PLEASE NOTE:


*

CCNet 75/2002 - 27 June 2002
----------------------------


"Asteroid impacts produce a number of environmental insults, several
of which are implicated in subsequent global cooling episodes. But the
formation of planetary rings by impacts is not a possible
contributor to our understanding of these events because it is excluded by
the laws of dynamics and physics."
--Tom Van Flandern, Meta Research, 26 June 2002


"In case you didn't notice, an asteroid barely missed hitting earth
last week. It's okay if you didn't see it, neither did the thousands
of scientists monitoring the skies until the asteroid had already gone
past the earth. It was only the largest asteroid to miss earth in over
two decades."
--Bermuda Sun, 26 June 2002


Comet

Frozen volatiles that jet in enigmatic geysers
from black mass of unknown stuff -comet!
Eager probes from planet Earth speed past
kevlar wrapped, staring, sampling, smelling
the gases, particles, molecules that glow
in skies now free from fear of unknown omens.

What's in that tiny core that masks itself
with luminous coma, streaming tails?
Mystery we hope to open up by hurling down
a copper missile from our probe to scatter
debris and provoke an outburst to reveal whatever
lurked inside that planetisimal since creation!

Malcolm Miller
27.6.2002


(1) BON VOYAGE, CONTOUR, AND HAPPY COMET CHASING
    European Space Agency, 27 June 2002

(2) CHASING A COMET'S TAIL
    The Guardian, 27 June 2002

(3) ASTEROIDS AND SOCCER BALLS: NEAR MISS OR NOT, THEY ALL END UP IN THE NET
    Otago Daily Times, 26 June 2002

(4) 'NO ADDITIONAL NEO TELESCOPES NEEDED ONLY UNTIL 2008': DAVE MORRISON'S
CLARIFICATION
    David Morrison, 26 June 2002

(5) TWO RECENT ASTEROID "NEAR MISSES"
    Asteroid and Comet Impact Hazard, 24 June 2002

(6) NEW NEO WEBSITE
    Alessandro Morbidelli <morby@obs-nice.fr>

(7) IMPACT CRATERS ON EARTH
    http://www.sciencemall-usa.com/impactposter.html

(8) RE: IMPACT-TRIGGERED ICE AGES?
    Mark Boslough <mbboslo@sandia.gov>

(9) Re: IMPACT-TRIGGERED ICE AGES?
    John Fleck <jfleck@abqjournal.com>

(10) PLANETARY RINGS NOT A FACTOR FOR ENVIRONMENTAL COOLING
     Tom Van Flandern <tomvf@metaresearch.org>

(11) AND FINALLY: THE END IS NIGH, AGAIN
     Reason Magazine, 26 June 2002

==============
(1) BON VOYAGE, CONTOUR, AND HAPPY COMET CHASING

http://sci.esa.int/content/news/index.cfm?aid=13&cid=36&oid=30185

Rosetta wishes CONTOUR luck chasing comets

27-Jun-2002 Comets are suddenly in vogue in space research. ESA is getting
ready to send its comet chaser Rosetta in January 2003 to rendezvous with
Comet Wirtanen and study it in immense detail. Rosetta aims to physically
drop a lander on a comet for the first time. Before that, however, on 1 July
2002, NASA will dispatch its CONTOUR spacecraft to fly past at least two
comets, and it has two other small comet missions planned.

What makes comets special is that they contain raw materials left over from
the birth of the Sun and the planets. Finding out what comets are made of
gives scientists priceless clues to both the origin of the Earth and the
origin of life. It is also important for planning possible defences, if a
comet should threaten to collide with the Earth, as Comet Shoemaker-Levy 9
did with the planet Jupiter in 1994.

Comets have always been attractive to scientists and to the general public.
However, they are elusive objects and catching one is very difficult. For
this reason, different space projects have different aims. In 1986, two
Japanese, two Soviet and one European spacecraft flew past Halley's Comet.
ESA's Giotto went closest to the nucleus of the comet. It sent back
wonderful pictures and data for scientists to analyse. Although damaged by
Halley's dust, Giotto went on to fly even closer to Comet Grigg-Skjellerup
in 1992.

In the follow-up, ESA has one major project, Rosetta, and NASA three small
ones, Stardust, CONTOUR, and Deep Impact. Stardust is already on its way to
gather dust from close to Comet Wild and return it to the Earth. CONTOUR,
leaving shortly, will make fast but very close fly-bys of Comets Encke and
Schwassmann-Wachmann 3, investigating why comets can be so different from
one another. Deep Impact, due for launch in January 2004, will shoot a large
copper ball into the nucleus of Comet Tempel 1. Its fireworks show, on 4
July 2005, will scatter subsurface comet matter into space for analysis by
telescopes back at the Earth.

ESA's Rosetta, however, is the one milestone mission that comet scientists
have wanted since the Space Age began. It will fly past Comet Wirtanen, go
into orbit around its nucleus, and drop an instrumented lander on it. Named
after the famous stone with inscriptions that held the key to understanding
ancient Egyptian civilisation, Rosetta will cruise alongside the comet for
17 months while Wirtanen nears the Sun. Unlike previous brief impressions,
Rosetta promises to give us the first complete picture of a comet's
composition and behaviour.

Comet scientists on both sides of the Atlantic are already cooperating
fully. For example, Jochen Kissel of Germany's Max-Planck-Institut f|r
extraterrestrische Physik is responsible for the comet dust analysers on
CONTOUR and Stardust, as well as on Rosetta. He is a veteran of the Soviet
and Giotto missions to Halley's Comet. The CONTOUR science team has Gerhard
Schwehm, who is also ESA's project scientist for Rosetta.

"We're all after the same knowledge," Schwehm comments "What we learn from
the NASA missions will help us to be even better prepared for our big task
at Comet Wirtanen. So all of us in ESA's Rosetta team say, 'Bon voyage,
CONTOUR, and happy comet chasing!' "

===========
(2) CHASING A COMET'S TAIL

>From The Guardian, 27 June 2002
http://www.guardian.co.uk/science/story/0,3605,744221,00.html
 
As another comet probe launches, Duncan Steel wonders what the future will
bring

On Monday morning, all being well, Nasa will launch another comet probe.
Contour is the next step in an international programme to explore these
celestial visitors that intrigue and worry us at the same time.

Last year, Deep Space 1 returned the best-ever pictures of a cometary
nucleus, when it flew past the comet Borrelly. Already Nasa has its Stardust
probe en route to the comet Wild 2, and should return a sample to Earth for
analysis in 2006. Another US probe, Deep Impact, will slam a projectile into
comet Tempel 1 in 2005, to create a crater large enough to show what comets
hide beneath their sooty surfaces.

Next year, the European Space Agency (ESA) will launch perhaps the most
ambitious mission, Rosetta. The mother craft will fly alongside comet
Wirtanen for several years, monitoring how its behaviour alters as it gets
closer to the sun, while a small lander takes a closer look at the surface.
ESA sent its Giotto probe to Halley's comet in 1986, accompanied by two
Soviet and two Japanese missions.

We've come a long way since Edmond Halley predicted, in the early 18th
century, the return of his famous comet. He was correct, although Halley
knew he would not live to see it. For the first time, comets became
predictable, marking their departure from superstition and their arrival in
science.

In the master list of comets maintained by astronomers, Halley's is number
one. For shorthand, we write it as 1P/Halley, where the P stands for
"periodic." In this case, it is visible once every 76 years.

Most comets observed are not periodic in that they tend to be seen once
only. These are icy bodies winging in from the Oort cloud, a reservoir of
trillions of comets that stretches a good fraction of the way to the nearest
stars. Every so often, something nudges one out of the cloud, and it falls
in toward the planets on a voyage that takes millions of years before we see
it. Then it is off again, most often never to return, at least during the
next millennium.

Next on the master list is 2P/Encke. Encke's comet shares a characteristic
with Halley's: it is named after the mathematician who investigated its
orbital motion. Johann Encke was born five years after the comet was
discovered in 1786, but he showed in 1822 that it returns with the shortest
orbital period of all, just three years and four months.

This makes comet Encke unique, because its orbit is entirely interior to
that of Jupiter. This was a long-term puzzle, since we think that periodic
comets are captured from elongated orbits falling from the Oort cloud
through close approaches to Jupiter, the most massive of the planets. How
could a comet reach an orbit that does not even cross that of Jupiter?

Six years ago, working with David Asher of the Armagh Observatory, I found
the solution. It is complicated and involves the combined effects of orbits
resonant against the time Jupiter takes to circuit the sun, and the forces
imposed by the outward jetting of evaporating ices from the cometary
nucleus. An analogy would be that in a random search for a radio station,
you're more likely to sweep across a frequency, and so boost the electrical
current in the radio circuit, if you give the knob large twists.

That aside, planetary scientists have recognised for a long time that comet
Encke is important. On a random night you might see 10 or so meteors (or
shooting stars) per hour. Up to 90% of these derive from comet Encke. This
comet seems to power most of the interplanetary complex of meteoroids and
dust. Much of the 100 tons per day of cosmic debris that cascades into our
atmosphere started out from this comet, or one of its siblings.

Apart from the random arrivals, a dozen specific meteor showers is linked to
this comet. Those occurring during the night are seen from October to
January, peak in November, and arrive from the Taurus constellation. In
consequence they are called the Taurids.

The broad stream of cometary debris also intersects the Earth between May
and July, but on the daytime side of the planet. The most intense meteor
shower of the year is active right now, although you will not have noticed
it. Using suitable radars, we are able to count the meteors burning up far
above our heads.

The last time our planet was struck by any sizeable object from space was on
the last day of June in 1908, when a 60-metre space rock blew up over
Tunguska in Siberia. The date fits in with the daytime Taurid showers, and
the direction it came from also coincides with what we would expect. It is
very likely, then, that comet Encke shares its orbit with a huge number of
pea-sized meteoroids, and also myriad larger lumps.

Comet Encke is the Contour spacecraft's primary target, scheduled for launch
on July 1. Contour - which stands for Comet Nucleus Tour - has a launch
window lasting just 12 seconds on Monday morning, at about 7:56 UK time.
That is shortly before 3am at Cape Canaveral. If there are any hitches,
there are other launch opportunities on most mornings throughout July.

Contour will fly past Encke's comet in November 2003, having used the
Earth's gravity to send it in to the required trajectory. Next on the agenda
is a visit to Comet Schwassmann-Wachmann 3 in 2006. Again we have a special
reason to be interested in this object. Shortly after its discovery by two
German astronomers, this comet flew close by the Earth in 1930, one of the
nearest passages ever observed.

What then? The original brief called for a fly-by of comet d'Arrest in 2008,
but comets are now discovered so frequently that it is very likely that a
target of opportunity - a newly found, non-periodic comet - will appear on a
trajectory that makes a rendezvous by Contour possible.

Such a target would be of scientific interest, because it would be
unaffected by the sun. Although comets share various basic characteristics,
we also realise they show huge diversity, contrasting with each other just
as the animals in a zoo are all different.

Contour, along with other space probe missions, will certainly answer many
of our questions, but will doubtless throw up many new puzzles. Who knows
what we'll be saying about comets in a decade's time?

Duncan Steel is reader in space technology at the University of Salford

Copyright 2002, The Guardian

==============
(3) ASTEROIDS AND SOCCER BALLS: NEAR MISS OR NOT, THEY ALL END UP IN THE NET

>From Otago Daily Times, 26 June 2002
http://www.odt.co.nz/

MOST browsers (not wowsers) lead to the Fifa World Cup these days and there
is rarely a web site which fails to have some reference to it.

Keeping up with the soccer frenzy has been a full-time occupation for many,
including e-mail correspondents who use OOARS (out of office automated
replies). I wonder what prospective clients thought of this one from a
business address in the United Kingdom: "Watching the soccer. Back in two
hours." Tot all that up and think of the billions it is costing the business
world when matches occur in office hours.

There have been many near misses on goal recently but none matched the one
out in space. There was some irony in the fact that an asteroid, said by
scientists to be the size of a football pitch, narrowly missed earth (by
about 120,000 km, a third the distance to the Moon) while we were all
watching the soccer. No-one on look out? Apparently not. Astronomers say it
is very difficult to see these lumps of rock until after they have passed,
which is the same problem soccer goalkeepers have.

According to Nature Science Update.com, British scientists have been trying
to find a way to help keepers predict where the ball is likely to go in
penalty shoot-outs, after England departed the 1998 World Cup. They offer no
advice on where asteroids are likely to strike but news sources say people
are working on the asteroids.

Now here is a striking coincidence. Scientists looking for asteroids and
those studying soccer penalties are colleagues at Liverpool John Moores
University. Where soccer balls go has to do with the stance and posture of
the striker in the split-second before he kicks, according to Mark Williams
in a research paper. His colleague Benny Peiser, an expert on near earth
objects said that most asteroids do not come as close as the one last week
but noted the latest "reminder" comes as Britain tests telescopes on the
Spanish island of La Palma to search for the objects.

"Such near misses do highlight the importance of detecting these objects,"
he said. And so say all of us!

... All we need now are sharp-eyed goalkeepers out in space. See if you can
guess right in tonight's soccer semifinal. Any volunteers to stand watch for
asteroids?

BOOKMARKS
www.nature.com/ for strikes on goalkeepers.
www.universetoday.com/ for strikes on Earth.

==============
(4) 'NO ADDITIONAL NEO TELESCOPES NEEDED ONLY UNTIL 2008': DAVE MORRISON'S
CLARIFICATION

As posted on MPML, 26 June 2002

Jay:

Thanks for noting that I must have been misquoted in the excerpts from the
TV interview that Benny circulated on CCNet yesterday. I would more
accurately say I was quoted out of context, but that amounts to nearly the
same thing.

My position on "blind spots" and such was clearly stated in NEO News
yesterday (which Benny chose not to print). It really does not matter
(except for radar work) whether a NEO is discovered on the incoming or
outbound leg of its flyby of Earth, as long as it is found. I am surprised
that someone with your knowledge would think otherwise! Perhaps you should
apply a "reality check" and tell me (or anyone) how we would have been
better off if 2002MN, for example, had been found on 12 June rather than 17
June.

It is also a fact that no additional telescopes are required to complete the
Spaceguard Goal of 90% of the NEAs larger than 1 km by 2008. Even if
construction were started on a new survey telescope today, it would not
likely come on-line in time to contribute much before 2008.

The real issue is what we do next. Go for 95% at 1 km? Go for 300 m
diameters? This has not been decided either internationally or within the
US, and it is an issue that needs discussion and planning.

It is also interesting to me that you decry "the US, with its paltry $3.5
million per year expenditure." So far the only searches are being done with
US funding. When the UK and other nations are actually willing to spend real
money, then we can move toward the international Spaceguard Survey that I
know we all want.

Dave [Morrison]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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FROM THE MINOR PLANET MAILING LIST [date]. For the full text or to
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==============
(5) TWO RECENT ASTEROID "NEAR MISSES"

>From Asteroid and Comet Impact Hazard
http://impact.arc.nasa.gov/

On June 15, asteroid 2002 MN came within 120,000 km of the Earth, while 2002
EM7 made a close flyby in March.

On June 17, the LINEAR Spaceguard system discovered Near Earth Asteroid
(NEA) 2002 MN, which had passed the Earth on June 15 at a distance of only
120,000 km, one of the closest asteroid fly-bys on record. Based on its
brightness, 2002 MN has a nominal diameter of about 100 m, large enough to
penetrate through the atmosphere to the surface if it struck the Earth. In
March, another asteroid, 2002 EM7, passed within 463,000 km. This asteroid
also was not found until after its flyby of Earth.

Considerable press interest in this objects has been evident, as well it
might be. The June 15 approach of 2002 MN was among the closest on record.
Unfortunately, however, some of the press coverage has been
sensationalistic. Some stories either decry that these NEAs were found after
closest approach (rather than before) or express concern about the "blind
spot" otherwise commonly known to astronomers as the daytime sky. It is
quite true that an asteroid close to the Sun in the sky cannot be seen.
However, if an NEA is approaching Earth from the daytime sky, it is quite
likely to pass into the night sky, where it can be discovered, as these two
asteroids were. Far from being a cause of concern, the discovery of NEAs
2002 EM7 and 2002 MN is an example of the success of the Spaceguard program;
there is no cause for "doom and gloom" in either of these asteroids.

Presumably a part of the problem is that many people do not understand the
Spaceguard Survey strategy to discover and catalog NEAs long in advance of
any possible threat, providing decades (or more) of warning if any NEA is
currently on a collision course. It makes no difference if a NEA is
discovered on approach or departure from the vicinity of the Earth. We don't
give extra points for an approaching NEA or demerits for one that has
already passed the Earth at discovery. The only effect of "blind spots",
whether they be due to sunlight or moonlight or bad weather or lack of a
southern hemisphere survey telescope, is to slow down the completion of the
NEA catalog. Objects in blind spots will be missed until they move into a
more favorable geometry, sometimes within a few days, otherwise usually
within a few years. Both of these asteroids were successfully found,
although they are well below the 1-km diameter that is emphasized by the
current Spaceguard effort.

To put the latest asteroid (2002 MN) in perspective, a 100-m asteroid hits
the Earth at an average interval of several millennia. One passes within the
orbit of the Moon, however, at least once per year. This has been happening
throughout history. What is new is that we are now beginning to discover
these objects, whereas previously they would have sped past undetected and
unheralded.

David Morrison

=============
(6) NEW NEO WEBSITE

>From Alessandro Morbidelli <morby@obs-nice.fr>

Hi Benny

I would like to notify that we have prepaered a website on our work on the
debiased orbital, magnitude and albedo distribution of NEOs, the impact
hazards on Earth, the prospects to achieve the Spaceguard goal.....

All this on http://www.obs-nice.fr/morby/ESA/esa.html

Cheers

A. Morbidelli

Alessandro Morbidelli
Observatoire de la Cote d'Azur
B.P. 4229 06304 Nice Cedex 4, France
TEL: (33) 492003126
FAX: (33) 492003033
EMAIL: morby@obs-nice.fr
http://www.obs-nice.fr/morby/

==========
(7) IMPACT CRATERS ON EARTH

http://www.sciencemall-usa.com/impactposter.html

A new poster featuring the contributions of noted impact scientists Drs
Bevin French
Carolyn Shoemaker
V.L. Sharpton
R.R. Anderson
C. Koeberl, and more

Meteorite Impact Craters on the Earth is a new full-size color poster that
provides a super introduction to the science of meteorite impacts and impact
craters. The fact is, there is a new understanding of impacts as a
fundamental geologic process in the solar system:

"In recent years, geoscientists have begun to realize the important role
that hypervelocity impacts have played in the formation and development of
the Earth and the many life forms that call it home. The Earth itself
appears to be the product of the accretion of smaller bodies through
countless impacts, and our Moon is probably the product of the impact of a
Mars-size body. Early impacts facilitated the crustal out-gassing that
produced our atmosphere, and the impacting bodies themselves may even have
contributed volatiles to it. Large impacts have affected the course of life
on the planet by altering the environment so dramatically that many forms of
life were driven to extinction." (Dr. Raymond. R. Anderson / Iowa Geological
Survey Bureau)

Meteorite Impact Craters on the Earth features a table with information
about the size, location, and features of 160 verified craters so far
discovered on Earth.

* See the world map, showing all 160 craters plotted geographically (and
keyed to the data table). Is there one near your home? (The most "visited"
crater in the world is under O'Hare Airport in Chicago, and thousands of
Chicagolanders actually live within its diameter!)

* See pictures of, and read about, some of the amazing rock and mineral
types that are created ONLY by hypervelocity impacts.

* Understand the way craters are formed when the meteorite hits the ground,
and the way differences in impactor size affect the type of crater produced.

* Learn about the way our Earth has been pounded throughout its history, by
following the colorful "Timeline and Relative Size of Impact Craters on
Earth".

* Discover the man called the "father of impact science".

* Also includes a 6-page information sheet with MANY more photos (meteorite
samples, too), and teachers' review questions and answers.

The 38.5 x 27 inch poster is printed in full color on heavyweight stock, and
is given a protective UV gloss coating that will even resist splashes of
water and alcohol!

Price (UV protective coated) $16.00
The wait is over....available NOW!

============================
* LETTERS TO THE MODERATOR *
============================

(8) RE: CCNet: IMPACT-TRIGGERED ICE AGES?

>From Mark Boslough <mbboslo@sandia.gov>

Hi Benny, 

Is this URL (http://abob.libs.uga.edu/bobk/ccc/ce120799.html) correct? I
couldn't find anything in Hoyle's essay about impact-induced ice ages. Is
there a reference to a scientific paper by Hoyle on this subject? Maybe you
were thinking of John A. O'Keefe or Peter Schultz, both of whom suggested
the existence of a terrestrial ring system and its climatic consequences,
but did not have the resources to model. We referenced O'Keefe and Schultz
in our paper, but may have overlooked any contributions by Hoyle. I hope you
can track down a reference so we can give proper credit next time!

Regards,

Mark Boslough

MODERATOR'S NOTE: Hoyle and Wickramasinghe have suggested a rather different
scenario in which cometary impacts into the oceans do the trick; see F.
Hoyle & C. Wickramasinghe: Cometary impacts and ice-ages, ASTROPHYSICS AND
SPACE SCIENCE, 275 (4): 367-376 MAR 2001; F. Hoyle, On the Causes of
Ice-Ages, EARTH MOON AND PLANETS, 31 (3): 229-248 1984. For an alternative
theory of ice ages due to cosmic dust-loading by giant comets, see: Bill
Napier, Temporal variation of the zodiacal dust cloud, MONTHLY NOTICES OF
THE ROYAL ASTRONOMICAL SOCIETY, 321 (3): 463-470 MAR 2001.

================
(9) Re: CCNet: IMPACT-TRIGGERED ICE AGES?

>From John Fleck <jfleck@abqjournal.com>

Benny -

Just a note to let you know that the Associated Press rewrite rather mangled
my original story on this. I noted in my story that Boslough is the one who
suggested to Fawcett that they try doing a ringworld climate simulation.
That became the above quote "The idea came from Boslough" line. Sigh.

In any case, I didn't want you or your readers to think Boslough is so
arrogant as to think he came up with the idea of impacts causing ice ages.
:-)

Unfortunately, for reasons obscure, my original story isn't on the web.

Cheers,
John
--
John Fleck, science writer
Albuquerque Journal, PO Drawer J, Albuquerque NM, 87110
(505) 823-3916
jfleck@abqjournal.com (w), jfleck@inkstain.net (h)
http://www.abqjournal.com/scitech/, http://www.inkstain.net/fleck/

================
(10) PLANETARY RINGS NOT A FACTOR FOR ENVIRONMENTAL COOLING

>From Tom Van Flandern <tomvf@metaresearch.org>

Benny,

>From Tom Van Flandern, Meta Research  <tomvf@metaresearch.org>

In CCNet for 2002/06/26, your first article cites an AP story announcing
that Peter Fawcett and Mark Boslough are trying to explain a 100,000-year
cold spell during the Eocene epoch 35 million years ago with planetary rings
formed during an asteroid impact event. However, one of the basic rules of
celestial mechanics is that "A single impulse from the surface of a body
can't inject anything into a stable orbit." So the idea that planetary rings
were responsible for the Eocene cooling is not credible.

The reason for this rule of dynamics is that the point where an impulse is
applied must remain a point on the resulting orbit. For example, if the
impulse results from an impact, every non-escaping bit of debris ejected
from the impact follows a trajectory that is an ellipse with the center of
the Earth at one focus. And the point of ejection, a point on the Earth's
surface, remains a point on the new elliptical trajectory. So any bit of
debris that survives an impact has only two possible fates: (1) escape to
interplanetary space if its speed exceeds escape velocity from the Earth, 11
km/s; or (2) entering an elliptical orbit that intersects the Earth's
surface, destined to collide with the ground again in less than one
revolution.

So achieving a stable orbit with a single impulse is dynamically impossible.
That is why nothing can be placed into Earth orbit by firing it from a canon
on the ground. It is also why the first stage (or two) of a
satellite-carrying rocket works to get the satellite up to some altitude
well above the Earth's atmosphere, and the final stage provides a new,
horizontal impulse that lifts the rest of the elliptical orbit above the
atmosphere. This is known as the "two-burn" problem in rocketry. You can't
reach stable orbit with a single thrust, however large.

There is a second problem with the planetary ring hypothesis as well. To
achieve a stable orbit, a satellite must have a speed of at least 7 km/s.
However, small bodies ejected from rest by a single impulse cannot be given
a speed of more than 3 km/s without totally vaporizing them from the energy
of the shock wave. [B.J. Gladman, J.A. Burns et al. (1996), "The exchange of
impact ejecta between terrestrial planets", Science, v. 271, pp. 1387-1392.]
This has long been known as a constraint on meteorites from the Moon (escape
speed 2.4 km/s), and is a problem often not addressed by scenarios that
hypothesize "SNAC meteorites" are from Mars (escape speed 5 km/s), as we
reported to CCNet for 2001/07/11 last year. So getting ring material into
Earth orbit without vaporizing it is also an insurmountable difficulty with
this new planetary-rings theory. The greatest distance to which ordinary
ejecta can be thrown by a terrestrial impact is roughly 1000 km, as we
mentioned in connection with our discussion of the K/T boundary event in
CCNet for 2002/02/01.

In conclusion, asteroid impacts produce a number of environmental insults,
several of which are implicated in subsequent global cooling episodes. But
the formation of planetary rings by impacts is not a possible contributor to
our understanding of these events because it is excluded by the laws of
dynamics and physics.

Best wishes. -|Tom|-

[response from Mark Boslough below]
==========
(11) AND FINALLY: THE END IS NIGH, AGAIN

>From Reason Magazine, 26 June 2002
http://reason.com/rb/rb062602.shtml

Environmentalists insist that humanity really has overshot the earth's
carrying capacity this time.

By Ronald Bailey

The United Nations Summit on Sustainable Development is coming up at the end
of August, so expect to see a spate of news stories warning that humanity is
on an unsustainable economic path. To bolster this notion, environmentalists
are positioning their views to make it easy for the press to echo them.

In an article published this week by the prestigious journal Proceedings of
the National Academy of Sciences (http://www.pnas.org/), a group of
environmentalists led by Mathis Wackernagel of Redefining Progress claim
that human consumption and waste production have overshot the earth's
capacity to create new resources and absorb waste. They calculate that
"humanity's load corresponded to 70% of the biosphere's capacity in 1961,"
and "this percentage grew to 120% in 1999." They explain that "20% overshoot
means that it would require 1.2 earths, or one earth 1.2 years, to
regenerate what humanity used in 1999."

Such worries about overpopulation and resource scarcity have a long history.
The Roman writer Tertullian warned in 200 A.D. that "we men have actually
become a burden to the earth" and that "the fruits of nature hardly suffice
to support us." In 1798 the Rev. Thomas Robert Malthus published An Essay on
the Principle of Population, in which he claimed that population growth
would always outstrip food supplies, inevitably resulting in famine,
pestilence, and war. Biologist Paul Ehrlich notoriously updated Malthus'
gloomy predictions in his 1968 book The Population Bomb, which predicted
that hundreds of millions of people would die of famine in the 1970s.

Well, are the alarmists right this time around? Is the end finally nigh? No.

Wackernagel et al. focus their analysis of how humanity uses the biosphere
on six areas: growing crops, grazing animals, harvesting timber, fishing,
building infrastructure, and getting energy from fossil fuels and nuclear
power. According to their own calculations, humanity has not exceeded the
biosphere's capacity in the first five of these areas, although they say we
are close to the limits for growing crops and fishing. This leaves fossil
fuels and nuclear energy, which they claim account for fully half of
humanity's biosphere use. By their account, then, humanity would be using
only 60 percent of the biosphere's capacity if energy use weren't a problem.

To estimate our impact on the biosphere, Wackernagel et al. calculate an
average of how many hectares it takes to support each person. The reason
energy use figures so prominently in their calculations is that they are
looking at how many hectares it would take to absorb the carbon dioxide
produced by burning fossil fuels. Their concern is that burning fossil fuels
adds carbon dioxide to the atmosphere, which traps heat, which leads to
global warming.

These calculations embody an ideal of stasis, both ecological and economic.
What the authors miss is that for every one of the six areas they are
looking at humanity's ecological footprint probably is going to become
smaller, not larger, during this century.

Jesse Ausubel, director of the Program for the Human Environment at
Rockefeller University, believes the 21st century will see the beginning of
a "Great Restoration" as humanity's productive activities increasingly
withdraw from the natural world. For example, Ausubel and his colleagues
calculate, "If the world farmer reaches the average yield of today's US corn
grower during the next 70 years, ten billion people eating as people now on
average do will need only half of today's cropland. The land spared exceeds
Amazonia." If 10 billion people choose meat-rich diets in 2070, then farmers
will need only 75 percent of today's cropland. In other words, through
technologically improved farming, millions of acres will revert to nature.

With regard to grazing animals, many environmentalists paradoxically oppose
intensive meat production that can spare millions of acres. "If you very
efficiently produce grain to feed chickens rather than allowing free range
cattle," explains Ausubel, "it's hard to see how you have a problem with
increased meat consumption."

Ausubel also notes that "forest regrowth appears part of modernity." He
points out that U.N. Food and Agriculture Organization studies "of forest
biomass for the decade of the 1990s in the boreal and temperate region in
more than 50 countries show the forests expanding in every one of them." As
global cropland and grazing area shrink, forests will continue to expand.
Ausubel estimates that humanity will need to use 20 percent or less of the
world's 3 billion hectares of forest to sustainably supply all of our wood
needs in the 21st century.

"The fish situation is much more difficult," Ausubel cautions. Many
fisheries are being harvested at or over their sustainable limits. Ausubel
notes that humanity consumes about 800 million tons of animal products--meat
and milk--produced on land, compared to 80 million tons caught wild in the
oceans. His solution to overfishing? "The ancient sparing of land animals by
farming shows us how to spare fish in the sea," he says. "We need to raise
the share we farm and lower the share we catch."

Already, 20 percent of seafood is produced by aquaculture that can be
expanded in sustainable ways, relieving pressure on wild species such as cod
and rockfish. In addition, as Iceland's and New Zealand's fisheries show,
privatizing fisheries dramatically increases the incentives to conserve and
protect wild stocks.

As for infrastructure, Ausubel calculates that if an additional 4 billion
people (who are unlikely to materialize, according to the latest U.N.
population projections) chose to occupy as much land as the average
Californian does today, they would cover 240 million hectares of land, about
2.5 percent of the earth's terrestrial surface.

So we come to Wackernagel et al.'s chief concern: energy use. "Some people
try to use the climate change issue as a trump card," says Ausubel. "It
sounds like they're doing that." Keep in mind that despite Wackernagel et
al.'s certitude, there are still serious questions about whether adding
cabon dioxide to the atmosphere is really causing significant problems for
humanity or the biosphere.

Assuming that man-made global warming is a real problem, there are plenty of
ways to handle it. One is to deploy technologies we already have to mitigate
its effects on humanity: heating, air conditioning, seawalls, irrigation of
farmland, crop switching, and so forth. We could also choose to sequester
extra carbon dioxide by pumping it back into the ground whence it came,
fertilizing the tropic ocean deserts so that they bloom with phytoplankton
that absorbs it from the air, or planting more trees.

In any case, Ausubel doesn't think that carbon dioxide is a long-term
problem because the world's energy system has been inexorably decarbonizing
for the past two centuries. His research traces humanity's steady progress
from wood to coal to oil to natural gas and, eventually, to hydrogen. At
each stage, consumers, without being commanded to do so by regulators, have
chosen fuels containing more hydrogen over fuels containing more carbon.

Ausubel sees that trend continuing until carbon-based fuels are eliminated
by the end of the century. He expects that carbon dioxide concentrations,
now about 360 parts per million (ppm), will peak at 450 ppm. That is 100 ppm
less than the U.N.'s sometimes stated goal of "stabilizing" carbon dioxide
at 550 ppm, and it would happen without draconian increases in energy prices
or the creation of global bureaucracies aimed at regulating the atmosphere.

So Wackernagel et al. are wrong on every measure they chose to analyze with
regard to the future sustainability of the human enterprise. How could they
get it so wrong?

"Biologists and ecologists tend to overlook the power of technical progress
compounded over the years," says Ausubel. "If you're trained in ecology and
botany, you think of technology as a bulldozer, but what it really is, is
efficiency, using less to do more."

Technological progress has already dramatically expanded the carrying
capacity of the earth. In the 21st century it will so outpace the increasing
demands of a growing and wealthier population that more and more land will
revert to nature.

"It looks like over the next 100 years, for most environmental concerns, we
will do better," concludes Ausubel. "You get smarter as you get richer."

Ausubel's own article in the June 11 issue of the Proceedings of the
National Academy of Sciences concludes, "An annual 2-3% progress in
consumption and technology over many decades and sectors provides a
benchmark for sustainability." In other words, economic growth and
technological progress are sustainable in the long run and make it less and
less likely that humanity will overshoot any limits the biosphere may have.

Let the Great Restoration begin!

Ronald Bailey, Reason's science correspondent, is the editor of Global
Warming and Other Eco Myths (Prima Publishing) and Earth Report 2000:
Revisiting the True State of the Planet(McGraw-Hill).

Copyright 2002, Reason Magazine


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*

NOTHING IN PHYSICS PROHIBITS IMPACT-PRODUCED RINGS
 
>From Mark Boslough <mbboslo@sandia.gov>

Tom,

Thanks for your detailed explanation of 2-body celestial mechanics. If
that had been the mechanism we had suggested for generating a planetary
ring system, I can assure you that the editors of JGR would have been
smart enough not to accept our paper! I realize that you do not have a
copy of our paper and could not have known what we suggested, but it is
based on the experimental work of Schultz and Gault (GSA Special Paper
247, 1990). 

Quoting from our paper:

"At low impact angles (30 degrees from the horizontal), the original
impactor disrupts and ricochets downrange at a significant fraction of
its incoming velocity. The ricochet component becomes embedded in and
accelerated by an expanding vapor cloud.  Continued interaction between
the solid debris and the turbulent expanding vapor cloud can potentially
provide the non-ballistic force that allows some fraction of the debris
to be inserted into orbit."  For a simulation of such an impact on a
planetary scale, see Dave Crawford's movies:
http://sherpa.sandia.gov/planet-impact/asteroid/.

According to Schultz & Gault (1990): "In general, conditions favoring
injection of significant quantities of projectile and target into orbit
appear to be a 10 to 20 degree impact between 15 and 20 km/s into an
ocean or into carbonate sediments... such an event for 10-km-diameter
body would be likely over a time interval of 300 m.y."  In my opinion,
our planet has had an impact-produced ring system many times in its
history. One does not need to run a fancy GCM to recognize that such a
ring would have had climatological consequences, but the GCM lets us get
a handle on second-order effects (first-order being the obvious cooling
from reduced insolation).

It is noteworthy also that the "giant impact" hypothesis for the
formation of the moon involves the formation of a ring system by impact,
albeit at a much greater scale. This is dynamically possible because,
again, it is not a simple 2-body celestial mechanics problem; there are
hydrodynamic forces as well as distributed body forces.

There are similar assumptions built into your second objection. Melosh
(Icarus 59, 234, 1984) showed how material can be ejected from a planet
to high velocity by shock-wave interference and non-uniaxial loading
effects without strong shock effects (let alone melting or vaporization).
Likewise, O'Keefe and Ahrens (Science 234, 346, 1986) modeled vapor-plume
entrainment as a way of getting weakly shocked rocks off a planet,
similar to what Schultz and Gault observed experimentally and what we
invoked. The Gladman et al. article you site does not question the
possibility of getting SNCs off Mars, as you implied.

Just in case you think these are contrived, egg-headed theoretical tricks
that could not ever really work, have a look at the proceedings of the
1992 Hypervelocity Impact Symposium. My colleague, Lalit Chhabildas,
cleverly applied similar ideas to enable the launching of an unmelted
projectile at speeds exceeding 12 km/s (Chhabildas et al., Int. J. Impact
Eng., 14, 1993). See Boslough et al. (Int. J. Impact Eng., 14, 1993) for
a flash x-ray radiograph of an unmelted, intact plate being launched to
10 km/sec by a single impulse!

The lesson is that when you do real-world physics, the idealizations you
were taught as an undergraduate do not always apply. Real life is
messier, and it is the messiness that is the most interesting!

Regards,

Mark Boslough

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beliefs and viewpoints of the moderator of this network.



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