter with the Comet Shoemaker-Levy. Because Jupiter is the
largest planet
in the solar system, its strong gravitational attraction will
tend to draw
asteroids toward it. However, the Sun is also tugging at them,
and some
near-earth objects (NEO's) may end up on trajectories
intercepting earth's
orbit. The evidence is irrefutable: exo-terrestrial objects have
struck the
earth, and will do so in the future. The laws of celestial
mechanics say
that earth is not immune to exo-catastrophe.
The impact of an NEO larger than about one-half mile in size
could produce
severe environmental damage. The only way to avoid the
destruction and death
from a large NEO is to detect and then deflect it. Several groups
around the
world, and especially in the United States and Britain, search
the skies for
NEO's, and then determine their orbits. That process allows the
probability
of a future collision with earth to be estimated. To date, about
half of
approximately 1,000 destructive asteroids that may cross the
earth's orbit
have been catalogued, and their orbits give assurance that there
would be
years of warning before a strike. But the unknown objects foment
anxiety:
there would be no warning that an undetected NEO is on a
collision course
with the earth, because the existence of that NEO would not yet
be
suspected.
The NASA Spaceguard Survey will improve the odds by attempting to
detect
about 90% of the NEO's by 2008. The idea is to locate, track and
deflect
these true exo-terrestrial hazards. On rough average, an asteroid
a bit
larger than a mile across strikes the earth every million years
or so, and
would present a major global catastrophe.
The detection and tracking technology is relatively
straightforward and
inexpensive, but requires constant vigilance. However, deflection
capability
is still in its infancy. Rockets fast enough to reach an asteroid
on
intercept course with earth would have to be deployed, with
energetic means
of shoving the asteroid onto a non-perilous orbit. That might
require
advanced nuclear devices that are detonated beside the asteroid,
to shove it
into another orbit, while avoiding shattering the asteroid into
uncontrollable pieces.
Deflection technology remains rudimentary, and no one yet knows
how quickly
it may be needed. But it will eventually be needed. As an aside,
if we
assume that the astronomers' estimates of an enormous number of
habitable
planets in the universe are correct, the cosmos may harbor
trillions of
intelligent species. On more than one of those planets, odds are
that a
putative intelligent species or two was cratered to oblivion -
perhaps just
before its technology dawned to avert a low-probability but
certain
exo-catastrophe.
The cosmic environment streams with hazards for earth and
earthlings.
Asteroid and comet strikes truly endanger life on earth. Until
the science
says otherwise, human-made global warming winds up low on the
list of
anxieties.
Copyright 2002, Tech Central Station
==============
(11) ROCKET FRAGMENT, NOT METEORITE, LANDED IN UGANDA
>From Ron Baalke <baalke@jpl.nasa.gov>
http://allafrica.com/stories/200204100271.html
Mubende Hit By Rocket Fragment, Says Police
Frederick Kiwanuka
New Vision (Kampala)
April 10, 2002
POLICE yesterday said the alien spherical object that landed in
Kasambya,
Kikandwa sub-county in Mubende district last month was not a
meteorite but a
suspected rocket fragment from outer space.
Police spokesman Asuman Mugenyi, whose personnel collected the
object for
scrutiny, said yesterday that they were still scrutinising the
object whose
whereabouts he did not disclose.
Full story here:
http://allafrica.com/stories/200204100271.html
==============
(12) AND FINALLY: CHINA METEOR MAY (OR MAY NOT) SOLVE MYTHICAL
DEATH OF
MYTHICAL EMPEROR
>From Ron Baalke <baalke@jpl.nasa.gov>
http://asia.cnn.com/2002/WORLD/asiapcf/east/04/09/china.emperor.reut/index.html
China meteor may solve death of mythic emperor
Reuters
April 9, 2002
BEIJING, China (Reuters) -- A 5,000-year-old meteorite unearthed
in
northwestern China may explain the legendary death of the man
celebrated as
the nation's earliest ancestor, the Yellow Emperor, state media
said.
The meteorite, found near a mausoleum for the Yellow Emperor in
the Shaanxi
province county of Huangling, may lie behind the cataclysmic
shattering of
land that historical records say killed China's enigmatic first
emperor, the
official China Daily said Tuesday.
The discovery also sheds light on a local legend that nine
dragons broke up
the ancient town of Huangling, the newspaper said, quoting Li
Yanjun, a
long-time Yellow Emperor researcher and one of those who found
the
meteorite.
Full story here:
http://asia.cnn.com/2002/WORLD/asiapcf/east/04/09/china.emperor.reut/index.html
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