PLEASE NOTE:
*
CCNet 140/2002 - 2 December 2002
--------------------------------
"With a new environmental hazard seeming to appear almost
each day,
it's almost comforting to know that at least one threat to the
Earth has
been downgraded. Still, it's a game of numbers. These objects,
also known
as minor planets, number in the hundreds of thousands. Asteroids
have given
in the past, just as they could take away in the future. But if
Nature is
to be believed, for now these identified flying objects can
recede from the
worry list."
--Los Angeles Times, 30 November 2002
"The human race, to which so many of my readers belong, has
been
playing at children's games from the beginning, and will probably
do it
till the end, which is a nuisance for the few people who grow up.
And
one of the games to which it is most attached is called, ''Keep
tomorrow dark,'' and which is also named (by the rustics in
Shropshire, I
have no doubt) ''Cheat the Prophet.'' The players listen very
carefully and
respectfully to all that the clever men have to say about what is
to
happen in the next generation. The players then wait until all
the
clever men are dead, and bury them nicely. Then they go and do
something
else. That is all. For a race of simple tastes, however, it is
great fun.
--Gilbert Keith Chesterton
(1) TINY ASTEROIDS SHARE EARTH'S ORBIT
The Ottawa Citizen, 1 December 2002
(2) APOCALYPSE NOT JUST NOW
Los Angeles Times, 30 November 2002
(3) LIFE SAVE FROM SUPERNOVAS?
Andrew Yee <ayee@nova.astro.utoronto.ca>
(4) SCIENTISTS USE VIDEO IN SEARCH FOR RAE METEORITE
NASA Jet Propulsion Laboratory <info@jpl.nasa.gov>
(5) WESTERN FIREBALL WAS SPACE JUNK, NOT METEOR
Associated Press, 29 November 2002
(6) JUPITER-LIKE PLANETS FORMED IN HUNDREDS - NOT MILLIONS - OY
YEARS
Andrew Yee <ayee@nova.astro.utoronto.ca>
(7) NEW PLANETS CAN FORM IN UNDER 1000 YEARS
UPI, 28 November 2002
(8) THE FIRST DECADAL REVIEW OF THE EDGEWORTH-KUIPER BELT:
TOWARDS NEW
FRONTIERS
Joel Parker <joel@boulder.swri.edu>
(9) ORBITAL CALCULATIONS
Alan Fitzsimmons <a.fitzsimmons@qub.ac.uk>
(10) MARTIAN METEORITE PATROL PICKS ONE UP
John Michael Williams <jwill@AstraGate.net>
==============
(1) TINY ASTEROIDS SHARE EARTH'S ORBIT
>From The Ottawa Citizen, 1 December 2002
http://www.canada.com/national/story.asp?id={F440DD22-306D-47A0-BA15-35D1CD109AA5}
Tiny asteroids share Earth's orbit
Canadian discovers space rocks unique in solar system
Tom Spears
Meet the neighbours you never knew about.
Earth has two heavenly bodies sharing our orbit in addition to
our moon -- a
pair of recent discoveries made by a Canadian, yet almost unknown
in this
country outside a tiny group of astronomers.
Not quite a second and third moon, not quite like anything else
in the solar
system, these two chunks of space rock follow a path much like
ours around
the sun, their orbits taking almost exactly one year each, like
ours.
But their strange orbital paths are more complex than ours,
tugged into a
looping shape a little like a telephone cord by the interplay of
Earth's
gravity, the sun's gravity and their own speed.
And every few hundred years they swing past Earth -- so close
that our
gravity actually pulls them in and slingshots them away again,
but without
ever hitting us.
The two not-quite-moons are asteroids. One is called Cruithne
(pronounced
Croo-een-ya), a name from ancient Scottish legend; the other has
no name.
Both have numbers: Cruithne is 3753 and the other is 2002AA29.
Most asteroids just go around and around the sun, mostly in a
"belt"
orbiting out past Mars. These two somehow leaked out of the
asteroid belt,
as a few asteroids do from time to time.
Maybe a collision pushed them out. Maybe they were caught in a
combination
of gravitational pulls from different directions.
However they left their old home, they ended up in our
neighbourhood. Each
stays an average of about 149 million kilometres from the sun,
like Earth, a
distance astronomers call one astronomical unit. (Orbits are
never quite
circles; they're always an ellipse, sort of a stretched circle,
so the
actual distance from the centre varies slightly.)
But what are these two companions of ours? Astronomers are having
a hard
time coming to grips with what to call them. For now, a lot of
discussion of
what they are centres mostly on what they're not.
They're not like our moon, which goes around and around Earth.
The two
asteroids' orbits are centred by the sun.
"We should really invent some kind of new word," says
Queen's University
astronomer Paul Wiegert, who found it. "Usually we call it
either a
companion asteroid or a co-orbital asteroid," but he feels
neither of those
terms really carries the right meaning.
It was in the 1990s that Mr. Wiegert, then at York University,
noticed the
path of Cruithne's orbit was a bit unusual.
"The unusualness is fairly subtle," he says now.
"That's why it hadn't been
noticed." Nonetheless it was noticeable, and he started
crunching numbers.
In 1997 he was ready to announce his discovery. He and his
Finnish partners
published it in Nature, a major British science journal where
scientists
announce new discoveries.
Mainstream media didn't pick it up. The public mostly didn't hear
of the new
Canadian discovery, perhaps because the relationship of Earth and
its two
little neighbours is so complex that Mr. Wiegert has to send
interviewers to
look at models before he can discuss it with them.
The relationship between Earth and little Cruithne is like two
cars going
the same direction around a traffic circle at the same average
speed. But
one car first speeds up and passes the second car, then slows
down and
allows itself to be passed. Then it speeds up and passes again
and slows
down, over and over.
Anyone watching from the side of the road just sees two cars
going the same
direction.
But someone in one car sees the other car moving ahead of it and
then behind
it, and then in front again.
That's what Cruithne does with us. For 385 years it travels very
slightly
faster than Earth, coming a little closer to us all the time
while orbiting
the sun. Finally it approaches us. But it doesn't hit us; as our
gravity
pulls at it, Cruithne's speed makes it swing around us and slow
down,
falling behind us again.
Even as Earth pulls in the asteroid, it speeds up and its speed
allows it to
escape from the Earth's pull. In this way Earth is protected from
impact,
despite the similarity of the asteroid's orbit to Earth's, Mr.
Wiegert says.
"It's in the same sense as the planets orbit the sun. The
sun attracts the
planets, but the planets aren't sucked in. There's a balance
between the
sun's gravity and the speed" of the planets.
"Essentially there's a barrier -- just the velocity of the
particle in
balance with gravity that just pushes the particle away," he
says. "The
particle needs more energy than it has to get over this, so it
just goes
back the other way.
"It's going to stay like that. It's a consistent as a brick
wall."
After another 385 years we'll be almost ready to pass the
asteroid. But
again it will swing around us, this time accelerating out in
front of us and
pulling away from Earth.
Cruithne is always going the same direction around the sun. But
relative to
Earth it appears to advance and retreat around the circle because
of this
faster-and-slower cycle.
Viewed from Earth, this kind of orbit is called a horseshoe. It's
so complex
that no one diagram can sum it up: One has to look at several
plots from
different viewpoints, each giving a pattern like a spirograph.
The best way to see it is on the discoverer's Web page, which
carries
animations of the asteroid's path:
www.astro.queensu.ca/~wiegert/3753/mpegs/rot6.mpg,
and also the main
Cruithne page at www.astro.queensu.ca/~wiegert/3753/3753.html.
But do Cruithne and asteroid 2002AA29 matter? Some experts say
they don't.
"They're really only of interest to dynamicists," the
people who plot the
paths of heavenly bodies and the forces that act on them, says
Peter Brown
of the University of Western Ontario's astronomy department.
Neither asteroid is going to hit us, and both differ from other
"near-Earth"
asteroids only because their orbits are attuned to ours, a
phenomenon that
scientists call resonance. They aren't even especially close to
us; both are
tiny little lifeless rocks -- scientists estimate Cruithne is
about five
kilometres in diameter -- that are always more distant than our
moon, even
at their closest approach. Cruithne, for instance, never comes
closer than
15 million kilometres to us.
They are, however, our neighbours, and our partners in an
intricate dance
lasting billions of years.
© Copyright 2002 The Ottawa Citizen
============
(2) APOCALYPSE NOT JUST NOW
>From Los Angeles Times, 30 November 2002
http://www.latimes.com/news/printedition/opinion/la-ed-asteroids30nov30.story
The doomsday scenario of an asteroid wiping out the Earth while
humans cower
helplessly in fear has always seemed unsporting -- a kind of
ultimate
drive-by shooting from outer space. But in the new issue of the
scientific
journal Nature, scientists have, well, exploded the notion that
asteroids
capable of causing catastrophic damage hit the Earth as often as
had
previously been reckoned. It turns out that the frequency is only
about once
every 1,000 years, instead of every 200 to 300 years.
With a new environmental hazard seeming to appear almost each
day, it's
almost comforting to know that at least one threat to the Earth
has been
downgraded. The researchers drew on formerly secret data held by
the
departments of Defense and Energy to conclude that even if an
asteroid of
the size that wiped out 700 square miles in Siberia in 1908 were
to hit the
Earth every 1,000 years, a city would probably be destroyed only
every
30,000 years because the planet is made up mostly of ocean.
Still, it's a game of numbers. These objects, also known as minor
planets,
number in the hundreds of thousands. They're the junk of space,
the residue
of a planet destroyed in the distant past. Most travel in a belt
between the
orbits of Mars and Jupiter. But some adventurous ones have taken
a detour
and headed for the Earth -- and a good thing too for us.
Scientists see an
asteroid that hit the Yucatan Peninsula 65 million years ago as
the cause of
a chilling climate change and the extinction of dinosaurs, and
perhaps the
rise of mammals.
Asteroids have given in the past, just as they could take away in
the
future. But if Nature is to be believed, for now these identified
flying
objects can recede from the worry list.
Copyright 2002, Los Angeles Times
===============
(3) LIFE SAVE FROM SUPERNOVAS?
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
[Extracted from inScight, Academic Press
http://www.academicpress.com/inscight/11262002/grapha.htm]
Tuesday, 26 November 2002, 5 pm PST
Life Safe from Supernovas?
By ROBERT IRION
Space is full of threats to life, especially asteroids that smack
into
Earth. An even more explosive hazard looms in deep space:
supernovas, which
can unleash enough radiation to zap our life-shielding ozone
layer. However,
a new study, accepted for publication in the Astrophysical
Journal,
concludes that a supernova must blow up within 25 light-years of
Earth to
wreak major havoc -- so close that it might happen just once or
twice in a
billion years.
In 1974, the risk seemed higher. Physicist Malvin Ruderman of
Columbia
University in New York City calculated that gamma rays and cosmic
rays from
a supernova about 50 light-years away would erase most of our
ozone for
decades, exposing Earth's surface to harmful ultraviolet (UV)
light
from the sun. Since then, researchers have debated how much
radiation
supernovas produce, how those rays damage the atmosphere, and how
often
stars explode near our sun. The latter estimates are "all
over the map,"
says astrophysicist Neil Gehrels of NASA's Goddard Space Flight
Center in
Greenbelt, Maryland. Some teams have claimed that recent
supernovas --
perhaps within the last few million years -- devastated life.
That's unlikely, according to work by Gehrels and his colleagues.
The team
used a detailed model of the atmosphere to gauge how nitrogen
oxides -- a
chemical species catalyzed by a supernova's radiation -- would
destroy
ozone. The researchers also used the energy from Supernova 1987A,
which
exploded in another galaxy in 1987, as a guide for how much
radiation would
reach
Earth. The results are good news for Earthlings: In order to thin
the ozone
layer so that twice as much UV light reaches the surface, a star
must
explode within 25 light-years. There are no massive stars -- the
ones that
die as supernovas -- that close to the Earth today. Moreover,
these stars
approach our solar system so seldom that a nearby supernova
should happen
only every 700 million years or so, on average, according to the
team's
analysis of stellar motions in the galaxy, making them minor
contributors to
the history of mass extinctions on earth.
The study surpasses other attempts to quantify the effects of
supernovas on
Earth's atmosphere, says astronomer John Scalo of the University
of Texas,
Austin. "Their result depends sensitively on many things,
but it's the best
we have right now," he says. Lower-level radiation from more
distant
supernovas still might have triggered episodes of genetic
mutation hundreds
or thousands of times during Earth's history, Scalo notes.
© 2002 The American Association for the Advancement of Science
=============
(4) SCIENTISTS USE VIDEO IN SEARCH FOR RAE METEORITE
>From NASA Jet Propulsion Laboratory <info@jpl.nasa.gov>
http://www.expressnews.ualberta.ca/expressnews/articles/news.cfm?p_ID=3443&s=e
Scientists use video in search for rare meteorite
By Phoebe Dey
University of Alberta, Canada
November 28, 2002
A University of Alberta astronomy camera captured a photograph of
a blazing
fireball, which may provide clues to finding a rare meteorite.
"If we could find the remains of the meteorite, it would be
quite
significant, not simply because it's another meteorite but
because we would
have the potential for determining its trajectory before it
struck the
earth," said U of A physics professor, Dr. Doug Hube.
"We might be able to
learn where in the solar system it came from."
The camera on the rooftop observatory on the U of A physics
building
captured the image moving from the southwest horizon to the
northwest for
about seven seconds at 5:10 a.m. early Wednesday morning. Hube
and Martin
Connors from Athabasca University are analysing the tape and
using
eyewitness reports to do a geometric triangulation, which will
determine a
more specific area to find the meteorite.
Videotape from the U of A's cameras is considered the final
authority. The
cameras record images of the sky 24 hours a day. About once a
year, the
cameras capture something worth following up, Hube said. The
camera is
mounted above a hemispherical mirror, which allows researchers to
monitor
the entire sky at one time.
If this latest meteorite can be found, it will offer insight to
its
celestial beginnings and teach us more about the larger
environment we live
in.
"Meteorites are the building blocks of the planets,"
Hube said. "They can
give us clues about circumstances in this corner of the universe
4.5 billion
years ago. Understanding them gives us a broader picture to
understand the
formation of the solar system, to understand the formation of
planets."
The University of Alberta's Earth and Atmospheric Sciences
department boasts
a meteorite collection second only to the national one in Ottawa.
It is
comprised of more than 130 different meteorites--13 of which were
found in
Alberta. Only 50 meteorites have been found in Canada.
===========
(5) WESTERN FIREBALL WAS SPACE JUNK, NOT METEOR
>From Associated Press, 29 November 2002
http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/1038534231870_105///?hub=SciTech
SEATTLE - A ball of fire streaking across the sky of western
North America
early Thursday had people throughout the region flooding radio
and
television stations with calls reporting a meteor shower.
It turned out the burning light came from a Russian rocket body
re-entering
the Earth's atmosphere about 6:15 a.m. PST.
The U.S. Strategic Command in Omaha, Neb., and the North American
Aerospace
Defence Command confirmed a Russian rocket fell back to Earth but
did not
immediately release further details.
Canadian navy spokesman Gerry Pash said the space junk could be
seen across
much of Western Canada and possibly as far inland as Montana.
The U.S. Federal Aviation Administration received calls from
Portland, Ore.,
to the Canadian border Thursday morning.
Callers assuming it was a meteor shower said the light appeared
to move more
slowly than a shooting star but faster than a plane. Witnesses
said it had a
long tail, which seemed to break into two pieces.
Copyright 2002, AP
==============
(6) JUPITER-LIKE PLANETS FORMED IN HUNDREDS - NOT MILLIONS - OY
YEARS
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
University of Washington
Seattle, Washington
FOR IMMEDIATE RELEASE: Nov. 28, 2002
FROM: Vince Stricherz, 206-543-2580, vinces@u.washington.edu
Jupiter-like planets formed in hundreds -- not millions -- of
years, study
shows
An accepted assumption in astrophysics holds that it takes more
than 1
million years for gas giant planets such as Jupiter and Saturn to
form from
the cosmic debris circling a young star. But new research
suggests such
planets form in a dramatically shorter period, as little as a few
hundred years.
The forming planets have to be able to survive the effects of
nearby stars
burning brightly, heating and dispersing the gases that
accumulate around
the giant planets. If the process takes too long, the gases will
be
dissipated by the radiation from those stars, said University of
Washington astrophysicist Thomas R. Quinn.
"If a gas giant planet can't form quickly, it probably won't
form at all,"
he said.
The standard model of planet formation holds that the spinning
disk of
matter, called a protoplanetary disk, that surrounds a young star
gradually
congeals into masses that form the cores of planets. That process
was
thought to take a million years or so, and then the giants
gradually
accumulate their large gaseous envelopes over perhaps another 1
million to
10 million years.
But the new research, culled from a much-refined mathematical
model,
suggests that the protoplanetary disk begins to fragment after
just a few
spins around its star. As the disk fragments, clusters of matter
begin to
form quickly and immediately start to draw in the gases that form
vapor
shrouds around gas giants.
"If these planets can't form quickly, then they should be a
relatively rare
phenomenon, whereas if they form according to this mechanism they
should be
a relatively common phenomenon," said Quinn, a UW research
assistant
astronomy professor.
The existence of gas giant planets, it turns out, seems to be
fairly common.
Since the mid-1990s, researchers have discovered more than 100
planets,
generally from the mass of Jupiter to 10 times that size,
orbiting stars
outside the solar system. Those planets were deduced by their
gravitational
effect on their parent stars, and their discovery lends credence
to the new
research, Quinn said.
Lucio Mayer, a former UW post-doctoral researcher who recently
joined the
University of Zurich, is lead author of a paper detailing the
work,
published in the Nov. 29 edition of Science. Besides Quinn,
co-authors are
James Wadsley of McMaster University, Hamilton, Ontario, Canada,
and Joachim
Stadel at the University of Victoria, British Columbia, Canada.
Their work
is supported by grants from the National Science Foundation and
the National
Aeronautics and Space Administration's Astrobiology Institute.
Since the early 1950s, some scientists have entertained the
notion that gas
giant planets were formed quickly. However, the model, using a
specialized
fluid dynamics simulation, had never been refined enough to show
what it
does now. The Mayer-Quinn team spent the better part of two years
refining
calculations and plugging them into the model to show what would
happen to a
protoplanetary disk over a longer time.
"The main criticism people had of this model was that it
wasn't quite ready
yet," Quinn said. "Nobody was making any predictions
out of it, but here we
are making predictions out of it."
The new model explains why two other giant planets in our system,
Uranus and
Neptune, don't have gas envelopes like Jupiter and Saturn, Quinn
said. At
the time those planets were being formed, the solar system was
part of a
star cluster. The outer planets of Uranus and Neptune were too
close to a
nearby star -- one that has since migrated away -- and therefore
lost
whatever gas envelopes they might have accumulated.
Neither the new model nor the standard model accounts for why
most of the
gas giant planets found outside the solar system are much nearer
their suns
than are Jupiter and Saturn, Quinn said. The most common belief
currently is
that the planets formed farther away from their stars and then
migrated
inward to the positions where they have been discovered.
The new model also doesn't account for the formation of
terrestrial planets,
like Earth and Mars, near our sun. But Quinn suspects that
perhaps the
smaller terrestrial planets were formed over longer periods by
processes
described by the standard planet-formation model, while the new
model
explains how the larger gas giants came to be.
"That's my bet at the moment," he said.
###
For more information, contact Quinn at (206) 685-9009 or
trq@astro.washington.edu,
or Mayer at (011) 41-1-6355740
or lucio@physik.unizh.ch
IMAGE CAPTION:
[ http://www.washington.edu/newsroom/news/images/disk-hr.jpg
(23KB)]
A computer simulation shows how a protoplanetary disk surrounding
a young
star begins, in a relatively short time, to fragment and form gas
giant
planets with stable orbits. (Photo credit: Mayer, Quinn, Wadsley,
Stadel)
================
(7) NEW PLANETS CAN FORM IN UNDER 1000 YEARS
>From UPI, 28 November 2002
[ http://www.upi.com/view.cfm?StoryID=20021127-112737-3013r
]
Thursday, November 28, 2002, 2:45 PM EST
New planets can form in under 1,000 years
(Reported by Charles Choi, UPI Science News, in New York)
SEATTLE (UPI) -- Instead of planets taking millions of years to
form as
previously thought, researchers said Thursday new calculations
suggest they
sometimes can form within a few centuries.
"The first one in our model pops up around 150 years,"
researcher Thomas
Quinn, an astrophysicist at the University of Washington in
Seattle, told
United Press International. "Things can happen
quickly."
When it comes to planetary formation, the standard theory says it
takes a
million years or more for the solid cores of gas giants such as
Jupiter or
Saturn to clump from the cosmic debris that whirls around young
stars. After
the cores appear, according to the theory, it takes another 1
million to 10
million years for envelopes of gas to enshroud them.
Recent surveys of some 1,000 stars reveal about 10 percent have
gas giants
orbiting them, generally ranging in size from about the mass of
Jupiter to
10 times that large. "If they take millions of years to
form, then they
probably would be a very rare phenomenon," Quinn said.
The new model from Quinn and colleagues suggests the spinning
disks of gas
that orbit stars break apart after only a few spins. Fragments
then quickly
begin to coalesce due to gravity. "If this really happens
out there, then it
would probably dominate the way planets form," Quinn told
UPI.
Although scientists have considered such a scenario for decades,
the
calculations involved have been forbidding. But in the Nov. 29
issue of the
journal Science, Quinn and his team reported simulating one
million clouds
of gas, each one-thirtieth of an Earth mass, at one-hour
intervals as they
interacted gravitationally for up to 350 years.
"We used a fraction of the machine at the Pittsburgh
Supercomputing Center
(at Carnegie-Mellon University) for a solid several weeks. It's
roughly like
having 100 of the fastest Pentium computers all running the same
calculations for a couple of weeks," Quinn said.
Refining the calculations took nearly two years, he added. The
results
suggest gas giants can grow in fewer than 1,000 years, and
accumulate masses
similar to those spotted around other stars.
Planetary scientist Jack Lissauer of NASA Ames Research Center in
Moffett
Field, Calif., remains skeptical.
"It's not that I think the calculations are bad. They're the
best
calculations on this facet of the problem that have ever been
done," he
said. However, Lissauer said, for planets to form this quickly,
the disks
from which they emerge need to be very unstable, and before any
forming
planet reached that stage slight instabilities would cause spiral
waves to
flatten out any clumps.
Also, Quinn said, the computer model does not explain how
rocklike planets
such as Earth form, for which the standard model can provide an
answer.
Neither model yet can explain why so many planets seen outside
our solar
system orbit so close to their stars, he added.
"Do I think this work is an important advance? Yes. Do I
think it is
definitive? No," said computational astrophysicist Richard
Durisen of
Indiana University in Bloomington. He and Quinn said future
calculations
need to take better account of the extremely complex role
temperature plays.
"That's actually quite hard," Quinn explained, noting
it would require at
least 2-to-10 times more computing power. "Fortunately,
computers always get
faster, so that makes it doable in a year's time or
whenever," he said.
Copyright © 2002 United Press International. All rights
reserved.
============
(8) THE FIRST DECADAL REVIEW OF THE EDGEWORTH-KUIPER BELT:
TOWARDS NEW
FRONTIERS
>From Joel Parker <joel@boulder.swri.edu>
Announcement
and Invitation for Participation
in
THE FIRST DECADAL REVIEW OF THE
EDGEWORTH-KUIPER BELT
TOWARDS NEW FRONTIERS
to be held
on 11 -- 14 March 2003
in Antofagasta/Chile
=========================================================================
Web page of the
Workshop:
http://tno.ucn.cl
Early registration
deadline:
2 January 2003
Paper Title & Abstract
Submission deadline: 2 January 2003
---------------------------------------------------
Special excursion and visit of the Very Large Telescope VLT
is foreseen
=========================================================================
Dear Colleague,
we would like to invite you to participate in our scientific
workshop on the
Edgeworth-Kuiper Belt to be held in March 2003 in Chile. The
workshop is
organized jointly by the European Southern Observatory and the
Universidad
Catolica del Norte in Antofagasta.
Science Program
---------------
The members of the scientific organizing committee
Antonella Barucci (Observatoire Meudon, France)
Hermann Boehnhardt (Max-Planck-Institute for
Astronomy Heidelberg, Germany)
John Davies (Royal Observatory Edinburgh, Great
Britain)
Dave Jewitt (University Hawaii, USA)
Olivier Hainaut (European Southern Observatory)
Scott Kenyon (Center for Astrophysics Cambridge,
USA)
Hal Levison (South-West Research Institute Boulder,
USA)
Dina Prialnik (University Tel Aviv, Israel)
Alan Stern (South-West Research Institute Boulder,
USA)
Gianni Strazzulla (Osservatorio Catania, Italy).
have defined the following key topics for this workshop
- The dynamical picture of the outer solar system.
- The taxonomic populations. (KBOs, Centaurs, satellites, comets)
- The formation, evolution and links between dynamical and
physical aspects.
- The modelling concepts and physical interpretations.
- The impact of laboratory studies.
- Mission targets: Pluto/Charon and the New Horizons mission,
cometary missions.
- The observational, modelling and experimental challenges.
(methods and key programs)
- The synoptic view of the outer solar system and bodies therein.
- "Edgeworth-Kuiper-Belts" around the Sun and other
Stars.
Visit at the Very Large Telescope VLT
-------------------------------------
The workshop will happen in Antofagasta, one of the largest
cities in Chile,
located about 1500km North of Santiago, and right in the heart of
the
Atacama dessert. About 2 1/2 hours drive South of Antofagasta the
Very Large
Telescope is operated by ESO at Cerro Paranal. The workshop
participants are
kindly invited in a one-day excursion to this observatory, one of
the most
exciting places of observational astronomy in the world.
For the Scientific and Local Organizing Committee
Hermann Boehnhardt
============================
* LETTERS TO THE MODERATOR *
============================
(9) ORBITAL CALCULATIONS
>From Alan Fitzsimmons <a.fitzsimmons@qub.ac.uk>
Dear Benny,
Just a couple of comments regarding Jay Tate's conclusions in
yesterdays
CCNET distribution.
First, a rather pedantic one. I believe Jay meant to say that no
NEAs had
been discovered by UK-funded programmes in the past 5 years, in
which he is
absolutely correct (to my knowledge). However PPARC supported
astronomers
have discovered tens, if not hundreds, of asteroids and other
minor bodies
during this same period. A bit off-topic, but I thought I'd
better stand up
for myself and my fellow observers!
Second, a more serious comment. Jay worries about the fact that
no (NEA)
orbits have been calculated by BNSC or PPARC funded astronomers
in a similar
period. This may be true, altough I'm not a dynamicist and am not
fully
aware of the research taking place in institutes such as Armagh
Observatory
and Queen Mary University of London. However, this _is_ done on a
24-hour
basis by 4 world-leading teams - the MPC, JPL, NEODYS and Lowell.
The
results of these calculations are made freely available by these
teams
shortly after calculation. It is not obvious that a 5th set of
orbital
elements would add anything new, or is warrented.
Best Wishes
Alan Fitzsimmons
==================
(10) MARTIAN METEORITE PATROL PICKS ONE UP
>From John Michael Williams <jwill@AstraGate.net>
Hi Benny.
> CCNet 139/2002 - 27 November 2002
> ---------------------------------
> (3) MARTIAN METEORITES MADE EASY
> >From Sky & Telescope, 25 November 2002
> http://skyandtelescope.com/news/current/article_803_1.asp
>
> By J. Kelly Beatty
> ...
> After much number crunching, however, impact
> modelers eventually deduced
> that it could be done - if the impact event were
> powerful enough to leave
> behind a crater at least 10 km across. ...
This is a reckless claim. The SIZE of the impact means nothing in
terms of
whether there is time in an impact to accelerate a rock without
destroying
it.
The reason no intact rock can be ejected by an impact is because
of the
properties of rock, not because of the properties of impacts.
From a body
with a lower escape speed (say, the Moon), or for rocks which
could conduct
sound at higher speed (say, 8 km/s), intact ejection MIGHT occur,
depending on the calculated effects of the impact.
So far as I know, there is one exception: An impact which
destroyed the
target, thus also lowering its gravitational field near the
"ejection"
region. Remove the planet from the rock.
The whole issue of rock and sound speed as a parameter is
explained in
http://publish.aps.org/eprint/gateway/eplist/aps1999jun25_002
One would wish that the kind of computation reported were
directed toward
more constructive effort, such as epidemiology or antiterrorism,
or the
design of missiles which could hit their target.
We read, at the Sky and Telescope link:
> ...
> James N. Head (Raytheon Missile Systems), who performed
> the computer modeling for his doctoral thesis at the
University
> of Arizona, also managed to solve another Martian-meteorite
> quandary. Most of these stones crystallized within the last
few
> hundred million years, ... The key, as Head and his
> colleagues explain, is that the meteorites must have
originally
> been buried in the layer of regolith, ...
Whence the need for a bigger impact. But, the simpler explanation
would be
that the "Martian meteorites" formed in space after
ejection in a fluid
state. Or, perhaps, the crystallization date also might be wrong,
and the
origin of the "Martian meteorites" might have nothing
to do with the modern
planet Mars.
--
John
jwill@AstraGate.net
John Michael Williams
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*
LIMITS ON THE ORIGINS AND SPACE TRANSPORT OF LIFE*
By Andrew Glikson
Australian National University
Canberra, ACT 0200
andrew.glikson@anu.edu.au
* reprinted from Meteorite, 2002, 8:8-13.
Preface
"Good planets are hard to come by" (anonymous)
In his classic novel, First and Last Man, Olaf Stapledon portrays
a future
generation of humans who, when faced with solar evolution into a
red giant
and planetary incineration, undertake the dissemination of
genetically coded
seeds into outer space. Toward the end of the second millennium -
space
exploration, the blurring of boundaries between science and
science fiction,
and human degradation of the biosphere, resulted in an emergence
of similar
sentiments, expressed by statements such as: "As the most
evolved and
capable of life forms, our main responsibility is to promote this
inherent
drive of life for propagation and expansion. These are the
principles of a
pan-biotic (or bio-cosmic) ethics that may propel us to seed the
galaxy"
(Mautner, Meteorite 8 (1) 2002). The history of science is full
of examples
of theories closely linked with human aspirations, myths and
transient
fashions, as recognized, for example, by Paul Davies: "I
want to make the
obvious point that all theories of life contain hidden
philosophical
assumptions". Our age is no exception, having degraded the
terrestrial
ecosystem, some crave for greener pastures in space. It may be no
accident
that, as a corollary to a human-destiny-in-space imperative,
theories
in-vogue regarding the origin of life tend to focus on outer
planets or
comets. This article reviews aspects of interplanetary and
interstellar
panspermia theories. It questions the significance of the effects
of
bio-transfer, had such taken place, in relation to the billions
of
years-long geological and biological evolution of the complex
terrestrial
biosphere.
Building blocks of life
Fundamental questions regarding the origin of life lie somewhere
between
science and philosophy. A universal nature of the yet
little-understood laws
that underlie synthesis of amino acids into DNA implies that, at
least in
principle, life can develop wherever suitable chemical and
physical
conditions occur. The operation of life-forming
"bio-friendly" laws (see
below) allows estimates on the probability of life in the
universe such as
given by Drake's equation (see Meteorite, 2000, 6 (4), p.14). By
contrast,
the probability of accidental synthesis of DNA from amino acids
faces odds
in the order of 1 to 10120 scale. According to Ockham's Razor
parsimony
principle, at the heart of the scientific method, a theory needs
to be
justified either by observation and/or by conceptual necessity.
Neither
requirement has been demonstrated in connection with the
suggestion of
interstellar panspermia.
One version of panspermia focuses on early accretion stages of
Earth, when
gravitational collapse of dust particles under temperatures in
excess of
about 1000*K was followed by late accretion of volatile and
organic
components. Delsemme (see Icarus, 1999, 146, p. 313-325) pointed
to the
significance of early cometary contributions to the volatile and
organic
inventory of the atmosphere and hydrosphere, from the deuterium
level in the
oceans. The left-hand and right-hand mirror image
structural symmetry
(termed "racemic") of amino acid molecules is a
promising criterion for
discrimination between terrestrial and extraterrestrial organic
components.
Extraterrestrial organic compounds found in carbonaceous
chondrites and in
K-T impact boundary deposits at Stevns Klint, Denmark, include
amino
isobutayric acid (AIB) and isovaline which possess
right-hand symmetries,
attributed to shock-induced structural effects. By contrast,
terrestrial
amino acids mostly possess left-hand symmetry, with exception
such as in
some fungi peptides (Zhao and Bada, 1989, Nature, 339, p.
463-464). Had
large-scale introduction and preservation of extra-terrestrial
amino acids
possessing right-hand symmetry been common, since these molecules
do not
appear to be metabolized by terrestrial micro-organisms they
should have
been extensively preserved, which is not the case. This evidence
potentially
argues against large-scale introduction of cometary organic
molecules into
the atmosphere and hydrosphere. More likely, the bulk of these
compounds
were destroyed on entry and meteoritic explosion.
The presence of Si-Al-rich granitic continental-type rocks and of
water on
the Earth's surface prior to the Late Heavy Bombardment (LHB:
3.95-3.8 Ga)
in the inner solar system is attested to by the occurrence of up
to ~4.4
Ga-old zircons (zirconium silicate) in Gascoyne Province, Western
Australia.
Formation of granitic magma involves partial melting processes in
the
presence of water. Carbon isotope studies of inclusions of
graphite within
apatite from early Archaean banded iron formations in
southwestern Greenland
suggest biogenic activity, although uncertainties exist about the
age of the
apatite. Oxygen isotope studies of inclusions in the early ~4.4
Ga zircons
provide evidence for low temperature conditions. The existence of
solid
crustal domains pre-3.8 Ga would allow the survival of
chemotropic bacteria
such as occur in deep crustal faults and fractures, and possibly
also of
transient photosynthesising near-surface bacterial colonies -
stromatolites.
The latter would have been severely perturbed by the cataclysmic
bombardment
about 3.95-3.8 Ga (LHB), which added further accumulation of dust
and
volatiles, contributing further to the hydrosphere and
atmosphere.
An early existence of a terrestrial hydrosphere requires
discrimination
between volatile and organic components introduced from
indigenous
terrestrial sources and extraterrestrial contributions. Organic
compounds
are continuously synthesized in terrestrial environments, for
example in
volcanic hydrothermal systems and submarine fumaroles
("black chimneys").
Comparisons between the volatile fraction of some comets: H-56%;
O-31%;
C-10%; N-2.7%; S-0.3%), and volatile fractions of volcanic
hydrothermal
fluids - Kilauea, Hawaii, 1918 eruption: H2O - 30%; H2 - 0.35%;
CO2 - 40%;
CO - 1.2%; SO2 - 28%; S2 - 0.04%; HCL - 0.034%, indicate
occurrence of
similar components, albeit in different proportions and at
different
oxidation states.
Laboratory experiments are consistent with the synthesis of
organic
molecules in the early terrestrial environment. Assumed starting
conditions
vary from reducing atmosphere rich in methane, ammonia, hydrogen
and water,
synthesized into amino acids by lightening (the famous
Miller-Urey
experiment) to a CO2-dominated atmosphere and interaction between
alkaline
fluids and low-pH surface water, resulting in precipitation of
colloidal FeS
membranes demonstrated more recently (1997) by Russell and Hall.
These
authors write: "The earliest truly replicating cells
probably required only
twenty or so elements ... all of them available at submarine hot
springs,
and a limited range of fundamental organic molecular
components..."
In the book, The Hot Deep Biosphere, Thomas Gold attributes the
origin of
the building blocks of life to leakage of methane from the
Earth's mantle
and its reduction in deep-seated fractures by thermophilic
(heat-seeking)
bacteria which metabolize hydrocarbons. Such micro-organisms are
found in
deep wells and include primitive Archaea (nuclei-free) and
Bacteria
(nuclei-bearing) super-kingdoms, which are thought to represent
relics of a
deep seated habitat that survived early extinctions caused by
extraterrestrial bombardment. It may be that Earth's earliest
habitats
consisted of methane-metabolizing thermophiles.
Terrestrial biological records suggests that evolution from
original
thermophile bacteria to multicellular genera requires geological
periods in
the order of 109 years. The evolving biosphere constitutes
associations of
multiple inter-dependent organisms, not colonies of single
independent
species. According to Kirschvink and Weiss, analyses based on the
three
fundamental biological groupings (or superkingdoms) - Bacteria,
Archaea, and
Eucarya, suggest that their last common ancestor (LCA) dates back
to about
4.0 Ga, in agreement with the possible occurrence of fossil
micro-organisms
and magneto-fossils in the 3.9-4.1 Ga ALH84001, and possibly with
the
isotopically light carbon in graphite in Greenland.
Inter-planetary and inter-stellar bio-transport
Recent support for inter-planetary transport of micro-organisms
within the
solar system arises from considerations of impact dynamics,
low-temperature
transport of ejecta, upper survival limits of captured microbial
spores, and
possibly evidence from likely Martian ejecta - meteorite
ALH84001. According
to Everett Gibson, Martian biogenic signatures in ALH84001
include (a)
magnetite crystals characteristic of magnetotactic bacteria; (b)
Reduced
carbon components containing no 14C signatures and therefore of
non-terrestrial origin (c) carbonate formation temperatures of
50oC; (d)
biofilms of polysaccarides from colonies of bacteria which appear
not to be
terrestrial, and (e) unique morphological structures which match
fossilized
terrestrial bacteria but occur in clays of interpreted Martian
origin.
However, recently similar magnetite crystals with distinct
crystal forms
(termed truncated hexaoctahedrals) were experimentally produced
in the
laboratory under non-biogenic conditions by a group led by D.C.
Golden and
D.W. Ming of NASA. The jury is still out on ALH84001.
The wide range of conditions under which terrestrial
'extremophile' and
'thermophile' bacteria exist include sub-freezing temperatures
under
Antarctic ice sheets, submarine fumaroles at temperatures near to
DNA
breaking point (~150 șC), high pressures at deep crustal
fractures (5-6 km),
extreme acid or alkaline conditions and high radiation levels. A
study of a
sub-bacterial class - nanobacteria, as small as 20-200 nm (1 nm =
1
billionth meter) located in fractures within sandstones drilled
off the
Western Australian coast, is yet in its infancy (Uwins et al.,
2000). The
nature of nanobacteria ("nanobes") has been and remains
controversial,
although the weight of the evidence appears to be in favor of a
biogenic
origin. A biogenic origin is supported for the following
reasons: (1)
nanobes form microcolonies at atmopsheric pressure and 22 șC;
(2) they are
very similar to, although smaller than, some fungi; (3) their
symmetries are
structurally similar to spores and filaments of membrane-bound
structures;
(4) they consist of O, C and N; (5) they contain central
cavities; (6) they
have non-crystalline wall structures, and (7) they may contain
DNA. Nanobes
are not likely to be amorphous or crystalline inorganic
substances because
they yield no reflections by electron diffraction in TEM, their
chemical
properties are inconsistent with condensed silica vapor,
silicates or
sulfides, nor are they composed of carbonate.
The direct interface between bacteria and minerals, in the
presence of
water, is demonstrated by SEM studies. Studies have demonstrated
bacterial
degradation of terrestrial minerals from filaments preserved in
borings
within spinel and magnetite, where bacterial metabolism may
combine ground
water-derived oxygen with ferrous iron. The remarkable resilience
of
microbial spores argues for their possible survival in the
interiors of
little-shocked ejecta. Inter-planetary bio-transport is supported
by
paleomagnetic studies that suggest temperatures in the interior
of meteorite
ALH84001 did not exceed 40 șC.
In contrast to inter-planetary bio-exchange, interstellar
panspermia remains
a theoretical proposition of diminishingly small probabilities.
With the
possible exception of a planetary micro-organism at ALH84001, no
extraterrestrial microbes have been identified in meteorites.
Claimed
observations of bacteria in meteorites are notoriously difficult
to confirm
due to their common contamination in the weathering zone by
ground water and
terrestrial micro-organisms.
The panspermia theory was anticipated the Greek philosopher
Anassagora
(500-428 B.C.) (cited by T. Gomperz "Griechische
Denker" (Lipsia, 1893) and
Aleksandr Oparin, 1941) and again by Lord Kelvin in 1865. Modern
versions of
the theory are promoted by the identification of organic
molecules in
carbonaceous chondrites, by spectral studies of inter-planetary
dust
particles (IDP), and molecular clouds. Fred Hoyle, the well known
British
cosmologist, proposed in the 1960s that Earth was
"seeded" by
extraterrestrial molecules - including amino-acids, polyaromatic
hydrocarbons (PAHs), and even nucleic acids. Experiments showing
formation
of complex organic molecules from carbon monoxide, carbon dioxide
and
ammonia-bearing ices upon ultraviolet irradiation, or formation
of cellular
membranes and vesicles from simple organic matter, have been
interpreted as
evidence for embryonic formation of cells in cometary
environments.
The probabilities of capture of planetary ejecta on the surfaces
of
extra-solar system planets are discussed by H.J. Melosh, who
estimates about
15 solar-system planetary meteorites fall on Earth each year. A
similar
number of fragments (larger than 10 cm) is ejected into outer
space at
velocities about 5±3 km/sec. Up to one-third of the ejecta from
solar system
planets is lost during encounters with the giant planets Jupiter
and Saturn.
Due to high meteoritic velocities (higher than 1 km/sec) and
large capture
cross-section, about one planetary fragment ejected from the
solar system is
captured by another stellar system every 100 million years. Any
microbes
carried by such fragments would have to reach a habitable zone.
Modeling
indicates the orbits of captured interstellar meteorites are
comet-like, and
for a wide range of assumptions about the location and size of a
target
terrestrial planet the probability of impact is only about 10-4.
This
translates to only a small chance that life can be transported
from one
stellar system to another. It seems that the origin of life on
Earth will
have to be sought within the confines of the solar system itself,
not abroad
in the galaxy.
The focus of current panspermia theories on comets as possible
bacterial
breeding grounds arises from the abundance of volatile
components. However,
liquid water, known to be essential for life, may not exist on
comets except
during transient solar grazing (near approach to the Sun) when
evaporation
of comet ices occurs. Depending on the size and composition of
rock
fragments, survival probabilities are reduced by the intensity of
cosmic
rays. Proponents of panspermia like Wickramasinghe and Hoyle,
suggest that,
for the theory to remain viable, it only requires survival of
less than 1 in
1020 transported micro-organisms. This does not reflect survival
probabilities of new inter-stellar arrivals on the actual surface
of
planets, nor can their effects on indigenous habitats be
estimated at
present. Had interplanetary or interstellar transport of
extremophile
bacteria occurred in special circumstances, the consequences may
have either
been major, causing genetic chain reactions, or alternatively
amounted to
minor perturbations in terms of the long-term evolution of
biospheres. The
micro-colonists may have thrived, survived or perished.
Life as an information system
Central to panspermia theories is a view of complex organic
molecules as
"pre-biotic" substances, which rarely acknowledges the
fundamental
distinction between amino acids and complex replicating nucleic
acids like
DNA, RNA, proteins, and enzymes. The term "organic", as
applied to
carbon-based molecules, is all-too-commonly mistaken for
"live" molecules.
Nor does the incredible resilience of micro-organisms, or their
possible
space transport, explain the origin of life as such. Paul Davies
states:
"For those like myself whose primary interest is in the
origin of life,
panspermia is a distinctly unhelpful theory, because it sidesteps
the entire
issue of how and where life ultimately originated.", and
"A hundred years
ago, when life was considered to be some sort of magic matter, it
was
reasonable to expect that there might be a life principle
manifested in
chemical affinities. Today, the living cell is regarded not as
magic matter,
but as an information processing system, so it is no surprise
that a search
for bio-friendliness in chemistry is unrewarding. If the universe
really is
bio-friendly, one might expect to discover that property instead
in the
principles that govern the behavior of information. It seems to
me plausible
that nature may have harnessed the extraordinary information
processing
power of quantum systems to build the first autonomous
information
replicators - what we call life."
Contributions of extraterrestrial organic molecules to the
terrestrial
inventory of organic matter hardly explain the origin of the
biosphere,
defined in the Encyclopedia Britannia as the "zone of life,
the total mass
of living organisms". The fundamental question inherent in
the origin of
life does not reside in the origin of organic "building
blocks" (amino
acids, PAHs, etc.) but in the - to date little understood - laws
which
underlie their synthesis into complex information-rich
bio-molecules
(peptides, nucleic acids, proteins, enzymes). Bio-molecules are
qualitatively unique, with a probability of forming by chance
given by
Davies as 1:10120- a fundamental quantum leap commonly overlooked
by
proponents of interstellar panspermia. Recent high pressure
experiments
indicate that certain peptide pairs can form from amino acid upon
shock
pressures. Whether the earliest bio-molecules formed by synthesis
of
components leaked from the mantle, derived from volcanic
emanations, and/or
from cometary impact contributions, may not provide the answer
for life's
origin.
A product cannot be explained by its building blocks but by the
nature and
structure of the information it contains. Thus, the logic of the
common
argument by panspermia proponents as if bio-molecules on Earth
are explained
by the introduction of amino acids from space, may be compared,
for example,
to the logic of an argument as if technology was introduced from
space,
citing as evidence the use by some humans of Ni-Fe meteorites
smelting
products to build machines! There is more to the origin and
evolution of
complex life systems than the raw materials of which their
products consist.
The total is greater than the sum of its parts!
Panspermia and the space cult
Long intervals exist between the appearance of Procaryotes,
Eucaryotes,
cross-fertilization, and multicellular organisms. Isolated
episodic
bio-exchanges, had such occurred, may have had a significant or
major effect
on the terrestrial biosphere or, alternatively, constituted no
more than
mere blips on the bio-cosmic radar. Corollaries between
panspermia theories
and the current cult of space travel and colonization may not be
accidental
but follow hidden philosophical assumptions. A hint to the latter
is the
fundamental absolutism of destiny-in-space prophecies, which tend
to have
more in common with Von Daniken Chariots of the Gods type myths
than with
science or humanism. Concepts of planetary and genetic
engineering often
betray limited understanding of, and even less reverence toward,
the
incredible complexity of a biosphere evolved over more than four
billion
years.
The natural willful growth-at-all-cost paradigm, all the way from
the DNA to
the GNP, constitutes a deterministic reality not easily
reconciled with
concepts of sustainability and survival, nor with human ideals of
free will.
Attempts at playing God by a species driven by age-old yearnings
for
immortality and omnipotence, fed by an overgrown neo-cortex, are
belied by
the poor credentials of predatory Homo Sapiens as a planetary
gardener, nor
does the record of the species bode well for the future of
colonized
planetary realms. The fast dwindling resources of the pillaged
biosphere are
needed for irrigation of deserts and marine farming of oceans,
rather than
for space havens for a privileged few escaping a planet in peril.
In the
words of Carl Sagan, our allegiance is to the Earth from which we
spring:
"For we are the local embodiment of a Cosmos grown to
self-awareness. We
have begun to contemplate our origins: starstuff pondering the
stars;
organized assemblages of ten billion billion billion atoms
considering the
evolution of atoms; tracing the long journey by which, here at
least,
consciousness arose. Our loyalties are to the species and the
planet. WE
speak for the Earth. Our obligation to survive is owed not just
to ourselves
but also to that Cosmos, ancient and vast, from which we
spring."
References
Davies, P., 1998. The Fifth Miracle. Penguin Books.
Dyson, F., 1985. Origins of Life. Cambridge University Press,
Cambridge.
Gold, T. 1999. The Deep Hot Biosphere. xiv+235 pp.
Springer-Verlag, Berlin.
Hoyle, F. and Wichramasinghe, N.C., 1980. Comets and the Origin
of Life (C.
Ponnaperuma, Ed.), Reidel, Dordrecht, 227 pp.
Sagan, C. and Shklovskii, I.S., 1966. Intelligent Life in the
Universe.
Picador, London.
Schopf, J.W., 1999. Cradle of Life: The Discovery of Earth's
Earliest
Fossils. Princeton University Press, Princeton, New Jersey.
Uwins, P.J.R., Taylor, A.P., Webb, R.I., 2000. Nanobacteria,
fiction or
fact? In: Glikson, M. and Mastalerz,M. (eds), Organic Matter and
Mineralisation. Kluwer Academic Publishers, Dordrecht.
Copyright 2002, Andrew Glikson
